Patent Grant
7918271
The invention provides method and apparatus to provide electrical connection in a wellhead for a downhole electrical device.
Power is often needed to be provided to downhole electrical devices such as pumps and heaters. Electrical heaters may be used to heat the subterranean formation by radiation and/or conduction, or the heater may resistively heat an element. U.S. Pat. No. 6,023,554 to Vinegar et al., assigned to Shell Oil Company, describes an electrical heating element that is positioned within a casing. The heating element generates radiant energy that heats the casing. A granular solid fill material may be placed between the casing and the formation. The casing may conductively heat the fill material, which in turn conductively heats the formation. While a large number of patents are directed to methods of heating a subterranean formation, very few patents provide the necessary teachings to provide wellhead equipment capable of providing the high voltages likely to be needed to heat heavy oil formations, while maintaining well control in pressure environments. For instance, in U.S. Pat. No. 7,004,247 to Cole et al., assigned to Shell Oil Company, it is noted that, for heaters greater than about 700 m in length, voltages greater than about 2000 V may be needed for generating heat, compared to voltages of about 480 V that may be used for heaters having lengths less than about 225 m.
U.S. Pat. No. 4,716,960 to Eastlund et al., describes electrically heating of the tubing of a petroleum well by passing a relatively low voltage current through the tubing to prevent formation of solids. Isolated tubing hangers are known in the oil and gas industry. They are often used when providing an electrical connection to one or more downhole electrical devices such as pumps or electrical instruments. However, for the most part, the power is supplied by electrical cables, which are accommodated through a tubing hanger by feed through connectors which provide electrical isolation from the hanger. Exemplary patents relating to insulated tubing hangers include U.S. Pat. No. 4,923,006 to Hartmann et al. and U.S. Pat. No. 6,763,882, issued Jul. 20, 2004 to Demny et al. U.S. Pat. No. 5,280,766 to Mohn describes a subsea wellhead system in which concentric tubular conductors with insulating sleeves therebetween are used to provide power to a pump. Few details for providing the electrical connection at the wellhead are provided.
In general, the prior art patents are not directed to the unique problems associated with the provision of high voltage to downhole electrical devices through wellhead tubing strings under pressure-containing and electrical isolating conditions. For instance, the current needed to run downhole instrumentation, pumps or even to heat a tubing to prevent a wax build up, is minor compared to that needed to run downhole heaters in heavy oil reservoirs.
As well, the patents relating to isolated tubing hangers suffer the disadvantage of not providing a feature for making an electrical connection at the wellhead when the well is under pressure.
In a broad aspect, the invention provides a wellhead assembly for providing a power connection to a downhole electrical device, including:
Preferably, the one or more body members form separate first and second tubing hanger profiles to support the grounding tubing hanger and the isolated tubing hanger in vertically stacked relationship in the vertical wellbore. Preferably, the conducting portion of the isolated tubing hanger includes a conducting neck portion extending upwardly relative to the housing of the isolated tubing hanger; and the hot electrical connection connects to the conducting neck portion outside the vertical wellbore.
The invention also broadly extends to a hot electrical connection assembly in a wellhead for providing a power connection to a tubing string extending to a downhole electrical device. The hot electrical connection assembly includes:
The invention also broadly extends to an isolated tubing hanger for suspending a conducting tubing string within a pressure-containing tubing head. The isolated tubing hanger includes:
In yet another broad aspect, the invention provides a method for providing a power connection from a source of current located at a wellhead to a downhole electrical device, wherein the wellhead includes one or more pressure-containing wellhead body members forming a vertical wellbore extending there through, the one or more wellhead body members being operative to support, in sealed relationship in the vertical wellbore, a first and a second tubing hanger, each tubing hanger being operative to suspend therefrom a tubing string such that a first and a second tubing string are concentrically spaced from each other. The method includes:
Preferably, the one or more wellhead body members form first and second tubing hanger profiles to support the first and second tubing hangers in vertically stacked relationship in the vertical wellbore. Preferably, the inner conducting portion of the first tubing hanger includes a conducting neck portion extending upwardly relative to the outer housing of the first tubing hanger, and the source of current is connected to the conducting neck portion outside the vertical wellbore.
It should be understood that the terms “electrical connection” or “electrically connected” as used herein and in the claims is meant to cover both a direct or an indirect electrical connection between the identified members. Thus, for example when it is stated that an electrical connection is provided from the hot electrical connection to the conducting tubing string, the hot electrical connection may make a direct connection to the conducting tubing string, or the connection may be made indirectly through, for example, the conducting portion of the isolated tubing hanger.
It should also be understood that the terms “conductive” or “conducting” when used as adjectives herein and in the claims means that the material for the part modified by these terms is made of one or more electrically conducting materials. Similarly, the terms “grounding” or “grounded” when used as adjectives herein and in the claims means that the material for the part modified by these terms is made of one or more electrically conductive materials.
The present invention provides both a method and apparatus for providing electrical connection at a wellhead for a downhole electrical device, such as a heater. The invention has utility in providing the electrical connection through to tubular conductors (generally concentric tubing strings), which in turn are electrically connected to the downhole electrical device. Five embodiments of the present invention are shown in the Figures, with like members being labeled with the same reference numerals. Once an element has been introduced for the first embodiment, it is denoted with a prime, double prime or triple prime after the reference numeral for the other embodiments in order to signify that the element is modified or that it is included in a modified part of that embodiment.
In general, the wellhead power connection assembly 10 of the present invention is shown in the Figures to include one or more wellhead body members 12 (multiple wellhead body members are shown in the Figures, although it is possible to combine one or more of these wellhead members in some applications), operative to cap a wellbore which has been drilled into an oil formation and contain pressure in a vertical wellbore 11, which extends through each of the body members 12 and is generally vertically aligned. Thus, each of the one or more wellhead body members is formed from pressure-containing metal, with all connections (such as ring seals, preferably provided as ring gasket seals between body members) being pressure-containing. Two concentric tubing strings (one of which could be the casing, but referred to herein as tubings or tubing strings) formed of electrically conductive material(s) (for instance copper clad steel) are suspended by the one or more wellhead body members 12. The Figures show these tubing strings as an inner conducting tubing string 14 and an outer grounding tubing string 16, but they could be reversed. The tubing strings 14, 16, along with an electrical downhole apparatus (not shown) are run into the wellbore. The tubing strings 14, 16 are suspended concentrically in stacked tubing heads 18, 20 in the wellhead assembly 10, and are used to conduct electricity to the downhole electrical device. The uppermost tubing head 18 forms a tubing hanger profile 22 operative to support and seal to an isolated tubing hanger 24. The conducting tubing 14 is suspended, for example by welding, from the lower end of the tubing hanger 24, to provide power to the downhole electrical device (not shown). The lower tubing head 20 (also termed grounding or neutral tubing head) forms a tubing hanger profile 26 operative to support and seal to a grounding tubing hanger 28, which in turn suspends the grounding tubing 16 from its lower end, for example by welding. A ground or neutral connection assembly 29, consisting of a grounding plate 29a and nut and bolt connectors 29b, provides a ground connection from the current source for the grounding tubing head 20 proximate the grounding tubing hanger 26. The circuit is completed through the downhole electrical device. Alternate means for suspending the tubing strings 14,16 from tubing hangers 24, 28 are known, and may be used within this invention, for example threaded, welded or slip connections. The preferred embodiments show the tubing hangers 24, 28, and the tubing hanger profiles 22, 26 to be generally cylindrical, with inwardly tapered sections to provide mating landing shoulders 22a, 26a, in order to support the tubing hangers 24, 28 within the tubing heads 18,20. However, other profile shapes may be used, as is well known in the art. The tubing strings 14,16 may also be otherwise suspended from one or more wellhead members 12, as well known in the art. For instance nested tubing hangers might be suspended from a wellhead. The tubing head could be altered to include a run-in landing shoulder. Still alternatively, the tubing head might include retractable load shoulders. Other variations within the invention will be well known to persons skilled in the art.
The wellhead assembly 10 is shown to preferably include a tubing head adapter 30 as a transition body member to the conventional wellhead equipment located thereabove (shown as a conventional gate valve 31 and a blind flange 32 in the
An electrical junction box 34 is mounted to, or alongside, the wellhead body member(s) 12. In
In
In
The present invention provides methods and apparatus for providing an electrical connection through the wellhead to provide electricity to the downhole electrical device. In its preferred embodiments of
In general, components of the present invention provide seals or are made of materials capable of providing high pressure, high voltage, and high current isolation at elevated temperatures, particularly for operation in conditions needed for electrical heating of a heavy oil reservoir. To limit eddy currents, certain components of the assembly 10 may be made from non-ferromagnetic materials. Electrically isolating materials used in the isolated tubing hanger 24 and the electrical isolation assembly 47 associated therewith, may be made from known electrically insulating materials, for example Teflon® (where not load bearing), and PEEK (polyetherethylketone) when load bearing. Alternate insulating materials such as NEMA Grade 7 through Grade 11 materials and others may be used, as known in the art.
In the first and fourth embodiments shown in the
The ram assembly 37 is sealed and electrically isolated in a horizontal conduit 43 in the tubing head 18. The conduit 43 is located to provide access through the tubing head 18 to the vertical bore 11 at a point to provide electrical connection either directly to the conducting tubing 14, or more preferably, to a conductive portion of the isolated tubing hanger 24, such as the conducting neck extension 38 of the tubing hanger 24, as shown in the Figures. The ram assembly 37 is shown to preferably include two ram assemblies, a conducting ram assembly 44 and a supporting ram assembly 46, located in the tubing head 18. The interface between the ram assemblies 44, 46 and the tubing head 18 is pressure sealed and electrically isolated through an electrical isolation assembly 47. The conducting actuation rod 48 and conducting ram 50 of the conducting ram assembly 44 are formed of an electrically conductive material such as copper, with one end of the rod 48 being connected to a source of current through the hot electrical connection assembly 35. The supporting ram assembly likewise includes a support ram 51 connected to a support actuation rod 49. The rams 50, 51 in each ram assembly 44, 46 move horizontally in and out of the vertical wellhead bore 11 of the tubing head 18. When fully protruding into the vertical wellhead bore 11 (see
The isolated tubing hanger 24 is formed with an outer, generally cylindrical housing 53 (which remains electrically isolated), and an inner, generally cylindrical landing coupling 54 which provides electrical contact between the rams 50 and the conducting tubing 14. O-ring seals 55 on the external circumference of the outer housing 53 seal the hanger 24 within a circumferential seat or shoulder 56 in the profile 22 for the isolated tubing hanger 24. The landing coupling 54 includes a widened diameter, circumferential landing shoulder 57 which seats on an inwardly extending circumferential landing seat 58 in the central bore 59 of the tubing hanger 24. The downwardly extending neck extension 38 is formed at the lower end of the landing coupling 54 and extends below the profile 22 for the tubing hanger 24. The conducting tubing 14 is suspended from the lower end of the neck extension 38, for example by welding, with the conducting ring 52 being bolted to the neck extension 38 at a location to align with the rams 50, 51. The landing coupling 54 is electrically isolated from the outer housing 53 by a pair of upper and lower electrical insulation plates 60, 61 made of an electrical insulation material which is load bearing such as PEEK, located above and below the landing shoulder 57 of the coupling 54. O-ring seals 62 above and below the lower insulation plate 61 seal the landing coupling 54 with the central bore 59 of the hanger housing 53. Spacing 63 or insulation are also provided between the housing 53 and the landing coupling 54 (see
The electrical isolation assembly 47 for the ram assemblies 44, 46 achieves electrical isolation of the isolation tubing head 18, while sealing the assemblies 44, 46 and allowing for horizontal reciprocating movement of the rams 50, 51. On the conducting ram side, the assembly 47 includes an electrically conductive actuation sleeve 67, fixed for example by welding, around the conducting actuation rod 48 and extending out of the tubing head 18. The actuation sleeve 67 is surrounded by an electrically conductive, static ram housing 68. An outer ring 69 fixed to or integral with the end of the actuation sleeve 67 opposite the ram 50, provides a widened diameter portion of the actuation sleeve 67. An actuation nut 70 is threaded onto the end of the housing 68 protruding from the tubing head 18. An inwardly extending lip 71 of the actuation nut 70 is positioned to contact the outer ring 69 of the actuation sleeve 67, such that rotation of the nut 70 pushes the sleeve 67 and thus the ram 50 into the wellbore 11 against the conducting ring 52. A ring 72 fixed to the end of the actuation sleeve 67 provides a shoulder for contact with the lip 71 of the actuation nut 70 such that on disengaging of the threads on the actuation nut 70, the actuation sleeve 67 and thus the ram 50 is retracted from the wellbore 11 to break the electrical contact. The horizontal conduit 43 includes a widened portion forming a circumferential seal pocket 73 at the outer wall of the tubing head 18. An outwardly extending sealing shoulder 74 fixed to or integral with the ram housing 68 seals in this seal pocket 73. Isolation sleeves 75, formed of an electrically isolating material of sufficient strength to handle the actuation and pressure loads (for example PEEK) are located on either side of the sealing shoulder 74 in the seal pocket 73. A retainer ring 76 is bolted to the outer wall of the tubing head 18 to retain and seal the ram assembly 44 within the conduit 43. O-ring seals 78 located around the inner of the isolation sleeves 75 provide a seal between the tubing head 18 and the ram housing 68. Similarly, O-ring seals 78 located between the actuation sleeve 67 and the ram housing 68 seal the actuation sleeve 67 within the housing 68. Spacing around the ram housing 68 and the wall of the horizontal bore 43 provide electrical isolation. Certain parts of the electrical isolation assembly, including sleeve 67, housing 68, nut 70 and rings 69 and 72 are preferably made of non-magnetic materials. Similar parts are included on the support ram side of the electrical isolation assembly to electrically isolate, seal and actuate the support ram 51 and support rod 49 in the conduit 43, except that the actuation sleeve and support actuation rod are combined in a single part labeled as 49.
The ground connection and grounding tubing head equipment for this embodiment is as described below for the third embodiment (sometimes termed neutral connection and neutral connection tubing head, but otherwise the same).
The rod and clamp connection assembly 40 provides a hot connection through to the conducting tubing 14 as for the first embodiment, but is preferably housed in a separate electric feed through spool 82 (also termed clamp head) connected above a tubing head 18′. The tubing head 18′ is similar in function to tubing head 18 of the first embodiment, in providing a tubing hanger profile 22′ for suspending an isolated tubing hanger 24′. However, whereas the first embodiment has provision in the tubing head 18 for the ram assembly 37 to make the electrical connection, this function is now provided by the electric feed through spool 82 of the second embodiment. As well, the isolated tubing hanger 24′ differs from that in the first embodiment, by providing an upwardly extending conducting neck extension 42, for connection to the rod and clamp connection assembly 40. Other aspects of these parts 18′ and 24′ which are shared with the first embodiment, are commonly labeled in
The rod and clamp assembly 40 provides a clamp assembly 80 inside the vertical bore 11 of the electrical feed through spool 82. A horizontal conductive rod 84 protrudes into the vertical bore 11 of the electrical feed through spool 82 and is clamped by the clamp assembly 80. The conductive rod 84 is pressure sealed and electrically isolated at each end by an electrical isolation assembly 85 within a horizontal conduit 86 which extends through the electrical feed through spool 82 to the vertical bore 11, more fully described below for the third embodiment. It is possible for the conductive rod 84 to end at the clamp assembly 80, but it is more preferably pressure balanced by extending across the vertical bore 11 with pressure sealing around both ends by the isolation assembly 85. The conductive rod 84 protrudes out one side of the electrical feed through spool 82 for connection to the hot electrical connection assembly 35. The clamp assembly 80 is mechanically attached (clamped) to the conductive rod 84 protruding into the vertical bore 11 of the electrical feed through spool 82. When in place, the clamp assembly 80 is positioned above the electrically isolated tubing hanger 24′ around the tubing hanger neck extension 42 which extends into the electrical feed through spool 82 (
The tubing hanger neck extension 42 preferably contains a back pressure valve thread and profile 92. Pressure can then be contained inside the conducting tubing 14 when a back pressure valve (not shown) is installed in the tubing hanger neck extension 42. This allows the electrical feed through spool 82 and clamp assembly 80 to be installed or removed while the conducting tubing 14 is under pressure.
A further embodiment of the clamp connection is shown in
In
The wellhead body members 12 of this invention may be combined as one or more wellhead body members within the scope of this invention. In this particular embodiment, the provision of the electrical feed through spool 82 above the tubing head 18″, with a back pressure valve being provided therein as described below, allows for ease in running the electrically isolated tubing hanger 24″ and making the electrical connection while the wellhead is under pressure.
The body member parts 82, 18″, and 20 are shown as having studded connections top and bottom, although alternate connectors such as threaded or flanged, are possible. Each of these body members, when connected, forms a vertical wellbore 11 extending there through. The tubing head 18″ forms a hanger profile 22 to land and seal the isolated tubing hanger 24″, while the grounding tubing head 20 forms a hanger profile 26 for the grounding tubing hanger 28, such that the tubing hangers 24″ and 28 are in a vertically stacked relationship to suspend respectively the conducting tubing 14 and the grounding tubing 16 in concentric relationship.
The hot electrical connection is provided from the hot electrical connection assembly 35 through the electrical feed through spool 82. The vertical wellbore 11 extends through the spool 82 to provide a clamp bore for the clamp assembly 80. The spool 82 is shown with top and bottom studded connections 100, 101 to wellhead equipment located above and below, although alternate connectors may be used. The spool 82 is formed with a horizontal conduit 86 extending there through, which provides access to the vertical bore 11. An electrical conductive rod 84 is sealed through an electrical isolation assembly 85 into the horizontal conduit 86 bore between an electrical connection end 102 and a plug end 104 of the bore 86. The electrical connection end 102 provides for hot electrical connection to an electrical connection plate 35a, which is bolted by connectors 35b to the rod 84 for connection to a source of current at the hot connection assembly 35. The conductive rod 84 is connected to the electrical clamp assembly 80, which in located in the vertical bore 11 to provide for electrical connection between the conductive rod 84 and the electrically isolated tubing hanger 24″. As shown in the Figures, the conductive rod 84 is preferably pressure balanced, so extends through the vertical bore 11 and is sealed in the horizontal conduit 86 of the spool 82 on both sides. Alternatively, the conductive rod 84 could end at the clamp assembly 80.
In order to seal and electrically isolate the conductive rod 84 from the spool 82, the rod 84 is held within the horizontal conduit 86 by an electrical isolation assembly 85. This assembly includes, around the conductive rod 84 at the clamp assembly 80, a pair of pack off bushings 106 such as Teflon® sleeves, a pair of pack off gland inserts 108, formed of a PEEK material, a pair of inner and outer packing rings 110, 112, such as Teflon®, and a pair of packing glands 114, formed from a PEEK material. At the plug end 104 of the horizontal conduit 86, the rod 84 is held within an end cap 116, formed from example Teflon®. A packing gland retainer 118 is threaded at its inner end into the end of the horizontal conduit 86 to retain the packing and electrical isolation items 106, 108, 110, 112, and 114. The outside diameter of the packing gland retainer 118 is threaded to mount a lock nut 120, which prevents the packing gland retainer 118 from backing out of the spool 82. The lock nut 120 is preferably formed from a non-magnetic material limit eddy current heating. A wiper ring 122 around the packing gland retainer 118 keeps the thread free of debris while preventing pressure build up at the end of the rod 84.
At the electrical connection end 102 of the horizontal conduit 86, the rod 84 is held within a bushing 124, formed for example from Teflon®, which in turn is held within a packing gland retainer 126 (similar to 118) which is threaded at its inner end into the horizontal conduit 86. The packing gland retainer 126 retains the packing and electrical isolation items 106, 108, 110, 112, 114 and 124. The outside diameter of the packing gland ring 126 is threaded to mount to a lock nut 120 (as above) with a wiper ring 122 (as above) to hold the packing gland ring 126 within the horizontal conduit 86. At the outer end of the packing gland retainer 126, a nut 128 is used to attach to the electrical box 34. Rubber washers 130 and flat washer 132 seal between the nut 128 and the packing gland retainer 126.
The clamp assembly 80 is held within the vertical bore 11 within an electrical isolation sleeve 134 (see
The clamp assembly 80 is formed of electrically conductive material with low electrical resistance, such as copper, which may be tin plated for good electrical connection to the conductive rod 84 and the tubing hanger 24″. The cap screw, bolts and washers (136a,b,c and 140a,b,c) may be made of silicon bronze to provide good electrical conductivity.
While it is within the scope of the present invention to have the clamp assembly 80 directly onto the conducting tubing string 14, it more preferably clamps onto the neck extension 42″ of the isolated tubing hanger 24″, as described herein.
The isolated tubing hanger 24″ is similar to that shown for the first and second embodiments, except that the spacings for insulation purposes are replaced by insulation sleeves, as described below. The hanger 24″ includes a pressure containing body housing 53″, operative to land and seal within the tubing hanger profile 22″ of the tubing head 18″. Double O-ring seals 55″ are provided in the external tapered surface of the housing 53″ to seal in the vertical bore 11 of the tubing head 18″. The housing 53″ forms a central bore 59″ extending there through with a landing seat 58″ at its lower end. A generally cylindrical landing coupling 54″ having a widened landing shoulder 57″ seats in the central bore 59″ on the landing seat 58″. The conducting tubing string 14 is welded at A to the lower end of the landing coupling 54″. Alternate connections for the conducting tubing string 14 may be used, for example slip lock or threaded connections, as are well known in the art, but welding is preferred for electrical conductivity.
The landing coupling 54″ is made of an electrically conductive material with good strength. The upper end of the landing coupling 54″ provides the upwardly extending neck extension 42″ of the isolated tubing hanger 24″onto which the clamp assembly 80 is fastened. The landing coupling 54″ forms a central bore 94″ operative to pass fluids, tools or instrumentation. Formed in the central bore 94″ within the neck extension 42″ is a back pressure valve profile 92″, top threaded for a back pressure valve (BPV) 147, which may be of known and varied design, but allows for the wellhead members located thereabove to be accessed while the well is under pressure. In the Figures the back pressure valve is shown as a Type H one way BPV (threaded in), but alternate one way or two way BPVs may be used, as known in the art. The provision of this back pressure valve in the isolated tubing hanger 24″ also allows for connection of the clamp assembly 80 for the hot electrical connection while the wellhead is under pressure.
In order to electrically isolate the landing coupling 54″ from the housing 53″, upper, mid and lower insulating sleeves 148a, 148b, 148c, made for example from Teflon®, are provided between landing coupling 54″ and the housing 53″. As well, upper and lower electrical insulation plates 60″, 61″ made from, for example, a PEEK material for electrical isolation and strength, are provided above and below the landing shoulder 57″ of the landing coupling 54″. An externally threaded retainer ring 64″ threads into the central bore 59″ at the top of the housing 53″ against a packing ring 149 to retain all internal components in the housing 53″ in electrically isolated and sealing arrangement. O-ring seals 62″ are provided above and below the lower electrical insulation plate 61″ to provide a seal between the landing coupling 54″ and the housing 53″.
The neutral or grounding connection tubing head 20 is shown in
The top flange 150 of the tubing head 20 is formed with a receptacle 154 proximate the grounding tubing hanger 28. A neutral rod connection assembly 156 connected to grounding connection assembly 29, is held in the receptacle 154 to provide a grounding connection to the grounding tubing string 16, thus grounding the tubing head 20.
The neutral rod connection assembly 156 includes an electrically conducting grounding rod 158, which may for example be made from tin plated copper rod for low electrical resistance. The grounding rod 158 transfers electrical current from the grounding tubing head 20 (and the hanger 28 and tubing string 16) to the ground connection assembly plate 29a, as above described. The rod 158 is bolted to the plate 29a by nut and bolt connectors 29b (see
The grounding tubing hanger 28 is best shown in
In some applications, it may be preferable to simplify the hot connection to the isolated tubing hanger, providing the hot electrical connection outside the wellhead, rather than through a conduit. Such applications include those where access to the bore of the conductive tubing is not needed, and/or applications where further wellhead equipment is not needed above the hot connection. In this fifth embodiment, a conduit in the wellhead body members 12 is eliminated, and the hot connection can be made directly or indirectly to the hot components of the isolated tubing hanger outside the wellhead.
In the preferred embodiment shown in
The hot electrical connection assembly 35′″ is shown in
The neutral and hot connection assemblies 29′″ and 35′″ are preferably housed in the electrical junction box 34′″, which in turn is bolted with bolts 320 above the tubing head adapter 30′″.
The tubing head 18′″, and isolated tubing hanger 24′″ are similar to that described above. The tubing hanger 24′″ may be modified as follows provided no vertical access is required to the conductive tubing string 14. Firstly, the landing coupling 54′″, with its extended neck portion 42′″, is formed preferably as a solid member (and thus without a central bore, and thus without the back pressure valve profile shown in the previous embodiments). This allows the electrical connection to be made to this extended neck portion 42′″ above the wellhead members. A landing tool profile 322 is formed at the upper end of the extended neck portion 42′″ in order to land the tubing hanger 24′″ in the tubing head 18′″. The upper, mid and lower insulating sleeves 148a′″, 148b′″, and 148c′″, and the upper and lower electrical insulation plates 60′″, 61′″ are all preferably threaded in order to connect to each other. This threaded connection of these insulation members is found to increase the surface area along the threads, to thereby increase the creepage gap provided by the threads. The result is better electrical isolation, making it possible to reduce the size of the components and spacing needed for high voltage applications.
The tubing head adapter 30′″ provides an extension to the vertical wellbore 11, which extends therethrough. The extended neck portion 42′″ of the landing coupling 54′″ extends through this central bore portion 323 of the vertical wellbore 11, preferably terminating outside the wellhead. In order to electrically isolate the tubing head adapter 30′″, additional pressure load supporting insulating rings 324, 326 and insulating sleeve 328 are provided, in ascending order, between the extended neck portion 42′″ and the central bore 323 in tight fitting, sealing and electrical isolating relationship. The insulating rings 324, 326 and sleeves 148a′″, 328 are preferably formed to slide together in a manner that provides overlap between the adjacent rings and/or sleeves so as to increase creepage gap and thus increase electrical isolation. Lower ring 324 is preferably formed with a downwardly projecting circular rim 330 to slide over sleeve 148a′″. A circular groove 332 is preferably formed in the upper surface of lower ring 324. Upper ring 326 is preferably formed with a downwardly projecting circular rim 334 at its lower surface to fit into the circular groove 332 of the lower ring 324. A plurality of V-shaped inner and outer packing rings 336, 337 are stacked in sets between the rings 324, 326, on either side of the downwardly projecting rim 334 to provide a seal to the central bore 323, and to further isolate the extended neck 42′″ of the tubing hanger 24′″. Other seals may be used, for example one set of V-shaped packing rings or other seals. However, the sets of V-shaped packing rings 336, 337 are preferred, since they provide reliable sealing and electrical isolation from the extended neck portion 42′″ for the temperatures encountered during operation. This is particularly useful in high voltage applications. The V-shaped packing rings 336, 337 may be of known sealing and electrically insulating materials, but are most preferably provided as Teflon® spring energized ring seals for electrical isolation and sealing. The upper ring 326 is formed with a circular cutout 340 adjacent the extended neck 42′″ in order to accommodate the insulating sleeve 328. The insulating sleeve 328 extends upwardly from the wellhead assembly 10 to insulate the extended neck 42′″ above the wellhead in the electrical junction box 34. A retainer ring 338 is bolted above the tubing head adapter 30′″, around the insulating sleeve 328. A widened portion 342 of the insulating sleeve 328 is held in a cut away portion 344 of the retainer ring 338, such that bolting down of the retainer ring 338 retains the packing rings 336, 337 to seal the bore 323 through the tubing head adapter 30′″.
As set forth above, the insulating sleeves which are not load bearing, including 148a′″, 148b′″, 148c′″ and 328 may be made from known insulating materials, preferably from Teflon®. The load bearing insulating components, including electrical insulating plates 60′″, 61′″, and rings 324 and 326 are preferably made from an insulating material that provides extra strength, for example PEEK. It should be understood that one or more of the insulating rings, sleeves or plates described for this and other embodiments, might be made varied within the scope of the invention. For instance, one or more of the insulating members may be formed integral with another insulating member. One example is that insulating sleeve 328 could be combined with insulating ring 326, in which case, this combined part is preferably formed from PEEK.
All references mentioned in this specification are indicative of the level of skill in the art of this invention. All references are herein incorporated by reference in their entirety to the same extent as if each reference was specifically and individually indicated to be incorporated by reference. However, if any inconsistency arises between a cited reference and the present disclosure, the present disclosure takes precedence. Some references provided herein are incorporated by reference herein to provide details concerning the state of the art prior to the filing of this application, other references may be cited to provide additional or alternative device elements, additional or alternative materials, additional or alternative methods of analysis or application of the invention.
The terms and expressions used are, unless otherwise defined herein, used as terms of description and not limitation. There is no intention, in using such terms and expressions, of excluding equivalents of the features illustrated and described, it being recognized that the scope of the invention is defined and limited only by the claims which follow. Although the description herein contains many specifics, these should not be construed as limiting the scope of the invention, but as merely providing illustrations of some of the embodiments of the invention.
One of ordinary skill in the art will appreciate that elements and materials other than those specifically exemplified can be employed in the practice of the invention without resort to undue experimentation. All art-known functional equivalents, of any such elements and materials are intended to be included in this invention. The invention illustratively described herein suitably may be practiced in the absence of any element or elements, limitation or limitations which is not specifically disclosed herein.
As used herein, “comprising” is synonymous with “including,” “containing,” or “characterized by,” and is inclusive or open-ended and does not exclude additional, unrecited elements. The use of the indefinite article “a” in the claims before an element means that one or more of the elements is specified, but does not specifically exclude others of the elements being present, unless the contrary clearly requires that there be one and only one of the elements.
This application is a Continuation of U.S. patent application Ser. No. 11/610,345, filed Dec. 13, 2006, which is a Continuation-In-Part of U.S. patent application Ser. No. 10/913,710, filed Aug. 5, 2004, which issued on Aug. 12, 2008 as U.S. Pat. No. 7,410,002. This application also claims the benefit of U.S. Provisional Application 60/493,097, filed Aug. 5, 2003. All applications are incorporated herein in their entirety to the extent not inconsistent herewith.
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| Number | Date | Country | |
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| Child | 12493697 | US |
| Number | Date | Country | |
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| Parent | 10913710 | Aug 2004 | US |
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