Patent Publication Number: US-9416640-B2

Title: Downhole wellbore heating system and method

Description:
RELATED APPLICATIONS 
     This application claims priority to U.S. Provisional Patent Application No. 61/703,464 filed on Sep. 20, 2012, the entire contents of which are incorporated herein by reference. 
    
    
     BACKGROUND 
     It is often beneficial to provide downhole heat in oil and/or gas wells and similar environments. For example, heat can be delivered to the production tubing in the well via a heater installation in order to heat the oil to be extracted, reducing its viscosity and improving extraction rates. In another example for heavy oil production, the heater installation can deliver heat to the oil reservoir itself to increase the amount of oil that enters the production tubing. Existing downhole heater installations typically require the use of a drilling or other rig. Further, the installation of a heater is usually managed by clamping heater cables to the exterior of the production tubing, which generally requires that a complete workover or similar operation must be performed. Such operations can be very time consuming and expensive processes. 
     In certain circumstances, heating systems of the present invention can be deployed within continuous tubing, frequently referred to as “coiled tubing” because it is sufficiently flexible to be coiled onto a spool and transported to the deployment site. Deployment of coiled tubing heaters improves heat transfer to a target medium because such coiled tubing heaters provide a larger surface area in contact with said medium, and can frequently be installed so as to be in direct contact with said medium. Further, because exposure of heater cables to well fluids can be problematic due to the chemical makeup of such fluids, installation of such heater cables within coiled tubing isolates and protects heater cables from such well fluids. In many applications, such continuous tubing heating devices can be installed without performing a workover, or requiring the use of a drilling or other rig. 
     Electric cables typically do not have sufficient tensile strength to be deployed independently within a tube, especially over relatively long vertical sections. Accordingly, various means of providing support to heater cables have been designed including, without limitation, for downhole skin-effect heaters like the skin-effect heating cable described in co-pending United States Patent Application Publication No. 2011/0233192, entitled “SKIN EFFECT HEATING SYSTEM HAVING IMPROVED HEAT TRANSFER AND WIRE SUPPORT CHARACTERISTICS”, which is incorporated herein by reference. Unfortunately, such existing methods are generally not suitable to use with multiple independent cables, such as mineral insulated (“MI”) cables, that comprise their own electrical circuit and do not need to be electrically attached to the coiled tubing to function. 
     In some cases, simple banding or clamping materials have been used to support cables in a desired position, including binding such cables to support rope. However, simple banding can come loose, particularly after thermal cycling of heating elements. Other methods of installing cables into tubes have been utilized in the oil and gas industry include: crimping the tube to the cables; using helical buckling to self support the cables; using high strength conductor materials; and tightly forming the tube over the cable during the tube manufacturing process. However, none of these methods provide the benefits of the present invention, which further addresses problems associated with supporting of heating cables and tubing containing such heating cables. 
     SUMMARY 
     Some embodiments of the invention provide a downhole heating apparatus having one or more electric heating cables, an elongated support member attached to the heating cables and receiving a mechanical load from the heating cables, and a cable hang-off configured to vertically suspend the heating cables and the support member. The cable hang-off can have a shell through which the heating cables and the support member are disposed, the shell having a bowl, and a plurality of slips that cooperate with each other and with the bowl to form a pinching member that grips and suspends the support member. The heating cables can be mineral insulated cables. The support member can be a wire rope attached to the heating cables at regular intervals with a cable support clamp. The cable support clamp can include at least one clamp body having a cable cavity for each heating cable and a rope cavity. The shell can have a cylindrical mount that receives an end of a length of coiled tubing, and the heating cables and support member can be disposed within the length of coiled tubing when the support member is suspended by the pinching member. The coiled tubing can be pressure-sealed at its opposite end from the shell, and can be filled with a dielectric fluid. 
     The slips can form a gripping channel in the pinching member, through which the support member is disposed when it is gripped by the pinching member. The gripping channel can have a non-slide surface formed by projections on a gripping surface of each of the slips. The slips can form one or more cable channels in the pinching member, through which the heating cables are disposed when the support member is gripped by the pinching member. 
     Other embodiments of the invention provide a downhole heating apparatus having one or more electric heating cables, an elongated support member that receives a mechanical load from the heating cables when the heating cables are suspended vertically by a cable hang-off, and a plurality of cable support clamps that attach the support member to the heating cables and transfer mechanical loads from the heating cables to the support member, the cable support clamps being attached to the support member and to the heating cables at regular intervals along the length of the support member. The heating cables can be mineral insulated cables. The support member can be a wire rope. In some embodiments, there are three heating cables and each cable support clamp includes a clamp body having a cylindrical center member with an outer surface and a rear surface, a first wing attached to the center member at the outer surface and having a first cable cavity and a second cable cavity, and a second wing attached to the center member at the outer surface diametrically opposite the first wing, the second wing having a third cable cavity and a rope cavity. The first and second wings can be flush with the rear of the center member, can be about twice the length of the center member in the center member&#39;s axial direction and can have an arcuate interior surface that conforms to the diameter of the center member and defines a mounting channel between the first wing and the second wing. Each of the first and second wings can further have a groove disposed in an outer surface of the wing. 
     Other embodiments of the invention provide a downhole heating apparatus for a wellbore, having a cable hang-off configured to be installed in a wellbore termination assembly, The cable hang-off can have a proximal end and a distal end and can include a cylindrical mount that is disposed in the distal end and receives an end of a length of coiled tubing disposed in the wellbore, a conical bowl that is disposed in the proximal end and connects with the mount, and a plurality of slips that cooperate with each other and with the bowl to form a pinching member having a gripping channel and a cable channel, an electric heating cable disposed in the coiled tubing and in the cable channel, and an elongated support member attached to the heating cable, disposed in the coiled tubing, and disposed in and gripped by the gripping channel. Each of the slips can be identical and wedge-shaped, and can have an arcuate outer surface that conforms to the bowl, a first inner surface adjacent to one end of the outer surface, and a second inner surface adjacent to the other end of the outer surface, the second inner surface being a mirror image of the first inner surface. Each of the inner surfaces can have a planar portion and an arcuate portion, the first inner surface of one slip cooperating with the second inner surface of an adjacent slip to form a cable channel in the pinching member. Each of the slips can further have an arcuate gripping surface that cooperates with the gripping surfaces of the other slips to form a gripping channel in the pinching member. 
    
    
     
       DESCRIPTION OF THE DRAWINGS 
         FIG. 1A  is a cross-sectional schematic diagram of a heating apparatus according to the present disclosure. 
         FIG. 1B  is a cross-sectional schematic diagram of a wellhead termination assembly of the heating apparatus of  FIG. 1A . 
         FIG. 2  is another cross-sectional schematic diagram of a heating apparatus according to the present disclosure. 
         FIG. 3  is a cross-sectional schematic diagram of a length of coiled tubing according to the present disclosure. 
         FIG. 4  is another cross-sectional schematic diagram of a length of coiled tubing according to the present disclosure. 
         FIG. 5  is a side perspective view of an inline cable splice of the present disclosure. 
         FIG. 6  is a side view of an inline cable splice of the present disclosure. 
         FIG. 7  is a front view of an inline cable splice of the present disclosure. 
         FIG. 8  is a side perspective view of a wye splice of the present disclosure. 
         FIG. 9  is a side view of a wye splice of the present disclosure. 
         FIG. 10  is a side view of a wye splice of the present disclosure. 
         FIG. 11  is an end view of a wye splice of the present disclosure. 
         FIG. 12  is a side perspective view of a cable support clamp of the present disclosure. 
         FIG. 13  is a side view of a cable support clamp of the present disclosure. 
         FIG. 14  is a front view of a cable support clamp of the present disclosure. 
         FIG. 15  is a rear view of a cable support clamp of the present disclosure. 
         FIGS. 16A-B  are side perspective views of assembly of a cable support clamp of the present disclosure. 
         FIG. 17  is a front perspective view of a cable hang-off of the present disclosure. 
         FIG. 18  is a side perspective view of a shell of a cable hang-off of the present disclosure. 
         FIG. 19  is a side perspective view of a shell half of a cable hang-off of the present disclosure. 
         FIG. 20  is a side view of a shell half of a cable hang-off of the present disclosure. 
         FIG. 21  is a top view of a shell half of a cable hang-off of the present disclosure. 
         FIG. 22  is a rear view of a shell half of a cable hang-off of the present disclosure. 
         FIG. 23  is a front perspective view of a slip of a cable hang-off of the present disclosure. 
         FIG. 24  is a top view of a slip of a cable hang-off of the present disclosure. 
         FIG. 25  is a side view of a slip of a cable hang-off of the present disclosure. 
         FIG. 25A  is an inset detail view of area  25 A of  FIG. 25 . 
         FIG. 26  is a front perspective view of a cable hang-off of the present disclosure being assembled over a proximal end of a coiled tubing. 
         FIG. 27  is a side view of a cable hang-off of the present disclosure being assembled over a proximal end of a coiled tubing. 
         FIG. 28  is a front perspective view of a cable hang-off of the present disclosure being assembled over a proximal end of a coiled tubing. 
         FIG. 29  is a side view of a cable hang-off of the present disclosure being assembled using a pressure plate. 
         FIG. 30  is a top view of a cable hang-off of the present disclosure being assembled using a pressure plate. 
         FIG. 31  is a side view of a cable hang-off of the present disclosure being assembled using a pressure plate. 
         FIG. 32  is a side view of a cable hang-off of the present disclosure being assembled using a pressure plate. 
         FIG. 33  is a side perspective view of a wellhead termination assembly of the present disclosure, shown with the terminal spool in broken lines. 
         FIG. 34  is a side view of a wellhead termination assembly of the present disclosure, shown with the terminal spool removed. 
         FIG. 35  is a plan view of a method of manufacturing the heating apparatus according to the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     Before any embodiments of the invention are explained in detail, it is to be understood that the invention is not limited in its application to the details of construction and the arrangement of components set forth in the following description or illustrated in the following drawings. The invention is capable of other embodiments and of being practiced or of being carried out in various ways. Also, it is to be understood that the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting. The use of “including,” “comprising,” or “having” and variations thereof herein is meant to encompass the items listed thereafter and equivalents thereof as well as additional items. Unless specified or limited otherwise, the terms “mounted,” “connected,” “supported,” and “coupled” and variations thereof are used broadly and encompass both direct and indirect mountings, connections, supports, and couplings. Further, “connected” and “coupled” are not restricted to physical or mechanical connections or couplings. 
     The following discussion is presented to enable a person skilled in the art to make and use embodiments of the invention. Various modifications to the illustrated embodiments will be readily apparent to those skilled in the art, and the generic principles herein can be applied to other embodiments and applications without departing from embodiments of the invention. Thus, embodiments of the invention are not intended to be limited to embodiments shown, but are to be accorded the widest scope consistent with the principles and features disclosed herein. The following detailed description is to be read with reference to the figures, in which like elements in different figures have like reference numerals. The figures, which are not necessarily to scale, depict selected embodiments and are not intended to limit the scope of embodiments of the invention. Skilled artisans will recognize the examples provided herein have many useful alternatives and fall within the scope of embodiments of the invention. 
     Referring to  FIGS. 1A, 1B, and 2 , the present invention encompasses various embodiments of installing an electric heating apparatus downhole within the production tubing  100  of a wellbore  102  for the purpose of providing thermal (heat) energy to the production tubing  100 , the wellbore  102 , the medium contained in the wellbore  102 , or the surrounding environment (i.e., reservoir). The apparatus can include a length of coiled tubing  40  containing one or more electric heating cables that provide the thermal energy. The coiled tubing  40  extends from a proximal end at or near the wellhead  104  downhole a predetermined distance to a distal end, which may be at, short of, or beyond the bottom of the production tubing  100 . A tubing plug  42  located at or near the bottom end of the coiled tubing  40  can provide a pressure-tight seal between the coiled tubing  40  and the surrounding environment. 
     The coiled tubing  40  can be attached at its proximal end to a wellhead termination assembly  50 . The wellhead termination assembly  50  can include a coiled tubing hanger  52 , a termination spool  54  disposed above the coiled tubing hanger  52 , and a wellhead cable hang-off  56  disposed within the termination spool  54 . The coiled tubing hanger  52  hangs the coiled tubing  40  at its proximal end, substantially coaxially with the production tubing  100  as is known in the art, allowing the proximal end of the coiled tubing  40  to interface with the cable hang-off  56 . The terminal spool  54  is a hollow metal cylinder that contains and protects the cable hang-off  56  and the heater termination attachments  58  for one or more electrical heating cables  70 . In some embodiments, the heater termination attachments  58  can be attached to a cold lead of each heating cable  70 . An electrical feedthrough  60  in the terminal spool  54  receives connecting wires  62  that connect to the termination attachments  58  and deliver power to the heating cables  70  from the transformer  66 . A heater control panel  68  can be disposed in the electrical circuit that includes the cables  70 , in order to control power supplied to the cables  70 . 
     Referring to  FIGS. 3 and 4 , the coiled tubing  40  can contain one or more electrical heating cables  70 , such as MI cables or polymer insulated cables, that extend along all or most of the length of the coiled tubing  40  and are isolated, and thereby protected, from the surrounding wellbore  102  environment. Specifically, the cables  70  are enclosed within the coiled tube  40  and sealed off from well fluids which often contain corrosive or harsh gases and liquids which can damage the cables  70 . Isolating the cables  70  from well fluids allows for the use of cables and related materials (such as, by way of illustration but not limitation, silver solder) that would otherwise not be possible in many applicable environments. Further, by allowing a broader range of materials to be used to construct the heating cables  70  and associated components, more cost effective systems can be manufactured. 
     One or more of the cables  70  may be comprised of cable segments  70 A, B, C, and adjacent segments may be spliced together with an inline cable splice  72 . The inline cable splice  72  depicted in  FIGS. 5-7  is a splice which can connect two or more heating cables from the same electrical circuit phase inline so as to facilitate longer circuit lengths. Typically, cable segments  70 A, B enter/exit the splice from opposite ends. In some embodiments, one or more of the cables  70  can be comprised of segments  70 A-C with different properties in order to deliver different amounts of thermal energy along the length of the coiled tubing  40 . For example, a cable  70  can have a cold lead  70 A that has a very narrow conductor or very thick insulator to radiate little or not thermal energy, a warm lead  70 B having properties that cause it to radiate some thermal energy, and a hot lead  70 C that comparatively delivers the most thermal energy to its surroundings. The lead segments  70 A-C can be further spliced with inline cable splices  72  as shown in  FIG. 3 . 
     Separate cables  70  may be spliced together or co-terminated with a wye splice  74  or end cap, respectively. The cable wye splice  74  (or end cap) depicted in  FIGS. 8-11  is a splice which connects two or more cables  70  from different electrical circuit phases together to form a closed circuit at the electrical terminal (i.e., distal) end of the heater system. While the wye splice  74  is disposed at the distal end of the coiled tubing  40  in  FIGS. 3 and 4 , it is not required to be so located, as it is possible to “loop back” cables  70  for some distance in order to increase power output in a portion of the coiled tubing  40 . Typically, all spliced cables  70  enter the wye splice  74  from the same end, and no cables  70  enter or exit the wye splice  74  from the opposite end. 
     Referring again to  FIGS. 3 and 4 , the coiled tubing  40  can further contain a high-strength, elongate support member  76 , such as a wire rope, extending along the length of the coiled tubing  40  substantially parallel and in proximity to the heating cables  70 . The support member  76  can be attached to the heating cables  70  for the purpose of transferring mechanical load onto the support member  76 . The support member  76  provides tensile strength for purposes of pulling the cables  70  into the coiled tubing  40  during the manufacturing or assembly process, and also for the purposes of providing additional tensile strength when the coiled tubing  40  and the cables  70  are disposed vertically inside the wellbore  102  or another installation. In some embodiments, the support member  76  can be attached to some or all of the cables  70  at regular intervals along the length of the support member  76  with cable support clamps  80 . The cable support clamp  80  is used to make a mechanical connection between cables  70  and the elongate support member  76  in order to transfer mechanical loads from the cables  70  to the support member  76 . A cable support clamp  80  can attach all or a subset of the cables  70  to the support member  76 . 
       FIGS. 12-16B  illustrate an exemplary cable support clamp  80  for the heating system of  FIGS. 3 and 4 , which has three cables  70  and one wire rope (i.e., support member  76 ). The cable support clamp  80  can include at least one clamp body  82  having a cylindrical center member  84  and substantially diametrically opposed wings  86 ,  88  attached to or integral with the center member  84  at the outer surface of the cylinder. The center member  84  can include a centrally disposed bore  90 . The bore  90  may be partially or completely threaded for receiving a bolt  128 , or may be otherwise configured to receive an attachment device for attaching another clamp body  82  as described below. Each wing  86 ,  88  is flush and coplanar with the rear of the center member  84  and is twice the length of the center member  84  in the axial direction, therefore extending past the front of the center member  84  for the length of the center member  84 . The front surfaces of the wings  86 ,  88  are coplanar. A mounting channel  92  separates the wings  86 ,  88  and is defined by an arcuate interior surface  92 A,B on each wing  86 ,  88  that conforms to the diameter of the center member  84 . 
     Each wing  86 ,  88  can include one or more cavities that are configured to cooperate with corresponding cavities in the corresponding wing  86 ,  88  of another clamp body  82 . A first wing  86  can include a first cable cavity  94 A and a second cable cavity  94 B, while the opposing second wing  88  can include a third cable cavity  94 C and a rope cavity  96 . The cable cavities  94 A-C each hold a cable  70  and therefore may be the same size (i.e., cavity radius). The rope cavity  96  can have a smaller radius than the cable cavities  94 A-C. Any of the cavities  94 A-C,  96  can further have a tapering profile, such that the cavity radius is larger at one end of the wing  88  than at the other. The tapering profile allows the cable support clamp  80  to pinch, and thereby grip, the cables  70  and support member  76  when the smaller cavity radius is less than the radius of a cable  70  or the support member  76 . Each wing  86 ,  88  can further include one or more grooves  98  disposed in the outer surface of the wing  86 ,  88 . The grooves  98  can facilitate the passage of a fluid that is used to fill the coiled tubing  40  if the coiled tubing  40  is being filled as described below when the cable support clamps  80  are present therein. 
     As shown in  FIGS. 16A-B , in some embodiments the cable support clamp  80  can include two substantially identical clamp bodies  82  oriented in opposite axial directions and at a 90-degree angle to each other. With the bores  90  of the clamp bodies  82  aligned, the clamp bodies  82  interface with each other, the central member  84  of one clamp body  82  sliding into the mounting channel  92  of the opposing clamp body until the central members  84  abut each other. A bolt  110  or other suitable attachment device can then be inserted through the bores  90  to attach the clamp bodies  82  to each other. Each cable cavity  94 A-C and the rope cavity  96  of one clamp body  82  cooperates with the corresponding cable cavities  94 A-C and rope cavity  96  of the other clamp body  82  to create clamp channels  97 A-D for each heating cable  70  and the support member  76 . 
     A suitable interval for attaching the cable support clamps  80  can depend on several factors, including the length and diameter of the cables  70  and support member  76 , the trajectory of the wellbore  102 , and the inherent material tolerances of the cable support clamp  80 . The apparatus can include cable support clamps  80  of different sizes, including clamp body  82  size and clamp channel  97 A-D diameters, for different sized heating cables  70 . The material of the clamp bodies  82  can have high heat tolerance to resist deformation that might cause the cables  70  or support member  76  to slip at high temperatures. In one working example, an apparatus disposed in vertically-hung and air-filled coiled tubing  40 , and having three heating cables  70  and one wire rope as the support member  76 , has the following characteristics: 
                                        Free-hanging cable total length   5195   ft.                     Cold lead segment 70A length (approx.)/dia.    320 ft./0.496 in.       Warm lead segment 70B length (approx.)/dia.   3395 ft./0.355 in.       Hot lead segment 70C length (approx.)/dia.   1500 ft./0.286 in.                         Approx. hanging weight of cables 70 and wire rope   10,134   lb.       Clamp 80 spacing   100   ft. (75 ft.               in cold               lead               segment               70A)       Clamp 80 quantity/load for cold lead segment 70A   6/115   lb.       Clamp 80 quantity/load for warm lead segment 70B   34/75   lb.       Clamp 80 quantity/load for hot lead segment 70C   15/48   lb.                    
The illustrated clamp  80  may be comprised substantially of carbon steel, in which case the clamps  80  of each of the three sizes needed for the working example can support a load of 275-300 lbs. at a temperature of 185 F-220 F. In other embodiments, the clamp  80  can be stainless steel or another suitable material.
 
     In some embodiments, the coiled tubing  40  may be filled with at least one fluid which serves a variety of beneficial purposes. Said at least one fluid can improve heat transfer between the cables and the tubing, thereby allowing higher power output and higher system operating temperature. Fluid filling also provides a means of tube integrity monitoring including, without limitation, by way of the measurement of the fluid pressure or level inside the tube. Fluid filling further provides a buoyancy effect on the heating cables  70  and support member  76 , relieving some of the mechanical load on the clamps  80  and cable hang-off  56 . In the working example, the coiled tubing  40  can receive approximately 400 gal. of a dielectric fluid, such as transformer oil, mineral oil, or another dielectric oil, leaving a safety gap of about 250 ft. to the wellhead, allowing sufficient expansion volume of the fluid at expected temperatures to prevent an overflow and keep air pressures within the system at a manageable level. This configuration relieves about 800 lb. of the above hanging weight. 
     Referring to  FIGS. 17-25 , the wellhead cable hang-off  56  can be used to suspend the cables  70  and support member  76  (e.g., wire rope) within the coiled tubing  40  or other structure, usually at the uppermost extent of the heater system where electrical power will be connected to the cables  70 . In particular, the cable hang-off  56  can provide the requisite mechanical support to hold the support member  56  at or near its proximal end, allowing the support member  56  and the cables  70  to extend downhole within the coiled tubing  40 . 
     Referring to  FIGS. 17-22 , the cable hang-off  56  can include a shell  120  having a distal end that fits over the proximal end of the coiled tubing  40 , and a proximal end that receives a plurality of slips  130 . The shell  120  can be divided into two halves  120 A,B that can be identical, or at least substantially symmetrical. The halves  120 A,B can be semi-cylindrical, with planar faces that abut each other and receive bolts or other attachment devices to hold the halves  120 A,B together. Each half  120 A,B of the shell  120  has a plurality of cavities that cooperate with the cavities of the opposing half  120 A,B to form a plurality of receptacles in the shell  120 : the proximal cavities  122 A,B cooperate to form a conical bowl  122  that receives the slips  130 ; and, the distal cavities  124 A,B cooperate to form a cylindrical mount  124  that receives the proximal end of the coiled tubing  40 . The proximal face of the shell  120  can include a plurality of bolt holes  126 . The distal end of the shell  120  can be beveled. 
     Referring to  FIGS. 23-25 , the slips  130  are wedge-shaped members that cooperate to form a conical pinching member that suspends the support member  76  via friction fit. Specifically, the slip  130  tapers from a proximal end to a distal end, and has an arcuate outer surface  132  that conforms to the radius of the bowl  122 . The slip  130  can have first and second inner surfaces  134 ,  136  that are adjacent to each end of the outer surface  132 . The first and second inner surfaces  134 ,  136  are mirror images of each other, each having a planar portion  134 A,  136 A and an arcuate portion  134 B,  136 B. In this configuration, the first inner surface  134  cooperates with the second inner surface  136  of an adjacent slip  130  to form a cable channel  140 . See  FIG. 17 . The slip  130  can further have an arcuate gripping surface  138  positioned to cooperate with the gripping surfaces  138  of the other slips  130  to create a substantially circular gripping channel  142  that is coaxial with the shell  120 . See  FIG. 17 . The gripping surface  138  may have studs, ribs, teeth, or other projections  138 A, as shown in  FIG. 25A , that give the gripping channel  142  a slide-resistant surface. 
     Referring to  FIGS. 26-32 , the halves  120 A,B of the shell  120  can be assembled over the coiled tubing  40 . For the example system having three cables  70  and one wire rope (i.e., support member  76 ), three slips  130  assemble by being inserted into the bowl  122  to form the pinching member  144 , with the gripping channel  142  encircling and gripping the wire rope, and the cable channels  140  disposed around the cables  70 . The slips  130  can be mechanically inserted into the bowl  122  into contact with the wire rope so that the gripping channel  142  grips the wire rope. The apparatus can then be allowed to hang, such that the friction between the gripping channel  142  and the wire rope pulls the slips  130  downward and inward within the bowl  122  to their tightest-fitting position. Additionally or alternatively, a pressure plate  150  as shown in  FIGS. 29-32  can be used to mechanically urge the slips  130  into their tightest-fitting position. The pressure plate  150  can have an arm  152  for contacting each of the slips  130 . The arms  152  meet at the center of the pressure plate  150 , and can define a fitting recess  154  that surrounds the wire rope so that the wire rope is centered at the center of the pressure plate  150 . The pressure plate  150  can push the slips  130  into place, and then can be attached to the shell  120 , such as with one or more bolts driven into the bolt holes  126 . 
     Referring to  FIGS. 33 and 34 , the proximal ends of the cables  70  can extend proximally out of the cable hang-off  56  and connect electrically to cable terminators  58 . The cable terminators  58 , in turn, connect electrically to wires  62  that extend out of the termination spool  54  through the electrical feedthrough(s)  60 . 
     Another feature or embodiment of the present invention comprises a method of manufacturing the apparatus by installing the cable into the coiled tubing  40 , such as with a sinker bar if the coiled tubing  40  is installed in a vertical well, or with a horizontal pull into horizontally-laid coiled tubing  40 . For horizontal installation, the coiled tubing  40  is laid flat and cut to length. One or more heating cable spools  200 , each carrying a heating cable  70 , and a support member spool  202  are positioned at the distal (i.e., downhole) end of the coiled tubing  40 . A cable alignment space A and a clamp installation space B (of at least 100 ft) may be left between the spools  200 ,  202  and the coiled tubing  40 . Protective members  204 , such as one or more sheets of plywood, may be laid in the path between the spools  200 ,  202  and the coiled tubing  40 . A funnel  210  can be attached to the distal end of the coiled tubing  40  to facilitate running the cables  70 . The cables  70  and support member  76  are paid out of the spools  200 ,  202 . The cables  70  can be run through a cable straightener  212  with the support member  76  being drawn out of the way of (i.e. alongside, under, or over) the straightener  212 . Then, the proximal ends of the cables  70  and support member  76  are attached to a pull-rope  206 , which is disposed inside the coiled tubing  40  and attached to a pull-rope spool  208  at the proximal end of the coiled tubing  40 . 
     Before drawing the cables  70  and support member  76  into the coiled tubing  40 , the first clamp  80  is installed about one foot from the proximal ends of the cables  70  and support member  76 . The cables  70  and support member  76  are then drawn into the coiled tubing  40  by slowly retracting the pull-rope  206 . As the pull-rope  206  is retracted, the clamps  80  can be continuously installed at the desired interval until the distal ends of the cables  70  are about three feet from the distal end of the coiled tubing  40 . If used, the wye splice  74  can be installed on the distal ends of the cables  70  using any suitable connection method. The wye splice  74  can be pushed into the end of the coiled tubing  40  and the tubing plug  42  installed. At the proximal ends, any slack in the cables  70  can be pulled out, and then the cables  70  and support member  76  can be separated from the pull-rope  206  and cut back to a desired length. Where the support member  76  is a wire rope, the wire rope can be left about one foot longer than the cables  70  to facilitate looping and crimping the wire rope for hanging. The coiled tubing  40  with the cables  70 , support member  76 , and clamps  80  installed can then be wound onto a shipping spool (not shown). 
     Another feature or embodiment of the present invention comprises a method of installing the apparatus in a wellbore  102 . The shipping spool and cable hang-off  56  are delivered to the installation site. The coiled tubing  40  is deployed into the production tubing  100  and then suspended by the coiled tubing hanger  52  as is known in the art, while the proximal end of the support member  76  is attached to a temporary hanging device, such as by placing the crimped loop on a hook (not shown in FIGS.). The shell  120  of the cable hang-off  56  can be split into its halves  120 A,B, see  FIG. 26 , and then bolted back together so that the proximal end of the coiled tubing  40  is disposed in the mount  124  of the shell  120  and the cables  70  and support member  76  project proximally out of the shell  120 . See  FIG. 27 . The cables  70  are spread apart and the pressure plate  150  is inserted around the support member  76 . See  FIGS. 29, 30 . The slips  130  are then positioned over the bowl  122  in contact with the underside of the pressure plate  150 , see  FIG. 31 , and then driven into place in the bowl  122 . See  FIGS. 28 and 32 . The pressure plate  150  can be attached to the shell  120  with bolts or other attachment devices. See  FIG. 32 . The slips  130  thereby form the pinching member  144  having its tightest-fitting position, gripping the support member  76 . The tension of the temporary hanging device can be drawn to zero to test for slippage of the support member  76  within the gripping channel  142 . If there is no slippage, the support member  76  can be cut or otherwise removed from the temporary hanging device and the termination attachments  128  can be attached to the cables  70 . See  FIG. 34 . 
     Structural/functional differences between the present invention and the prior art include, without limitation, the following: 
     1. Use of steel wire rope or other support member to support electric downhole heater elements inside continuous tubing for purposes of wellbore heating; 
     2. Components used to clamp cables to wire rope; 
     3. Components used to hang-off cable system within a wellhead; 
     4. Use of dielectric fluid(s) to fill continuous tubing; 
     5. Ease of retrievability of the heater system of the present invention; and 
     6. Ability to pull (install) relatively low tensile strength heating elements into coiled tube using the high strength rope. 
     Advantages of the present invention over the prior art include, without limitation, the following: 
     1. Ease of installation of the present invention, especially on very long cable systems into tubing (cable supports); 
     2. Provides requisite clamping force and tensile strength for long or deep heater systems (cable supports); 
     3. Maintains grip and strength after thermal cycling of the heating element(s); 
     4. Easier to install the heater system of the present invention into a well than existing prior art methods; 
     5. Heater elements are protected from wellbore fluids; 
     6. Use of dielectric fluid(s) for heat transfer, tube integrity monitoring (through pressure monitoring and/or other methods) and improved dielectric performance; 
     7. Use of dielectric fluid(s) to reduce tension and hanging load of cables and rope (due to buoyancy); and 
     8. Protection of heater cables and components from well fluids. 
     It will be appreciated by those skilled in the art that while the invention has been described above in connection with particular embodiments and examples, the invention is not necessarily so limited, and that numerous other embodiments, examples, uses, modifications and departures from the embodiments, examples and uses are intended to be encompassed by the claims attached hereto. The entire disclosure of each patent and publication cited herein is incorporated by reference, as if each such patent or publication were individually incorporated by reference herein. Various features and advantages of the invention are set forth in the following claims.