Note: Descriptions are shown in the official language in which they were submitted.
CA 02645630 2008-12-01
ELECTRIFIED COILED TUBING
Field of the Invention
[0001] This invention relates to a system and method for transmitting
electrical power and
electrical data to a submersible electrical pump in a downhole position.
Backeround of the Invention
[0002] Oil and gas well production is commonly carried out using a submersible
electric pump
that is lowered into a downhole position on the end of a length of coiled
tubing. Upon activation,
the electric pump draws in fluid from the proximate bore hole cavity through
an intake and then
forces the fluid to the surface through the interior space of the coiled
tubing. With such a system
there is a need to supply electrical power to the remote downhole electric
pump. There is also a
need to electronically communicate with the electric pump in its downhole
position to regulate
its activity and to monitor variables such as flow rate.
[0003] There are a number of prior art systems designed to transmit electrical
power and data
from the surface to the electric pump in its downhole position at the end of
the coiled tubing.
One such system comprises strapping cables to the outside of the coiled
tubing. This system is
labour intensive both on installation and during pump removal operations and
the external
connection of the cables to the electric pump on the downhole assembly
frequently is attributed
to pump system failures.
[0004] In another system, power lines are conveyed via an internal concentric
coiled tubing
string in a pipe-within-a-pipe configuration. This system and method is also
labour intensive
both on installation and during pump removal operations since two concentric
coiled tubing
strings must be assembled in an operation separate to the installation of the
electric pumping
system installation.
[0005] In a further prior art system, the power line is conveyed singularly
inside the primary
coiled tubing string. This method is also labour intensive requiring
additional labour to insert the
CA 02645630 2008-12-01
electrical wire inside the primary coiled tubing in advance of installing the
electric pump into the
downhole environment.
[0006] What is needed is a system and method of transmitting electrical power
and electrical
data to a submersible electric pump in a downhole location that overcomes the
limitations of the
prior art.
Summary of the Invention
[0007] The present invention relates to a system and method for transmitting
electrical power
and electrical data to a submersible electrical pump in a downhole position.
[0008] In one aspect, the invention comprises a length of coiled tubing for
oil and gas well
servicing or production; the tubing comprising an inner tubing, an outer
extruded polymer
protective coating, and at least one electrical power conductor disposed
between the inner tubing
and the outer extruded polymer protective coating.
[0009] In one embodiment, the inner tubing has an inner surface and an outer
surface, the
outer surface of the inner tubing having at least one recess extending along
its length, the recess
having sufficient depth to accommodate the electrical power conductor.
[00010] In one embodiment, the length of coiled tubing fiuther comprises at
least one data
transmission cable disposed between the inner tubing and the outer extruded
polymer protective
coating.
[00011] In one embodiment, the electrical power conductor and data
transmission cable have a
polymer protective layer.
[00012] In one embodiment, the inner tubing has two recesses. In one
embodiment, the
recesses are opposing. In one embodiment, the recesses are adjacent.
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[00013] In one embodiment, the inner tubing is stainless steel. In one
embodiment, the outer
extruded polymer protective coating is selected from high density polyethylene
or polyvinyl
chloride.
[000141 In another aspect, the invention comprises a system for conducting
electrical power
from the surface of a well to a submersible electric pump in a downhole
position, the system
comprising:
a) a length of coiled tubing having a first end at the surface and a second
end
attached to the pump, the tubing comprising an inner tubing, an outer extruded
polymer
protective coating, and at least one electrical power conductor disposed
between the inner tubing
and the outer extruded polymer protective coating or embedded within the outer
external
polymer protective coating;
b) a source of electrical power connected to the power conductor at the first
end of
the tubing; and
c) an electrical connect'ion between the power conductor at the second end of
the
tubing and the pump.
[00015] - In one embodiment, the system further comprises at least one data
transmission cable
disposed between the inner tubing and the outer extruded polymer protective
coating.
[00016) In another aspect, the invention comprises a method of conducting
electrical power
from the surface of a well to a submersible electric pump in a downhole
position, the method
comprising:
a) connecting the pump to a length of coiled tubing, the tubing comprising an
inner
tubing, an outer extruded polymer protective coating, and at least one
electrical power conductor
disposed between the inner tubing and the outer extruded polymer protective
coating; and
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b) connecting one end of the power conductor to a source of electrical power
and
connecting the other end of the power conductor to the pump.
[00017] In one ernbodiment, the method further comprises at least one data
transmission cable
disposed between the inner tubing and the outer extruded polymer protective
coating.
[000181 In yet another aspect, the invention comprises a method of forming the
above length
of coiled tubing, comprising the steps of:
a) forming at least one recess in the outer surface of the inner tubing, the
recess
extending along its length and having sufficient depth to accommodate the
electrical power
conductor;
b) placing the electrical power conductor into the recess; and
c) coating the outer surface of the inner tubing with the outer extruded
polymer
protective coating to seal the electrical power conductor within the recess.
[00019) In one embodiment, two recesses are formed. In one embodiment, the
recesses are
opposing. In one embodiment, the recesses are adjacent.
[00020] In one embodiment, step (b) further comprises placing at least one
data transmission
cable into the recess.
[00021] In one embodiment, the method includes steps prior to step (a)
comprising rolling a
flat sheet of metal into a tubular shape; welding the sheet after being rolled
into the tubular shape
for forming the tubing; scarfing the tubing to remove weld bead from the inner
and outer
diameters of the tubiiig; and coiling the tubin.g onto a reel.
[00022] In one embodiment, step (a) further comprises the step of heating the
inner tubing. In
one embodiment, the inner tubing is heated by induction heating.
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[00023] In one ennbodiment, the electrical power conductor and data
transmission cable have a
polymer protective layer.
[00024] In one embodiment, step (b) further comprises the step of applying a
copolymer
adhesive over the electrical power conductor and the data transmission cable.
[00025] In one embodiment, the inner tubing is stainless steel. In one
eznbodiment, the outer
extruded polymer protective coating is selected from high density polyethylene
or polyvinyl
chloride.
[00026] Additional aspects and advantages of the present invention will be
apparent in view of
the description, which follows. It should be understood, however, that the
detailed description
and the specific examples, while indicating preferred embodiments of the
invention, are given by
way of illustration only, since various changes and modifications within the
spirit and scope of
the invention will become apparent to those skilled in the art from this
detailed description.
Brief Description of the Drawings
[00027] The invention will now be described by way of an exemplary embodiment
with
reference to the accompanying simplified, diagrammatic, not-to-scale drawings.
[00028] In the drawings, like elements are assigned like reference numerals.
The drawings are
not necessarily to scale, with the emphasis instead placed upon the principles
of the present
invention. Additionally, each of the embodiments depicted are but one of a
number of possible
arrangements utilizing the fundamental concepts of the present invention. The
drawings are
briefly described as follows:
[00029] Figure IA is a partial isometric cutaway view of one embodiment of a
system of the
present invention.
[000301 Figure 1B is a cross sectional view of one embodiment of a system of
Figure 1A.
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1000311 Figure 2A is a partial isometric cutaway view of one embodiment of a
system of the
present invention.
[00032] Figure 2B is a cross sectional view of one embodiment of a system of
Figure 2A.
[00033] Figure 2C is an enlarged view of a partially cut away section shown in
the circle in
Figure 2B, indicating the detail of the electrical power conductors and data
transmission cables.
[00034] Figure 3A is a side view of one embodiment of a system of the present
invention.
[00035] Figure 3B is a top view of one embodiment of a system of Figure 3A.
[00036] Figure 3C is a cross sectional view of one embodiment of a system of
Figure 3A.
[00037] Figure 4 is a diagrammatic representation of a conventional prior art
method for
producing coiled tubing.
[00038] Figure 5 is a diagrammatic representation of a method for producing
one embodiment
of a system of the present invention.
[00039] Figure 6 is a diagrammatic representation of a motor in a downhole
position on the
end of a length of coiled tubing.
Detailed Description of Preferred Embodiments
[00040] When describing the present invention, all terms not defined herein
have their
common art-recognized meanings. To the extent that the following-description
is of a specific
embodiment or a particular use of the invention, it is intended to be
illustrative only, and not
limiting of the claimed invention. The following description is intended to
cover all alternatives,
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CA 02645630 2008-12-01
modifications and equivalents that are included in the spirit and scope of the
invention, as
defined in the appended claims.
[00041] The terms "coiled tubing" and "coiled tubing inember" mean small-
diameter metal
tubulars commonly employed in oil and gas servicing, completion and production
operations, the
tubulars having sufficient flexibility that they can.be stored on a reel and
can be uncoiled or
coiled repeatedly as required.
[00042] The present invention is directed to a system and a method of
transmitting electrical
power and electrical data to a submersible electric pump in a downhole
position, and in particular
to a method of transmitting electrical power and electrical data along a
length of coiled tubing to
a submersible electric pump in a downhole position.
[00043] The electrified coiled tubing of the present invention may be used to
connect to a
bottom hole electrical submersible pumping system such as that described in
Applicant's co-
pending United States Application Serial No. 12/325,677, filed December 1,
2008, entitled
"Bottom Hole Hollow Core Electric Submersible Pumping System".
[00044] In one aspect, the invention comprises a length of coiled tubing for
oil and gas well
servicing or production, the tubing comprising an inner tubing, an outer
extruded polymer
protective coating, and at least one electrical power conductor disposed
between the inner tubing
and the outer extruded polymer protective coating.
[00045] In one aspect, the invention comprises a system for conducting
electrical power from
the surface of a well to a submersible electric pump in a downhole position,
the system
comprising:
(a) a length of coiled tubing having a first end at the surface and a second
end attached to
the pump, the tubing comprising. an inner tubing, an outer extruded polymer
protective coating,
and at least one electrical power conductor disposed between the inner tubing
and the outer
extruded polymer protective coating;
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(b) a source of electrical power connected to the power conductor at the first
end of the
tubing; and
(c) an electrical connection between the power conductor at the second end of
the tubing
and the pump.
[00046] As shown in the Figures, the systern (10) comprises a length (1) of a
coiled tubing
member (13) having a first end (40) and a second end (42), the tubing member
(13) comprising
an inner tubing (12), an outer extruded polymer protective coating (14) and at
least one electrical
power conductor (18) disposed between the inner tubing (12) and the outer
extruded polymer
protective coating (14). The inner tubing (12) has an inner surface (24) and
an outer surface
(26). In one embodiment, the outer surface (26) of the inner tubing (12) has
at least one recess
(16) extending along its length (1), the recess (16) having sufficient depth
to accommodate at
least one electrical power conductor (18). The outer extruded polymer
protective coating (14)
seals the electrical power conductor (18) within the recess (16), protecting
and insulating it from
the exterior environment.
[00047] As shown in the Figures, more than one recess (16) may be utilized to
accommodate
more power conductors. In one embodiment, dual recesses (16) are used. In one
embodiment,
the dual recesses (16) are opposing, as shown in Figures 1A and 1B. In one
embodiment, the
dual recesses (16) are adjacent, as shown in Figures 2A-C and Figures 3A-C.
However, it will
be understood by those skilled in the art that other arrangements of recesses
(16) may be suitable.
[00048J As shown in the Figures, a plurality of electrical power conductors
(18) may be
inserted into the recess (16). A plurality of data transmission cables (20)
may also positioned
within the recess (16). The electrical power conductors (18) and data
transmission cables (20)
may themselves have a polymer protective layer (22) such as PVC. The
electrical power
conductors (18) may be constructed from any suitable material as would be
selected by one
skilled in the art such as copper. Any suitable data transmission cable (20)
may be used such as
a fibre optic cable, such suggestion intended not to be limiting.
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[00049] In one aspect, the invention comprises a method of conducting
electrical power from
the surface of a well to a submersible electric pump in a downhole position,
the method
comprising:
(a) connecting the pump to a length of coiled tubing, the tubing comprising an
inner
tubing, an outer extruded polymer protective coating, and at least one
electrical power conductor
disposed between the inner tubing and the outer extruded polymer protective
coating; and
(b) connecting one end of the power conductor to a source of electrical power
and
connecting the other end of the power conductor to the pump.
1000501 At the first and second ends of the coiled tubing member (40, 42), the
electrical power
conductors (18) and data transmission cables (20) are dressed and attached to
appropriate end
connectors (not shown) designed to conduct the electricity and data
transmissions from the
coiled tubing (13) to the well head (34) at the surface (36) or the motor (30)
in the bore hole (38)
respectively (Figure 6). The electrical power conductors (18) carry electric
power to the electric
motor (30), while the data transmission cables (20) carry electrical signals
used to regulate the
activity of the pump (32) and to monitor pre-selected variables by receiving
data from downhole
sensors.
[00051] In general, the coiled tubing member (13) is produced by making the
inner tubing (12)
machined with the recess (16) and by then placing the electrical power
conductors (18) and the
data transmission cables (20) into the recess (16). The outer surface (16) of
the inner tubing (12)
is then coated with the outer extruded polymer protective coating (14) to seal
the electrical power
conductors (18) and the data transmission cables (20) within the recess (16).
The inner tubing
(12) and the outer extruded polymer protective coating (14) may be constructed
from materials
commonly used in the pipeline industry to manufacture coated pipes. In one
embodiment, the
inner tubing (12) is steel or stainless steel. Alternatively, the inner tubing
may comprise a plastic
material which is the same or similar to the outer extruded polymer material.
In one
embod'iment, the outer extruded polymer protective coating (14) is selected
from higYl density
polyethylene or polyvinyl chloride. The pipe may be mass produced in long
lengths and then cut
at a desired point. The ends are dressed for connectivity as described above.
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[00052] In one embodiment, the method of producing the coiled tubing member
(13)
comprises the steps shown schematically in Figures 4 and 5. In one embodiment,
the method of
producing the coiled tubing member (13) comprises the steps shown
schematically in Figure 5
using commercially available coiled tubing.
[00053] As shown in Figure 4, the coiled tubing (60) is produced in a
continuous mill
operation from a flat sheet (44). In one embodiment, the flat.sheet (44) may
comprise carbon
steel. The flat sheet (44) is uncoiled from the reel, and fed into the tube
mill to form a tube (46).
As the edges of the sheet (44) are forced together by pressure rolls within
the tube mill, high
frequency current is introduced by an HF (high frequency) induction coil
around the tube. High
frequency induction welding (48) is commonly preferred for higher quality
pipe. The current is
concentrated along the edges and heats the edges to a sufficient temperature
such that a
homogeneous, longitudinal weld is formed when the pressure rolls force the
edges together to
form the tube.
[00054] Welding creates upset or weld bead (i.e., sharp or rough zones) on
either or both of
the inner diameter (ID) and outer diameter (OD) of the tubing. Weld bead is
removed to ensure
that the ID and OD are uniform, and that the weld does not obstruct the flow
of fluid through the
tubing. Weld bead is removed by scarfing (50) the tubing immediately after
welding (48) while
the tube is still hot.
[00055] As the tube cools, shrinkage can occur which in turn, may introduce
residual stress
and both longitudinal and rotational distortion. The tube passes through a
seaming assembly
(52) which heats the weld to restore the grain structure in the weld to a
finer structure which is
equal to that of the parent metal, thereby reducing the amount of residual
stress. The tube is then
cooled using air or a water bath (54). The tube may then pass through an
additional assembly
(56) to remove any remaining residual stress (i.e., full body stress relief).
The tube is then
_ . _ ..
cooled using air or a water bath (58) and coiled on a reel (60).
[00056] As shown in Figure 5, the coiled tubing (60) is used in a continuous
mill operation to
form the coiled tubing member (13). The coiled tubing is uncoiled from the
reel (60) and fed
CA 02645630 2008-12-01
into a mill (62) which machines at least one recess (16). The coiled tubing is
then heated. In one
embodiment, the coiled tubing is heated by induction heating involving
electromagnetic
induction where eddy currents are generated within the metal and resistance
leads to Joule
heating of the metal. An induction heater (64) comprises an electromagnet
through which a high
frequency alternating current is passed.
[00057] The coiled tubing is then coated with a fusion-bonded epoxy coating
(66) to ensure
that the electrical power conductors (18), data transmission cables (20) and
copolymer adhesive
(70) bond to the coiled tubing. The electrical power conductors (18) and data
transmission
cables (20) (depicted as coiled on a reel (68) in Figure 5) are placed into
the recess (16) of the
coiled tubing. The copolymer adhesive (70) is then applied over the electrical
power conductors
(18) and data transmission cables (20). Finally, the outer extruded polymer
protective coating
(14) is applied over the copolymer adhesive (70) to seal the electrical power
conductors (18) and
data transmission cables (20) within the recess (16). In one embodiment, the
outer extruded
polymer protective coating (14) is applied using a high-density polyethylene
(HDPE) extrusion
unit (72). In one embodiment, the outer extruded polymer protective coating
(14) is applied
using the technique or a technique similar to that described in CSA Z245.21-06
System B1
("External fusion bond epoxy coating for steel pipe" and "External
polyethylene coating for
pipe," Canadian Standards Association, 2006). Quenching with water (74)
solidifies the
extrusion process. As previously discussed, the coiled tubing member (13) may
be mass
produced in long lengths and then cut at a desired point. The ends are dressed
for connectivity.
[00058] In an alternative embodiment, the power conductors (18) and data
transmission cables
(20) may be embedded in the protective coating (14) prior to bonding of the
coating to the inner
tubing. Alternatively, the power conductors and data transmission cables may
be extruded with
the protective coating as it is being applied to the inner tubing.
[00059] The coiled tubing of the present invention provides a single pre-
manufactured coiled
tubing string with all the electrical power conductors and data transmission
cables inteznal to the
wall of the pipe so as to be protected from the exterior environment. The
configuration of the
present invention allows the installation of the system in a live well without
having to kill the
well in advance. Further, this design of coil tubing facilitates the clean out
of the wells with a
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smaller coil tubing string and circulation of the solids either down the
interior diameter of the
tubing or down the annular space. With the present system, there are no
conductive lines
interfering with the operation whether it is carried out down the annulus or
in the interior
diameter of the inner tubing.
[00060] The coiled pipe of the present invention may have connections which
convey the
electrical conduits and this allows easy field preparation of the components.
Further, the coiled.
tubing of the present invention provides an electrified coil in standard
lengths which can be cut
and prepared in the field with connections inclusive of the electrical power
conductors and the
fiber optic transmission lines. Consequently, only a single service (coiled
tubing rig) and one
operation is required to install or remove the pumping system. Cleanout
service jobs are
dramatically simplified whether it is in the tubing or annulus since there are
no power conduits to
interfere with the operation.
[00061] As will be apparent to those skilled in the art, various
modifications, adaptations and
variations of the foregoing specific disclosure can be made without departing
from the scope of
the invention claimed herein.
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