Note: Descriptions are shown in the official language in which they were submitted.
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ELECTRICAL CABLE
BACKGROUND
[0001] The invention generally relates to an electrical cable, such as
(as an
example) a multi-conductor electrical cable of the type used in an oilfield
wireline
logging operation for purposes of analyzing geologic formations adjacent a
wellbore.
[0002] Generally, geologic formations within the earth that contain
oil and/or
petroleum gas have properties that may be linked with the ability of the
formations to
contain such products. For example, formations that contain oil or petroleum
gas
have higher electrical resistivities than those that contain water. Formations
that
primarily include sandstone or limestone may contain oil or petroleum gas.
Formations that primarily include shale, which may also encapsulate oil-
bearing
formations, may have porosities much greater than that of sandstone or
limestone,
but, because the grain size of shale is very small, it may be very difficult
to remove
the oil or gas trapped therein. Accordingly, logging operations are often
conducted in
the well before its completion for purposes of measuring various
characteristics of the
geologic formations adjacent to the well to help in determining the location
of an oil-
and/or petroleum gas-bearing formation, as well as the amount of oil and/or
petroleum gas trapped within the formation and the ease of removing the oil
and/or
petroleum gas from the formation.
[0003] Therefore, after a well is drilled, it is common to log certain
sections of the
well with electrical instruments called logging tools. A wireline instrument
is one
type of logging tool. The wireline instrument is lowered downhole on a cable
called a
"wireline cable" for purposes of measuring the properties of geologic
formations as
the instrument traverses the well. The wireline cable electrically connects
the
wireline instrument with equipment at the earth's surface, as well as provides
structural support to the instrument as it is lowered and raised in the well
during the
logging operation.
[0004] The wireline cable typically contains an infrastructure to
communicate
power to the wireline instrument and communicate telemetry data from the
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instrument to a surface logging unit. Because downhole temperatures and
pressures
may reach, for example, 500 Fahrenheit (F) and sometimes up to 25,000 pounds
per
square inch (psi), the wireline cable typically is designed to withstand
extreme
environmental conditions. Because wells are being drilled to deeper depths,
the
electricity and telemetry requirements of the wireline cable are ever
increasing. Thus,
in view of these more stringent requirements, the wireline cable designer is
presented
with challenges related to maintaining or increasing the signal-to-noise ratio
(SNR) of
the telemetry signals, minimizing telemetry signal attenuation, as well as
accommodating the delivery of high power downhole.
SUMMARY
[0005] In an embodiment of the invention, an electrical cable includes
insulated
primary conductors and at least one insulated secondary conductor, which
extend
along the cable. The primary conductors define interstitial spaces between
adjacent
primary conductors, and the primary conductors have approximately the same
diameter. The primary conductors include power conductors and at least one
telemetric conductor. The secondary conductor(s) preferably each have a
diameter
that is smaller than each of the diameters of the primary conductors, and each
secondary conductor is at least partially nested in one of the interstitial
spaces. The
electrical cable also includes at least one armor wire layer, which surrounds
the
primary and secondary conductors.
[0006] In another embodiment of the invention, an electrical cable includes
insulated primary conductors; at least one insulated secondary conductor;
layers of
inner and outer armor wires; a polymeric material; and an outer jacket. The
insulated
primary conductors extend along the cable, and a telemetric primary conductor
extends along the cable and defines interstices between adjacent primary
conductors.
The insulated primary conductors and the telemetric conductor have
approximately
the same diameter. Each secondary conductor has a diameter that is smaller
than the
diameter of each of the primary conductors and extends along the longitudinal
axis of
the cable. Each secondary conductor is at least partially nested in one of the
interstices. The layer of inner armor wires surrounds the insulated primary
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conductors, the telemetric primary conductor and the secondary conductor(s).
The layer of
outer armor wires surrounds the layer of inner armor wires. The polymeric
material is
disposed in the interstitial spaces that are formed between the inner armor
wires and the outer
armor wires and interstitial spaces that are formed between the inner armor
wire layer and the
insulated conductor. The polymeric material forms a continuously bonded layer,
which
separates and encapsulates armor wires forming the inner armor wire layer and
the outer wire
layer. The outer jacket is disposed around and bonded to the polymeric
material.
[0007] In yet another embodiment of the invention, a method includes
providing a
cable in a well; and including insulating primary conductors in the cable,
which define
interstitial spaces between adjacent primary conductors and have approximately
the same
diameter. The primary conductors include power conductors and a telemetric
conductor. The
method includes disposing at least one insulated secondary conductor having a
diameter
smaller than the primary conductor at least partially in one of the
interstitial spaces defined by
the primary conductors; and encasing the cable with an armor shield.
[0007a] In still another embodiment of the invention, there is provided an
electrical
cable defining a longitudinal axis and usable with a well, comprising: a
plurality of insulated
primary power conductors extending along the cable and a shielded telemetric
primary
conductor extending along the cable and defining interstices between adjacent
primary
conductors, the insulated primary conductors and the telemetric primary
conductor having
approximately the same diameter, the telemetric primary conductor including a
plurality of
telemetry conductors; a plurality of insulated secondary conductors each
having a diameter
smaller than the diameter of each of the primary conductors and extending
along the
longitudinal axis of the cable, each of said secondary conductors at least
partially nested in
one of the interstices; a layer of inner armor wires surrounding said
insulated primary
conductors, said telemetric primary conductor, and said at least one insulated
secondary
conductor; a layer of outer armor wires surrounding the layer of inner armor
wires, said
primary conductors, said secondary conductor, and said armor wires defining
interstices
therebetween; a polymeric material disposed in the interstices formed between
the inner armor
wires and the outer armor wires and in interstitial spaces formed between the
inner armor wire
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layer and insulated conductor, the polymeric material forming a continuously
bonded layer
which separates and encapsulates said inner armor wire layer and said outer
armor wire layer;
and an outer jacket disposed around and bonded with said polymeric material.
[0008] Advantages and other features of the invention will become
apparent from the
detailed description, drawing and claims.
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BRIEF DESCRIPTION OF THE DRAWING
[0009] Fig. 1 is a schematic diagram of a wireline-based logging
acquisition
system according to an embodiment of the invention.
[0010] Fig. 2 is a cross-sectional view of a wireline cable taken along
line 2-2 of
Fig. 1 according to an embodiment of the invention.
[0011] Fig. 3 is a cross-sectional view of a primary power conductor of the
wireline cable according to an embodiment of the invention.
[0012] Fig. 4 is a cross-sectional view of a primary telemetric conductor
of the
wireline cable according to an embodiment of the invention.
[0013] Fig. 5 is a cross-sectional view of a secondary conductor of the
wireline
cable according to an embodiment of the invention.
[0014] Fig. 6 depicts signal level versus frequency plots for the wireline
cable of
Fig. 1 and for a conventional wireline cable.
[0015] Figs. 7, 9, 10, 11 and 12 are cross-sectional views of wireline
cables
according to other embodiments of the invention.
[0016] Fig. 8 is a perspective view of a wireline cable depicting a partial
cut-away
section according to another embodiment of the invention.
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DETAILED DESCRIPTION
[0017] Fig. 1 depicts a wireline-based logging acquisition
system 10 in
accordance with embodiments of the invention. The system 10 includes a
wireline
logging instrument, or tool 28, which is deployed in a cased (as shown) or
uncased
borehole 20 and a wireline cable 24 that structurally and electrically
connects the
wireline logging tool 28 with equipment at the earth's surface. As described
herein,
the wireline cable 24 includes power and telemetry conductors for purposes of
communicating power and telemetry data between the equipment at the surface
and
the tool 28. The well being logged by the system 10 may be a subterranean or
subsea
well.
[0018] As depicted in Fig. 1, the wireline cable 24 may be
deployed via a truck
15, which contains a wireline spool, which lowers and raises the wireline tool
28 into
the borehole 20 in connection with the logging operation. The logging tool 28
may
include a gamma-ray emitter/receiver, a caliper device, a resistivity-
measuring
device, a neutron emitters/receivers or a combination of these devices, as
just a few
examples.
[0019] Referring to Fig. 2, in accordance with embodiments of
the invention
described herein, the wireline cable 24 has features that, as compared to
prior art
cables, provide a relatively high power delivery capacity; a relatively high
degree of
structural integrity; and a relatively high signal strength, a relatively low
noise floor
and a relatively wide bandwidth for the telemetry communications. To
accomplish
this, the wireline cable 24 includes heavy gauge (i.e., large diameter)
primary
conductors: two similarly-sized primary conductors 60 for purposes of
communicating a high level of power downhole; and a primary telemetric
conductor
80, which has a diameter that is approximately the same as each of the primary
power
conductors 60. By using relatively heavy gauge primary conductors, more
conductive material, such as copper, may be packed into a given cross-
sectional area
of the wireline cable 24. Thus, the cable 24 provides increased power delivery
capacity when compared to a standard heptacable, for example. Furthermore, the
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cabling of the three relatively large diameter primary conductors together
creates a
mechanically stable base for the cable 24.
[0020] The wireline cable 24 also includes secondary conductors 70 (three
conductors 70, for example), which are smaller in size (i.e., have relatively
smaller
diameters) than the primary conductors 60 and 80 and which may be used, for
example, for purposes of communicating three phase power to the logging tool
28
(see Fig. 1). Alternatively, the secondary conductors 70 may be used for
purposes of
communicating low power, such as DC or single phase power, and one of the
secondary conductors 70 may be used as a spare, for example. As another
variation,
one of the secondary conductors 70 may be used as a return path for power that
is
communicated downhole via the primary power conductors 60. Thus, many
applications of the secondary conductors 70 are contemplated and are within
the
scope of the appended claims. Also, combinations between the primary power
conductors 60 and the secondary power conductors 70 may be used to create
alternative telemetry modes.
[0021] As depicted in Fig. 2, in accordance with embodiments of the
invention,
the primary conductors 60 and 80 are arranged in a triangular configuration
about a
longitudinal axis of the wireline cable 24, an arrangement which defines
interstitial
spaces 40 between each pair of adjacent primary conductors 60, 80. Each
secondary
conductor 70, being smaller in size, is preferably at least partially nested
in one of the
interstitial spaces 40, in accordance with some embodiments of the invention.
The
primary conductors 60 and 80 may be twisted or wound about the longitudinal
axis of
the wireline cable 24, in accordance with some embodiments of the invention.
Alternatively, the primary conductors 60 and 80 are twisted together about at
least
one secondary conductor 70.
[0022] The primary telemetric conductor 80, primary power conductors 60 and
secondary power conductors 70 each preferably includes metallic conductors
that are
encased in an insulated jacket. Any suitable metallic conductors may be used.
Examples of metallic conductors include, but are not necessarily limited to,
copper,
nickel coated copper, or aluminum. While any suitable number of metallic
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conductors may be used in forming one of these insulated conductors,
preferably
from 1 to about 60 metallic conductors are used in a particular insulated
conductor,
and more preferably 7, 19, or 37 metallic conductors may be used.
[0023] The insulated jackets may include any of a wide variety of suitable
materials. Examples of suitable insulated jacket materials include, but are
not
necessarily limited to, polytetrafluoroethylene-perfluoromethylvinylether
polymer
(MFA), perfluoro-alkoxyalkane polymer (PFA), polytetrafluoroethylene polymer
(PTFE), ethylene-tetrafluoroethylene polymer (ETFE), ethylene-propylene
copolymer
(EPC), poly(4-methy1-1 -pentene) (TPX available from Mitsui Chemicals, Inc.),
other polyolefins, other fluoropolymers, polyaryletherether ketone polymer
(PEEK),
polyphenylene sulfide polymer (PPS), modified polyphenylene sulfide polymer,
polyether ketone polymer (PEK), maleic anhydride modified polymers, Parmax
SRP polymers (self-reinforcing polymers manufactured by Mississippi Polymer
Technologies, Inc based on a substituted poly (1,4-phenylene) structure where
each
phenylene ring has a sub stituent R group derived from a wide variety of
organic
groups), or the like, and any mixtures thereof.
[0024] As depicted in Fig. 3, the primary power conductor 60 has a diameter
Di
and includes inner metallic conductors 62 at the core of the conductor 60,
which
extend along the primary power conductor's 60 longitudinal axis. The inner
metallic
conductors 62 are surrounded by an insulated jacket 63.
[0025] Referring to Fig. 4, the primary telemetric conductor 80 is, in
accordance
with some embodiments of the invention, a coaxial conductor that includes an
inner
core of metallic conductors 82 that extend along the telemetric conductor's 80
longitudinal axis. Although the inner metallic core of the telemetric primary
conductor 80 is smaller than the corresponding inner metallic core of the
primary
power conductor 60, the primary telemetric conductor 80 includes a relatively
larger
insulative jacket 84 such that the diameter (called "D2" in Fig. 4) of the
primary
telemetric conductor 80 is approximately the same size as the DI diameter (see
Fig. 3)
of the primary power conductor 60.
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[0026] As also depicted in Fig. 4, the primary telemetric conductor 80
includes an
outer metallic shield 86 (a copper or copper alloy, as examples) for purposes
of
shielding the inner metallic conductors 82 of the conductor 80 from
interference that
might otherwise originate, for example, from the power transmissions that
occur via
the primary power 60 and secondary 70 conductors.
[0027] The metallic shield 86 may be any suitable metal or material, which
serves
to substantially decouple the telemetry that is provided by the inner
conductors 82 of
the conductor 80 from power transmission. Alternatively, the outer metallic
shield 86
is surrounded by a tape or polymeric layer 87 that is disposed on top of the
layer 86,
in accordance with some embodiments of the invention.
[0028] The inner metallic conductors of the primary 60, 80 and secondary 70
conductors may be of any suitable size, also known as American Wire Gauge
(AWG). In some embodiments, the metallic conductors range in gauge from 8 AWG
to 32 AWG, including all gauges sizes therebetween (i.e. 9, 10, 11, 12,13, 14,
15, 16,
17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, and 31 AWG). In some
embodiments of the invention, metallic conductors that are used in the
telemetric
primary conductor 80 may be in a range from 28 AWG to 18 AWG in size. In some
embodiments of the invention, the metallic conductors in the primary power
conductors 60 are in a range from 14 AWG to 10 AWG. In some embodiments of the
invention, the secondary conductor 70 includes metallic conductors of wire
gauge
ranging from 16 AWG to 24 AWG.
[0029] Referring back to Fig. 2, in accordance with embodiments of the
invention, the wireline cable 24 includes a multiple layer armor wire housing,
or
shield 50, which surrounds the primary 60, 80 and secondary 70 conductors of
the
cable 24. In this regard, in accordance with some embodiments of the
invention, the
armor shield 50 includes an inner armor wire wrapping 50b that helically
extends in a
first direction (a counter clockwise direction, for example) about the cable's
longitudinal axis and a second outer helical wrapping 50a that helically
extends in the
opposite wrapping direction (a clockwise direction, for example) about the
cable's
longitudinal axis. Thus, the wrappings 50a and 50b are contra-helically wound
armor
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wire layers, in accordance with some embodiments of the invention. The wires
used
to form the armor shield 50 may be steel wires, metals, bimetallics wires,
wire rope
strands and non-metal wires, as just a few examples. Thus, many variations are
contemplated and are within the scope of the appended claims.
[0030] The primary 60, 80 and secondary 70 conductors define various
interstitial
spaces (in addition to the interstitial spaces 40 which at least partially
receive the
secondary conductors 70), and the cable 24 includes an insulative material
100, such
as a polymeric material, that is disposed in these spaces. Furthermore,
although not
depicted in Fig. 2, the wireline cable 24 may include additional insulative
material,
such as polymeric material, that is disposed in the interstitial spaces formed
between
the armor wire wrappings 50a and 50b. Also, the polymeric material may form a
polymeric jacket around an outer or second layer of armor wires. The polymeric
material may be chosen and processed in such a way as to prevent a
continuously
bonded layer of material and which may encase the armor shield 50.
[0031] As examples, suitable polymeric materials include EPDM, polyolefins
(such as EPC or polypropylene), other polyolefins, polyaryletherether ketone
(PEEK),
polyaryl ether ketone (PEK), polyphenylene sulfide (PPS), modified
polyphenylene
sulfide, polymers of ethylene-tetrafluoroethylene (ETFE), polymers of poly(1,4-
phenylene), polytetrafluoroethylene (PTFE), perfluoroalkoxy (PFA) polymers,
fluorinated ethylene propylene (FEP) polymers, polytetrafluoroethylene-
perfluoromethylvinylether (MFA) polymers, Parmax , and any mixtures thereof
Other polymeric materials that may be used include ethylene-
tetrafluoroethylene
polymers, perfluoroalkoxy polymers, fluorinated ethylene propylene polymers,
polytetrafluoroethylene-perfluoromethylvinylether polymers, and any mixtures
thereof
[0032] The wireline cable 24 may also include a bedding layer 94, such as a
layer
formed from a binder tape and a polymeric material, which surrounds the
primary 60,
80 and secondary 70 conductors.
[0033] In accordance with some embodiments of the invention, the wireline
cable
24 may have an overall diameter, which includes the armor shield 50, of less
than
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about 2.5 centimeters, such as approximately 1.4 centimeters, as a more
specific and
non-limiting example. Furthermore, in accordance with some embodiments of the
invention, the wireline cable 24 may have a minimum bending radius of about
10.1
centimeters. The wireline cable 24 may have other suitable overall diameters,
bending stiffnesses and other physical characteristics, in accordance with
other
embodiments of the invention, as will be appreciated by those skilled in the
art.
[0034] Among the particular advantages of the wireline cable 24, the cable
24
combines high mechanical stability, high power capability and shielded co-
axial
telemetry. Mechanical stability is provided by the basic design, as the three
large
components, i.e., the primary conductors 60 and 80, are less likely to shift
under
pressure and thus, less likely to allow smaller conductors, such as the
secondary
conductors 70 and other communication lines (further described below) of the
cable
24 to become damaged. Because the larger primary power conductors 60 are used
for
the larger power requirements, the conductors 60 have lower impedances, which
translates to lower cable losses and deeper reach, as compared to power
conductors in
conventional wireline cables. It is noted that lower power transmission may be
handled by the relatively lower secondary power conductors 70. As noted above,
all
three conductors 70 may be configured to provide three phase power, in
accordance
with some embodiments of the invention.
[0035] Fig. 6 depicts a signal level versus frequency plot 130 of the
telemetry
channel provided by wireline cable 24, in accordance with some embodiments of
the
invention. As shown by the plot 130, the frequency response rolls off at a
significantly higher frequency than a frequency plot 120 which characterizes
the
telemetry channel of a heptacable, for example. As a result, the wireline
cable 24 has
a significantly higher data capacity 132 than a data capacity 122 of the
heptacable, for
example.
[0036] Fig. 7 depicts a cross-sectional view of a wireline cable 150 in
accordance
with an embodiment of the invention. The wireline cable 150 has a similar
design to
the wireline cable 24, with like reference numerals being used to identify
similar
components. However, unlike the wireline cable 24, the wireline cable 150
includes a
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filler rod (a fluoropolymer rod, for example) or an optical fiber 154 disposed
in one of
the primary power conductors 60; and the wireline cable 150 also includes a
filler rod
or optical fiber 158 disposed along the longitudinal axis of the wireline
cable 150 in
the center interstitial space that is created between the three primary
conductors 60
and 80. Thus, in accordance with embodiments of the invention, an optical
fiber or
filler rod component may be placed at the center of the cable 150 or may be
incorporated into one of the primary 60, 80 or secondary 70 conductors.
[0037] Fig. 8 depicts a perspective view of a wireline cable 170 in
accordance
with an embodiment of the invention. The wireline cable 170 has a similar
design to
the wireline cable 150 (see Fig. 7) with like reference numerals being used to
identify
similar components. Unlike the wireline cable 150, the wireline cable 170
includes a
single filler rod/optical fiber 158 that extends along the longitudinal axis
of the cable
170 and does not include an optical fiber or filler rod in any of the
conductors. As
depicted in Fig. 8, the wireline cable 170 may have tape 176 disposed over the
conductors and polymeric material 100, as well as the outer metallic shield 86
for the
primary telemetric conductor 80. The wireline cable 170 may also include a
bedding
layer or jacket 94, such as a layer formed from a binder tape and a polymeric
material, which surrounds the primary 60, 80 and secondary 70 conductors.
[0038] Fig. 9 depicts a cross-sectional view of a wireline cable 200 in
accordance
with an embodiment of the invention. In general, the wireline cable 200 has a
similar
design to the wireline cable 24 of Fig. 2, with like reference numerals being
used to
identify similar components. However, the wireline cable 200 has a primary
telemetric conductor 202 that replaces the primary telemetric conductor 80 of
the
wireline cable 24. The primary telemetric cable 202, in general, has
approximately
the same diameter as the two primary power conductors 60, but unlike the
conductor
80 of the wireline cable 24, the conductor 202 employs quad or quadrature
telemetry.
In this regard, the conductor 202 has four telemetry conductors 210 that are
located
and shielded by the surrounding metallic shield 86, an arrangement that
permits two
orthogonal telemetry transmission paths.
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[0039] The primary telemetric conductor 202 may also include filler rods
225 and
drain wires 220, which may be alternated with the filler rods at the outside
interstitial
spaces formed between the conductors 210.
[0040] The shielded design is advantageous for applications requiring high
signal-to-noise ratios and lower frequencies. Alternatively, the shield may be
omitted
if lower signal-to-noise ratios and higher frequencies are desired.
[0041] Fig. 10 depicts a cross-sectional view of a wireline cable 250 in
accordance with an embodiment of the invention. In general, the wireline cable
250
has a similar design to the wireline cable 200, with like reference numerals
being
used to identify similar components. However, unlike the wireline cable 200,
the
wireline cable 250 includes an optical cable 254 that extends along the center
of one
of the primary power conductors 60. Also, an optical fiber 265 may extend
along the
longitudinal axis of the cable 250. Furthermore, the center filler rods 220 of
the
wireline cable 200 in the primary telemetric conductor 202 is replaced in Fig.
10 with
an optical fiber 260.
[0042] Fig. 11 depicts a cross-sectional view of a wireline cable 300,
which has a
similar design to the wireline cable 24 of Fig. 2 with like reference numerals
being
used to identify similar components. However, the primary telemetric conductor
80
of the wireline cable 24 is replaced in the wireline cable 300 with a primary
telemetric conductor 301. The primary telemetric conductor 301 includes two
telemetry conductors 310, which may have approximately the same diameter as
each
of the secondary power conductors 70. The telemetry conductors 310 are
arranged in
a twisted-pair configuration. The primary telemetry conductor 301 may also
include
drain wires or filler rods 312 that are placed on the outside of the
conductors 310 in
interstitial spaces formed between the conductors 310.
[0043] The wireline cable 300 may further be enhanced by adding optical
components at various locations throughout the cable core. In this regard, in
an
embodiment of the invention, a wireline cable 350 (see Fig. 12) has a similar
design
to the wireline cable 300, with like reference numerals being used to identify
similar
components. Unlike the wireline cable 300, the wireline cable 350 includes
optical
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fibers 320 and 326, which may be disposed at the center of one of the primary
power
conductors 60 and the center of the cable 300, respectively.
[0044] In some embodiments of the invention, the insulated power
conductors,
primary and/or secondary, are stacked dielectric insulated conductors, with
electric
field suppressing characteristics, such as those used in the cables described
in U.S.
Patent No. 6,600,108 (Mydur, et al.). Such stacked dielectric insulated
conductors
generally include a first insulating jacket layer disposed around the metallic
conductors wherein the first insulating jacket layer has a first relative
permittivity,
and, a second insulating jacket layer disposed around the first insulating
jacket layer
and having a second relative permittivity that is less than the first relative
permittivity. The first relative permittivity is preferably within a range of
about 2.5 to
about 10.0, and the second relative permittivity is preferably within a range
of about
1.8 to about 5Ø
[0045] As discussed above, cables, such as the cables 24, 150,
170, 200 and 250,
according to embodiments of the invention include at least one layer of armor
wires,
such as the armor wire wrappings 50a or 50b, surrounding the primary 60, 80
and
secondary 70 conductors. The armor wires may be generally made of any high
tensile strength material including, but not necessarily limited to,
galvanized
improved plow steel, a layered mixture of metals such in bimetallic form,
alloy steel,
or the like. In some embodiments of the invention, the cable includes an inner
armor
wire layer surrounding the conductors and an outer armor wire layer served
around
the inner armor wire layer. A protective polymeric coating may be applied to
each
strand of armor wire for corrosion protection or even to promote bonding
between the
armor wire and polymeric material disposed in the interstitial spaces.
[0046] As used herein, the term "bonding" is meant to include
chemical bonding,
mechanical bonding, or any combination thereof Examples of coating materials
which may be used include, but are not necessarily limited to, fluoropolymers,
fluorinated ethylene propylene (FEP) polymers, ethylene-tetrafluoroethylene
polymers (Tefze10), perfluoro-alkoxyalkane polymer (PFA),
polytetrafluoroethylene
polymer (PTFE), polytetrafluoroethylene-perfluoromethylvinylether polymer
(MFA),
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polyaryletherether ketone polymer (PEEK), or polyether ketone polymer (PEK)
with
fluoropolymer combination, polyphenylene sulfide polymer (PPS), PPS and PTFE
combination, latex or rubber coatings, and the like.
[0047] Each armor wire, such as the armor wire wrappings 50a or 50b, may
also
be plated with materials for corrosion protection or even to promote bonding
between
the armor wire and polymeric material. Nonlimiting examples of suitable
plating
materials include brass, copper alloys, and the like. Plated armor wires may
even
comprise cords such as tire cords. While any effective thickness of plating or
coating
material may be used, a thickness from about 10 microns to about 100 microns
may
be used, as an example.
[0048] In some cables, such as the cables 24, 150, 170, 200 and 250,
polymeric
material, such as the polymeric material 100 or the like, may be disposed in
the
interstitial spaces formed between armor wires, and interstitial spaces formed
between the armor wire layer and insulated conductor. It is believed that
disposing a
polymeric material throughout the armor wires interstitial spaces, or unfilled
annular
gaps, among other advantages, prevents dangerous well gases from migrating
into
and traveling through these spaces or gaps upward toward regions of lower
pressure,
where it becomes a fire, or even explosion hazard.
[0049] In cables, such as the cables 24, 150, 170, 200 and 250, according
to
embodiments of the invention, the armor wires are preferably partially or
completely
sealed by a polymeric material, such as the polymeric material 100 or the
like, that
completely fills all interstitial spaces, therefore eliminating any conduits
for gas
migration. Further, incorporating a polymeric material in the interstitial
spaces
provides torque balanced two armor wire layer cables, since the outer armor
wires are
locked in place and protected by a tough polymer jacket, and larger diameters
are not
required in the outer layer, thus mitigating torque balance problems.
Additionally,
since the interstitial spaces filled, corrosive downhole fluids cannot
infiltrate and
accumulate between the armor wires. The polymeric material may also serve as a
filter for many corrosive fluids. By minimizing exposure of the armor wires
and
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preventing accumulation of corrosive fluids, the useful life of the cable may
be
significantly increased.
[0050] When incorporated, filling the interstitial spaces between armor
wires and
separating the inner and outer armor wires with a polymeric material reduces
point-
to-point contact between the armor wires, thus improving strength, extending
fatigue
life, and while avoiding premature armor wire corrosion. Because the
interstitial
spaces are filled, the cable core is completely contained and creep is
mitigated, and as
a result, cable diameters are much more stable and cable stretch is
significantly
reduced. The creep-resistant polymeric materials used in embodiments of the
invention may minimize core creep in two ways: first, locking the polymeric
material
and armor wire layers together greatly reduces cable deformation; and
secondly, the
polymeric material also may eliminate any annular space into which the cable
core
might otherwise creep.
[0051] Cables, such as the cables 24, 150, 170, 200 and 250, according to
embodiments of the invention may improve problems encountered with caged armor
designs, since the polymeric material encapsulating the armor wires may be
continuously bonded it cannot be easily stripped away from the armor wires.
Because
the processes described herein allow standard armor wire coverage (93-98%
metal) to
be maintained, cable strength may not be sacrificed in applying the polymeric
material, as compared with typical caged armor designs.
[0052] The polymeric material, such as the polymeric material 100 or the
like,
used in some embodiments of the invention may be disposed continuously and
contiguously from the insulated conductors to the layer of armor wires, or may
even
extend beyond the outer periphery thus forming a polymeric jacket that
completely
encases the armor wires. The polymeric material forming the jacket and armor
wire
coating material may be optionally selected so that the armor wires are not
bonded to
and can move within the polymeric jacket.
[0053] In some embodiments of the invention, the polymeric material, such
as the
polymeric material 100 or the like, may not have sufficient mechanical
properties to
withstand high pull or compressive forces as the cable is pulled, for example,
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sheaves, and as such, may further include short fibers. While any suitable
fibers may
be used to provide properties sufficient to withstand such forces, examples
include,
but are not necessarily limited to, carbon fibers, fiberglass, ceramic fibers,
Kevtar
fibers, Vectran0 fibers, quartz, nanocarbon, or any other suitable material.
Further,
as the friction for polymeric materials including short fibers may be
significantly
higher than that of the polymeric material alone, an outer jacket of polymeric
material
without short fibers may be placed around the outer periphery of the cable so
the
outer surface of cable has low friction properties.
[0054] The polymeric material, such as the polymeric material 100 or the
like,
used to form the polymeric jacket or the outer jacket of cables according to
embodiments of the invention may also include particles which improve cable
wear
resistance as it is deployed in wellbores. Examples of suitable particles
include
CeramerTm, boron nitride, PTFE, graphite, nanoparticles (such as nanoclays,
nanosilicas, nanocarbons, nanocarbon fibers, or other suitable nano-
materials), or any
combination of the above.
[0055] Wireline cables, such as the cables 24, 150, 170, 200 and 250,
according
to embodiments of the invention may also have one or more of the armor wires
replaced with coated armor wires. The coating may include the same material as
those polymeric materials described hereinabove. This may help improve torque
balance by reducing the strength, weight, or even size of the outer armor wire
layer,
while also improving the bonding of the polymeric material to the outer armor
wire
layer.
[0056] The materials forming the insulating layers and the polymeric
materials
used in the cables according to embodiments of the invention may further
include a
fluoropolymer additive, or fluoropolymer additives, in the material admixture
to form
the cable. Such additive(s) may be useful to produce long cable lengths of
high
quality at high manufacturing speeds. Suitable fluoropolymer additives
include, but
are not necessarily limited to, polytetrafluoroethylene, perfluoroalkoxy
polymer,
ethylene tetrafluoroethylene copolymer, fluorinated ethylene propylene,
perfluorinated poly(ethylene-propylene), and any mixture thereof.
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[0057] The fluoropolymers may also be copolymers of tetrafluoroethylene and
ethylene and optionally a third comonomer, copolymers of tetrafluoroethylene
and
vinylidene fluoride and optionally a third comonomer, copolymers of
chlorotrifluoroethylene and ethylene and optionally a third comonomer,
copolymers
of hexafluoropropylene and ethylene and optionally third comonomer, and
copolymers of hexafluoropropylene and vinylidene fluoride and optionally a
third
comonomer.
[0058] The fluoropolymer additive should have a melting peak temperature
below
the extrusion processing temperature, and preferably in the range from about
200 C
to about 350 C. To prepare the admixture, the fluoropolymer additive is mixed
with
the insulating jacket or polymeric material. The fluoropolymer additive may be
incorporated into the admixture in the amount of about 5% or less by weight
based
upon total weight of admixture, preferably about 1% by weight based or less
based
upon total weight of admixture, more preferably about 0.75% or less based upon
total
weight of admixture.
[0059] Components used in cables according to embodiments of the invention
may be positioned at zero lay angle or any suitable lay angle relative to the
center or
longitudinal axis of the cable. Generally, the central component is positioned
at zero
lay angle, while strength members surrounding the central component(s) are
helically
positioned around the central component(s) at desired lay angles.
[0060] In accordance with some embodiments of the invention, the cable may
include at least one filler rod component, such as the filler rods 158, 220,
225, and
312, or the like, in the armor wire layer. In such cables, one or more armor
wires are
replaced with a filler rod component, which may include bundles of synthetic
long
fibers or long fiber yarns. The synthetic long fibers or long fiber yarns may
be coated
with any suitable polymers, including those polymeric materials described
hereinabove. The polymers may be extruded over such fibers or yarns to promote
bonding with the polymeric jacket materials. This may further provide
stripping
resistance. Also, as the filler rod components replace outer armor wires,
torque
balance between the inner and outer armor wire layers may further be enhanced.
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[0061] The cable, such as the cables 24, 150, 170, 200 and 250, in
accordance
with embodiments of the invention, may include armor wires employed as
electrical
current return wires, which provide paths to ground for downhole equipment or
tools.
The armor wires may be used for current return while minimizing electric shock
hazard. In some embodiments of the invention, the polymeric material isolates
at least
one armor wire in the first layer of armor wires thus enabling their use as
electric
current return wires.
[0062] The cables, such as the cables 24, 150, 170, 200 and 250, that
are
disclosed herein may be used with wellbore devices to perform operations in
wellbores penetrating geologic formations that may contain gas and oil
reservoirs.
The cables may be used to interconnect well logging tools, such as gamma-ray
emitters/receivers, caliper devices, resistivity- measuring devices, seismic
devices,
neutron emitters/receivers, and the like, to one or more power supplies and
data
logging equipment outside the well, among any other suitable application.
[0063] The cables, such as the cables 24, 150, 170, 200 and 250,
disclosed herein
may also be used in non-wireline applications, such as in seismic operations,
which
include subsea and subterranean seismic operations. As another example, the
cables
disclosed herein may be used as permanent monitoring cables for wellbores and
for
well completions. Thus, many variations and applications of the cables
disclosed
herein are contemplated and are within the scope of the appended claims.
[0064] While the present invention has been described with respect to a
limited
number of embodiments, those skilled in the art, having the benefit of this
disclosure,
will appreciate numerous modifications and variations therefrom. It is
intended that
the appended claims cover all such modifications and variations as fall within
the
scope of this present invention.
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