Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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METHODS FOR JOINING INSULATED CONDUCTORS
BACKGROUND
1. Field of the Invention
[0001] The present invention relates to systems for insulated conductors used
in heater
elements. More particularly, the invention relates to fittings to splice
together insulated
conductor cables.
2. Description of Related Art
[0002] Hydrocarbons obtained from subterranean formations are often used as
energy
resources, as feedstocks, and as consumer products. Concerns over depletion of
available
hydrocarbon resources and concerns over declining overall quality of produced
hydrocarbons have led to development of processes for more efficient recovery,
processing
and/or use of available hydrocarbon resources. In situ processes may be used
to remove
hydrocarbon materials from subterranean formations that were previously
inaccessible
and/or too expensive to extract using available methods. Chemical and/or
physical
properties of hydrocarbon material in a subterranean formation may need to be
changed to
allow hydrocarbon material to be more easily removed from the subterranean
formation
and/or increase the value of the hydrocarbon material. The chemical and
physical changes
may include in situ reactions that produce removable fluids, composition
changes,
solubility changes, density changes, phase changes, and/or viscosity changes
of the
hydrocarbon material in the formation.
[0003] Heaters may be placed in wellbores to heat a formation during an in
situ process.
There are many different types of heaters which may be used to heat the
formation.
Examples of in situ processes utilizing downhole heaters are illustrated in
U.S. Patent Nos.
2,634,961 to Ljungstrom; 2,732,195 to Ljungstrom; 2,780,450 to Ljungstrom;
2,789,805 to
Ljungstrom; 2,923,535 to Ljungstrom; 4,886,118 to Van Meurs et al.; and
6,688,387 to
Wellington et al.
[0004] Mineral insulated (MI) cables (insulated conductors) for use in
subsurface
applications, such as heating hydrocarbon containing formations in some
applications, are
longer, may have larger outside diameters, and may operate at higher voltages
and
temperatures than what is typical in the MI cable industry. There are many
potential
problems during manufacture and/or assembly of long length insulated
conductors.
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[0005] For example, there are potential electrical and/or mechanical problems
due to
degradation over time of the electrical insulator used in the insulated
conductor. There are
also potential problems with electrical insulators to overcome during assembly
of the
insulated conductor heater. Problems such as core bulge or other mechanical
defects may
occur during assembly of the insulated conductor heater. Such occurrences may
lead to
electrical problems during use of the heater and may potentially render the
heater
inoperable for its intended purpose.
[0006] In addition, for subsurface applications, the joining of multiple MI
cables may be
needed to make MI cables with sufficient length to reach the depths and
distances needed
to heat the subsurface efficiently and to join segments with different
functions, such as
lead-in cables joined to heater sections. Such long heaters also require
higher voltages to
provide enough power to the farthest ends of the heaters.
[0007] Conventional MI cable splice designs are typically not suitable for
voltages above
1000 volts, above 1500 volts, or above 2000 volts and may not operate for
extended
periods without failure at elevated temperatures, such as over 650 C (about
1200 F), over
700 C (about 1290 F), or over 800 C (about 1470 F). Such high voltage,
high
temperature applications typically require the compaction of the mineral
insulant in the
splice to be as close as possible to or above the level of compaction in the
insulated
conductor (MI cable) itself.
[0008] The relatively large outside diameter and long length of MI cables for
some
applications requires that the cables be spliced while oriented horizontally.
There are
splices for other applications of MI cables that have been fabricated
horizontally. These
techniques typically use a small hole through which the mineral insulation
(such as
magnesium oxide powder) is filled into the splice and compacted slightly
through vibration
and tamping. Such methods do not provide sufficient compaction of the mineral
insulation
or even allow any compaction of the mineral insulation, and are not suitable
for making
splices for use at the high voltages needed for these subsurface applications.
[0009] Thus, there is a need for splices of insulated conductors that are
simple yet can
operate at the high voltages and temperatures in the subsurface environment
over long
durations without failure. In addition. the splices may need higher bending
and tensile
strengths to inhibit failure of the splice under the weight loads and
temperatures that the
cables can be subjected to in the subsurface. Techniques and methods also may
be utilized
to reduce electric field intensities in the splices so that leakage currents
in the splices are
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reduced and to increase the margin between the operating voltage and
electrical
breakdown. Reducing electric field intensities may help increase voltage and
temperature
operating ranges of the splices.
[0010] In addition, there may be problems with increased stress on the
insulated
conductors during assembly and/or installation into the subsuiface of the
insulated
conductors. For example, winding and unwinding of the insulated conductors on
spools
used for transport and installation of the insulated conductors may lead to
mechanical
stress on the electrical insulators and/or other components in the insulated
conductors.
Thus, more reliable systems and methods are needed to reduce or eliminate
potential
problems during manufacture, assembly, and/or installation of insulated
conductors.
SUMMARY
[0011] Embodiments described herein generally relate to systems, methods, and
heaters for
treating a subsurface formation. Embodiments described herein also generally
relate to
heaters that have novel components therein. Such heaters can be obtained by
using the
systems and methods described herein.
[0012] In certain embodiments, the invention provides one or more systems,
methods,
and/or heaters. In some embodiments, the systems, methods, and/or heaters are
used for
treating a subsurface formation.
[0013] In certain embodiments, a method for coupling ends of two insulated
conductors
includes: coupling an end portion of a core of a first insulated conductor to
an end portion
of a core of a second insulated conductor, wherein at least a part of the end
portions of the
cores are at least partially exposed; placing electrically insulating material
over the exposed
portions of the cores; placing a sleeve over end portions of the two insulated
conductors to
be coupled, the sleeve comprising one or more raised portions, wherein the end
portions
comprise the exposed portions of the cores; coupling the sleeve to jackets of
the two insulated
conductors; and mechanically compressing the raised portions of the sleeve
until the raised
portions of the sleeve have a diameter substantially similar to a remainder of
the sleeve,
wherein the compression of the raised portions of the sleeve compacts the
electrically
insulating material inside the sleeve.
[0014] In certain embodiments, a method for coupling ends of two insulated
conductors
includes: coupling an end portion of a core of a first insulated conductor to
an end portion
of a core of a second insulated conductor, wherein at least a part of the end
portions of the
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cores are at least partially exposed; placing electrically insulating material
over the exposed
portions of the cores; placing an inner sleeve over end portions of the two
insulated
conductors to be coupled, wherein the end portions comprise the exposed
portions of the
cores; placing an outer sleeve over the inner sleeve, wherein there is an open
volume
between the inner sleeve and the outer sleeve, and the outer sleeve comprises
a port;
coupling the inner sleeve and the outer sleeve to jackets of the two insulated
conductors; and
providing a pressurized fluid into the open volume between the inner sleeve
and the outer
sleeve to compress the inner sleeve into the electrically insulating material
and compact the
electrically insulating material.
[0015] In certain embodiments, a fitting for coupling ends of insulated
conductors
includes: an inner sleeve placed over end portions of a first insulated
conductor and a
second insulated conductor during use, wherein the inner sleeve is placed over
at least
partially exposed end portions of cores of the insulated conductors and
electrically
insulating material is placed over the exposed end portions of the cores
inside the sleeve
during use; and an outer sleeve comprising a port placed over the inner
sleeve, wherein
there is an open volume between the inner sleeve and the outer sleeve; wherein
the inner
sleeve and the outer sleeve are coupled to jackets of the insulated conductors
during use;
and wherein the inner sleeve is compressed during use by a pressurizing fluid
provided into
the open volume between the inner sleeve and the outer sleeve, and wherein
compression
of the inner sleeve compacts the electrically insulating material inside the
inner sleeve.
[0016] In certain embodiments, a method for coupling ends of cores of three
insulated
conductors includes: placing an end termination over end portions of the three
insulated
conductors, wherein the end termination comprises three separate openings that
pass
through the end termination longitudinally, each of the insulated conductors
passing
.. through one of the openings with end portions of the insulated conductors
protruding from
one side of the end termination; exposing cores of the end portions of the
insulated
conductors protruding from the end termination by removing jackets and
electrical
insulation from the end portions; coupling the ends of the jackets of the
insulated
conductors to the end termination; coupling a cylinder to the side of the end
termination
from which the end portions of the insulated conductors protrude; filling the
cylinder with
electrically insulating material such that at least a portion of the cores
remain exposed;
coupling an electrical bus to the exposed portion of the cores; filling the
cylinder with
electrically insulating material such that the cores are substantially
enclosed in the
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electrically insulating material; and coupling an end cap to the cylinder to
seal off the
interior of the cylinder.
[0017] In certain embodiments, a fitting for coupling ends of cores of three
insulated
conductors includes: an end termination placed over end portions of the three
insulated
conductors, wherein the end termination comprises three separate openings that
pass
through the end termination longitudinally, each of the insulated conductors
passing
through one of the openings with end portions of the insulated conductors
protruding from
one side of the end termination, exposed cores of the end portions of the
insulated
conductors protruding from the end termination; a cylinder coupled to the side
of the end
termination from which the end portions of the insulated conductors protrude;
an electrical
bus coupled to the exposed portion of the cores; electrically insulating
material filling the
cylinder such that the cores are substantially enclosed in the electrically
insulating material;
and an end cap coupled to the cylinder to seal off the interior of the
cylinder.
[0018] In certain embodiments, a method for converting a three-phase heater
with a
ground-faulted leg to single-phase operation using a three-phase power supply
includes:
placing a resistor between a neutral of the power supply and the ground-
faulted leg of the
three-phase heater such that little or no current flows through the ground-
faulted leg,
wherein the resistor is in series with the ground-faulted leg; providing
electrical power to
the remaining two legs of the heater from the power supply such that the two
legs operate
as a single phase heater with current running into the formation through one
leg and
returning on the other leg, wherein the two legs are coupled in the subsurface
using a
fitting having: an end termination placed over end portions of the three
insulated
conductors, wherein the end termination comprises three separate openings that
pass
through the end termination longitudinally, each of the insulated conductors
passing
through one of the openings with end portions of the insulated conductors
protruding from
one side of the end termination, exposed cores of the end portions of the
insulated
conductors protruding from the end termination; a cylinder coupled to the side
of the end
termination from which the end portions of the insulated conductors protrude;
an electrical
bus coupled to the exposed portion of the cores; electrically insulating
material filling the
cylinder such that the cores are substantially enclosed in the electrically
insulating material;
and an end cap coupled to the cylinder to seal off the interior of the
cylinder.
[0019] In certain embodiments, a fitting for coupling an end of a first
insulated conductor
to an end of a second insulated conductor includes: a sleeve configured to be
placed over
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the end of the first insulated conductor and the end of the second insulated
conductor; and a
core coupling located inside the sleeve, the core coupling being configured to
fit around an
end of a core of the first insulated conductor and an end of a core of the
second insulated
conductor, wherein the cores of the insulated conductors are configured to be
moved together
in the core coupling when the ends of the insulated conductors are moved into
the fitting, and
wherein the ends of the cores have a selected clearance between them; wherein
an interior
volume of the sleeve is configured to be at least partially filled with
electrically insulating
material, and the electrically insulating material is configured to be
compressed with an end
portion of an electrical insulator in the first insulated conductor and an end
portion of an
electrical insulator in the second insulated conductor when the fitting is
coupled to the
insulated conductors.
[0019a] In certain embodiments, a method for coupling ends of two insulated
conductors,
comprises: coupling an end portion of a core of a first insulated conductor to
an end portion of
a core of a second insulated conductor; placing electrically insulating
material over one or
more exposed portions of the cores; placing a sleeve over end portions of the
two insulated
conductors to be coupled, the sleeve comprising one or more raised portions,
wherein the end
portions comprise the exposed portions of the cores; coupling the sleeve to
jackets of the two
insulated conductors; and mechanically compressing the raised portions of the
sleeve until the
raised portions of the sleeve have a diameter substantially similar to a
remainder of the sleeve,
wherein the compression of the raised portions of the sleeve compacts the
electrically
insulating material inside the sleeve.
[0020] In further embodiments, features from specific embodiments may be
combined with
features from other embodiments. For example, features from one embodiment may
be
combined with features from any of the other embodiments.
[0021] In further embodiments, treating a subsurface formation is performed
using any of the
methods, systems, power supplies, or heaters described herein.
[0022] In further embodiments, additional features may be added to the
specific embodiments
described herein.
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BRIEF DESCRIPTION OF THE DRAWINGS
[0023] Features and advantages of the methods and apparatus of the present
invention will be
more fully appreciated by reference to the following detailed description of
presently
preferred but nonetheless illustrative embodiments in accordance with the
present invention
when taken in conjunction with the accompanying drawings.
[0024] FIG. 1 shows a schematic view of an embodiment of a portion of an in
situ heat
treatment system for treating a hydrocarbon containing formation.
[0025] FIG. 2 depicts an embodiment of an insulated conductor heat source.
[0026] FIG. 3 depicts an embodiment of an insulated conductor heat source.
[0027] FIG. 4 depicts an embodiment of an insulated conductor heat source.
[0028] FIG. 5 depicts a side view cross-sectional representation of one
embodiment of a
fitting for joining insulated conductors.
[0029] FIG. 6 depicts an embodiment of a cutting tool.
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[0030] FIG. 7 depicts a side view cross-sectional representation of another
embodiment of
a fitting for joining insulated conductors.
[0031] FIG. 8A depicts a side view of a cross-sectional representation of an
embodiment of
a threaded fitting for coupling three insulated conductors.
[0032] FIG. 8B depicts a side view of a cross-sectional representation of an
embodiment of
a welded fitting for coupling three insulated conductors.
[0033] FIG. 9 depicts an embodiment of a torque tool.
[0034] FIG. 10 depicts an embodiment of a clamp assembly that may be used to
compact
mechanically a fitting for joining insulated conductors.
[0035] FIG. 11 depicts an exploded view of an embodiment of a hydraulic
compaction
machine.
[0036] FIG. 12 depicts a representation of an embodiment of an assembled
hydraulic
compaction machine.
[0037] FIG. 13 depicts an embodiment of a fitting and insulated conductors
secured in
clamp assemblies before compaction of the fitting and insulated conductors.
[0038] FIG. 14 depicts a side view representation of yet another embodiment of
a fitting
for joining insulated conductors.
[0039] FIG. 15 depicts a side view representation of an embodiment of a
fitting with an
opening covered with an insert.
[0040] FIG. 16 depicts an embodiment of a fitting with electric field reducing
features
between the jackets of the insulated conductors and the sleeves and at the
ends of the
insulated conductors.
[0041] FIG. 17 depicts an embodiment of an electric field stress reducer.
[0042] FIG. 18 depicts a cross-sectional representation of a fitting as
insulated conductors
are being moved into the fitting.
[0043] FIG. 19 depicts a cross-sectional representation of a fitting with
insulated
conductors joined inside the fitting.
[0044] FIG. 20 depicts a cross-sectional representation of yet another
embodiment of a
fitting as insulated conductors are being moved into the fitting.
[0045] FIG. 21 depicts a cross-sectional representation of yet another
embodiment of a
fitting with insulated conductors joined inside the fitting.
[0046] FIG. 22 depicts an embodiment of blocks of electrically insulating
material in
position around cores of joined insulated conductors.
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[0047] FIG. 23 depicts an embodiment of four blocks of electrically insulating
material in
position surrounding the cores of joined insulated conductors.
[0048] FIG. 24 depicts an embodiment of an inner sleeve placed over joined
insulated
conductors.
[0049] FIG. 25 depicts an embodiment of an outer sleeve placed over an inner
sleeve and
joined insulated conductors.
[0050] FIG. 26 depicts an embodiment of a chamfered end of an insulated
conductor after
compression.
[0051] FIG. 27 depicts an embodiment of a first half of a compaction device to
be used for
compaction of electrically insulating material at a coupling of insulated
conductors.
[0052] FIG. 28 depicts an embodiment of a device coupled together around
insulated
conductors.
[0053] FIG. 29 depicts a side view of an insulated conductor inside a device
with a first
plunger in position above the insulated conductor with exposed core.
[0054] FIG. 30 depicts a side view of an insulated conductor inside a device
with a second
plunger in position above the insulated conductor with exposed core.
[0055] FIGS. 31A-D depict other embodiments of a second plunger.
[0056] FIG. 32 depicts an embodiment with the second half of a device removed
to leave
the first half and electrically insulating material compacted around the
coupling between
insulated conductors.
[0057] FIG. 33 depicts an embodiment of electrically insulating material
shaped around the
coupling between insulated conductors.
[0058] FIG. 34 depicts an embodiment of a sleeve placed over electrically
insulating
material.
[0059] FIG. 35 depicts a representation of an embodiment of a hydraulic press
machine
that may be used to apply force to a plunger to hydraulically compact
electrically insulating
material inside a device.
[0060] FIG. 36 depicts an embodiment of a sleeve that is used in
circumferential
mechanical compression.
[0061] FIG. 37 depicts an embodiment of a sleeve on insulated conductors after
the sleeve
and ribs have been circumferentially compressed.
[0062] FIG. 38 depicts an embodiment of reinforcement sleeves on joined
insulated
conductors.
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[0063] FIG. 39 depicts an exploded view of another embodiment of a fitting
used for
coupling three insulated conductors.
[0064] FIGS. 40-47 depict an embodiment of a method for installation of a
fitting onto
ends of insulated conductors.
[0065] FIG. 48 depicts an embodiment of a compaction tool that can be used to
compact
electrically insulating material.
[0066] FIG. 49 depicts an embodiment of another compaction tool that can be
used to
compact electrically insulating material.
[0067] FIG. 50 depicts an embodiment of a compaction tool that can be used for
the final
compaction of electrically insulating material.
[0068] While the invention is susceptible to various modifications and
alternative forms,
specific embodiments thereof are shown by way of example in the drawings and
will
herein be described in detail. The drawings may not be to scale. It should be
understood
that the drawings and detailed description thereto are not intended to limit
the invention to
.. the particular form disclosed, but to the contrary, the intention is to
cover all modifications,
equivalents and alternatives falling within the spirit and scope of the
present invention as
defined by the appended claims.
DETAILED DESCRIPTION
[0069] The following description generally relates to systems and methods for
treating
hydrocarbons in the formations. Such formations may be treated to yield
hydrocarbon
products, hydrogen, and other products.
[0070] "Alternating current (AC)" refers to a time-varying current that
reverses direction
substantially sinusoidally. AC produces skin effect electricity flow in a
ferromagnetic
conductor.
[0071] "Coupled" means either a direct connection or an indirect connection
(for example,
one or more intervening connections) between one or more objects or
components. The
phrase "directly connected" means a direct connection between objects or
components
such that the objects or components are connected directly to each other so
that the objects
or components operate in a "point of use" manner.
[0072] A "formation" includes one or more hydrocarbon containing layers, one
or more
non-hydrocarbon layers, an overburden, and/or an underburden. "Hydrocarbon
layers"
refer to layers in the formation that contain hydrocarbons. The hydrocarbon
layers may
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contain non-hydrocarbon material and hydrocarbon material. The "overburden"
and/or the
"underburden" include one or more different types of impermeable materials.
For
example, the overburden and/or underburden may include rock, shale, mudstone,
or
wet/tight carbonate. In some embodiments of in situ heat treatment processes,
the
overburden and/or the underburden may include a hydrocarbon containing layer
or
hydrocarbon containing layers that are relatively impermeable and are not
subjected to
temperatures during in situ heat treatment processing that result in
significant characteristic
changes of the hydrocarbon containing layers of the overburden and/or the
underburden.
For example, the underburden may contain shale or mudstone, but the
underburden is not
allowed to heat to pyrolysis temperatures during the in situ heat treatment
process. In some
cases, the overburden and/or the underburden may be somewhat permeable.
[0073] "Formation fluids" refer to fluids present in a formation and may
include
pyrolyzation fluid, synthesis gas, mobilized hydrocarbons, and water (steam).
Formation
fluids may include hydrocarbon fluids as well as non-hydrocarbon fluids. The
term
"mobilized fluid" refers to fluids in a hydrocarbon containing formation that
are able to
flow as a result of thermal treatment of the formation. "Produced fluids"
refer to fluids
removed from the formation.
[0074] A "heat source" is any system for providing heat to at least a portion
of a formation
substantially by conductive and/or radiative heat transfer. For example, a
heat source may
include electrically conducting materials and/or electric heaters such as an
insulated
conductor, an elongated member, and/or a conductor disposed in a conduit. A
heat source
may also include systems that generate heat by burning a fuel external to or
in a formation.
The systems may be surface burners, downhole gas burners, flameless
distributed
combustors, and natural distributed combustors. In some embodiments, heat
provided to or
generated in one or more heat sources may be supplied by other sources of
energy. The
other sources of energy may directly heat a formation, or the energy may be
applied to a
transfer medium that directly or indirectly heats the formation. It is to be
understood that
one or more heat sources that are applying heat to a formation may use
different sources of
energy. Thus, for example, for a given formation some heat sources may supply
heat from
electrically conducting materials, electric resistance heaters, some heat
sources may
provide heat from combustion, and some heat sources may provide heat from one
or more
other energy sources (for example, chemical reactions, solar energy, wind
energy, biomass,
or other sources of renewable energy). A chemical reaction may include an
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reaction (for example, an oxidation reaction). A heat source may also include
an
electrically conducting material and/or a heater that provides heat to a zone
proximate
and/or surrounding a heating location such as a heater well.
[0075] A "heater" is any system or heat source for generating heat in a well
or a near
wellbore region. Heaters may be, but are not limited to, electric heaters,
burners,
combustors that react with material in or produced from a formation, and/or
combinations
thereof.
[0076] "Hydrocarbons" are generally defined as molecules formed primarily by
carbon and
hydrogen atoms. Hydrocarbons may also include other elements such as, but not
limited
to, halogens, metallic elements, nitrogen, oxygen, and/or sulfur. Hydrocarbons
may be, but
are not limited to, kerogen, bitumen, pyrobitumen, oils, natural mineral
waxes, and
asphaltites. Hydrocarbons may be located in or adjacent to mineral matrices in
the earth.
Matrices may include, but are not limited to, sedimentary rock, sands,
silicilytes,
carbonates, diatomites, and other porous media. "Hydrocarbon fluids" are
fluids that
include hydrocarbons. Hydrocarbon fluids may include, entrain, or be entrained
in non-
hydrocarbon fluids such as hydrogen, nitrogen, carbon monoxide, carbon
dioxide,
hydrogen sulfide, water, and ammonia.
[0077] An "in situ conversion process" refers to a process of heating a
hydrocarbon
containing formation from heat sources to raise the temperature of at least a
portion of the
formation above a pyrolysis temperature so that pyrolyzation fluid is produced
in the
formation.
[0078] An "in situ heat treatment process" refers to a process of heating a
hydrocarbon
containing formation with heat sources to raise the temperature of at least a
portion of the
formation above a temperature that results in mobilized fluid, visbreaking,
and/or pyrolysis
of hydrocarbon containing material so that mobilized fluids, visbroken fluids,
and/or
pyrolyzation fluids are produced in the formation.
[0079] "Insulated conductor" refers to any elongated material that is able to
conduct
electricity and that is covered, in whole or in part, by an electrically
insulating material.
[0080] "Nitride" refers to a compound of nitrogen and one or more other
elements of the
Periodic Table. Nitrides include, but are not limited to, silicon nitride,
boron nitride, or
alumina nitride.
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[0081] "Perforations" include openings, slits, apertures, or holes in a wall
of a conduit,
tubular, pipe or other flow pathway that allow flow into or out of the
conduit, tubular, pipe
or other flow pathway.
[0082] "Pyrolysis" is the breaking of chemical bonds due to the application of
heat. For
example, pyrolysis may include transforming a compound into one or more other
substances by heat alone. Heat may be transferred to a section of the
formation to cause
pyrolysis.
[0083] "Pyrolyzation fluids" or "pyrolysis products" refers to fluid produced
substantially
during pyrolysis of hydrocarbons. Fluid produced by pyrolysis reactions may
mix with
other fluids in a formation. The mixture would be considered pyrolyzation
fluid or
pyrolyzation product. As used herein, "pyrolysis zone" refers to a volume of a
formation
(for example, a relatively permeable formation such as a tar sands formation)
that is
reacted or reacting to form a pyrolyzation fluid.
[0084] -Thickness" of a layer refers to the thickness of a cross section of
the layer, wherein
the cross section is normal to a face of the layer.
[0085] The term "wellbore" refers to a hole in a formation made by drilling or
insertion of
a conduit into the formation. A wellbore may have a substantially circular
cross section, or
another cross-sectional shape. As used herein, the terms "well" and "opening."
when
referring to an opening in the formation may be used interchangeably with the
term
.. "wellbore."
[0086] A formation may be treated in various ways to produce many different
products.
Different stages or processes may be used to treat the formation during an in
situ heat
treatment process. In some embodiments, one or more sections of the formation
are
solution mined to remove soluble minerals from the sections. Solution mining
minerals
may be performed before, during, and/or after the in situ heat treatment
process. In some
embodiments, the average temperature of one or more sections being solution
mined may
be maintained below about 120 C.
[0087] In some embodiments, one or more sections of the formation are heated
to remove
water from the sections and/or to remove methane and other volatile
hydrocarbons from
the sections. In some embodiments, the average temperature may be raised from
ambient
temperature to temperatures below about 220 C during removal of water and
volatile
hydrocarbons.
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[0088] In some embodiments, one or more sections of the formation are heated
to
temperatures that allow for movement and/or visbreaking of hydrocarbons in the
formation. In some embodiments, the average temperature of one or more
sections of the
formation are raised to mobilization temperatures of hydrocarbons in the
sections (for
example, to temperatures ranging from 100 C to 250 C, from 120 C to 240 C,
or from
150 C to 230 C).
[0089] In some embodiments, one or more sections are heated to temperatures
that allow
for pyrolysis reactions in the formation. In some embodiments, the average
temperature of
one or more sections of the formation may be raised to pyrolysis temperatures
of
hydrocarbons in the sections (for example, temperatures ranging from 230 C to
900 C,
from 240 C to 400 C or from 250 C to 350 C).
[0090] Heating the hydrocarbon containing formation with a plurality of heat
sources may
establish thermal gradients around the heat sources that raise the temperature
of
hydrocarbons in the formation to desired temperatures at desired heating
rates. The rate of
temperature increase through the mobilization temperature range and/or the
pyrolysis
temperature range for desired products may affect the quality and quantity of
the formation
fluids produced from the hydrocarbon containing formation. Slowly raising the
temperature of the formation through the mobilization temperature range and/or
pyrolysis
temperature range may allow for the production of high quality, high API
gravity
hydrocarbons from the formation. Slowly raising the temperature of the
formation through
the mobilization temperature range and/or pyrolysis temperature range may
allow for the
removal of a large amount of the hydrocarbons present in the formation as
hydrocarbon
product.
[0091] In some in situ heat treatment embodiments, a portion of the formation
is heated to
a desired temperature instead of slowly heating the temperature through a
temperature
range. In some embodiments, the desired temperature is 300 C, 325 C, or 350
C. Other
temperatures may be selected as the desired temperature.
[0092] Superposition of heat from heat sources allows the desired temperature
to be
relatively quickly and efficiently established in the formation. Energy input
into the
formation from the heat sources may be adjusted to maintain the temperature in
the
formation substantially at a desired temperature.
[0093] Mobilization and/or pyrolysis products may be produced from the
formation
through production wells. In some embodiments, the average temperature of one
or more
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sections is raised to mobilization temperatures and hydrocarbons are produced
from the
production wells. The average temperature of one or more of the sections may
be raised to
pyrolysis temperatures after production due to mobilization decreases below a
selected
value. In some embodiments, the average temperature of one or more sections
may be
raised to pyrolysis temperatures without significant production before
reaching pyrolysis
temperatures. Formation fluids including pyrolysis products may be produced
through the
production wells.
[0094] In some embodiments, the average temperature of one or more sections
may be
raised to temperatures sufficient to allow synthesis gas production after
mobilization and/or
pyrolysis. In some embodiments, hydrocarbons may be raised to temperatures
sufficient to
allow synthesis gas production without significant production before reaching
the
temperatures sufficient to allow synthesis gas production. For example,
synthesis gas may
be produced in a temperature range from about 400 C to about 1200 C, about
500 C to
about 1100 C, or about 550 C to about 1000 C. A synthesis gas generating
fluid (for
example, steam and/or water) may be introduced into the sections to generate
synthesis
gas. Synthesis gas may be produced from production wells.
[0095] Solution mining, removal of volatile hydrocarbons and water, mobilizing
hydrocarbons, pyrolyzing hydrocarbons, generating synthesis gas, and/or other
processes
may be performed during the in situ heat treatment process. In some
embodiments, some
processes may be performed after the in situ heat treatment process. Such
processes may
include, but are not limited to, recovering heat from treated sections,
storing fluids (for
example, water and/or hydrocarbons) in previously treated sections, and/or
sequestering
carbon dioxide in previously treated sections.
[0096] FIG. 1 depicts a schematic view of an embodiment of a portion of the in
situ heat
treatment system for treating the hydrocarbon containing formation. The in
situ heat
treatment system may include barrier wells 200. Barrier wells are used to form
a barrier
around a treatment area. The barrier inhibits fluid flow into and/or out of
the treatment
area. Barrier wells include, but are not limited to, dewatering wells, vacuum
wells, capture
wells, injection wells, grout wells, freeze wells, or combinations thereof. In
some
embodiments, barrier wells 200 are dewatering wells. Dewatering wells may
remove
liquid water and/or inhibit liquid water from entering a portion of the
formation to be
heated, or to the formation being heated. In the embodiment depicted in FIG.
1, the barrier
wells 200 are shown extending only along one side of heat sources 202, but the
barrier
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wells typically encircle all heat sources 202 used, or to be used, to heat a
treatment area of
the formation.
[0097] Heat sources 202 are placed in at least a portion of the formation.
Heat sources 202
may include heaters such as insulated conductors, conductor-in-conduit
heaters, surface
burners, flameless distributed combustors, and/or natural distributed
combustors. Heat
sources 202 may also include other types of heaters. Heat sources 202 provide
heat to at
least a portion of the formation to heat hydrocarbons in the formation. Energy
may be
supplied to heat sources 202 through supply lines 204. Supply lines 204 may be
structurally different depending on the type of heat source or heat sources
used to heat the
formation. Supply lines 204 for heat sources may transmit electricity for
electric heaters,
may transport fuel for combustors, or may transport heat exchange fluid that
is circulated
in the formation. In some embodiments, electricity for an in situ heat
treatment process
may be provided by a nuclear power plant or nuclear power plants. The use of
nuclear
power may allow for reduction or elimination of carbon dioxide emissions from
the in situ
heat treatment process.
[0098] When the formation is heated, the heat input into the formation may
cause
expansion of the formation and geomechanical motion. The heat sources may be
turned on
before, at the same time, or during a dewatering process. Computer simulations
may
model formation response to heating. The computer simulations may be used to
develop a
pattern and time sequence for activating heat sources in the formation so that
geomechanical motion of the formation does not adversely affect the
functionality of heat
sources, production wells, and other equipment in the formation.
[0099] Heating the formation may cause an increase in permeability and/or
porosity of the
formation. Increases in permeability and/or porosity may result from a
reduction of mass
in the formation due to vaporization and removal of water, removal of
hydrocarbons,
and/or creation of fractures. Fluid may flow more easily in the heated portion
of the
formation because of the increased permeability and/or porosity of the
formation. Fluid in
the heated portion of the formation may move a considerable distance through
the
formation because of the increased permeability and/or porosity. The
considerable
distance may be over 1000 m depending on various factors, such as permeability
of the
formation, properties of the fluid, temperature of the formation, and pressure
gradient
allowing movement of the fluid. The ability of fluid to travel considerable
distance in the
formation allows production wells 206 to be spaced relatively far apart in the
formation.
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[0100] Production wells 206 are used to remove formation fluid from the
formation. In
some embodiments, production well 206 includes a heat source. The heat source
in the
production well may heat one or more portions of the formation at or near the
production
well. In some in situ heat treatment process embodiments, the amount of heat
supplied to
the formation from the production well per meter of the production well is
less than the
amount of heat applied to the formation from a heat source that heats the
formation per
meter of the heat source. Heat applied to the formation from the production
well may
increase formation permeability adjacent to the production well by vaporizing
and
removing liquid phase fluid adjacent to the production well and/or by
increasing the
permeability of the formation adjacent to the production well by formation of
macro and/or
micro fractures.
[0101] More than one heat source may be positioned in the production well. A
heat source
in a lower portion of the production well may be turned off when superposition
of heat
from adjacent heat sources heats the formation sufficiently to counteract
benefits provided
by heating the formation with the production well. In some embodiments, the
heat source
in an upper portion of the production well may remain on after the heat source
in the lower
portion of the production well is deactivated. The heat source in the upper
portion of the
well may inhibit condensation and reflux of formation fluid.
[0102] In some embodiments, the heat source in production well 206 allows for
vapor
phase removal of formation fluids from the formation. Providing heating at or
through the
production well may: (1) inhibit condensation and/or refluxing of production
fluid when
such production fluid is moving in the production well proximate the
overburden, (2)
increase heat input into the formation, (3) increase production rate from the
production
well as compared to a production well without a heat source, (4) inhibit
condensation of
high carbon number compounds (C6 hydrocarbons and above) in the production
well,
and/or (5) increase formation permeability at or proximate the production
well.
[0103] Subsurface pressure in the formation may correspond to the fluid
pressure
generated in the formation. As temperatures in the heated portion of the
formation
increase, the pressure in the heated portion may increase as a result of
thermal expansion of
in situ fluids, increased fluid generation and vaporization of water.
Controlling rate of
fluid removal from the formation may allow for control of pressure in the
formation.
Pressure in the formation may be determined at a number of different
locations, such as
near or at production wells, near or at heat sources, or at monitor wells.
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[0104] In some hydrocarbon containing formations, production of hydrocarbons
from the
formation is inhibited until at least some hydrocarbons in the formation have
been
mobilized and/or pyrolyzed. Formation fluid may be produced from the formation
when
the formation fluid is of a selected quality. In some embodiments, the
selected quality
includes an API gravity of at least about 200, 300, or 40 . Inhibiting
production until at
least some hydrocarbons are mobilized and/or pyrolyzed may increase conversion
of heavy
hydrocarbons to light hydrocarbons. Inhibiting initial production may minimize
the
production of heavy hydrocarbons from the formation. Production of substantial
amounts
of heavy hydrocarbons may require expensive equipment and/or reduce the life
of
production equipment.
[0105] In some hydrocarbon containing formations, hydrocarbons in the
formation may be
heated to mobilization and/or pyrolysis temperatures before substantial
permeability has
been generated in the heated portion of the formation. An initial lack of
permeability may
inhibit the transport of generated fluids to production wells 206. During
initial heating,
fluid pressure in the formation may increase proximate heat sources 202. The
increased
fluid pressure may be released, monitored, altered, and/or controlled through
one or more
heat sources 202. For example, selected heat sources 202 or separate pressure
relief wells
may include pressure relief valves that allow for removal of some fluid from
the formation.
[0106] In some embodiments, pressure generated by expansion of mobilized
fluids,
pyrolysis fluids or other fluids generated in the formation may be allowed to
increase
although an open path to production wells 206 or any other pressure sink may
not yet exist
in the formation. The fluid pressure may be allowed to increase towards a
lithostatic
pressure. Fractures in the hydrocarbon containing formation may form when the
fluid
approaches the lithostatic pressure. For example, fractures may form from heat
sources
202 to production wells 206 in the heated portion of the formation. The
generation of
fractures in the heated portion may relieve some of the pressure in the
portion. Pressure in
the formation may have to be maintained below a selected pressure to inhibit
unwanted
production, fracturing of the overburden or underburden, and/or coking of
hydrocarbons in
the formation.
[0107] After mobilization and/or pyrolysis temperatures are reached and
production from
the formation is allowed, pressure in the formation may be varied to alter
and/or control a
composition of formation fluid produced, to control a percentage of
condensable fluid as
compared to non-condensable fluid in the formation fluid, and/or to control an
API gravity
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of formation fluid being produced. For example, decreasing pressure may result
in
production of a larger condensable fluid component. The condensable fluid
component
may contain a larger percentage of olefins.
[0108] In some in situ heat treatment process embodiments, pressure in the
formation may
be maintained high enough to promote production of formation fluid with an API
gravity
of greater than 200. Maintaining increased pressure in the formation may
inhibit formation
subsidence during in situ heat treatment. Maintaining increased pressure may
reduce or
eliminate the need to compress formation fluids at the surface to transport
the fluids in
collection conduits to treatment facilities.
[0109] Maintaining increased pressure in a heated portion of the formation may
surprisingly allow for production of large quantities of hydrocarbons of
increased quality
and of relatively low molecular weight. Pressure may be maintained so that
formation
fluid produced has a minimal amount of compounds above a selected carbon
number. The
selected carbon number may be at most 25, at most 20, at most 12, or at most
8. Some
high carbon number compounds may be entrained in vapor in the formation and
may be
removed from the formation with the vapor. Maintaining increased pressure in
the
formation may inhibit entrainment of high carbon number compounds and/or multi-
ring
hydrocarbon compounds in the vapor. High carbon number compounds and/or multi-
ring
hydrocarbon compounds may remain in a liquid phase in the formation for
significant time
periods. The significant time periods may provide sufficient time for the
compounds to
pyrolyze to form lower carbon number compounds.
[0110] Generation of relatively low molecular weight hydrocarbons is believed
to be due,
in part, to autogenous generation and reaction of hydrogen in a portion of the
hydrocarbon
containing formation. For example, maintaining an increased pressure may force
hydrogen
generated during pyrolysis into the liquid phase within the formation. Heating
the portion
to a temperature in a pyrolysis temperature range may pyrolyze hydrocarbons in
the
formation to generate liquid phase pyrolyzation fluids. The generated liquid
phase
pyrolyzation fluids components may include double bonds and/or radicals.
Hydrogen (H2)
in the liquid phase may reduce double bonds of the generated pyrolyzation
fluids, thereby
reducing a potential for polymerization or formation of long chain compounds
from the
generated pyrolyzation fluids. In addition, H2 may also neutralize radicals in
the generated
pyrolyzation fluids. H2 in the liquid phase may inhibit the generated
pyrolyzation fluids
from reacting with each other and/or with other compounds in the formation.
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[0111] Formation fluid produced from production wells 206 may be transported
through
collection piping 208 to treatment facilities 210. Formation fluids may also
be produced
from heat sources 202. For example, fluid may be produced from heat sources
202 to
control pressure in the formation adjacent to the heat sources. Fluid produced
from heat
sources 202 may be transported through tubing or piping to collection piping
208 or the
produced fluid may be transported through tubing or piping directly to
treatment facilities
210. Treatment facilities 210 may include separation units, reaction units,
upgrading units,
fuel cells, turbines, storage vessels, and/or other systems and units for
processing produced
formation fluids. The treatment facilities may form transportation fuel from
at least a
portion of the hydrocarbons produced from the formation. In some embodiments,
the
transportation fuel may be jet fuel, such as JP-8.
[0112] An insulated conductor may be used as an electric heater element of a
heater or a
heat source. The insulated conductor may include an inner electrical conductor
(core)
surrounded by an electrical insulator and an outer electrical conductor
(jacket). The
electrical insulator may include mineral insulation (for example, magnesium
oxide) or
other electrical insulation.
[0113] In certain embodiments, the insulated conductor is placed in an opening
in a
hydrocarbon containing formation. In some embodiments, the insulated conductor
is
placed in an uncased opening in the hydrocarbon containing formation. Placing
the
insulated conductor in an uncased opening in the hydrocarbon containing
formation may
allow heat transfer from the insulated conductor to the formation by radiation
as well as
conduction. Using an uncased opening may facilitate retrieval of the insulated
conductor
from the well, if necessary.
[0114] In some embodiments, an insulated conductor is placed within a casing
in the
formation; may be cemented within the formation; or may be packed in an
opening with
sand, gravel, or other fill material. The insulated conductor may be supported
on a support
member positioned within the opening. The support member may be a cable. rod,
or a
conduit (for example, a pipe). The support member may be made of a metal,
ceramic,
inorganic material, or combinations thereof. Because portions of a support
member may
be exposed to formation fluids and heat during use, the support member may be
chemically
resistant and/or thermally resistant.
[0115] Ties, spot welds, and/or other types of connectors may be used to
couple the
insulated conductor to the support member at various locations along a length
of the
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insulated conductor. The support member may be attached to a wellhead at an
upper
surface of the formation. In some embodiments, the insulated conductor has
sufficient
structural strength such that a support member is not needed. The insulated
conductor
may, in many instances, have at least some flexibility to inhibit thermal
expansion damage
when undergoing temperature changes.
[0116] In certain embodiments, insulated conductors are placed in wellbores
without
support members and/or centralizers. An insulated conductor without support
members
and/or centralizers may have a suitable combination of temperature and
corrosion
resistance, creep strength, length, thickness (diameter), and metallurgy that
will inhibit
failure of the insulated conductor during use.
[0117] FIG. 2 depicts a perspective view of an end portion of an embodiment of
insulated
conductor 212. Insulated conductor 212 may have any desired cross-sectional
shape such
as, but not limited to, round (depicted in FIG. 2), triangular, ellipsoidal,
rectangular,
hexagonal, or irregular. In certain embodiments, insulated conductor 212
includes core
214, electrical insulator 216, and jacket 218. Core 214 may resistively heat
when an
electrical current passes through the core. Alternating or time-varying
current and/or direct
current may be used to provide power to core 214 such that the core
resistively heats.
[0118] In some embodiments, electrical insulator 216 inhibits current leakage
and arcing to
jacket 218. Electrical insulator 216 may thermally conduct heat generated in
core 214 to
jacket 218. Jacket 218 may radiate or conduct heat to the formation. In
certain
embodiments, insulated conductor 212 is 1000 m or more in length. Longer or
shorter
insulated conductors may also be used to meet specific application needs. The
dimensions
of core 214, electrical insulator 216, and jacket 218 of insulated conductor
212 may be
selected such that the insulated conductor has enough strength to be self
supporting even at
upper working temperature limits. Such insulated conductors may be suspended
from
wellheads or supports positioned near an interface between an overburden and a
hydrocarbon containing formation without the need for support members
extending into
the hydrocarbon containing formation along with the insulated conductors.
[0119] Insulated conductor 212 may be designed to operate at power levels of
up to about
1650 watts/meter or higher. In certain embodiments, insulated conductor 212
operates at a
power level between about 500 watts/meter and about 1150 watts/meter when
heating a
formation. Insulated conductor 212 may be designed so that a maximum voltage
level at a
typical operating temperature does not cause substantial thermal and/or
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breakdown of electrical insulator 216. Insulated conductor 212 may be designed
such that
jacket 218 does not exceed a temperature that will result in a significant
reduction in
corrosion resistance properties of the jacket material. In certain
embodiments, insulated
conductor 212 may be designed to reach temperatures within a range between
about 650
C and about 900 C. Insulated conductors having other operating ranges may be
formed
to meet specific operational requirements.
[0120] FIG. 2 depicts insulated conductor 212 having a single core 214. In
some
embodiments, insulated conductor 212 has two or more cores 214. For example, a
single
insulated conductor may have three cores. Core 214 may be made of metal or
another
electrically conductive material. The material used to form core 214 may
include, but not
be limited to, nichrome, copper, nickel, carbon steel, stainless steel, and
combinations
thereof. In certain embodiments, core 214 is chosen to have a diameter and a
resistivity at
operating temperatures such that its resistance, as derived from Ohm's law,
makes it
electrically and structurally stable for the chosen power dissipation per
meter, the length of
the heater, and/or the maximum voltage allowed for the core material.
[0121] In some embodiments, core 214 is made of different materials along a
length of
insulated conductor 212. For example, a first section of core 214 may be made
of a
material that has a significantly lower resistance than a second section of
the core. The
first section may be placed adjacent to a formation layer that does not need
to be heated to
as high a temperature as a second formation layer that is adjacent to the
second section.
The resistivity of various sections of core 214 may be adjusted by having a
variable
diameter and/or by having core sections made of different materials.
[0122] Electrical insulator 216 may be made of a variety of materials.
Commonly used
powders may include, but are not limited to, MgO, A1203, Zirconia, Be0,
different
chemical variations of Spinels, and combinations thereof. MgO may provide good
thermal
conductivity and electrical insulation properties. The desired electrical
insulation
properties include low leakage current and high dielectric strength. A low
leakage current
decreases the possibility of thermal breakdown and the high dielectric
strength decreases
the possibility of arcing across the insulator. Thermal breakdown can occur if
the leakage
current causes a progressive rise in the temperature of the insulator leading
also to arcing
across the insulator.
[0123] Jacket 218 may be an outer metallic layer or electrically conductive
layer. Jacket
218 may be in contact with hot formation fluids. Jacket 218 may be made of
material
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having a high resistance to corrosion at elevated temperatures. Alloys that
may be used in
a desired operating temperature range of jacket 218 include, but are not
limited to, 304
stainless steel, 310 stainless steel, Incoloy 800, and Inconel 600 (Inco
Alloys
International, Huntington, West Virginia, U.S.A.). The thickness of jacket 218
may have
to be sufficient to last for three to ten years in a hot and corrosive
environment. A
thickness of jacket 218 may generally vary between about 1 mm and about 2.5
mm. For
example. a 1.3 mm thick. 310 stainless steel outer layer may be used as jacket
218 to
provide good chemical resistance to sulfidation corrosion in a heated zone of
a formation
for a period of over 3 years. Larger or smaller jacket thicknesses may be used
to meet
specific application requirements.
[0124] One or more insulated conductors may be placed within an opening in a
formation
to form a heat source or heat sources. Electrical current may be passed
through each
insulated conductor in the opening to heat the formation. Alternately,
electrical current
may be passed through selected insulated conductors in an opening. The unused
conductors may be used as backup heaters. Insulated conductors may be
electrically
coupled to a power source in any convenient manner. Each end of an insulated
conductor
may be coupled to lead-in cables that pass through a wellhead. Such a
configuration
typically has a 180 bend (a "hairpin" bend) or turn located near a bottom of
the heat
source. An insulated conductor that includes a 180 bend or turn may not
require a bottom
termination, but the 180 bend or turn may be an electrical and/or structural
weakness in
the heater. Insulated conductors may be electrically coupled together in
series, in parallel,
or in series and parallel combinations. In some embodiments of heat sources,
electrical
current may pass into the conductor of an insulated conductor and may be
returned through
the jacket of the insulated conductor by connecting core 214 to jacket 218
(shown in FIG.
2) at the bottom of the heat source.
[0125] In some embodiments, three insulated conductors 212 are electrically
coupled in a
3-phase wye configuration to a power supply. FIG. 3 depicts an embodiment of
three
insulated conductors in an opening in a subsurface formation coupled in a wye
configuration. FIG. 4 depicts an embodiment of three insulated conductors 212
that are
removable from opening 220 in the formation. No bottom connection may be
required for
three insulated conductors in a wye configuration. Alternately, all three
insulated
conductors of the wye configuration may be connected together near the bottom
of the
opening. The connection may be made directly at ends of heating sections of
the insulated
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conductors or at ends of cold pins (less resistive sections) coupled to the
heating sections at
the bottom of the insulated conductors. The bottom connections may be made
with
insulator filled and sealed canisters or with epoxy filled canisters. The
insulator may be the
same composition as the insulator used as the electrical insulation.
[0126] Three insulated conductors 212 depicted in FIGS. 3 and 4 may be coupled
to
support member 222 using centralizers 224. Alternatively, insulated conductors
212 may
be strapped directly to support member 222 using metal straps. Centralizers
224 may
maintain a location and/or inhibit movement of insulated conductors 212 on
support
member 222. Centralizers 224 may be made of metal, ceramic, or combinations
thereof.
The metal may be stainless steel or any other type of metal able to withstand
a corrosive
and high temperature environment. In some embodiments, centralizers 224 are
bowed
metal strips welded to the support member at distances less than about 6 m. A
ceramic
used in centralizer 224 may be, but is not limited to, A1203, MgO, or another
electrical
insulator. Centralizers 224 may maintain a location of insulated conductors
212 on support
member 222 such that movement of insulated conductors is inhibited at
operating
temperatures of the insulated conductors. Insulated conductors 212 may also be
somewhat
flexible to withstand expansion of support member 222 during heating.
[0127] Support member 222, insulated conductor 212, and centralizers 224 may
be placed
in opening 220 in hydrocarbon layer 226. Insulated conductors 212 may be
coupled to
bottom conductor junction 228 using cold pin 230. Bottom conductor junction
228 may
electrically couple each insulated conductor 212 to each other. Bottom
conductor junction
228 may include materials that are electrically conducting and do not melt at
temperatures
found in opening 220. Cold pin 230 may be an insulated conductor having lower
electrical
resistance than insulated conductor 212.
[0128] Lead-in conductor 232 may be coupled to wellhead 234 to provide
electrical power
to insulated conductor 212. Lead-in conductor 232 may be made of a relatively
low
electrical resistance conductor such that relatively little heat is generated
from electrical
current passing through the lead-in conductor. In some embodiments, the lead-
in
conductor is a rubber or polymer insulated stranded copper wire. In some
embodiments,
the lead-in conductor is a mineral insulated conductor with a copper core.
Lead-in
conductor 232 may couple to wellhead 234 at surface 236 through a sealing
flange located
between overburden 238 and surface 236. The sealing flange may inhibit fluid
from
escaping from opening 220 to surface 236.
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[0129] In certain embodiments, lead-in conductor 232 is coupled to insulated
conductor
212 using transition conductor 240. Transition conductor 240 may be a less
resistive
portion of insulated conductor 212. Transition conductor 240 may be referred
to as "cold
pin" of insulated conductor 212. Transition conductor 240 may be designed to
dissipate
about one-tenth to about one-fifth of the power per unit length as is
dissipated in a unit
length of the primary heating section of insulated conductor 212. Transition
conductor 240
may typically be between about 1.5 m and about 15 m, although shorter or
longer lengths
may be used to accommodate specific application needs. In an embodiment, the
conductor
of transition conductor 240 is copper. The electrical insulator of transition
conductor 240
may be the same type of electrical insulator used in the primary heating
section. A jacket
of transition conductor 240 may be made of corrosion resistant material.
[0130] In certain embodiments, transition conductor 240 is coupled to lead-in
conductor
232 by a splice or other coupling joint. Splices may also be used to couple
transition
conductor 240 to insulated conductor 212. Splices may have to withstand a
temperature
equal to half of a target zone operating temperature. Density of electrical
insulation in the
splice should in many instances be high enough to withstand the required
temperature and
the operating voltage.
[0131] In some embodiments, as shown in FIG. 3, packing material 242 is placed
between
overburden casing 244 and opening 220. In some embodiments, reinforcing
material 246
may secure overburden casing 244 to overburden 238. Packing material 242 may
inhibit
fluid from flowing from opening 220 to surface 236. Reinforcing material 246
may
include, for example, Class G or Class H Portland cement mixed with silica
flour for
improved high temperature performance, slag or silica flour, and/or a mixture
thereof. In
some embodiments, reinforcing material 246 extends radially a width of from
about 5 cm
to about 25 cm.
[0132] As shown in FIGS. 3 and 4, support member 222 and lead-in conductor 232
may be
coupled to wellhead 234 at surface 236 of the formation. Surface conductor 248
may
enclose reinforcing material 246 and couple to wellhead 234. Embodiments of
surface
conductors may extend to depths of approximately 3m to approximately 515 m
into an
opening in the formation. Alternatively, the surface conductor may extend to a
depth of
approximately 9 m into the formation. Electrical current may be supplied from
a power
source to insulated conductor 212 to generate heat due to the electrical
resistance of the
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insulated conductor. Heat generated from three insulated conductors 212 may
transfer
within opening 220 to heat at least a portion of hydrocarbon layer 226.
[0133] Heat generated by insulated conductors 212 may heat at least a portion
of a
hydrocarbon containing formation. In some embodiments, heat is transferred to
the
formation substantially by radiation of the generated heat to the formation.
Some heat may
be transferred by conduction or convection of heat due to gases present in the
opening.
The opening may be an uncased opening, as shown in FIGS. 3 and 4. An uncased
opening
eliminates cost associated with thermally cementing the heater to the
formation, costs
associated with a casing, and/or costs of packing a heater within an opening.
In addition,
heat transfer by radiation is typically more efficient than by conduction, so
the heaters may
be operated at lower temperatures in an open wellbore. Conductive heat
transfer during
initial operation of a heat source may be enhanced by the addition of a gas in
the opening.
The gas may be maintained at a pressure up to about 27 bars absolute. The gas
may
include, but is not limited to, carbon dioxide and/or helium. An insulated
conductor heater
in an open wellbore may advantageously be free to expand or contract to
accommodate
thermal expansion and contraction. An insulated conductor heater may
advantageously be
removable or redeployable from an open wellbore.
[0134] In certain embodiments, an insulated conductor heater assembly is
installed or
removed using a spooling assembly. More than one spooling assembly may be used
to
install both the insulated conductor and a support member simultaneously.
Alternatively,
the support member may be installed using a coiled tubing unit. The heaters
may be un-
spooled and connected to the support as the support is inserted into the well.
The electric
heater and the support member may be un-spooled from the spooling assemblies.
Spacers
may be coupled to the support member and the heater along a length of the
support
member. Additional spooling assemblies may be used for additional electric
heater
elements.
[0135] Temperature limited heaters may be in configurations and/or may include
materials
that provide automatic temperature limiting properties for the heater at
certain
temperatures. Examples of temperature limited heaters may be found in U.S.
Patent Nos.
6,688,387 to Wellington et al.; 6,991,036 to Sumnu-Dindoruk et al.; 6.698,515
to
Karanikas et al.; 6,880,633 to Wellington et al.; 6,782,947 to de Rouffignac
et al.;
6,991,045 to Vinegar et al.; 7,073,578 to Vinegar et al.; 7,121,342 to Vinegar
et al.;
7,320,364 to Fairbanks; 7,527,094 to McKinzie et al.; 7,584,789 to Mo et al.;
7,533,719 to
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Hinson et al.; and 7,562.707 to Miller; U.S. Patent Application Publication
Nos. 2009-
0071652 to Vinegar et al.; 2009-0189617 to Burns et al.; 2010-0071903 to
Prince-Wright
et al.; and 2010-0096137 to Nguyen et al. Temperature limited heaters are
dimensioned to
operate with AC frequencies (for example, 60 Hz AC) or with modulated DC
current.
[0136] In certain embodiments, ferromagnetic materials are used in temperature
limited
heaters. Ferromagnetic material may self-limit temperature at or near the
Curie
temperature of the material and/or the phase transformation temperature range
to provide a
reduced amount of heat when a time-varying current is applied to the material.
In certain
embodiments, the ferromagnetic material self-limits temperature of the
temperature limited
heater at a selected temperature that is approximately the Curie temperature
and/or in the
phase transformation temperature range. In certain embodiments, the selected
temperature
is within about 35 C, within about 25 C, within about 20 C, or within about
10 C of the
Curie temperature and/or the phase transformation temperature range. In
certain
embodiments, ferromagnetic materials are coupled with other materials (for
example,
highly conductive materials, high strength materials, corrosion resistant
materials, or
combinations thereof) to provide various electrical and/or mechanical
properties. Some
parts of the temperature limited heater may have a lower resistance (caused by
different
geometries and/or by using different ferromagnetic and/or non-ferromagnetic
materials)
than other parts of the temperature limited heater. Having parts of the
temperature limited
heater with various materials and/or dimensions allows for tailoring the
desired heat output
from each part of the heater.
[0137] Temperature limited heaters may be more reliable than other heaters.
Temperature
limited heaters may be less apt to break down or fail due to hot spots in the
formation. In
some embodiments, temperature limited heaters allow for substantially uniform
heating of
the formation. In some embodiments, temperature limited heaters are able to
heat the
formation more efficiently by operating at a higher average heat output along
the entire
length of the heater. The temperature limited heater operates at the higher
average heat
output along the entire length of the heater because power to the heater does
not have to be
reduced to the entire heater, as is the case with typical constant wattage
heaters, if a
temperature along any point of the heater exceeds, or is about to exceed, a
maximum
operating temperature of the heater. Heat output from portions of a
temperature limited
heater approaching a Curie temperature and/or the phase transformation
temperature range
of the heater automatically reduces without controlled adjustment of the time-
varying
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current applied to the heater. The heat output automatically reduces due to
changes in
electrical properties (for example, electrical resistance) of portions of the
temperature
limited heater. Thus, more power is supplied by the temperature limited heater
during a
greater portion of a heating process.
[0138] In certain embodiments, the system including temperature limited
heaters initially
provides a first heat output and then provides a reduced (second heat output)
heat output,
near, at, or above the Curie temperature and/or the phase transformation
temperature range
of an electrically resistive portion of the heater when the temperature
limited heater is
energized by a time-varying current. The first heat output is the heat output
at
temperatures below which the temperature limited heater begins to self-limit.
In some
embodiments, the first heat output is the heat output at a temperature about
50 C, about 75
C, about 100 C, or about 125 C below the Curie temperature and/or the phase
transformation temperature range of the ferromagnetic material in the
temperature limited
heater.
[0139] The temperature limited heater may be energized by time-varying current
(alternating current or modulated direct current) supplied at the wellhead.
The wellhead
may include a power source and other components (for example, modulation
components,
transformers, and/or capacitors) used in supplying power to the temperature
limited heater.
The temperature limited heater may be one of many heaters used to heat a
portion of the
formation.
[0140] In certain embodiments, the temperature limited heater includes a
conductor that
operates as a skin effect or proximity effect heater when time-varying current
is applied to
the conductor. The skin effect limits the depth of current penetration into
the interior of the
conductor. For ferromagnetic materials, the skin effect is dominated by the
magnetic
permeability of the conductor. The relative magnetic permeability of
ferromagnetic
materials is typically between 10 and 1000 (for example, the relative magnetic
permeability of ferromagnetic materials is typically at least 10 and may be at
least 50, 100,
500, 1000 or greater). As the temperature of the ferromagnetic material is
raised above the
Curie temperature, or the phase transformation temperature range, and/or as
the applied
electrical current is increased, the magnetic permeability of the
ferromagnetic material
decreases substantially and the skin depth expands rapidly (for example, the
skin depth
expands as the inverse square root of the magnetic permeability). The
reduction in
magnetic permeability results in a decrease in the AC or modulated DC
resistance of the
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conductor near, at, or above the Curie temperature, the phase transformation
temperature
range, and/or as the applied electrical current is increased. When the
temperature limited
heater is powered by a substantially constant current source, portions of the
heater that
approach, reach, or are above the Curie temperature and/or the phase
transformation
.. temperature range may have reduced heat dissipation. Sections of the
temperature limited
heater that are not at or near the Curie temperature and/or the phase
transformation
temperature range may be dominated by skin effect heating that allows the
heater to have
high heat dissipation due to a higher resistive load.
[0141] An advantage of using the temperature limited heater to heat
hydrocarbons in the
formation is that the conductor is chosen to have a Curie temperature and/or a
phase
transformation temperature range in a desired range of temperature operation.
Operation
within the desired operating temperature range allows substantial heat
injection into the
formation while maintaining the temperature of the temperature limited heater,
and other
equipment, below design limit temperatures. Design limit temperatures are
temperatures at
which properties such as corrosion, creep, and/or deformation are adversely
affected. The
temperature limiting properties of the temperature limited heater inhibit
overheating or
burnout of the heater adjacent to low thermal conductivity "hot spots" in the
formation. In
some embodiments, the temperature limited heater is able to lower or control
heat output
and/or withstand heat at temperatures above 25 C, 37 C, 100 C, 250 C, 500
C, 700 C,
800 C, 900 C, or higher up to 1131 C, depending on the materials used in
the heater.
[0142] The temperature limited heater allows for more heat injection into the
formation
than constant wattage heaters because the energy input into the temperature
limited heater
does not have to be limited to accommodate low thermal conductivity regions
adjacent to
the heater. For example, in Green River oil shale there is a difference of at
least a factor of
3 in the thermal conductivity of the lowest richness oil shale layers and the
highest richness
oil shale layers. When heating such a formation, substantially more heat is
transferred to
the formation with the temperature limited heater than with the conventional
heater that is
limited by the temperature at low thermal conductivity layers. The heat output
along the
entire length of the conventional heater needs to accommodate the low thermal
.. conductivity layers so that the heater does not overheat at the low thermal
conductivity
layers and burn out. The heat output adjacent to the low thermal conductivity
layers that
are at high temperature will reduce for the temperature limited heater, but
the remaining
portions of the temperature limited heater that are not at high temperature
will still provide
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high heat output. Because heaters for heating hydrocarbon formations typically
have long
lengths (for example, at least 10 m, 100 m, 300 m, 500 m, 1 km or more up to
about 10
km), the majority of the length of the temperature limited heater may be
operating below
the Curie temperature and/or the phase transformation temperature range while
only a few
portions are at or near the Curie temperature and/or the phase transformation
temperature
range of the temperature limited heater.
[0143] The use of temperature limited heaters allows for efficient transfer of
heat to the
formation. Efficient transfer of heat allows for reduction in time needed to
heat the
formation to a desired temperature. For example, in Green River oil shale,
pyrolysis
typically requires 9.5 years to 10 years of heating when using a 12 m heater
well spacing
with conventional constant wattage heaters. For the same heater spacing,
temperature
limited heaters may allow a larger average heat output while maintaining
heater equipment
temperatures below equipment design limit temperatures. Pyrolysis in the
formation may
occur at an earlier time with the larger average heat output provided by
temperature limited
heaters than the lower average heat output provided by constant wattage
heaters. For
example. in Green River oil shale, pyrolysis may occur in 5 years using
temperature
limited heaters with a 12 m heater well spacing. Temperature limited heaters
counteract
hot spots due to inaccurate well spacing or drilling where heater wells come
too close
together. In certain embodiments, temperature limited heaters allow for
increased power
output over time for heater wells that have been spaced too far apart, or
limit power output
for heater wells that are spaced too close together. Temperature limited
heaters also supply
more power in regions adjacent the overburden and underburden to compensate
for
temperature losses in these regions.
[0144] Temperature limited heaters may be advantageously used in many types of
formations. For example, in tar sands formations or relatively permeable
formations
containing heavy hydrocarbons, temperature limited heaters may be used to
provide a
controllable low temperature output for reducing the viscosity of fluids,
mobilizing fluids,
and/or enhancing the radial flow of fluids at or near the wellbore or in the
formation.
Temperature limited heaters may be used to inhibit excess coke formation due
to
overheating of the near wellbore region of the formation.
[0145] In some embodiments, the use of temperature limited heaters eliminates
or reduces
the need for expensive temperature control circuitry. For example, the use of
temperature
limited heaters eliminates or reduces the need to perform temperature logging
and/or the
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need to use fixed thermocouples on the heaters to monitor potential
overheating at hot
spots.
[0146] The temperature limited heaters may be used in conductor-in-conduit
heaters. In
some embodiments of conductor-in-conduit heaters, the majority of the
resistive heat is
generated in the conductor, and the heat radiatively, conductively and/or
convectively
transfers to the conduit. In some embodiments of conductor-in-conduit heaters,
the
majority of the resistive heat is generated in the conduit.
[0147] In some embodiments, a relatively thin conductive layer is used to
provide the
majority of the electrically resistive heat output of the temperature limited
heater at
temperatures up to a temperature at or near the Curie temperature and/or the
phase
transformation temperature range of the ferromagnetic conductor. Such a
temperature
limited heater may be used as the heating member in an insulated conductor
heater. The
heating member of the insulated conductor heater may be located inside a
sheath with an
insulation layer between the sheath and the heating member.
[0148] Mineral insulated (MI) cables (insulated conductors) for use in
subsurface
applications, such as heating hydrocarbon containing formations in some
applications, are
longer, may have larger outside diameters, and may operate at higher voltages
and
temperatures than what is typical in the MI cable industry. For these
subsurface
applications, the joining of multiple MI cables is needed to make MI cables
with sufficient
.. length to reach the depths and distances needed to heat the subsurface
efficiently and to
join segments with different functions, such as lead-in cables joined to
heater sections.
Such long heaters also require higher voltages to provide enough power to the
farthest ends
of the heaters.
[0149] Conventional MI cable splice designs are typically not suitable for
voltages above
.. 1000 volts, above 1500 volts, or above 2000 volts and may not operate for
extended
periods without failure at elevated temperatures, such as over 650 C (about
1200 F), over
700 C (about 1290 F), or over 800 C (about 1470 F). Such high voltage,
high
temperature applications typically require the compaction of the mineral
insulant in the
splice to be as close as possible to or above the level of compaction in the
insulated
.. conductor (MI cable) itself.
[0150] The relatively large outside diameter and long length of MI cables for
some
applications requires that the cables be spliced while oriented horizontally.
There are
splices for other applications of MI cables that have been fabricated
horizontally. These
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techniques typically use a small hole through which the mineral insulation
(such as
magnesium oxide powder) is filled into the splice and compacted slightly
through vibration
and tamping. Such methods do not provide sufficient compaction of the mineral
insulation
or even, in some cases, allow any compaction of the mineral insulation, and,
thus may not
be suitable for making splices for use at the high voltages needed for these
subsurface
applications.
[0151] Thus, there is a need for splices of insulated conductors that are
simple yet can
operate at the high voltages and temperatures in the subsurface environment
over long
durations without failure. In addition, the splices may need higher bending
and tensile
strengths to inhibit failure of the splice under the weight loads and
temperatures that the
cables can be subjected to in the subsurface. Techniques and methods also may
be utilized
to reduce electric field intensities in the splices to reduce leakage currents
in the splices and
to increase the margin between the operating voltage and electrical breakdown.
Reducing
electric field intensities may help increase voltage and temperature operating
ranges of the
splices.
[0152] FIG. 5 depicts a side view cross-sectional representation of one
embodiment of a
fitting for joining insulated conductors. Fitting 250 is a splice or coupling
joint for joining
insulated conductors 212A, 212B. In certain embodiments, fitting 250 includes
sleeve 252
and housings 254A, 254B. Housings 254A. 254B may be splice housings, coupling
joint
housings, or coupler housings. Sleeve 252 and housings 254A, 254B may be made
of
mechanically strong, electrically conductive materials such as, but not
limited to, stainless
steel. Sleeve 252 and housings 254A, 254B may be cylindrically shaped or
polygon
shaped. Sleeve 252 and housings 254A, 254B may have rounded edges, tapered
diameter
changes, other features, or combinations thereof, which reduce electric field
intensities in
fitting 250.
[0153] Fitting 250 may be used to couple (splice) insulated conductor 212A to
insulated
conductor 212B while maintaining the mechanical and electrical integrity of
the jackets
(sheaths), insulation, and cores (conductors) of the insulated conductors.
Fitting 250 may
be used to couple heat producing insulated conductors with non-heat producing
insulated
conductors, to couple heat producing insulated conductors with other heat
producing
insulated conductors, or to couple non-heat producing insulated conductors
with other non-
heat producing insulated conductors. In some embodiments, more than one
fitting 250 is
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used to couple multiple heat producing and non-heat producing insulated
conductors to
provide a long insulated conductor.
[0154] Fitting 250 may be used to couple insulated conductors with different
diameters, as
shown in FIG. 5. For example, the insulated conductors may have different core
(conductor) diameters, different jacket (sheath) diameters, or combinations of
different
diameters. Fitting 250 may also be used to couple insulated conductors with
different
metallurgies, different types of insulation, or combinations thereof.
[0155] As shown in FIG. 5, housing 254A is coupled to jacket (sheath) 218A of
insulated
conductor 212A and housing 254B is coupled to jacket 218B of insulated
conductor 212B.
In certain embodiments, housings 254A, 254B are welded, brazed, or otherwise
permanently affixed to insulated conductors 212A, 212B. In some embodiments,
housings
254A, 254B are temporarily or semi-permanently affixed to jackets 218A, 218B
of
insulated conductors 212A, 212B (for example, coupled using threads or
adhesives).
Fitting 250 may be centered between the end portions of the insulated
conductors 212A,
212B.
[0156] In certain embodiments, the interior volumes of sleeve 252 and housings
254A,
254B are substantially filled with electrically insulating material 256. In
certain
embodiments, "substantially filled" refers to entirely or almost entirely
filling the volume
or volumes with electrically insulating material with substantially no
macroscopic voids in
the volume or volumes. For example, substantially filled may refer to filling
almost the
entire volume with electrically insulating material that has some porosity
because of
microscopic voids (for example, up to about 40% porosity). Electrically
insulating
material 256 may include magnesium oxide, talc, ceramic powders (for example,
boron
nitride), a mixture of magnesium oxide and another electrical insulator (for
example, up to
about 50% by weight boron nitride), ceramic cement, mixtures of ceramic
powders with
certain non-ceramic materials (such as tungsten sulfide (WS2)), or mixtures
thereof. For
example, magnesium oxide may be mixed with boron nitride or another electrical
insulator
to improve the ability of the electrically insulating material to flow, to
improve the
dielectric characteristics of the electrically insulating material, or to
improve the flexibility
of the fitting. In some embodiments, electrically insulating material 256 is
material similar
to electrical insulation used inside of at least one of insulated conductors
212A, 212B.
Electrically insulating material 256 may have substantially similar dielectric
characteristics
to electrical insulation used inside of at least one of insulated conductors
212A, 212B.
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[0157] In certain embodiments, first sleeve 252 and housings 254A, 254B are
made up (for
example, put together or manufactured) buried or submerged in electrically
insulating
material 256. Making up sleeve 252 and housings 254A, 254B buried in
electrically
insulating material 256 inhibits open space from forming in the interior
volumes of the
portions. Sleeve 252 and housings 254A, 254B have open ends to allow insulated
conductors 212A, 212B to pass through. These open ends may be sized to have
diameters
slightly larger than the outside diameter of the jackets of the insulated
conductors.
[0158] In certain embodiments, cores 214A, 214B of insulated conductors 212A,
212B are
joined together at coupling 258. The jackets and insulation of insulated
conductors 212A,
212B may be cut back or stripped to expose desired lengths of cores 214A, 214B
before
joining the cores. Coupling 258 may be located in electrically insulating
material 256
inside sleeve 252.
[0159] Coupling 258 may join cores 214A, 214B together, for example, by
compression,
crimping, brazing, welding, or other techniques known in the art. In some
embodiments,
core 214A is made of different material than core 214B. For example, core 214A
may be
copper while core 214B is stainless steel, carbon steel, or Alloy 180. In such
embodiments, special methods may have to be used to weld the cores together.
For
example, the tensile strength properties and/or yield strength properties of
the cores may
have to be matched closely such that the coupling between the cores does not
degrade over
.. time or with use.
[0160] In some embodiments, a copper core may be work-hardened before joining
the core
to carbon steel or Alloy 180. In some embodiments, the cores are coupled by in-
line
welding using filler material (for example, filler metal) between the cores of
different
materials. For example, Monel (Special Metals Corporation, New Hartford, NY,
U.S.A.)
nickel alloys may be used as filler material. In some embodiments, copper
cores are
buttered (melted and mixed) with the filler material before the welding
process.
[0161] In an embodiment, insulated conductors 212A, 212B are coupled using
fitting 250
by first sliding housing 254A over jacket 218A of insulated conductor 212A
and, second,
sliding housing 254B over jacket 218B of insulated conductor 212B. The
housings are slid
over the jackets with the large diameter ends of the housings facing the ends
of the
insulated conductors. Sleeve 252 may be slid over insulated conductor 212B
such that it is
adjacent to housing 254B. Cores 214A, 214B are joined at coupling 258 to
create a robust
electrical and mechanical connection between the cores. The small diameter end
of
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housing 254A is joined (for example, welded) to jacket 218A of insulated
conductor 212A.
Sleeve 252 and housing 254B are brought (moved or pushed) together with
housing 254A
to form fitting 250. The interior volume of fitting 250 may be substantially
filled with
electrically insulating material while the sleeve and the housings are brought
together. The
interior volume of the combined sleeve and housings is reduced such that the
electrically
insulating material substantially filling the entire interior volume is
compacted. Sleeve 252
is joined to housing 254B and housing 254B is joined to jacket 218B of
insulated
conductor 212B. The volume of sleeve 252 may be further reduced, if additional
compaction is desired.
[0162] In certain embodiments, the interior volumes of housings 254A, 254B
filled with
electrically insulating material 256 have tapered shapes. The diameter of the
interior
volumes of housings 254A, 254B may taper from a smaller diameter at or near
the ends of
the housings coupled to insulated conductors 212A, 212B to a larger diameter
at or near the
ends of the housings located inside sleeve 252 (the ends of the housings
facing each other
or the ends of the housings facing the ends of the insulated conductors). The
tapered
shapes of the interior volumes may reduce electric field intensities in
fitting 250. Reducing
electric field intensities in fitting 250 may reduce leakage currents in the
fitting at increased
operating voltages and temperatures, and may increase the margin to electrical
breakdown.
Thus, reducing electric field intensities in fitting 250 may increase the
range of operating
voltages and temperatures for the fitting.
[0163] In some embodiments, the insulation from insulated conductors 212A,
212B tapers
from jackets 218A, 218B down to cores 214A, 214B in the direction toward the
center of
fitting 250 in the event that the electrically insulating material 256 is a
weaker dielectric
than the insulation in the insulated conductors. In some embodiments, the
insulation from
insulated conductors 212A, 212B tapers from jackets 218A, 218B down to cores
214A,
214B in the direction toward the insulated conductors in the event that
electrically
insulating material 256 is a stronger dielectric than the insulation in the
insulated
conductors. Tapering the insulation from the insulated conductors reduces the
intensity of
electric fields at the interfaces between the insulation in the insulated
conductors and the
electrically insulating material within the fitting.
[0164] FIG. 6 depicts a tool that may be used to cut away part of the inside
of insulated
conductors 212A, 212B (for example, electrical insulation inside the jacket of
the insulated
conductor). Cutting tool 260 may include cutting teeth 262 and drive tube 264.
Drive tube
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264 may be coupled to the body of cutting tool 260 using, for example, a weld
or a braze.
In some embodiments, no cutting tool is needed to cut away electrical
insulation from
inside the jacket.
[0165] Sleeve 252 and housings 254A, 254B may be coupled together using any
means
known in the art such as brazing, welding, or crimping. In some embodiments,
as shown in
FIG. 7, sleeve 252 and housings 254A, 254B have threads that engage to couple
the pieces
together.
[0166] As shown in FIGS. 5 and 7, in certain embodiments, electrically
insulating material
256 is compacted during the assembly process. The force to press the housings
254A,
254B toward each other may put a pressure on electrically insulating material
256 of, for
example, at least 25,000 pounds per square inch up to 55,000 pounds per square
inch in
order to provide acceptable compaction of the insulating material. The tapered
shapes of
the interior volumes of housings 254A, 254B and the make-up of electrically
insulating
material 256 may enhance compaction of the electrically insulating material
during the
assembly process to the point where the dielectric characteristics of the
electrically
insulating material are, to the extent practical, comparable to that within
insulated
conductors 212A, 212B. Methods and devices to facilitate compaction include,
but are not
limited to, mechanical methods (such as shown in FIG. 10), pneumatic,
hydraulic (such as
shown in FIGS. 11 and 12), swaged, or combinations thereof.
[0167] The combination of moving the pieces together with force and the
housings having
the tapered interior volumes compacts electrically insulating material 256
using both axial
and radial compression. Both axial and radial compressing electrically
insulating material
256 provides more uniform compaction of the electrically insulating material.
In some
embodiments, vibration and/or tamping of electrically insulating material 256
may also be
used to consolidate the electrically insulating material. Vibration (and/or
tamping) may be
applied either at the same time as application of force to push the housings
254A, 254B
together, or vibration (and/or tamping) may be alternated with application of
such force.
Vibration and/or tamping may reduce bridging of particles in electrically
insulating
material 256.
[0168] In the embodiment depicted in FIG. 7, electrically insulating material
256 inside
housings 254A, 254B is compressed mechanically by tightening nuts 266 against
ferrules
268 coupled to jackets 218A, 218B. The mechanical method compacts the interior
volumes of housings 254A, 254B because of the tapered shape of the interior
volumes.
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Ferrules 268 may be copper or other soft metal ferrules. Nuts 266 may be
stainless steel or
other hard metal nut that is movable on jackets 218A, 218B. Nuts 266 may
engage threads
on housings 254A, 254B to couple to the housings. As nuts 266 are threaded
onto
housings 254A, 254B, nuts 266 and ferrules 268 work to compress the interior
volumes of
the housings. In some embodiments, nuts 266 and ferrules 268 may work to move
housings 254A, 254B further onto sleeve 252 (using the threaded coupling
between the
pieces) and compact the interior volume of the sleeve. In some embodiments,
housings
254A, 254B and sleeve 252 are coupled together using the threaded coupling
before the nut
and ferrule are swaged down on the second portion. As the interior volumes
inside
housings 254A, 254B are compressed, the interior volume inside sleeve 252 may
also be
compressed. In some embodiments. nuts 266 and ferrules 268 may act to couple
housings
254A, 254B to insulated conductors 212A, 212B.
[0169] In certain embodiments, multiple insulated conductors are spliced
together in an
end fitting. For example, three insulated conductors may be spliced together
in an end
fitting to couple electrically the insulated conductors in a 3-phase wye
configuration. FIG.
8A depicts a side view of a cross-sectional representation of an embodiment of
threaded
fitting 270 for coupling three insulated conductors 212A, 212B, 212C. FIG. 8B
depicts a
side view of a cross-sectional representation of an embodiment of welded
fitting 270 for
coupling three insulated conductors 212A. 212B, 212C. As shown in FIGS. 8A and
8B,
insulated conductors 212A, 212B, 212C may be coupled to fitting 270 through
end cap
272. End cap 272 may include three strain relief fittings 274 through which
insulated
conductors 212A, 212B, 212C pass.
[0170] Cores 214A, 214B, 214C of the insulated conductors may be coupled
together at
coupling 258. Coupling 258 may be, for example, a braze (such as a silver
braze or copper
braze), a welded joint, or a crimped joint. Coupling cores 214A. 214B, 214C at
coupling
258 electrically join the three insulated conductors for use in a 3-phase wye
configuration.
[0171] As shown in FIG. 8A, end cap 272 may be coupled to main body 276 of
fitting 270
using threads. Threading of end cap 272 and main body 276 may allow the end
cap to
compact electrically insulating material 256 inside the main body. At the end
of main body
276 opposite of end cap 272 is cover 278. Cover 278 may also be attached to
main body
276 by threads. In certain embodiments, compaction of electrically insulating
material 256
in fitting 270 is enhanced through tightening of cover 278 into main body 276,
by crimping
of the main body after attachment of the cover, or a combination of these
methods.
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[0172] As shown in FIG. 8B, end cap 272 may be coupled to main body 276 of
fitting 270
using welding, brazing, or crimping. End cap 272 may be pushed or pressed into
main
body 276 to compact electrically insulating material 256 inside the main body.
Cover 278
may also be attached to main body 276 by welding, brazing, or crimping. Cover
278 may
be pushed or pressed into main body 276 to compact electrically insulating
material 256
inside the main body. Crimping of the main body after attachment of the cover
may
further enhance compaction of electrically insulating material 256 in fitting
270.
[0173] In some embodiments, as shown in FIGS. 8A and 8B, plugs 280 close
openings or
holes in cover 278. For example, the plugs may be threaded, welded, or brazed
into
openings in cover 278. The openings in cover 278 may allow electrically
insulating
material 256 to be provided inside fitting 270 when cover 278 and end cap 272
are coupled
to main body 276. The openings in cover 278 may be plugged or covered after
electrically
insulating material 256 is provided inside fitting 270. In some embodiments,
openings are
located on main body 276 of fitting 270. Openings on main body 276 may be
plugged with
plugs 280 or other plugs.
[0174] In some embodiments, cover 278 includes one or more pins. In some
embodiments, the pins are or are part of plugs 280. The pins may engage a
torque tool that
turns cover 278 and tightens the cover on main body 276. An example of torque
tool 282
that may engage the pins is depicted in FIG. 9. Torque tool 282 may have an
inside
diameter that substantially matches the outside diameter of cover 278
(depicted in FIG.
8A). As shown in FIG. 9, torque tool 282 may have slots or other depressions
that are
shaped to engage the pins on cover 278. Torque tool 282 may include recess
284. Recess
284 may be a square drive recess or other shaped recess that allows operation
(turning) of
the torque tool.
[0175] FIG. 10 depicts an embodiment of clamp assemblies 286A,B that may be
used to
mechanically compact fitting 250. Clamp assemblies 286A,B may be shaped to
secure
fitting 250 in place at the shoulders of housings 254A, 254B. Threaded rods
288 may pass
through holes 290 of clamp assemblies 286A,B. Nuts 292, along with washers, on
each of
threaded rods 288 may be used to apply force on the outside faces of each
clamp assembly
and bring the clamp assemblies together such that compressive forces are
applied to
housings 254A, 254B of fitting 250. These compressive forces compact
electrically
insulating material inside fitting 250.
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[0176] In some embodiments, clamp assemblies 286 are used in hydraulic,
pneumatic, or
other compaction methods. FIG. 11 depicts an exploded view of an embodiment of
hydraulic compaction machine 294. FIG. 12 depicts a representation of an
embodiment of
assembled hydraulic compaction machine 294. As shown in FIGS. 11 and 12, clamp
assemblies 286 may be used to secure fitting 250 (depicted, for example, in
FIG. 5) in
place with insulated conductors coupled to the fitting. At least one clamp
assembly (for
example, clamp assembly 286A) may be moveable together to compact the fitting
in the
axial direction. Power unit 296, shown in FIG. 11, may be used to power
compaction
machine 294.
[0177] FIG. 13 depicts an embodiment of fitting 250 and insulated conductors
212A. 212B
secured in clamp assembly 286A and clamp assembly 286B before compaction of
the
fitting and insulated conductors. As shown in FIG. 13, the cores of insulated
conductors
212A, 212B are coupled using coupling 258 at or near the center of sleeve 252.
Sleeve 252
is slid over housing 254A, which is coupled to insulated conductor 212A.
Sleeve 252 and
housing 254A are secured in fixed (non-moving) clamp assembly 286B. Insulated
conductor 212B passes through housing 254B and movable clamp assembly 286A.
Insulated conductor 212B may be secured by another clamp assembly fixed
relative to
clamp assembly 286B (not shown). Clamp assembly 286A may be moved towards
clamp
assembly 286B to couple housing 254B to sleeve 252 and compact electrically
insulating
material inside the housings and the sleeve. Interfaces between insulated
conductor 212A
and housing 254A, between housing 254A and sleeve 252, between sleeve 252 and
housing 254B, and between housing 254B and insulated conductor 212B may then
be
coupled by welding, brazing, or other techniques known in the art.
[0178] FIG. 14 depicts a side view representation of an embodiment of fitting
298 for
joining insulated conductors. Fitting 298 may be a cylinder or sleeve that has
sufficient
clearance between the inside diameter of the sleeve and the outside diameters
of insulated
conductors 212A, 212B such that the sleeve fits over the ends of the insulated
conductors.
The cores of insulated conductors 212A, 212B may be joined inside fitting 298.
The
jackets and insulation of insulated conductors 212A, 212B may be cut back or
stripped to
expose desired lengths of the cores before joining the cores. Fitting 298 may
be centered
between the end portions of insulated conductors 212A, 212B.
[0179] Fitting 298 may be used to couple insulated conductor 212A to insulated
conductor
212B while maintaining the mechanical and electrical integrity of the jackets,
insulation,
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and cores of the insulated conductors. Fitting 298 may be used to couple heat
producing
insulated conductors with non-heat producing insulated conductors, to couple
heat
producing insulated conductors with other heat producing insulated conductors,
or to
couple non-heat producing insulated conductors with other non-heat producing
insulated
conductors. In some embodiments, more than one fitting 298 is used in to
couple multiple
heat producing and non-heat producing insulated conductors to produce a long
insulated
conductor.
[0180] Fitting 298 may be used to couple insulated conductors with different
diameters.
For example, the insulated conductors may have different core diameters,
different jacket
diameters, or combinations of different diameters. Fitting 298 may also be
used to couple
insulated conductors with different metallurgies, different types of
insulation, or a
combination thereof.
[0181] In certain embodiments, fitting 298 has at least one angled end. For
example, the
ends of fitting 298 may be angled relative to the longitudinal axis of the
fitting. The angle
may be, for example, about 45 or between 30 and 60 . Thus, the ends of
fitting 298 may
have substantially elliptical cross-sections. The substantially elliptical
cross-sections of the
ends of fitting 298 provide a larger area for welding or brazing of the
fitting to insulated
conductors 212A, 212B. The larger coupling area increases the strength of
spliced
insulated conductors. In the embodiment shown in FIG. 14, the angled ends of
fitting 298
give the fitting a substantially parallelogram shape.
[0182] The angled ends of fitting 298 provide higher tensile strength and
higher bending
strength for the fitting than if the fitting had straight ends by distributing
loads along the
fitting. Fitting 298 may be oriented so that when insulated conductors 212A,
212B and the
fitting are spooled (for example, on a coiled tubing installation), the angled
ends act as a
transition in stiffness from the fitting body to the insulated conductors.
This transition
reduces the likelihood of the insulated conductors to kink or crimp at the end
of the fitting
body.
[0183] As shown in FIG. 14, fitting 298 includes opening 300. Opening 300
allows
electrically insulating material (such as electrically insulating material
256, depicted in
FIG. 5) to be provided (filled) inside fitting 298. Opening 300 may be a slot
or other
longitudinal opening extending along part of the length of fitting 298. In
certain
embodiments, opening 300 extends substantially the entire gap between the ends
of
insulated conductors 212A, 212B inside fitting 298. Opening 300 allows
substantially the
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entire volume (area) between insulated conductors 212A, 212B, and around any
welded or
spliced joints between the insulated conductors, to be filled with
electrically insulating
material without the insulating material having to be moved axially toward the
ends of the
volume between the insulated conductors. The width of opening 300 allows
electrically
insulating material to be forced into the opening and packed more tightly
inside fitting 298,
thus, reducing the amount of void space inside the fitting. Electrically
insulating material
may be forced through the slot into the volume between insulated conductors
212A, 212B,
for example, with a tool with the dimensions of the slot. The tool may be
forced into the
slot to compact the insulating material. Then, additional insulating material
may be added
and the compaction is repeated. In some embodiments, the electrically
insulating material
may be further compacted inside fitting 298 using vibration, tamping, or other
techniques.
Further compacting the electrically insulating material may more uniformly
distribute the
electrically insulating material inside fitting 298.
[0184] After filling electrically insulating material inside fitting 298 and,
in some
embodiment, compaction of the electrically insulating material, opening 300
may be
closed. For example, an insert or other covering may be placed over the
opening and
secured in place. FIG. 15 depicts a side view representation of an embodiment
of fitting
298 with opening 300 covered with insert 302. Insert 302 may be welded or
brazed to
fitting 298 to close opening 300. In some embodiments, insert 302 is ground or
polished
so that the insert if flush on the surface of fitting 298. Also depicted in
FIG. 15, welds or
brazes 304 may be used to secure fitting 298 to insulated conductors 212A,
212B.
[0185] After opening 300 is closed, fitting 298 may be compacted mechanically,
hydraulically, pneumatically, or using swaging methods to compact further the
electrically
insulating material inside the fitting. Further compaction of the electrically
insulating
material reduces void volume inside fitting 298 and reduces the leakage
currents through
the fitting and increases the operating range of the fitting (for example, the
maximum
operating voltages or temperatures of the fitting).
[0186] In certain embodiments, fitting 298 includes certain features that may
further
reduce electric field intensities inside the fitting. For example, fitting 298
or coupling 258
of the cores of the insulated conductors inside the fitting may include
tapered edges,
rounded edges, or other smoothed out features to reduce electric field
intensities. FIG. 16
depicts an embodiment of fitting 298 with electric field reducing features at
coupling 258
between insulated conductors 212A. 212B. As shown in FIG. 16, coupling 258 is
a welded
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joint with a smoothed out or rounded profile to reduce electric field
intensity inside fitting
298. In addition, fitting 298 has a tapered interior volume to increase the
volume of
electrically insulating material inside the fitting. Having the tapered and
larger volume
may reduce electric field intensities inside fitting 298.
[0187] In some embodiments, electric field stress reducers may be located
inside fitting
298 to decrease the electric field intensity. FIG. 17 depicts an embodiment of
electric field
stress reducer 306. Reducer 306 may be located in the interior volume of
fitting 298
(shown in FIG. 16). Reducer 306 may be a split ring or other separable piece
so that the
reducer can be fitted around cores 214A. 214B of insulated conductors 212A,
212B after
they are joined (shown in FIG. 16).
[0188] FIGS. 18 and 19 depict cross-sectional representations of another
embodiment of
fitting 250 used for joining insulated conductors. FIG. 18 depicts a cross-
sectional
representation of fitting 250 as insulated conductors 212A, 212B are being
moved into the
fitting. FIG. 19 depicts a cross-sectional representation of fitting 250 with
insulated
conductors 212A, 212B joined inside the fitting. In certain embodiments,
fitting 250
includes sleeve 252 and coupling 258.
[0189] Fitting 250 may be used to couple (splice) insulated conductor 212A to
insulated
conductor 212B while maintaining the mechanical and electrical integrity of
the jackets
(sheaths), insulation, and cores (conductors) of the insulated conductors.
Fitting 250 may
be used to couple heat producing insulated conductors with non-heat producing
insulated
conductors, to couple heat producing insulated conductors with other heat
producing
insulated conductors, or to couple non-heat producing insulated conductors
with other non-
heat producing insulated conductors. In some embodiments, more than one
fitting 250 is
used to couple multiple heat producing and non-heat producing insulated
conductors to
provide a long insulated conductor.
[0190] Fitting 250 may be used to couple insulated conductors with different
diameters.
For example, the insulated conductors may have different core (conductor)
diameters,
different jacket (sheath) diameters, or combinations of different diameters.
Fitting 250
may also be used to couple insulated conductors with different metallurgies,
different types
of insulation, or combinations thereof.
[0191] Coupling 258 is used to join and electrically couple cores 214A, 214B
of insulated
conductors 212A, 212B inside fitting 250. Coupling 258 may be made of copper
or
another suitable electrical conductor. In certain embodiments, cores 214A,
214B are press
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fit or pushed into coupling 258. In some embodiments, coupling 258 is heated
to enable
cores 214A, 214B to be slid into the coupling. In some embodiments, core 214A
is made
of different material than core 214B. For example, core 214A may be copper
while core
214B is stainless steel, carbon steel, or Alloy 180. In such embodiments,
special methods
may have to be used to weld the cores together. For example, the tensile
strength
properties and/or yield strength properties of the cores may have to be
matched closely
such that the coupling between the cores does not degrade over time or with
use.
[0192] In some embodiments, coupling 258 includes one or more grooves on the
inside of
the coupling. The grooves may inhibit particles from entering or exiting the
coupling after
the cores are joined in the coupling. In some embodiments, coupling 258 has a
tapered
inner diameter (for example, tighter inside diameter towards the center of the
coupling).
The tapered inner diameter may provide a better press fit between coupling 258
and cores
214A, 214B.
[0193] In certain embodiments, electrically insulating material 256 is located
inside sleeve
252. In some embodiments, electrically insulating material 256 is magnesium
oxide or a
mixture of magnesium oxide and boron nitride (80% magnesium oxide and 20%
boron
nitride by weight). Electrically insulating material 256 may include magnesium
oxide,
talc, ceramic powders (for example, boron nitride), a mixture of magnesium
oxide and
another electrical insulator (for example, up to about 50% by weight boron
nitride),
ceramic cement, mixtures of ceramic powders with certain non-ceramic materials
(such as
tungsten sulfide (WS2)), or mixtures thereof. For example, magnesium oxide may
be
mixed with boron nitride or another electrical insulator to improve the
ability of the
electrically insulating material to flow, to improve the dielectric
characteristics of the
electrically insulating material, or to improve the flexibility of the
fitting. In some
embodiments, electrically insulating material 256 is material similar to
electrical insulation
used inside of at least one of insulated conductors 212A, 212B. Electrically
insulating
material 256 may have substantially similar dielectric characteristics to
electrical insulation
used inside of at least one of insulated conductors 212A, 212B.
[0194] In certain embodiments, the interior volumes of sleeve 252 are
substantially filled
with electrically insulating material 256. In certain embodiments,
"substantially filled"
refers to entirely or almost entirely filling the volume or volumes with
electrically
insulating material with substantially no macroscopic voids in the volume or
volumes. For
example, substantially filled may refer to filling almost the entire volume
with electrically
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insulating material that has some porosity because of microscopic voids (for
example, up to
about 40% porosity).
[0195] In some embodiments, sleeve 252 has one or more grooves 308. Grooves
308 may
inhibit electrically insulating material 256 from moving out of sleeve 252
(for example, the
grooves trap the electrically insulating material in the sleeve).
[0196] In certain embodiments, electrically insulating material 256 has
concave shaped
end portions at or near the edges of coupling 258, as shown in FIG. 18. The
concave
shapes of electrically insulating material 256 may enhance coupling with
electrical
insulators 216A, 216B of insulated conductors 212A, 212B. In some embodiments,
electrical insulators 216A, 216B have convex shaped (or tapered) end portions
to enhance
coupling with electrically insulating material 256. The end portions of
electrically
insulating material 256 and electrical insulators 216A, 216B may comingle or
mix under
the pressure applied during joining of the insulated conductors. The
comingling or mixing
of the insulation materials may enhance the coupling between the insulated
conductors.
[0197] In certain embodiments, insulated conductors 212A, 212B are joined with
fitting
250 by moving (pushing) the insulated conductors together towards the center
of the
fitting. Cores 214A, 214B are brought together inside coupling 258 with the
movement of
insulated conductors 212A, 212B. After insulated conductors 212A, 212B are
moved
together into fitting 250, the fitting and end portions of the insulated
conductors inside the
.. fitting may be compacted or pressed to secure the insulated conductors in
the fitting and
compress electrically insulating material 256. Clamp assemblies or other
similar devices
may be used to bring together insulated conductors 212A, 212B and fitting 250.
In certain
embodiments, the force to compress electrically insulating material 256 is,
for example, at
least 25,000 pounds per square inch up to 55,000 pounds per square inch in
order to
provide acceptable compaction of the insulating material. The compaction of
electrically
insulating material 256 during the assembly process may provide dielectric
characteristics
for the electrically insulating material that are, to the extent practical,
comparable to that
within insulated conductors 212A, 212B. Methods and devices to facilitate
compaction
include, but are not limited to, mechanical methods, pneumatic, hydraulic,
swaged, or
combinations thereof.
[0198] In some embodiments, end portions of sleeve 252 are coupled (welded or
brazed) to
jackets 218A, 218B of insulated conductors 212A, 212B. In some embodiments, a
support
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sleeve and/or strain reliefs are placed over fitting 250 to provide additional
strength to the
fitting.
[0199] FIGS. 20 and 21 depict cross-sectional representations of yet another
embodiment
of fitting 250 used for joining insulated conductors. FIG. 20 depicts a cross-
sectional
representation of fitting 250 as insulated conductors 212A, 212B are being
moved into the
fitting. FIG. 21 depicts a cross-sectional representation of fitting 250 with
insulated
conductors 212A, 212B joined inside the fitting in a final position. The
embodiment of
fitting 250 depicted in FIGS. 20 and 21 may be similar to the embodiment of
fitting 250
depicted in FIGS. 18 and 19.
[0200] In certain embodiments, fitting 250, as shown in FIGS. 20 and 21,
includes sleeve
252 and coupling 258. Coupling 258 is used to join and electrically couple
cores 214A,
214B of insulated conductors 212A, 212B inside fitting 250. Coupling 258 may
be made
of copper or another suitable soft metal conductor. In some embodiments,
coupling 258 is
used to couple cores of different diameters. Thus, coupling 258 may have
halves with
different inside diameters to match the diameters of the cores.
[0201] In certain embodiments, cores 214A, 214B are press fit or pushed into
coupling 258
as insulated conductors 212A, 212B are pushed into sleeve 252. In some
embodiments,
coupling 258 has a tapered inner diameter (for example, tighter inside
diameter towards the
center of the coupling), as shown in FIG. 20. The tapered inner diameter may
provide a
.. better press fit between coupling 258 and cores 214A, 214B and increase the
interface
length between the cores and the coupling. Increasing the interface length
between
coupling 258 and cores 214A, 214B decreases resistance between the cores and
the
coupling and inhibits arcing when electrical power is applied to insulated
conductors 212A,
212B.
[0202] In certain embodiments, cores 214A, 214B are pushed together to the
final position
depicted in FIG. 21 with clearance 309 between the ends of the cores.
Clearance 309 is a
gap or space between the ends of cores 214A, 214B. In some embodiments,
clearance 309
is between about 1 mil and about 15 mils or between about 2 mils and about 5
mils.
[0203] With clearance 309 between the ends of cores 214A, 214B, movement of
insulated
conductors 212A, 212B as the insulated conductors are pushed into sleeve 252
is limited
by compression of electrical insulators 216A, 216B against electrically
insulating material
256 and not the interface between the ends of the cores. Thus, maintaining
clearance 309
between the ends of cores 214A, 214B provides better (more) compression of
electrically
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insulating material 256 and electrical insulators 216A, 216B inside sleeve 252
in the final
position depicted in FIG. 21. Better compression of electrically insulating
material 256
and electrical insulators 216A, 216B provides a more reliable fitting 250 with
better
electrical characteristics.
[0204] Additionally, maintaining clearance 309 between the ends of cores 214A,
214B
inhibits the cores from being pushed against each other and causing buckling
or other
deformation of the cores. Pushing cores 214A, 214B together inside coupling
258 allows
for the cores to be coupled without welding, heating, or otherwise raising the
temperature
of the cores. Keeping the temperature of cores 214A, 214B reduced during
joining of the
cores keeps the core material (copper) from softening or flowing. Maintaining
the
hardness of cores 214A, 214B may provide better electrical performance of
fitting 250.
[0205] In certain embodiments, electrically insulating material 256 has
concave shaped
end portions at or near the edges of coupling 258, as depicted in FIG. 20. The
concave
shaped end portions may have angled edges to form a female type angle shape,
as depicted
............................................................... in FIG.
20. The concave shaped end portions of electrically insulating material 256
may
enhance coupling with electrical insulators 216A, 216B of insulated conductors
212A,
212B. In some embodiments, electrical insulators 216A, 216B have convex shaped
(or
male angled edges) end portions to enhance coupling with electrically
insulating material
256. Compressing the shaped end portions against each other may spread out the
edges of
the end portions and remove discontinuities between the end portions. Having
shaped end
portions of electrically insulating material 256 and electrical insulators
216A. 216B
improves compression and/or bridging between the electrically insulating
material and
electrical insulators under the pressure applied during joining of insulated
conductors
212A, 212B. Compression of the insulation materials enhances the electrical
insulation
properties of fitting 250.
[0206] In certain embodiments, insulated conductors 212A, 212B are moved a
selected
distance into fitting 250 to provide a desired compression of insulation
material in the
fitting and a desired coupling between cores 214A. 214B and coupling 258. In
some
embodiments, insulated conductors 212A, 212B are moved the selected distance
with a
selected amount of force to provide the desired compression and desired
coupling.
Hydraulic pressure may be used to provide the force to push insulated
conductors 212A,
212B into fitting 250. As an example, insulated conductors 212A, 212B may each
be
moved between about 7/8" (about 2.2 cm) and about 1" (about 2.5 cm) into
fitting 250 with
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a hydraulic pressure of between about 2800 psi (19,300 kPa) and about 3000 psi
(about
20,680 kPa).
[0207] FIG. 22 depicts an embodiment of blocks of electrically insulating
material in
position around cores of joined insulated conductors. Core 214A of insulated
conductor
212A is coupled to core 214B of insulated conductor 212B at coupling 258.
Cores 214A,
214B are exposed by removing portions of electrical insulators 216A, 216B and
jackets
218A, 218B surrounding the cores at the ends of insulated conductors 212A,
212B.
[0208] In some embodiments, cores 214A, 214B have different diameters. In such
embodiments, coupling 258 may taper from the diameter of core 214A to the
diameter of
core 214B. In some embodiments, cores 214A. 214B include different materials.
Coupling 258 may compensate for the different materials in the cores. For
example,
coupling 258 may include a blend or mixture of materials in the cores.
[0209] In certain embodiments, one or more blocks of electrically insulating
material 256
are placed around the exposed portions of cores 214A, 214B, as shown in FIG.
22. Blocks
of electrically insulating material 256 may be made of, for example, magnesium
oxide or a
mixture of magnesium oxide and another electrical insulator. The blocks of
electrically
insulating material 256 may be hard or soft blocks of material depending on
the type of
compaction desired. A desired number of blocks of electrically insulating
material 256
may be placed around the exposed portions of cores 214A, 214B such that the
blocks
substantially completely surround the exposed core portions. The number of
blocks of
electrically insulating material 256 may vary based on, for example, the
length and/or
diameter of the exposed core portions and/or the size of the blocks of
electrically insulating
material. In certain embodiments, four blocks of electrically insulating
material 256 are
used to surround the exposed portions of the cores.
[0210] FIG. 22 depicts two blocks of electrically insulating material 256A,
256B
surrounding one half (a semi-circle) of the exposed portions of cores 214A,
214B. The
depicted blocks of electrically insulating material 256 are semi-circular
blocks that fit
snugly around the outside diameters of the exposed core portions. In the
embodiment
depicted in FIG. 22, two additional blocks of electrically insulating material
256 would be
placed on the exposed core portions to surround the exposed core portions with
electrically
insulating material. FIG. 23 depicts an embodiment of four blocks of
electrically
insulating material 256A, 256B, 256C, 256D in position surrounding the cores
of joined
insulated conductors 212A, 212B.
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[0211] In certain embodiments, blocks of electrically insulating material 256
have inside
diameters sized and/or shaped to match the outside diameters of the exposed
portions of
cores 214A, 214B. Matching the inside diameters of the blocks with the outside
diameters
of the exposed core portions may provide a snug fit between the blocks and the
exposed
core portions and inhibit or reduce gap formation during compaction of the
blocks.
[0212] In some embodiments, one or more blocks of electrically insulating
material 256
have a tapered inside diameter to match a tapered outer diameter of coupling
258 and/or
the exposed portions of cores 214A, 214B, as shown in FIG. 22. The inside
diameter of
the blocks of electrically insulating material 256 may be formed by sanding or
grinding the
inner diameter of the blocks to the desired tapered shape.
[0213] After blocks of electrically insulating material 256 have been placed
around the
exposed portions of the cores (as shown in FIG. 23), a sleeve or other
cylindrical covering
is placed over the joined insulated conductors to substantially cover the
blocks and at least
a portion of each of the insulated conductors. FIG. 24 depicts an embodiment
of inner
sleeve 252A placed over joined insulated conductors 212A, 212B. Inner sleeve
252A may
be a material the same as or similar to material used for jackets 218A, 218B
of insulated
conductors 212A, 212B. For example, inner sleeve 252A and jackets 218A, 218B
may be
304 stainless steel. Inner sleeve 252A and jackets 218A, 218B are typically
made of
materials that can be welded together.
[0214] Inner sleeve 252A has a tight or snug fit over jackets 218A, 218B of
insulated
conductors 212A, 212B. In some embodiments, inner sleeve 252A includes axial
and/or
radial grooves in the outer surface of the sleeve. In certain embodiments,
inner sleeve
252A includes alignment ridge 310. Alignment ridge 310 is located at or near a
center of
the coupling between insulated conductors 212A, 212B.
[0215] After the inner sleeve has been placed around the blocks of
electrically insulating
material (as shown in FIG. 24), an outer sleeve or other cylindrical covering
is placed over
the inner sleeve. FIG. 25 depicts an embodiment of outer sleeve 252B placed
over inner
sleeve 252A and joined insulated conductors 212A, 212B. In certain
embodiments, outer
sleeve 252B has a shorter length than inner sleeve 252A. In certain
embodiments, outer
sleeve 252B has opening 312. Opening 312 may be located at or near a center of
outer
sleeve 252B. Opening 312 may be aligned with alignment ridge 310 on inner
sleeve 252A
(the alignment ridge is viewed through the opening). In some embodiments,
outer sleeve
252B is made of two or more pieces. For example, the outer sleeve may be two-
pieces put
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together in a clam-shell configuration. The pieces may be welded or otherwise
coupled to
form the outer sleeve. In some embodiments, outer sleeve 252B includes axial
and/or
radial grooves in the inner surface of the sleeve.
[0216] Outer sleeve 252B may be a material the same as or similar to material
used for
inner sleeve 252A and jackets 218A, 218B (for example, 304 stainless steel).
Outer sleeve
252B may have a tight or snug fit over inner sleeve 252A. After outer sleeve
252B and
inner sleeve 252A are placed over jackets 218A, 218B of insulated conductors
212A,
212B, the sleeves may be permanently coupled (for example, welded) to jackets
218A.
218B. Sleeves 252A, 252B may be permanently coupled to jackets 218A, 218B such
that
the ends of the sleeves are substantially sealed (there are no leaks at the
ends of the sleeves
that allow air or other fluids to enter or exit the ends of the sleeves).
After coupling of
sleeves 252A, 252B to jackets 218A, 218B, opening 312 is the only port for
fluid to
enter/exit outer sleeve 252B and there the interior of inner sleeve 252A is
substantially
sealed.
[0217] In certain embodiments, fluid (for example, hydraulic fluid) is
provided into the
interior volume of outer sleeve 252B through opening 312. In certain
embodiments, the
fluid is hydraulic oil. In some embodiments, the fluid includes other fluids
such as molten
salt or gas. In some embodiments, the fluid is heated during pressurization.
[0218] The fluid provided into the interior volume of outer sleeve 252B may be
pressurized to compact or compress inner sleeve 252A and electrically
insulating material
256. For example, the fluid may be hydraulically pressurized using a hand pump
or
another suitable hydraulic pressurizing pump. Pressurizing the fluid inside
outer sleeve
252B may provide isostatic pressure to compress inner sleeve 252A.
[0219] Outer sleeve 252B may be hard or non-susceptible to compaction under
pressure
while inner sleeve 252A is susceptible to compaction under pressure. For
example, inner
sleeve 252A may be thinner than outer sleeve 252B and/or the inner sleeve may
be heat
treated (annealed) to be softer than the outer sleeve.
[0220] The fluid inside outer sleeve 252B is pressurized to a selected
pressure or into a
selected pressure range to compact inner sleeve 252A and electrically
insulating material
256 to a desired compaction level. In some embodiments, the fluid inside outer
sleeve
252B is pressurized to a pressure between about 15,000 psi (about 100,000 kPa)
and about
20,000 psi (about 140,000 kPa). In some embodiments, the fluid may be
pressurized to
higher pressures (for example, pressurized up to about 35,000 psi (about
240,000 kPa)).
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[0221] Pressurizing the fluid to such pressures deforms inner sleeve 252A by
compressing
the inner sleeve and compacts electrically insulating material 256 inside the
inner sleeve.
Inner sleeve 252A may be uniformally deformed by the fluid pressure inside
outer sleeve
252B. In certain embodiments, electrically insulating material 256 is
compacted such that
the electrically insulating material has dielectric properties similar to or
better than the
dielectric properties of the electrical insulator in at least one of the
joined insulated
conductors. Using the pressurized fluid to compress and compact inner sleeve
252A and
electrically insulating material 256 may allow the insulated conductors to be
joined in the
sleeves in a horizontal configuration. Joining the insulated conductors in a
horizontal
configuration allows longer lengths of insulated conductors to be joined
together without
the need for complicated or expensive cable hanging systems.
[0222] In some embodiments, the ends of insulated conductors may have chamfers
or other
tapering to allow for compression of the inner sleeve. FIG. 26 depicts an
embodiment of a
chamfered end of an insulated conductor after compression. Insulated conductor
212
includes chamfer 314 inside inner sleeve 252A. Chamfer 314 may inhibit kinking
or
buckling of inner sleeve 252A during compression.
[0223] In some embodiments, electrically insulating material powder is added
into the
interior of inner sleeve 252A before sealing and compaction of the inner
sleeve. The
electrically insulating material powder may penetrate and fill voids inside
the inner sleeve
(such as in the recess formed between a chamfer on the insulated conductor and
the inner
sleeve). Use of electrically insulating material powder may also reduce the
number of
interfaces in compacted electrically insulating material. In some embodiments,
electrically
insulating material powder is used instead of blocks of electrically
insulating material.
[0224] In some embodiments, an additive such as a dopant or another additional
material
may be added to the electrically insulating material. The additive may improve
the
dielectric properties of the electrically insulating material. For example.
the additive may
increase the dielectric strength of the electrically insulating material.
[0225] In certain embodiments, mechanical and/or hydraulic compaction is used
to radially
compact electrically insulating material (for example, electrically insulating
material in
powder form) at the coupling of joined insulated conductors. FIG. 27 depicts
an
embodiment of first half 316A of compaction device 316 to be used for
compaction of
electrically insulating material at a coupling of insulated conductors. The
second half of
device 316 has a similar shape and size as first half 316A depicted in FIG.
27. The first
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half and second half of device 316 are coupled together to form the device
around a section
of insulated conductors to be joined together.
[0226] FIG. 28 depicts an embodiment of device 316 coupled together around
insulated
conductors 212A, 212B. The jackets and electrical insulator surrounding the
cores of
insulated conductors 212A, 212B have been removed to expose the portions of
the cores
located inside device 316.
[0227] As shown in FIG. 27, first half 316A includes first half 318A of
opening 318 that is
formed in the top of device 316 when the two halves of the device are coupled
together.
Opening 318 allows electrically insulating material and/or other materials to
be provided
into the space around exposed cores of the insulated conductors. In certain
embodiments,
electrically insulating material powder is provided into device 316.
[0228] As shown in FIG. 28, after at least some electrically insulating
material is provided
through opening 318 into device 316 around the exposed cores, first plunger
320A is
inserted into the opening. First plunger 320A is used to compact (for example,
by applying
mechanical and/or hydraulic force to the top of the plunger) electrically
insulating material
inside device 316. For example, force may be applied to first plunger 320A
using a
hammer (mechanical compaction) or a hydraulically driven piston (hydraulic
compaction).
[0229] FIG. 29 depicts a side view of insulated conductor 212 inside device
316 with first
plunger 320A in position above the insulated conductor with exposed core 214.
In certain
embodiments, first plunger 320A has a bottom with recess 322A. Recess 322A may
have a
shape that is substantially similar to the shape of the exposed portions of
the cores. First
plunger 320A may include stops 324, shown in FIG. 28, that inhibit the depth
the first
plunger can go into device 316. For example, stops 324 may inhibit first
plunger 320A
from going to a depth inside device 316 that would bend or deform the cores of
the
insulated conductors. In some embodiments, first plunger 320A is designed to
go to a
selected depth that does not bend or deform the cores of the insulated
conductors without
the use of stops (for example. the top plate of the plunger acts as the stop).
[0230] First plunger 320A may be used to compact electrically insulating
material 256 to a
first level inside device 316. For example, as shown in FIG. 29, electrically
insulating
.. material 256 is compacted to level that surrounds a lower portion (for
example, a lower
half) of exposed core 214. The process of adding electrically insulating
material and
compacting the material with the first plunger may be repeated until a desired
level of
compaction is achieved around a lower portion of the core.
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[0231] FIG. 30 depicts a side view of insulated conductor 212 inside device
316 with
second plunger 320B in position above the insulated conductor with exposed
core 214. In
certain embodiments, second plunger 320B has a bottom with recess 322B. Recess
322B
may have a shape that is substantially similar to the outer shape of the
insulated conductor.
[0232] In some embodiments, recess 322B in second plunger 320B has other
shapes or
there is no recess. FIGS. 31A-D depict other embodiments of second plunger
320B. In
FIG. 31A, second plunger 320B has no recess. In FIG. 31B, recess 322B has 30
angled
edges. In FIG. 31C, recess 322B has 15 angled straight edges. In FIG. 31D,
recess 322B
is slightly shallower (shorter sides) than the recess shown in FIG. 30.
[0233] Second plunger 320B may be used to compact electrically insulating
material 256
to a second level inside device 316. For example, as shown in FIG. 30,
electrically
insulating material 256 is compacted to level that surrounds exposed core 214.
The
process of adding electrically insulating material and compacting the material
with the
second plunger may be repeated until a desired level of compaction is achieved
around the
core. For example, the process may be repeated until the desired level of
compaction of
electrically insulating material is achieved in a shape and outside diameter
similar to the
shape and outside diameter of the insulated conductor.
[0234] After compaction of a desired amount of electrically insulating
material, device 316
may be removed from around the coupling of the insulated conductors. FIG. 32
depicts an
embodiment with the second half of device 316 removed to leave first half 316A
and
electrically insulating material 256 compacted around the coupling between
insulated
conductors 212A, 212B.
[0235] After removal of device 316, compacted electrically insulating material
256 may be
shaped into a substantially cylindrical shape with the outside diameter
relatively similar to
the outside diameter of insulated conductors 212A. 212B, as shown in FIG. 33.
Compacted electrically insulating material 256 may be formed into its final
shape by
removing excess portions of the compacted material. For example, excess
portions of
compacted electrically insulating material 256 may be axially removed using a
saw blade, a
sleeve with a shaving edge slid over the compacted material, and/or other
techniques
known in the art.
[0236] After electrically insulating material 256 is formed into the final
shape, sleeve 252
is placed over the electrically insulating material, as shown in FIG. 34.
Sleeve 252 may
include two or more portions placed over the electrically insulating material
and coupled
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(welded) together to form the sleeve. In some embodiments, the two or more
portions of
sleeve 252 are compressed using a pressurized fluid inside an outer sleeve
(such as
described in the embodiments of inner sleeve 252A and outer sleeve 252B
depicted in
FIGS. 24 and 25) and/or by mechanically crimping the sleeve portions together
(such as
described in the embodiments of sleeve 252 depicted in FIGS. 36 and 37).
Compression
using the pressurized fluid and/or mechanically crimping sleeve 252 may close
gaps
between portions of the sleeve such that no weld is needed to join the
portions together.
Additionally, compression using the pressurized fluid and/or mechanically
crimping may
bring down the interface (make a tighter interference fit) between sleeve 252
and
electrically insulating material 256. Sleeve 252 may be coupled (welded) to
jackets of
insulated conductors 212A, 212B. Sleeve 252 may be made of materials similar
to the
jackets of insulated conductors 212A, 212B. For example, sleeve 252 may be 304
stainless
steel.
[0237] In certain embodiments, electrically insulating material 256 that is
compacted in
device 316 includes a mixture of magnesium oxide and boron nitride powders. In
an
embodiment, electrically insulating material 256 that is compacted in device
316 includes
an 80% by weight magnesium oxide, 20% by weight boron nitride powder mixture.
Other
electrically insulating materials and/or other mixtures of electrically
insulating materials
may also be used. In some embodiments, a combination of electrically
insulating material
powder and blocks of electrically insulating material are used.
[0238] FIG. 35 depicts a representation of an embodiment of hydraulic press
machine 426
that may be used to apply force to a plunger to hydraulically compact
electrically insulating
material inside a device (for example, device 316 depicted in FIGS. 27-32).
Hydraulic
press machine 426 may include piston 428 and device holder 430. In certain
embodiments,
.. insulated conductors may be fed through clamps 432 of hydraulic press
machine 426 such
that end portions of the insulated conductors are positioned under piston 428
and above
device holder 430. Clamps 432 may be used to secure the ends of the insulated
conductors
on machine 426. Positioners 434 may be used to make fine tuning adjustments in
the
positions of the insulated conductors.
[0239] A device, such as device 316 depicted in FIGS. 27-32, may be placed
around the
ends of the insulated conductors at device holder 430 (for example, the two
halves of the
device are put together around the ends of the insulated conductors). Device
holder 430
may support the device during compaction of material in the device. During
compaction,
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piston 428 may apply force to a plunger (for example, first plunger 320A
depicted in FIGS.
28-29 and/or second plunger 320B depicted in FIG. 30) to compact electrically
insulating
material around the ends of the insulated conductors. In some embodiments,
piston 428
provides forces of up to about 50 tons force (about 100,000 pounds force).
[0240] Hydraulic compaction of electrically insulating material in device 316,
depicted in
FIGS. 27-32, may provide compaction levels (for example, up to about 85%
compaction)
in the electrically insulating material that are similar to compaction levels
in the insulated
conductors. Such compaction levels will produce splices that are suitable for
operating
temperatures up to at least about 1300 F (about 700 C). Hydraulic compaction
of
electrically insulating material in device 316 may provide more controlled
compaction
and/or more repeatable compaction (repeatable from splice to splice).
Hydraulic
compaction may be achieved with less movement or variation to provide more
even and
consistent pressure than mechanical compaction.
[0241] In some embodiments, hydraulic compaction is used in combination with
mechanical compaction (for example, the electrically insulating material is
first compacted
mechanically and then further compacted using hydraulic compaction). In some
embodiments, the electrically insulating material is compacted while at
elevated
temperatures. For example, the electrically insulating material may be
compacted at a
temperature of about 90 C or higher. In some embodiments, first plunger 320A
and/or
second plunger 320B are coated with non-stick materials. For example, the
plungers may
be coated with non-metallic materials such as ceramics or DLC (Diamond-Like
Carbon)
coatings available from Morgan Technical Ceramics (Berkshire, England).
Coating the
plungers may inhibit metal transfer into the electrically insulating material
and/or sticking
of the electrically insulating material to the plungers.
[0242] In certain embodiments, a sleeve is mechanically compressed
circumferentially
around the sleeve to compress the sleeve. FIG. 36 depicts an embodiment of
sleeve 252
that is used in circumferential mechanical compression. Sleeve 252 may be
placed around
blocks and/or powder of electrically insulating material. For example, sleeve
252 may be
placed around blocks of electrically insulating material depicted in FIG. 23,
compacted
electrically insulating material powder depicted in FIG. 33, or combinations
of the depicted
blocks and powder.
[0243] In certain embodiments, sleeve 252 includes ribs 326. Ribs 326 may be
raised
portions of sleeve 252 (for example, high spots on the outer diameter of the
sleeve.). Ribs
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326 may be shaped and sized to match the crimping portions of a press used to
mechanically compress sleeve 252. For example, sleeve 252 may be compressed
using a
hydraulically actuated mechanical compression system that circumferentially
compresses
the sleeve circumferentially. For example, sleeve 252 may be compressed using
a
Pyplok swage tool available from Tube-Mac Industries (Stoney Creek, Ontario.
Canada).
[0244] Crimping portions of the press compress ribs 326 until the ribs are
compressed to
about the outer diameter of the remaining portions of sleeve 252 (the ribs
have a diameter
substantially similar to the diameter of the remainder of the sleeve). FIG. 37
depicts an
embodiment of sleeve 252 on insulated conductors 212A, 212B after the sleeve
and ribs
326 have been circumferentially compressed. Compression of ribs 326
circumferentially
(radially) compresses electrically insulating material inside sleeve 252 and
couples the
sleeve to insulated conductors 212A, 212B. Sleeve 252 may be further coupled
to
insulated conductors 212A, 212B. For example, the ends of sleeve 252 may be
welded to
the jackets of insulated conductors 212A, 212B.
[0245] The fittings depicted herein (such as, but not limited to, fitting 250
(depicted in
FIGS. 5, 7, 18, 19, 20, and 21), fitting 270 (depicted in FIG. 8), fitting 298
(depicted in
FIGS. 14,15, and 16), embodiments of the fitting formed from inner sleeve 252A
and outer
sleeve 252B (depicted in FIGS. 22-25), and embodiments of sleeve 252 (depicted
in FIGS.
34, 36, and 37) may form robust electrical and mechanical connections between
insulated
conductors. For example, fittings depicted herein may be suitable for extended
operation
at voltages above 1000 volts, above 1500 volts, or above 2000 volts and
temperatures of at
least about 650 C, at least about 700 C, at least about 800 C.
[0246] In certain embodiments, the fittings depicted herein couple insulated
conductors
used for heating (for example, insulated conductors located in a hydrocarbon
containing
layer) to insulated conductors not used for heating (for example, insulated
conductors used
in overburden sections of the formation). The heating insulated conductor may
have a
smaller core and different material core than the non-heating insulated
conductor. For
example, the core of the heating insulated conductor may be a copper-nickel
alloy,
stainless steel, or carbon steel while the core of the non-heating insulated
conductor may be
copper. Because of the difference in sizes and electrical properties of
materials of the
cores, however, the electrical insulation in the sections may have
sufficiently different
thicknesses that cannot be compensated in a single fitting joining the
insulated conductors.
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Thus, in some embodiments, a short section of intermediate heating insulated
conductor
may be used in between the heating insulated conductor and the non-heating
insulated
conductor.
[0247] The intermediate heating insulated conductor may have a core diameter
that tapers
from the core diameter of the non-heating insulated conductor to the core
diameter of the
heating insulated conductor while using core material similar to the non-
heating insulated
conductor. For example, the intermediate heating insulated conductor may be
copper with
a core diameter that tapers to the same diameter as the heating insulated
conductor. Thus,
the thickness of the electrical insulation at the fitting coupling the
intermediate insulated
conductor and the heating insulated conductor is similar to the thickness of
the electrical
insulation in the heating insulated conductor. Having the same thickness
allows the
insulated conductors to be easily joined in the fitting. The intermediate
heating insulated
conductor may provide some voltage drop and some heating losses because of the
smaller
core diameter, however, the intermediate heating insulated conductor may be
relatively
short in length such that these losses are minimal.
[0248] In certain embodiments, a fitting for joining insulated conductors is
compacted or
compressed to improve the electrical insulation properties (dielectric
characteristics) of
electrically insulating material inside the fitting. For example, compaction
of electrically
insulating material inside the fitting may increase the uniformity of the
electrically
insulating material and/or remove voids or other interfaces in the
electrically insulating
material.
[0249] In some embodiments, blocks of electrically insulating material (for
example,
magnesium oxide) are compacted in the fitting. In some embodiments,
electrically
insulating material powder is compacted in the fitting. In some embodiments,
combinations of powder and/or blocks of electrically insulating material are
used in the
fitting. In addition, combinations of different types of electrically
insulating material may
be used (for example, a combination of magnesium oxide and boron nitride).
[0250] In embodiments described herein that use electrically insulating
material powder,
the powder has selected properties that provide for better compaction (higher
density when
compacted). In some embodiments, the powder has a selected particle size
distribution (for
example. the size distribution may average between about 100 1.tm and about
200 [tm for
magnesium oxide powder). A desired range may be selected such that the powder
compacts to a desired density. Other properties of the powder that may be
selected to
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provide a desired density under compaction include, but are not limited to,
particle shape,
impurity properties (for example, ratios of impurities such as silicon or
calcium), wall
friction properties (wall friction angle), compactibility under standardized
force
(compaction in a standard size cylinder under the same force), and hopper
angle to achieve
mass flow in a hopper. The combination of one or more of these properties may
be
indicators the compactibility of the powder and/or the ability of the powder
to flow during
compression or compaction.
[0251] A fitting used to join insulated conductors may be compacted
mechanically.
pneumatically, and/or hydraulically. Compaction of the fitting may improve the
dielectric
characteristics of the electrically insulating material such that the
electrically insulating
material has dielectric characteristics that are similar to the dielectric
characteristics of
electrical insulation in the insulated conductors. In some embodiments,
compacted
electrically insulating material in the fitting may have dielectric
characteristics that are
better than the dielectric characteristics of electrical insulation in the
insulated conductors.
[0252] As an example, electrical insulation (magnesium oxide) in an insulated
conductor
typically has a density of between about 78% and about 82%. Uncompacted
magnesium
oxide powder may have a density of between about 50% and about 55%. Magnesium
oxide blocks may have a density of about 70%. In certain embodiments of
fittings
described herein, the electrical insulation inside the fitting after
compaction or compression
has a density that is at least within about 15%, within about 10%, or within
about 5% of the
density of the insulated conductors coupled to the fitting. In some
embodiments described
herein, the electrical insulation inside the fitting after compaction or
compression has a
higher density than the density of the insulated conductors coupled to the
fitting. For
example, the electrical insulation inside the fitting may have a density up to
about 85%.
[0253] In certain embodiments described herein, a reinforcement sleeve or
other strain
relief is placed at or near the coupling of insulated conductors. FIG. 38
depicts an
embodiment of reinforcement sleeves 328 on joined insulated conductors 212A,
212B.
Reinforcement sleeves 328 provide strain relief to strengthen the coupling
between the
insulated conductors. Reinforcement sleeves 328 allow the joined insulated
conductors to
be spooled, unspooled, and pulled in tension for installation/removal in
wellbores and/or in
an installation conduit (for example, coiled tubing installation).
[0254] FIG. 39 depicts an exploded view of another embodiment of fitting 270
used for
coupling three insulated conductors 212A, 212B, 212C. In certain embodiments,
fitting
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270 includes strain relief fitting 274, electrical bus 330, cylinder 332, and
end cap 272.
FIGS. 40-47 depict an embodiment of a method for installation of fitting 270
onto ends of
insulated conductors 212A, 212B, 212C.
[0255] In FIG. 40, insulated conductors 212A. 212B, 212C are passed through
longitudinal
openings in strain relief fitting 274. Strain relief fitting 274 may be an end
termination for
insulated conductors 212A, 212B, 212C. After installation of insulated
conductors 212A,
212B, 212C into strain relief fitting 274, insulated conductors 212A, 212B,
212C are
aligned in the strain relief fitting and a portion of cores 214A, 214B, 214C
protruding from
the fitting are exposed. Cores 214A, 214B, 214C are exposed by removing end
portions of
the jackets and electrical insulators of insulated conductors 212A, 212B, 212C
that extend
through strain relief fitting 274.
[0256] In certain embodiments, end portions of cores 214A, 214B, 214C
extending
through strain relief fitting 274 are brazed to the strain relief fitting.
Examples of materials
for brazing include, but are not limited to, nickel brazes such as AWS 5.8 BNi-
2 for low
sulfur environments and AWS 5.8 BNi-5A for high sulfur environments. The
brazing
material may flow during brazing and fill and seal any gaps between cores
214A, 214B,
214C and strain relief fitting 274. Sealing the gaps prevent fluids from
flowing into the
inside of fitting 270. Brazing end portions of cores 214A, 214B, 214C to
strain relief
fitting 274 may allow for the cores to be spaced closer together and reduce
the size of the
strain relief fitting. Having a smaller strain relief fitting 274 may allow
fitting 270 and the
wellbore for the heater to be smaller in diameter as typically the end
termination (fitting
270) is the determining factor in wellbore size. In some embodiments, the
jackets of
insulated conductors 212A, 212B, 212C are coupled to strain relief fitting
274. For
example, the jackets may be welded (seam welded) to strain relief fitting 274.
[0257] In FIG. 41, first cylinder 332A is coupled to the end of strain relief
fitting 274 with
protruding cores 214A, 214B, 214C. First cylinder 332A may be welded into
place on the
end of strain relief fitting 274. First cylinder 332A may have a longitudinal
length less
than the length of protruding cores 214A, 214B, 214C. Thus, at least some
portion of the
cores may extend beyond the length of first cylinder 332A.
[0258] Following coupling of first cylinder 332A to strain relief fitting 274,
electrically
insulating material 256 is added into the cylinder to at least partially cover
cores 214A,
214B, 214C, as shown in FIG. 42. Thus, at least a portion of the cores remain
exposed
above electrically insulating material 256. Electrically insulating material
256 may include
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powder and/or blocks of electrically insulating material (for example,
magnesium oxide).
In certain embodiments, electrically insulating material 256 is compacted
inside first
cylinder 332A. Electrically insulating material 256 may be hydraulically
and/or
mechanically compacted using a compaction tool. For example, force may be
applied to
the compaction tool using a piston of a hydraulic compaction machine. FIG. 48
depicts an
embodiment of compaction tool 334A that can be used to compact electrically
insulating
material 256. Compaction tool 334A may have openings that allow the tool to
fit over
cores 214A, 214B, 214C while compacting electrically insulating material.
After
compaction in the above step and later described steps, the surface of
electrically insulating
material 256 may be scarred. Scarring the surface of electrically insulating
material 256
promotes bonding between layers of electrically insulating material during
compaction of
the layers.
[0259] In certain embodiments, after compaction of electrically insulating
material 256 in
cylinder 332A, the portion cores 214A, 214B, 214C that remain exposed are
coupled to
electrical bus 330, as shown in FIG. 43. Electrical bus 330 may be, for
example, copper or
another material suitable for electrically coupling cores 214A. 214B, 214C
together. In
some embodiments, electrical bus 330 is welded to cores 214A, 214B, 214C.
[0260] After coupling electrical bus 330 to cores 214A, 214B, 214C, second
cylinder 332B
may be coupled to first cylinder 332A to form cylinder 332 around the exposed
portions of
the cores, as shown in FIG. 44. In some embodiments, cylinder 332 is a single
cylinder
coupled to strain relief fitting 274 in a single step. In some embodiments,
cylinder 332
includes two or more cylinders coupled to strain relief fitting 274 in
multiple steps.
[0261] Second cylinder 332B may be welded into place on the end first cylinder
332A. As
shown in FIG. 44, completed cylinder 332 may have a longitudinal length that
extends
beyond the length of protruding cores 214A, 214B, 214C. Thus, the cores may
are
contained within the boundaries of cylinder 332.
[0262] Following formation of cylinder 332, electrically insulating material
256 is added
into the cylinder to a level that is about even with the top of cores 214A,
214B, 214C and
electrical bus 330, as shown in FIG. 45. In certain embodiments, electrically
insulating
material 256 at the level shown in FIG. 45 is compacted (for example,
mechanically
compacted). FIG. 49 depicts an embodiment of compaction tool 334B that can be
used to
compact electrically insulating material 256. Compaction tool 334B may have an
annulus
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that allows the tool to fit over electrical bus 330 and cores 214A, 214B, 214C
while
compacting electrically insulating material.
[0263] Following compaction of material at the level of the top of electrical
bus 330 and
cores 214A, 214B, 214C, additional electrically insulating material 256 is
added into the
cylinder to completely cover the electrical bus and the cores, as shown in
FIG. 46. Thus,
the cores and electrical bus are substantially enclosed in electrically
insulating material
256. In certain embodiments, electrically insulating material 256 added into
cylinder 332
to enclose the cores is compacted (for example, mechanically compacted). FIG.
50 depicts
an embodiment of compaction tool 334C that can be used for the final
compaction of
electrically insulating material 256.
[0264] After final compaction of electrically insulating material 256, end cap
272 is
coupled (welded) to cylinder 332 to form fitting 270. In some embodiments, end
cap 272
is shaped to be used as a guide for guiding the installation of insulated
conductors 212A,
212B, 212C into a wellbore or a deployment device (for example, coiled tubing
installation). In some embodiments, fitting 270 is used with insulated
conductors operating
as single phase heaters. For example, fitting 270 may be used with two
insulated
conductors coupled in a hairpin configuration with the insulated conductors
coupled inside
the fitting to have one insulated conductor as the supply conductor and one as
the return
conductor. Fitting 270 may also be used with one insulated conductor that uses
the jacket
of the insulated conductor to return current to the surface of the formation.
[0265] Mechanical compaction of electrically insulating material inside
fitting 270 may
produce a fitting with a higher mechanical breakdown voltage and/or operating
temperature than fittings that are filled with electrically insulating
material and vibrated for
compaction of the electrically insulating material. For example, fitting 270
may be
operable at voltages above about 6 kV and temperatures above about 1300 F
(about 700
C). Because fitting 270 (the heater end termination) is operable at
temperatures above
about 700 C, the fitting may be usable in heated layers of a subsurface
formation (for
example, layers undergoing pyrolyzation). Thus, the end of a heater does not
have to be
placed in a cooler portion of the formation and the heater wellbore may not
need to be
drilled as deep into the formation or into different types of formation.
[0266] In certain embodiments, a failed three-phase heater is converted to
single-phase
operation using the same power supply. If, for example, one leg of a three-
phase heater
fails (ground-faults), the remaining two legs of the heater can be used as a
single-phase
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heater with one leg being the supply conductor and the other leg being the
return
conductor. To convert the heater to single-phase operation, a high impedance
resistor may
be put between the neutral of the three-phase power supply (transformer) and
the ground-
faulted leg of the heater. The resistor is put in series with the ground-
faulted leg of the
heater. Because of the high resistance of the resistor, voltage is taken off
the ground-
faulted leg and put across the resistor. Thus, the resistor is used to
disconnect power to the
ground-faulted leg with little or no current passing through the ground-
faulted leg. After
the resistor is put between the neutral of the transformer and the ground-
faulted leg, the
remaining two legs of the heater operate in a single-phase mode with current
going down
one leg, passing through an end termination, and returning up the other leg.
[0267] During three-phase operation of the heater, the voltage at the end
termination is
near zero as the three legs operate 120 out of phase to balance the voltages
between the
three legs (voltage may not be exactly zero if there is any misbalance between
the legs in
the circuit). The end termination is typically isolated from ground for the
three-phase
heater. When the heater is converted to single-phase, the voltage on the end
termination
increases from the near zero voltage to about half the output voltage of the
power supply.
The voltage on the end termination increases during single-phase operation as
current now
passes linearly through the two operating legs with the end termination being
at the
halfway point of the circuit. As an example, during three-phase operation with
a 480V
power supply, each leg may be at about 277 V with about 0 V at the end
termination at the
bottom of the heater. After conversion to single-phase operation with the
resistor in series
with the ground-faulted leg, the legs operating in single-phase produce a
voltage of about
240V at the end termination at the bottom of the heater.
[0268] Because voltages for heating subsurface or hydrocarbon containing
formations to
mobilization and/or pyrolyzation temperatures are typically very high due to
the long
lengths of the heaters (for example, about 1 kV or higher), the end
termination needs to be
able to operate at even higher voltages to be used for single-phase operation.
Current end
terminations used in subsurface heating are not typically operable at such
high voltages.
Because fitting 270, however, is operable at voltages above 6 kV, fitting 270
allows a
.. failed high voltage three-phase subsurface heater to be converted to a
single-phase
operation.
Examples
[0269] Non-restrictive examples are set forth below.
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Samples using fitting embodiment depicted in FIG. 5
[0270] Samples using an embodiment of fitting 250 similar to the embodiment
depicted in
FIG. 5 were fabricated using a hydraulic compaction machine with a medium
voltage
insulated conductor suitable for use as a subsurface heater on one side of the
fitting and a
medium voltage insulated conductor suitable for use as an overburden cable on
the other
side of the fitting. Magnesium oxide was used as the electrically insulating
material in the
fittings. The samples were 6 feet long from the end of one mineral insulated
conductor to
the other. Prior to electrical testing, the samples were placed in a 6-1/2 ft
long oven and
dried at 850 F for 30 hours. Upon cooling to 150 F, the ends of the mineral
insulated
conductors were sealed using epoxy. The samples were then placed in an oven 3
feet long
to heat up the samples and voltage was applied to the samples using a 5 kV
(max) hipot
(high potential) tester, which was able to measure both total and real
components of the
leakage current. Three thermocouples were placed on the samples and averaged
for
temperature measurement. The samples were placed in the oven with the fitting
at the
center of the oven. Ambient DC (direct current) responses and AC (alternating
current)
leakage currents were measured using the hipot tester.
[0271] A total of eight samples were tested at about 1000 F and voltages up
to 5 kV. One
individual sample tested at 5 kV had a leakage current of 2.28 mA, and another
had a
leakage current of 6.16 mA. Three more samples with cores connected together
in parallel
were tested to 5 kV and had an aggregate leakage current of 11.7 mA, or 3.9 mA
average
leakage current per cable, and the three samples were stable. Three other
samples with
cores connected together in parallel were tested to 4.4 kV and had an
aggregate leakage
current of 4.39 mA, but they could not withstand a higher voltage without
tripping the
hipot tester (which occurs when leakage current exceeds 40 mA). One of the
samples
tested to 5 kV underwent further testing at ambient temperature to breakdown.
Breakdown
occurred at 11 kV.
[0272] A total of eleven more samples were fabricated for additional breakdown
testing at
ambient temperature. Three of the samples had insulated conductors prepared
with the
mineral insulation cut perpendicular to the jacket while the eight other
samples had
insulated conductors prepared with the mineral insulation cut at a 300 angle
to the jacket.
Of the first three samples with the perpendicular cut, the first sample
withstood up to 10.5
kV before breakdown, the second sample withstood up to 8 kV before breakdown,
while
the third sample withstood only 500 V before breakdown, which suggested a flaw
in
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fabrication of the third sample. Of the eight samples with the 300 cut, two
samples
withstood up to 10 kV before breakdown, three samples withstood between 8 kV
and 9.5
kV before breakdown, and three samples withstood no voltage or less than 750
V, which
suggested flaws in fabrication of these three samples.
Samples using fitting embodiment depicted in FIG. 8B
[0273] Three samples using an embodiment of fitting 270 similar to the
embodiment
depicted in FIG. 8B were made. The samples were made with two insulated
conductors
instead of three and were tested to breakdown at ambient temperature. One
sample
withstood 5 kV before breakdown, a second sample withstood 4.5 kV before
breakdown,
and a third sample could withstand only 500 V, which suggested a flaw in
fabrication.
Samples using fitting embodiment depicted in FIGS. 14 and 15
[0274] Samples using an embodiment of fitting 298 similar to the embodiment
depicted in
FIGS. 14 and 15 were used to connect two insulated conductors with 1.2"
outside
diameters and 0.7" diameter cores. MgO powder (Muscle Shoals Minerals,
Greenville,
Tennessee, U.S.A.) was used as the electrically insulating material. The
fitting was made
from 347H stainless steel tubing and had an outside diameter of 1.5" with a
wall thickness
of 0.125" and a length of 7.0". The samples were placed in an oven and heated
to 1050 F
and cycled through voltages of up to 3.4 kV. The samples were found to viable
at all the
voltages but could not withstand higher voltages without tripping the hipot
tester.
[0275] In a second test, samples similar to the ones described above were
subjected to a
low cycle fatigue-bending test and then tested electrically in the oven. These
samples were
placed in the oven and heated to 1050 F and cycled through voltages of 350 V,
600 V, 800
V, 1000 V, 1200 V, 1400 V, 1600 V, 1900 V, 2200 V, and 2500 V. Leakage current
magnitude and stability in the samples were acceptable up to voltages of 1900
V. Increases
in the operating range of the fitting may be feasible using further electric
field intensity
reduction methods such as tapered, smoothed, or rounded edges in the fitting
or adding
electric field stress reducers inside the fitting.
[0276] It is to be understood the invention is not limited to particular
systems described
which may, of course, vary. It is also to be understood that the terminology
used herein is
for the purpose of describing particular embodiments only, and is not intended
to be
limiting. As used in this specification, the singular forms "a", "an" and
"the" include
plural referents unless the content clearly indicates otherwise. Thus, for
example,
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reference to "a core" includes a combination of two or more cores and
reference to "a
material" includes mixtures of materials.
[0277] Further modifications and alternative embodiments of various aspects of
the
invention will be apparent to those skilled in the art in view of this
description.
Accordingly, this description is to be construed as illustrative only and is
for the purpose of
teaching those skilled in the art the general manner of carrying out the
invention. It is to be
understood that the forms of the invention shown and described herein are to
be taken as
the presently preferred embodiments. Elements and materials may be substituted
for those
illustrated and described herein, parts and processes may be reversed, and
certain features
of the invention may be utilized independently, all as would be apparent to
one skilled in
the art after having the benefit of this description of the invention. Changes
may be made
in the elements described herein without departing from the spirit and scope
of the
invention as described in the following claims.
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