GB2363683A

GB2363683A - Coiled well tubing with indentations

Info

Publication number: GB2363683A
Application number: GB0123277A
Authority: GB
Inventors: David H Neuroth; Larry V Dalrymple; Earl B Brookbank; Tim W Pinkston; Don C Cox
Original assignee: Baker Hughes Inc
Current assignee: Baker Hughes Holdings LLC
Priority date: 1997-05-23
Filing date: 1998-05-22
Publication date: 2002-01-02
Anticipated expiration: 2018-05-22
Also published as: GB0123277D0; GB2363683B

Abstract

A length of coiled tubing 11 for supporting an electrical cable 15 in a well as disclosed in parent application GB 2326536 A, the invention being directed to the feature of the at least one indentation, eg dimples 37', being filled with an inlay of rigid material 39 to prevent the interior surface of the indentation flattening while running the tubing in and out of the well.

Description

2363683 1 2 3 4 COILED TUBING SUPPORTED ELECTRICAL CABLE HAVING

INDENTATIONS 6 7 8 12 This invention relates in general to power cable for 13 electrical submersible well pumps and in particular to an 14 electrical cable installed within a string of coiled metal tubing.

18 Conventional electrical submersible well pumps for 19 oil and deep water wells are supported on a string of production tubing The production tubing comprises 21 sections of steel pipe screwed together, each section 22 being about thirty feet ( 9 1 m) in length The pump is a 23 centrifugal pump driven by an AC motor located below the 24 pump A power cable extends from the surface alongside the tubing for supplying power to the motor The power 26 cable is strapped to the tubing at frequent intervals to 27 support the weight of the power cable.

1 One disadvantage of the conventional pump assembly 2 described above is that when the pump must be pulled for 3 repair or replacement, the procedure is expensive The 4 operator needs a workover rig with the capability of pulling the sections of tubing Pumps of this nature 6 must be pulled typically at least every eighteen months.

7 Considering the cost of the workover rig as well as the 8 down time for the well, the periodic expense is 9 significant.

A few installations have been made employing coiled 11 tubing Coiled tubing is a continuous string of metal 12 tubing which is brought to the well site on a large reel.

13 The coiled tubing unit unreels the tubing and forces it 14 into the well Coiled tubing has been used for various purposes in the past, and recently used to suspend 16 electrical submersible pumps An advantage of a coiled 17 tubing supported pump is that it does not need a workover 18 rig to pull it Also, pulling and replacing it should be 19 faster than production tubing.

One proposal in the past was to produce production 21 fluid from the pump through the coiled tubing and strap 22 the cable to the exterior of the coiled tubing A 23 disadvantage of this assembly is that a separate reel is 1 needed for the power cable Securing the straps would 2 slow down the installation and pulling procedure.

3 Furthermore, commercially available coiled tubing is not 4 large enough in diameter for desired production in many cases.

6 Some installations have been made with the 7 electrical cable installed within the coiled tubing.

8 Production fluid from the pump flows through a casing 9 surrounding the coiled tubing The electrical cable is a three-phase cable having fairly large metal conductors.

11 The weight of the cable is such that it will not support 12 itself in a deep well Even if inserted within coiled 13 tubing, the weight of the electrical cable needs to be 14 supported by the coiled tubing In one type of is installation, separate mechanical anchors are spaced 16 along the length of the insulated electrical cable The 17 cable is inserted into the coiled tubing with the anchors 18 retracted The anchors are then shifted to a weight 19 supporting position, gripping the inner diameter of the coiled tubing U S Patent 5,435,351, Head, July 25, 21 1995, describes such a system.

22 Another proposal shown in U S Patent 5,191,173, 23 Sizer et al, March 2, 1993, describes using an 1 elastomeric jacket of a type that will swell when exposed 2 to a hydrocarbon liquid The jacket is extruded over the 3 insulated conductors during manufacturing The jacketed 4 electrical cable is then inserted into the coiled tubing.

Then liquid hydrocarbon is pumped into the annular space 6 surrounding the jacket, causing it to swell to 7 frictionally grip the coiled tubing In another 8 embodiment, metal sleeves are bonded to the cable After 9 installation, the coiled tubing and sleeves are crimped to each other.

13 The coiled tubing of this invention has indentations 14 formed in the sidewall to create ledges for supporting is elements within such as an electrical cable In the case 16 of electrical cable, it is supported within the coiled 17 tubing by retainers on the cable which are supported on 18 indentations in the coiled tubing The retainers are 19 secured to the exterior of the electrical cable at various points The retainers have an outer diameter 21 that is less than the inner diameter of the coiled tubing 22 to allow the electrical cable to be inserted into the 23 coiled tubing Subsequently, the retainers are located 1 and an indentations are placed in the coiled tubing next 2 to the retainer.

3 Each indentation is a dimple which protrudes inward 4 sufficiently to create a ledge which interferes with movement of the retainer This causes the retainer to 6 rest on the ledge, transferring load of the cable weight 7 to the coiled tubing Preferably, a first set of at 8 least three indentations are spaced just below each of 9 the retainers A second set is positioned a short distance below the first set The second set provides 11 support in the event the first set allows slippage after 12 several trips of the cable in and out of the well Also, 13 preferably, the outside of each of the dimples is filled 14 with weld material to reduce the tendency for the coiled tubing injector from flattening the dimples.

16 Various embodiments of the present invention will now 17 be described, by way of example only, and with reference to 18 the accompanying drawings in which:

19 Figure 1 is a partial sectional view taking along line 1-1 of Figure 3 and illustrating an electrical cable and 21 coiled tubing assembly constructed in accordance with an 22 embodiment of the present invention.

23 Figure 2 is a sectional view of the assembly of Figure 1, taken along the line of 2-2 of Figure 1.

-5 1 Figure 3 is a sectional view of the assembly of 2 Figure 1, taken along the line of 3-3 of Figure 1.

3 Figure 4 is a side view of a portion of the coiled 4 tubing of Figure 1, showing one of the dimples.

Figure 5 is a sectional view of an alternate 6 embodiment of an electrical cable in coiled tubing.

9 Referring to Figure 1, the electrical power line for a submersible pump includes a string of continuous coiled 11 tubing 11 Coiled tubing 11 is steel, has an inner 12 diameter 13, a longitudinal axis 14 and is of 13 conventional materials and dimensions Coiled tubing 11 14 is capable of being wound on a large reel for transport to a well site, then forced into the well An electrical 16 cable 15 is shown inserted through the length of coiled 17 tubing 11 Electrical cable 15 is a type particularly 18 for supplying AC power from the surface to a downhole 19 motor for driving a centrifugal pump (not shown) which is located at the lower end of coiled tubing 11.

21 As shown in Figure 3, electrical cable 15 has three 22 conductors 17, each surrounded by an insulation layer 19.

23 An elastomeric jacket 21 is extruded over the three 1 insulated conductors 17 Jacket 21 has a cylindrical 2 outer diameter 23 containing a plurality of parallel 3 longitudinal grooves (not shown) Outer diameter 23 is 4 helically wrapped with a metal strip of armor 27 that is also of metal In one embodiment, jacket 21 is of a 6 material, such as Nitrile rubber, which resists swelling 7 when exposed to hydrocarbon liquid In this embodiment, 8 the tightly wrapped armor 27 deforms jacket 21 and 9 provides adequate frictional engagement between jacket 21 and armor 27, preventing slippage due to the weight of 11 power cable 15.

12 Referring to Figure 1, a plurality of retainers 29 13 are mounted to cable 15 at selected intervals Each 14 retainer 29 is a metal member of at least two portions, preferably two halves Each half has a semi-cylindrical 16 recess 30, as shown in Figure 2 The recesses 30 mate 17 with each other to form a circular hole with a diameter 18 which is approximately the same as the outer diameter of 19 armor 27 Furthermore, each recess 30 contains a plurality of helically spaced grooves 31 that form a set 21 of threads The pitch and configuration of grooves 31 22 are such that they mate with the strips of helical armor 1 27 Fasteners 31 are used to secure the two halves of 2 retainer 29 together, defining a sleeve.

3 Retainer 29 has an outer diameter 35 that is less 4 than coiled tubing inner diameter 13 The annular clearance allows power cable 15 with its retainers 29 to 6 be readily drawn into coiled tubing 11 In a typical 7 instance, coiled tubing 11 will have an outer diameter of 8 2-3/8 " ( 0 635-0 953 cm) and a wall thickness of about 0 159 " 9 ( 0 404 cm) Retainer 29 will have an outer diameter 35 that is about 0 050 " to 0 100 " ( 0 127-0 254 cm) less than inner 11 diameter 13 Each retainer 29 has a downward facing shoulder 12 36 which is located at the lower end and is perpendicular to 13 the longitudinal axis of tubing 11 Each retainer has an 14 upward facing shoulder 38 which is located at the upper end and is perpendicular to the longitudinal axis 14 of tubing 16 11 Shoulders 36, 38 are identical, allowing cable 15 to be 17 used in an inverted manner from that shown.

18 To be able to transfer the weight of cable 15 to 19 coiled tubing 11, a plurality of indentations or dimples 37 are formed in coiled tubing 11 after power cable 15 21 has been installed Dimples 37 are formed by using a 22 press or punch Each dimple 37 is generally circular or 23 hemispherical in configuration as shown in Figure 4, -8 1 having an axis perpendicular to tubing axis 14, and a 2 diameter of about 0 5 inch ( 1 27 cm) Preferably, each 3 dimple 37 will protrude inward only as far as it needs to 4 for providing a ledge or stop to be engaged by one of the retainers 29 The amount of protrusion is typically about 6 O 125 " ( 0 318 cm), which provides at least an interference 7 of 0 025 " ( 0 064 cm) even if retainer 29 is located off to 8 the far side of dimple 37.

9 Preferably there will be three dimples 37 within each set 37 a, 37 b, as shown in Figure 3 The dimples 37 11 within each set 37 a, 37 b are spaced circumferentially 120 12 degrees apart from each other in a common plane normal or 13 perpendicular to axis 14 Each set 37 a, 37 b of dimples 14 37 circumscribes a diameter 40 which is less than outer diameter 35 of retainer 29.

16 A primary set 37 a of dimples 37 will be located 17 slightly below each load shoulder 36 Optionally a 18 primary set 37 a of dimples may be located slightly above 19 each retainer 29 so that cable 15 does not need to be oriented in up and down directions Typically, the 21 spacing between the primary sets 37 a of dimples 37 for 22 each retainer 29 will be one to two inches ( 2 5-5 1 cm) 23 greater than the longitudinal length of retainers 29 Some 1 longitudinal movement of each retainer 29 relative to 2 dimples 37 can thus occur when cable 15 moves from a 3 stretched out horizontal condition during installation of 4 cable 15 in coiled tubing 11 to a coiled condition on a reel and to a linear vertical position in a well.

6 Also, preferably a secondary set 37 b is located about 7 two inches ( 5 1 cm) from each primary set 37 a, and spaced 8 farther from one of the retainers 29 Dimples 37 in 9 secondary sets 37 b are the same as in primary sets 37 a, however they are circumferentially staggered from dimples 11 37 in the adjacent primary set 37 a, as shown in Figure 3.

12 Each dimple 37 in secondary set 37 b is located 60 degrees 13 circumferentially from a dimple 37 in primary set 37 a.

14 Secondary sets 37 b serve as ledges in the same manner as primary sets 37 a in the event that any of the primary 16 sets 37 a allows slippage to occur after several trips of 17 tubing 11 into the well.

18 Generally, there will be a retainer 29 about every 300 19 feet ( 91 m) A typical cable will provide a load on each retainer 29 of about 450 to 750 lbs ( 200-340 kg), which is 21 transmitted through dimples 37 to coiled tubing 11.

22 In the method of assembly, technicians will install 23 retainers 29 on electrical cable 15 at the selected I ' 1 intervals The technician secures the two halves of 2 retainers 29 around electrical cable 15, aligning grooves 3 31 with armor 27 Electrical cable 15 is then inserted 4 within coiled tubing 11 This may be done in one method by pushing a stiff wire from one end of coiled tubing 11 6 out the other Then electrical cable 15 will be 7 connected to the protruding end of the rigid wire, and 8 the wire will be winched back onto a reel, drawing 9 electrical cable 15 through coiled tubing 11 Then, the technician will locate the retainers 29 within coiled 11 tubing 11 by ultrasonic scanning or the like The 12 technician then forms dimples 37 using a press or other 13 type of deformation device.

14 Coiled tubing 11 with cable 15 installed is then wound on a reel and transported to a well Coiled tubing 16 11 is drawn from the reel and a submersible pump and 17 motor (not shown) are attached to the lower end of coiled 18 tubing 11 The lower end of electrical cable 15 is 19 joined to a motor lead of the motor The assembly is then inserted into the well using a conventional coiled 21 tubing injector As coiled tubing 11 is inserted into 22 the well, cable 15 will move downward slightly in coiled 23 tubing 11 due to the weight of cable 15 Lower shoulder 1 36 of each retainer 29 moves into supporting engagement 2 with the lower primary set 37 a of dimples 37 The lower 3 primary set 37 a of dimples 37 transfers the weight of 4 cable 15 to coiled tubing 11 Coiled tubing 11 supports the weight of the pump and motor Once at the proper 6 depth, the upper end of electrical cable 15 is connected 7 to a power supply for supplying power to the pump.

8 The coiled tubing 11 will be pulled from time to 9 time for maintenance or replacement of the pump and motor After several trips, the ledges created by the 11 dimples 37 tend to flatten due to being squeezed by the 12 coiled tubing injector If slippage occurs of any of 13 retainers 29 past primary dimple sets 37 a, the slipping 14 retainers 29 will contact and be supported by secondary dimple sets 37 b.

16 In the alternate embodiment of Figure 5, each dimple 17 37 ' creates an exterior depression which is filled with 18 an inlay 39 of rigid material Preferably, inlay 39 is 19 performed by electric welding, then the weld material is ground smooth The welding would normally be performed 21 immediately after dimple 37 ' has been made, thus after 22 power cable 15 has been installed Inlay 39 creates a 23 hard inward protruding dimple 37 which resists /' 1 deformation by the coiled tubing injector while being run 2 in and pulled from a well Other than inlays 39, dimples 3 37 ' will be spaced and sized in the same manner as in the 4 first embodiment In this embodiment, however, there is no need for the secondary dimples 37 a as in the first 6 embodimer because inlay 39 resists deformation of the 7 dimple 37 Also, as in the case of the first embodiment, 8 it is optional whether or not to locate a dimple 37 ' a 9 short distance above each retainer 29 '.

The invention has significant advantages The 11 indentations and retainers provide support for the weight 12 of the cable The retainers are simple in construction 13 and inexpensive, avoiding complex anchoring mechanisms 14 that have to be internally set after the cable has been inserted into the coiled tubing The indentations allow 16 a number of trips into and out of the well, before 17 replacement is needed.

18 While the invention has been shown in only one of 19 its forms, it should be apparent to those skilled in the art that it is not so limited but is susceptible to 21 various changes without departing from the scope of the 22 invention For example, although the dimp Les of the 23 coiled tubing are shown only for supporting the weight of 1 electrical pump power cable, they have other uses There 2 are many down-hole tools installed and retrieved within 3 well tubulars that depend upon no-go stops to locate or 4 anchor the tools within the pipe or tubing ID In threaded pipe, short nipples with such ID profiles are 6 made up into the pipe string as it is run into the well.

7 With coiled tubing such short pieces can be spliced into 8 the tubing by welding or with several types of special 9 tubing connectors Such splicing compromises the structural and pressure integrity of the tubing and often 11 results in problems handling and running the coiled 12 tubing with standard equipment The dimples of this 13 invention can be formed into the tubing in the field at

14 whatever desired location and do not compromise the integrity or handling of the coiled tubing The dimples 16 can serve as no-go stops to locate, selectively locate or 17 anchor down-hole tools Such tool and dimple 18 combinations are limited only by the imagination of the 19 designer.

68340 344

Claims

1 An apparatus for installation in a well for transmitting power to a well pump, comprising:

a tubing having an interior passage; an electrical cable having at least one insulated electrical conductor embedded within an elast-omeric jacket, the electrical cable extending longitudinally through the interior passage of the tubing; at least one retainer mounted to the electrical cable and having at least one load shoulder; and at least one indentation formed in the tubing is adjacent the load shoulder, the indentation protruding into the interior passage of the tubing and creating a ledge which is contacted by the load shoulder when the apparatus is installed in the well to transfer weight of the electrical cable to the tubing.

2 The apparatus according to claim 1, wherein the retainer comprises at least two portions which are clamped together around the electrical cable by fasteners.

3 The apparatus according to claim 1 or 2, wherein the load shoulder is located on an end of the retainer.

4 The apparatus according to claim 1, 2 or 3, wherein the indentation comprises a dimple having a dimple axis which is perpendicular to a longitudinal axis of the tubing.

The apparatus according to any preceding claim, wherein the indentation has a depressed exterior surface which is filled with a rigid material.

6 The apparatus according to claim 5, wherein the rigid material is weld material.

7 The apparatus according to any preceding claim, wherein said at least one indentation comprises at least one set of dimples formed in the tubing adjacent the load shoulder, the dimples within the set being spaced apart circumferentially around the tubing.

8 The apparatus according to claim 7 wherein:

each of the dimples within the set has an axis, the axes of the dimples within the set being located in a common plane which is normal to a longitudinal axis of the tubing; and each of the dimples has a depressed exterior surface which is filled with a rigid material.

9 The method according to claim 7 or 8, further comprising inserting a member into the tubing and supporting the member on the ledge after step (d)

9 The apparatus according to any of claims 1-4 or 7, wherein said at least one indentation comprises a primary set and a secondary set of dimples formed in the tubing below the load shoulder of the retainer, the dimples within each of the sets being spaced apart circumferentially around the tubing, the primary and secondary sets for the load shoulder being spaced longitudinally apart from each other.

The apparatus according to any preceding claim, wherein:

the retainer has an opposite shoulder facing oppositely from the load shoulder; and wherein said at least one indentation comprises an additional indentation formed in the tubing adjacent the opposite shoulder.

11 An apparatus for installation in a well for transmitting power to a well pump, comprising:

a continuous metal tubing having an inner diameter; an electrical cable having at least one insulated electrical conductor embedded within an elastomeric jacket, the electrical cable extending longitudinally through the tubing; at least one retainer mounted to the electrical cable and having an outer diameter which is less than the inner diameter of the tubing; and at least one primary set of dimples integrally formed in the tubing, the dimples within the primary set being spaced circumferentially apart from each other and protruding into the tubing a distance which circumscribes a clearance diameter which is less than the outer diameter of the retainer, creating ledges which are engaged by the retainer when the apparatus is installed in the well.

12 The apparatus according to claim 11, wherein there are at least three of the dimples within the primary set, each of the dimples being circular and having an axis, the axes of the dimples within the primary set being in a common plane normal to a longitudinal axis of the tubing.

13 The apparatus according to claim 11 or 12, wherein said at least one primary set of dimples comprises a pair of primary sets of the dimples, one of the primary sets being located adjacent to each end of the retainers.

14 The apparatus according to claim 13, wherein a longitudinal distance between the primary sets of dimples for the retainer is greater than a length of the retainer to allow limited longitudinal movement of the retainer in the tubing relative to the dimples.

The apparatus according to any of claims 11-14, wherein the retainer comprises at least two portions 18 - which are clamped together around the electrical cable by fasteners.

16 The apparatus according to claim 11 or 12, wherein each of the dimples has a depressed exterior surface which is filled with a rigid material.

17 The apparatus according to claim 16, wherein the rigid material is weld material.

18 The apparatus according to any of claims 11-15, further comprising:

at least one secondary set of dimples formed in the tubing, the secondary set being spaced longitudinally a short distance from the primary set, the dimples within each of the adjacent primary and secondary sets being staggered circumferentially from each other.

19 A length of coiled tubing for use in a well, comprising:

at least one indentation integrally formed in the tubing, the indentation having an interior surface protruding into an interior passage of the tubing for creating a ledge; and wherein the indentation creates an exterior depression which is filled with an inlay of rigid material to prevent the interior surface of the indentation from flattening while running the tubing in and out of the well.

The coiled tubing according to claim 19, wherein the indentation is a dimple having a dimple axis which is perpendicular to a longitudinal axis of the tubing.

21 The coiled tubing according to claim 19 or 20, wherein the rigid material is steel weld material.

22 The coiled tubing according to claim 19, 20 or 21, wherein the indentation is a circular dimple.

23 The coiled tubing according to any of claims 19-22, wherein said at least one indentation comprises a plurality of dimples spaced around a circumference of the tubing in a common plane perpendicular to an axis of the tubing.

24 The coiled tubing according to claim 23, wherein each of the dimples is circular and the rigid material is steel weld material.

A method of installing an electrical cable within tubing for use in a well, the electrical cable having at least one insulated electrical conductor embedded within an elastomeric jacket, comprising:

(a) mounting at least one retainer to the electrical cable, the retainer having a load shoulder which is adapted to face downward when installed within a well; (b) inserting the electrical cable into the tubing; and (c) locating the retainer within the tubing and forming at least one load supporting indentation in the tubing adjacent to and spaced a short distance from the load shoulder, the load supporting indentation protruding into the tubing to create a ledge for engagement by the load shoulder when the tubing is installed within a well.

26 The method according to claim 25, wherein step (a) further comprises providing the retainer with an opposite shoulder which is adapted to face upward when installed within a well; and wherein the method further comprises:

forming at least one indentation in the tubing () 20 - adjacent to and spaced a short distance from the opposite shoulder for engagement by the opposite shoulder.

27 A method of deploying coiled tubing in a well, comprising:

(a) forming at least one indentation in the tubing having an interior surface which protrudes into an interior passage of the tubing for creating a ledge; and (b) filling an exterior depression created by the indentation with an inlay of rigid material; then (c) running the tubing into the well.

28 The method according to claim 27, wherein step (b) comprises filling the depression with a weld material.

29 The method according to claim 27 or 28, further comprising inserting a member into the tubing and supporting the member on the ledge after step (d) Apparatus for installation in a well for transmitting power to a well pump substantially as hereinbefore described with reference to the accompanying drawings.

31 A method of installing an electrical cable within tubing for use in a well substantially as hereinbefore described with reference to the accompanying drawings.

Amended claims have been filed as follows 68340001 357 Claims 1 A length of coiled tubing for use in a well, comprising:

2 The coiled tubing according to claim 1, wherein the indentation is a dimple having a dimple axis which is perpendicular to a longitudinal axis of the tubing.

3 The coiled tubing according to claim 1 or 2, wherein the rigid material is steel weld material.

4 The coiled tubing according to claim 1, 2 or 3, wherein the indentation is a circular dimple.

The coiled tubing according to any of claims 1-4, wherein said at least one indentation comprises a plurality of dimples spaced around a circumference of the tubing in a common plane perpendicular to an axis of the tubing.

6 The coiled tubing according to claim 5, wherein each of the dimples is circular and the rigid material is steel weld material.

7 A method of deploying coiled tubing in a well, comprising:

8 The method according to claim 7, wherein step (b) comprises filling the depression with a weld material.