ASSEMBLY WITH TIGHTLY CONTROLLED AXIAL SPACE FOR INSULATING THREADED CONNECTOR ON VACUUM INSULATED PIPE

Abstract

An insulated tubular assembly comprising joined insulated pipe segments, all with inner and outer tubes concentrically arranged to define a vacuum ring between and closed at both ends by annular bridges; insulated pipe segments are provided with either male or female threads to thread together and form a joint directly with one another or via a coupling attached to adjacent insulated pipe segments;An insulating sleeve retained around such a joint comprises a first tubular shell adapted to cover at least part of an insulated tubular segment and a second tubular shell overlapping either internally or externally on part of the first tubular shell, such that the second tubular shell extends axially around the threaded joint from an annular bridge to the adjacent one, with high tolerances in lengths of the insulated pipe segment extension that extends beyond their respective annular bridges.

Description

ASSEMBLY WITH TIGHTLY CONTROLLED AXIAL SPACE FOR INSULATING THREADED CONNECTOR ON VACUUM INSULATED PIPE CROSS REFERENCE TO RELATED APPLICATIONS This application claims priority to U.S. Provisional Patent Application No. 63 / 003,424, filed on April 1, 2020; the full text of the foregoing is incorporated herein by reference. FIELD OF INVENTION This invention relates to insulated pipe strings for use in hydrocarbon recovery wells. More particularly, this invention relates to a tubular assembly made of inner and outer tubes forming insulated segments and having an improved insulated joint between those insulated tubular segments. Oil and gas recovery wells involve using long strings of tubing to transport hydrocarbons from the downhole reservoir to the surface. In many cases, it is desirable to maintain temperature and minimize heat loss from the substances flowing through the tubing string. In conventional oil recovery operations, the oil may already be highly fluid within the reservoir. However, because oil viscosity increases as it cools, minimizing heat loss helps the oil maintain fluidity, making it easier and less expensive to produce. In some recovery operations, however, the oil can be very viscous within the reservoir. It may then be necessary to heat the bottom of the oil well in order to produce it in economically viable quantities. Minimizing heat loss in the well string is therefore more critical. In these situations, hot steam is typically passed to the bottom of the well through the pipe string to loosen the thickened or trapped oil, making it fluid. Insulated pipe strings minimize heat loss from both the steam and the oil. BACKGROUND OF THE INVENTION Insulated pipe strings involve joining double-walled, insulated pipe segments. U.S. Patent No. 3,763,937 describes a type of insulated pipe string where insulated pipe segments are joined together by each thread in a separate, conventional sleeve-type coupling that is well known in the art. Generally, each pipe segment The insulated pipe (PQC7 ίη / 77Π7 / E / YΙΛΙ) has an outer tube arranged around an inner tube, defining an annular space between them. The annular space is sometimes filled with insulating material. Alternatively, a vacuum can be created in the annular space to insulate the pipe. Therefore, heat transfer is minimized between the inner wall, which may be exposed to hot oil and steam, and the outer wall, which may be exposed to the cooler interior of the wellbore or the atmosphere. The primary purpose of such insulated pipes is to dramatically reduce heat transfer through convection, conduction, and radiation between the inner and outer pipes. A major problem with joining insulated pipe segments is that excessive heat loss can occur at the joint between segments. One of the inner or outer pipes is shorter in length to allow the longer inner or outer pipe to be turned and fitted with a pin or box fitting. Pins and boxes are necessary to thread insulated pipe segments together to form joints throughout the insulated pipe string. However, at the joint location, there is what we might call a single-walled pipe, which cannot provide the same insulation as double-walled insulated pipe segments. Insulated pipe segments are not insulated at their ends. Therefore, heat can be conducted away from the inside of the pipe along a conductive flow path at each joint, at a much higher rate than through the insulated portion of the pipe. This results in greater heat loss and reduced efficiency. Several solutions have been proposed to minimize heat loss at the joint between insulated pipe segments. U.S. Patent No. 4,518,175 describes an insulated tubular assembly comprising a highly specific coupling arrangement joined between insulated pipe segments. The specific coupling is threaded to join the shorter inner and outer pipe segments at both ends. A space is defined by the inner peripheral surface of the specific coupling, the free ends of the longer inner and outer pipe segments, and an additional inner ring welded to both adjacent free ends of the longer inner and outer pipe segments. Insulating material is filled in the space. U.S. Patent No. 4,518,175 provides continuous insulation along a tubular assembly, minimizing heat loss at the joint. Insulating pipe joints and previous methods have the disadvantage that the insulation at the joint is fitted internally to the coupler. Applying insulation during the fabrication of each pipe segment in this way can be complicated and expensive. For example, the insulation must be installed so that the coupler will subsequently fit around it when joining two insulated pipe segments. If the coupler is not fitted properly during insulation, it may not be corrected in the field during installation, while it is still away from the intended use. PQC7 iη / 77P7 / E / YILI manufacturing facility. If the insulation is then applied in the field during installation, this can be a complicated or time-consuming step. Another complication with the above-mentioned pipe joints is that it can be difficult or impossible to repair or replace the insulation once in the field. If the insulation needs replacing, it can be difficult or impossible to discern because it is hidden within the joint. Especially in a long pipe string, considerable effort is required to separate the joint whose insulation needs inspection or repair. Thus, to improve on-site repairs without the need to disassemble a pipe string, U.S. Patent No. 7,845,373 describes an insulator adapted to surround the joint and a locking joint protector adapted to surround the insulator and retain it against the joint. This insulator is purported to reduce heat loss through vacuum-insulated pipe string joints by 95%. However, this solution is expensive, increases the outside diameter of the pipe string, and is not providing entirely satisfactory tooling results. To minimize costs and achieve a better balance between cost and insulation efficiency, U.S. Patent No. 7,207,603 describes adding a polypropylene ring insulation sleeve when preparing insulated pipe segments. To reduce costs, this sleeve is mass-produced, and the invention allows it to fit approximately all sizes. This sleeve is not designed for a specific pipe fitting but rather for a particular outside diameter of the insulated pipe segments. However, due to production tolerances and the need for extra length at the pipe ends to allow for re-cutting and re-threading of threaded sections for insulated pipe segments, an axial gap between adjacent insulated pipe segments is frequently not covered by the sleeve.While providing a very economical solution for heat reduction and transfer at the joint location, U.S. Patent No. 7,207,603, the solution is not sufficiently satisfactory in terms of heat transfer reduction, especially when considering that insulated pipe segments have production tolerances. The disadvantages of the prior art are overcome by the present invention. An insulated tubular assembly is provided that has an improved insulated joint which is easier and less expensive to manufacture, install, repair, re-thread, and replace. There is a need to improve heat transfer in the coupling area without increasing the cost of such insulation materials, and without considering the coupling of a more difficult-to-lay insulated pipe string, while still being able to maintain a very homogeneous insulation solution for the entire range of accepted values, including extreme values ​​within the entire range of accepted values ​​in terms of outside diameter, inside diameter and / or length of the respective inside and outside pipe, and consequently the length of the free ends of the most PQC7 ίη / 77Ω7 / Β / YΙΛΙ long of the inner and outer pipe of such insulated pipe segments. BRIEF DESCRIPTION OF THE INVENTION An insulated tubular assembly for passing fluids through the center of a hydrocarbon recovery well is described. The tubular assembly is formed by joining double-walled pipe segments. The assembly features an improved insulated joint between pipe segments, making it easier and less expensive to manufacture, install, repair, and replace. In a preferred embodiment, the assembly includes a plurality of sequentially joined insulated pipe segments. Each pipe segment includes an inner tube, an outer tube, and two opposite ends. Opposite ends may be of the inner or outer tube, depending on which inner or outer tube is longer than the other. The longer the inner or outer tube, the longer it forms an outwardly extending extension, at least at one end of the first insulated pipe segment, and preferably at both opposite ends. An inner tube defines an internal passage for transporting fluids. An outer tube is arranged concentrically around the inner tube, defining an annular space between the inner and outer tubes. An annular bridge at each end connects the inner tube to the outer tube. Together, the annular bridges seal the ring between the inner and outer tubes, such as to maintain a vacuum and / or contain an insulating material. An annular bridge is any type of joint made between an inner tube and an outer tube. According to a first embodiment of the invention, wherein the outer tube is shorter in length compared to the inner tube, the annular bridge defines an outer surface that connects an outer peripheral surface of the outer tube to an outer peripheral surface of the inner tube. According to a second embodiment of the invention, wherein the inner tube is shorter in length compared to the outer tube, the annular bridge defines an inner surface that connects an inner peripheral surface of the outer tube to an inner peripheral surface of the inner tube. An annular bridge is made of at least one material, for example, a welding material that matches the pipe's strength and is applied using conventional welding techniques such as GMAW. Inner and outer tubes may be formed, with either or both varying in their internal or external diameter at their respective opposite ends to facilitate the welding process. In some cases where the radial gap is larger than a welding process would allow for direct joining, an additional round piece made of steel, such as a spool or spacer ring, may be added to provide support for the structure. PQC7 ίη / 77Π7 / E / YΙΛΙ welds to the inner tube and the outer tube respectively. Welding can provide a truncated conical surface with a taper of 40 to 60 degrees with the longitudinal axis of the insulated pipe segment. In accordance with the first embodiment, where the inner tube has an extension projecting outward from the outer tube, a pin member is provided on the inner tube. In accordance with the second embodiment, where the outer tube has an extension projecting outward from the outer tube, a pin member is provided on the outer tube. The insulated pipe segments are joined by a threaded connection retained between a pin member connecting to a box member provided on either the second insulated pipe segment or a coupling attached to such second insulated pipe segment. The second insulated pipe member may be provided with such a box member, or in the case that the second insulated pipe member is provided with a pin member like the first insulated pipe segment, then the coupling has box members at both ends to join pin members of adjacent first and second insulated pipe segments. The coupling has opposing threaded first and second box ends, and a central passage for fluid to flow through them. The first and second pipe segments are joined by threading the pin end of the first pipe segment into the first box end of the tubular coupling, and threading the pin end of the second pipe segment into the second box end of the tubular coupling. An insulating sleeve surrounds the joint. The insulating sleeve comprises a first tubular shell adapted to cover at least part of an extension of the first insulated tubular segment, and a second tubular shell that overlaps either internally or externally with part of the first tubular shell, such that the second tubular shell extends axially around the threaded joint. According to the first embodiment, the first tubular shell covers at least part of that outer extension surface. According to the second embodiment, the first tubular shell covers at least part of that inner extension surface. The threaded connection or threaded joint corresponds to a location along a longitudinal axis of the first insulated pipe segment, where a thread of the first insulated pipe segment is threaded into the thread of the second box member provided either on the second insulated pipe segment or on a coupling attached to such second insulated pipe segment. A feature of this invention is that the first tubular casing can be adapted to cover at least part of the annular bridge of the first insulated tubular segment. For example, the PQC7 iη / 77P7 / E / YILI first tubular shell may comprise a first bevel adapted to expand over the annular bridge of the first insulated tubular segment so that the first tubular shell axially covers, on any axial side of that annular bridge, parts of both the inner and outer tube of the first insulated pipe segment. Preferably, the first tubular housing can be adjacent to the pin member, so that the first tubular housing does not impede the pin member, and at least would not impede the male threads of that pin member. Preferably, the second tubular shell can expand over the box member and can even be longer than the box member. According to a preferred embodiment of the invention, the insulating sleeve can extend from at least part of the annular bridge of the first tube segment to at least part of an annular bridge of the second tube segment. Such an insulating sleeve provides continuous thermal insulation between the two insulated pipe segments, neither of which is provided with a double wall and an insulated annular space between them. According to this preferred embodiment, zero axial spacing between the outer tubes and such an insulating sleeve would be achieved for the first embodiment of the invention, and zero axial spacing between the inner tubes and such an insulating sleeve would be achieved for the second embodiment of the invention. In this preferred embodiment of the invention, the insulating sleeve can be expanded so that, according to the first embodiment, it covers portions of both outer tubes of the first and second insulated pipe segments, and according to the second embodiment, it covers portions of both inner tubes of the first and second insulated pipe segments. The insulating sleeve helps reduce the finning effect around portions of the tubes near the annular bridge weld. Another feature is that the sleeve can be long enough to extend across the entire exposed portion of the pipe joint. A related advantage is that the insulation of the pipe assembly is continuous along the otherwise exposed portion of the pipe joint between the insulated pipe segments. Another related advantage is that the transition from one pipe segment, through the sleeve / joint, to the next can be substantially smooth. Alternatively, the sleeve can be longer to completely cover and extend beyond the entire exposed portion of the pipe joint, substantially overlapping with the annular space of each attached pipe segment. Advantageously, the insulating sleeve can be an assembly of two sleeves when the box member is provided on the second insulated pipe segment, so that the second tube casing can extend partially around the first tube casing. PQC7 ίη / 77Π7 / E / YΙΛΙ to at least part of an outer surface of an extension of the second insulated pipe segment. Alternatively, the insulating sleeve may be an assembly of three sleeves where the female thread of a box member is provided in a coupling attached to such a second insulated pipe member, the second insulated tubular member comprising a second extension with a second pin member therein, in order to thread the second pin member into another box member of the coupling forming another threaded joint. The insulating sleeve would then comprise a third tubular shell, such that the third tubular shell is adapted to cover at least part of the second extension, the second tubular shell overlapping either internally or externally apart from the first tubular shell and also part of the third tubular shell, such that the second tubular shell extends axially around both threaded joints, the second tubular shell extending from the first tubular shell to the third tubular shell.With such a configuration of three insulating sleeves, the second sleeve has a greater axial length than the coupling, in order to expand from both axial ends of such a coupling. In accordance with this alternative arrangement with an insulating sleeve consisting of three sleeves, the first and third tubular casings may preferably be identical, especially when insulated pipe segments are of the same type, with identical nominal outside diameter and nominal inside diameter. Diameters of a VIT string may typically range from 44.5 mm (1.751 in) as the minimum nominal inside diameter and up to 406.4 mm (16 in) as the nominal outside diameter. According to the invention, before assembling a string of insulated pipe segments, the first tubular sleeve can be held at a distal end of the first insulated pipe segment by a protector, to be removed at the time of assembly. For example, when the first and second insulated pipe segments are provided as a pin member at both ends, then before being supplied at the equipment site, preferably still at the mill site, the first tubular segment is held at one end by a protector, and a coupling is provided at the other end of each insulated pipe segment, so that the second and third sleeves can be held around the coupling by a coupling protector, to be removed at the time of assembly. Preferably, with a three-sleeve insulating sleeve, prior to preparation of the first insulated pipe segment with coupling, and such sleeve with the second insulated pipe segment, the first tubular sleeve can be forcibly fitted or supported against the annular bridge of the first insulated pipe segment, a third tubular sleeve can be forcibly fitted or supported against the annular bridge of the second insulated pipe segment, and the second PQC7 ίη / 77Π7 / E / YΙΛΙ tubular housing is fitted around the coupling so that the second tubular housing expands axially from the coupling at both axial ends in order to overlap with the first and third tubular housings after preparation. Such a tubular casing may comprise a rigid material selected from the group consisting of plastics and metals, for example, preferably selected from polymeric materials, particulate expanded inorganic materials, expanded graphite, and mixtures thereof. If the first tubular casing is made entirely of polymeric material, it is preferably fitted in a snug manner around the first extension. In this way, various polymeric materials can be used, either alone or in a mixture of fillers. Non-limiting examples of such polymeric materials include biaxially oriented polytetrafluoroethylene, polyurethane, etc. Additionally, the insulating material of the sleeve can be made of expanded exfoliated graphite, as well as various hidden inorganic materials such as silicate materials, including vermiculite, etc. When inorganic and mineral materials such as silicates, expanded graphite, etc., are used, they can include reinforcing fillers such as fiberglass, carbon fibers, etc., as well as binders, which can be incorporated and provide the insulating material with structural integrity. A preferred insulating material may comprise an inorganic material such as an expanded silicate, along with a binder, the binder being any of numerous polymeric materials, both thermoplastic and thermoset in nature. For example, each tubular shell can be a unitary tubular body. Preferably, the retaining mechanism in the respective insulated pipe segment, the tubular housing, may comprise an outer metal sleeve welded to one of the first or second insulated pipe segments. Such a metal sleeve may be machined from metal tubing. According to the first embodiment of the invention, the metal sleeve may be welded to the outer tube and / or the annular bridge. For example, the tubular housing may be a two-layer housing with an inner polymer core and the outer metal sleeve surrounding it. The polymer core may be press-fitted or expanded into the metal sleeve, for example, before welding, or press-fitted between the metal sleeve and an outer surface of the extension when the metal sleeve is welded first. Such a metal sleeve may also increase the durability of the sleeve, which is especially advantageous when the sleeve is also used as a bumper.The metal sleeve is made of, for example, aluminum, stainless steel, etc. The first tube shell may be fixed in an axial position relative to the annular bridge of the first insulated pipe segment, either snugly or by shrinking around the first insulated tube segment, since the first tube shell is made of a softer material than the first insulated tube segment, or welded at some point to the first tube segment. PQC7 ίη / 77Π7 / Ε / ΥΙΛΙ isolated. Preferably, to limit production costs of such an insulating sleeve, the second tubular shell comprises a substantially uniform wall thickness, and the first tubular shell further comprises a second bevel to allow overlapping of the second tubular shell over the second bevel. This option reduces costs, since only the first tubular shell requires a specific inner and outer dimension to accommodate the annular bridge and the second tubular shell, respectively. Thanks to the invention, the insulating sleeve can be defined with an outer diameter within tolerances of + or -5% of the nominal outer diameter of the first and second insulated pipe segments. Preferably, the insulating sleeve is leveled within tolerances of the nominal insulated pipe segment dimensions. The invention also aims at an insulated tubular segment adapted to be part of an insulated tubular assembly as defined in the invention, comprising a protector fitted at one end to retain a first tubular housing around an extension of such first insulated tubular segment, the protector being removed during preparation time. The invention also relates to a process for insulating an insulated pipe assembly as previously mentioned, wherein prior to preparing the first insulated pipe segment with the second insulated pipe segment, the first tubular sleeve is inserted into a first distal end of the first insulated pipe segment, and the first tubular sleeve is adjusted to a longitudinal position of the extension, and then turned with a specific pattern determined as a function of a distance from a free end of such first insulated pipe segment. The first tubular sleeve is adjusted to length to allow almost zero gap between the insulating sleeve and adjacent annular bridges after assembly. This process allows for optimization of the assembly of the box member, and optimization of the insulating joint between the first tubular shell and the second tubular shell. Also, to improve thermal insulation, before preparing the first insulated pipe segment with the second insulated pipe segment, the second tubular casing can be inserted through a free end of either the second insulated pipe segment or the coupling attached to it. The second tubular casing is then turned to a specific pattern determined by a distance from that free end. Preferably, before preparation, the first insulated pipe segment can be positioned with its longitudinal axis vertical, the first tubular casing held around the annular bridge even when oriented towards the ground, and then threaded onto the same second insulated pipe or the coupling attached to it. PQC7 ίη / 77Π7 / Ε / ΥΙΛΙ already vertical. An optimized process for increasing the service life of such an insulated tubular assembly may comprise the step of breaking the threaded coupling of the pin member to the housing member. The pin member is then trimmed and turned to another external male thread on the trimmed pin member, such that the first tubular housing is also turned to a specific pattern determined as a function of a distance from the newly trimmed free end. In this way, the first tubular housing is again adjusted to length to allow near-zero clearance between the insulating sleeve and adjacent annular bridges after assembly. BRIEF DESCRIPTION OF THE FIGURES Figures 1a to 1d illustrate different embodiments of a first isolated segment end part of a tubular assembly in accordance with the invention. Figures 2 and 3 illustrate one embodiment of the tubular assembly, wherein the joint comprises a male thread on a first insulated tubular segment coupled with a female thread on a second insulated tubular segment. An insulating sleeve according to the invention surrounds the joint. Figures 4 to 6 illustrate an alternate embodiment of the tubular assembly, in which the joint comprises a threaded coupling provided with two box members that respectively join the male threaded ends of two tubular segments. Figures 4 to 6 differ from each other in how the insulating sleeve is constructed to surround the insulated joint. Figure 7 illustrates an alternate joint according to a second embodiment of the invention in which the outer tubes have threaded extensions for joining insulated pipe segments, and the insulating sleeve is internal to the tube assembly. DETAILED DESCRIPTION OF THE INVENTION Figure 2 shows one embodiment of an insulated pipe assembly 10, having a connection 12 between two insulated pipe segments 14, 16. An insulating sleeve 18 surrounds the connection 12. Each insulated pipe segment 14, 16 has a double-walled insulated construction, comprising an inner tube 20, 21, an outer tube 22, 23 arranged concentrically around the inner tube 20, 21, and a ring 24, 25 between the inner tube 20, 21 and the outer tube 22, 23. Each end of each pipe segment 14, 16 has an annular bridge 26, 27, connecting the pipe PQC7 Ln / Zznz / E / YILI inner tube 20, 21 to outer tube 22, 23. The annular bridge 26, TJ may be a fillet weld joining the outer tubes 22, 23 respectively to inner tubes 20, 21, optionally in a stamped portion as 22a or an expanded or upset portion as 21a, to seal an annular space 24, 25 from the atmosphere. The annular space 24, 25 may thereby support a space and / or contain an insulating material, to isolate each pipe segment 14, 16. The inner tube 20, 21 of pipe segments 14, 16 each has an extension 30, 31 that projects outward from at least one end of each pipe segment 14, 16. For example, the extensions 30, 31 can be portions of the inner tubes 20, 21 that extend beyond the bridges 26, 27, respectively. A threaded connection links the extension 40 to the extension 41. In Figure 2, this threaded connection includes a male thread or pin 32 on extension 30, and a female thread or box 33 on extension 31. In this way, the pipe segments 14, 16 can be threaded together to form an integral connection 12. The pin 32 has a shorter axial length than the extension 30, and similarly the box 33 has a shorter axial length than the extension 31, compared to the axial longitudinal axis of the assembly X.Pin 32 is closest to a free end 34 of such an extension 30 of the first insulated tubular segment 14, such that an unthreaded portion 36 is defined between pin 32 and the annular bridge 26. The box 33 is provided on an inner surface of such an extension 31, an outer surface 37 of such an extension 31 is unthreaded between an end face 35 of such an extension 31 and the annular bridge 27. The threaded connection of extension 30 may also include, in addition to the thread, a sealing surface and / or edge surface that is in contact with corresponding surfaces of the threaded connection of extension 31. Turning of the threaded portion on extension 30 is performed at a predetermined location from the free end 34. Turning is preferably performed from the free end 34. A conductive flow path occurs where the inner tube 20, 21 meets the outer tube 22, 23 of each pipe segment 14, 16. Thus, despite the insulating properties of pipe segments 14, 16 around the annular space 24, 25, excessive heat transfer can occur where the insulated pipe segments are with a single wall, especially between the annular bridges 26 and 27, and even more so at the connection location 12. To minimize heat loss at that location, the insulating sleeve 18 is provided around the connection 12. The insulating sleeve 18 comprises a first tubular shell 50 adapted to cover at least part of the extension 30 of the first insulated tubular segment and a second tubular shell 51 that overlaps externally to part of the first tubular shell 50, such that the second tubular shell extends axially around the threaded joint 12. pqcz ίη / ζζηζ / Ε / γίΛΐ Figure 2 is the first tubular shell 50 that expands over the annular bridge 26 of the first insulated tubular segment, such that the first tubular shell 50 expands from both the axial side of that annular bridge 26 and covers parts of both the inner tube 20 and the outer tube 21 of the first insulated pipe segment. Figure 1a shows the first tubular casing 50 comprising a first bevel 52 on its inner surface adapted to rest on the annular bridge 26. The first tubular casing 50 comprises a first portion 50a, a transition portion 50b comprising that bevel 52, and a second portion 50c adapted to cover the stamped portion of the outer tube 22. The second portion 50c may be truncated conical. The first portion 50a of the embodiment of Figures 1a and 2 is cylindrical. To increase the reliability and effectiveness of the insulation, the first tubular casing 50 may be extended beyond the connection to substantially overlap with the annular space 24 within the first insulated pipe segment 14. The first tubular casing is made entirely of material, for example a polymeric material such as PTFE. Preferably, the first tubular shell 50 is shrink-fitted over the first insulated pipe segment 14. With the shrink-fit process, the first tubular shell has its external shape adapted to the external geometry provided in the annular bridge 26 and axially around. As shown in Figure 2, the outside diameter of the first isolated pipe segment, 50a, is less than the outside diameter of the second portion, 50c, and a second bevel, 53. Preferably, the outside diameter of the second portion is less than the outside diameter of the outer tube, 22, or within a tolerance of + / -5% of the nominal accepted outside diameter dimension for that outer tube, 22, 23. The transition portion, 50b, is held between the first bevel, 52, and the second bevel, 53. The outside diameter of the sleeve may be less than or substantially equal to those of the adjacent pipe segments, so that the sleeve is protected from damage as the tubular assembly is moved into the well.Alternatively, the outer diameter of the sleeve can be larger than that of adjacent pipe segments, to radially space the pipe segments from the wellbore, thereby acting as a bumper to protect the tubular assembly. According to a preferred process for isolating an isolated tubular assembly of the invention, the first tubular housing is held in a fixed axial location around the extension 30, and the extension 30 is then turned to provide the threaded connection. Preferably, the first tubular housing 50 is also prevented from rotating about the longitudinal axis X, under forces not exceeding the turning forces of cutting tools, in order to permit turning of the first tubular housing 50 once it is in place on the extension. PQC7 ίη / 77Π7 / E / YΙΛΙ 30. The first insulated housing is turned on the same lathe, and preferably with the same turning tool, to turn the outer surface of the first portion 50a and the second chamfer 53. The advantage of using the same lathe is that extremely tight tolerances can be maintained for the first tubular housing structure, even if turning tools are changed on the lathe. A first distal end 54 of the first insulated housing 50 is oriented towards the free end 34 of the extension 30, which can also be turned to have a controlled distance between the first distal end 54, the second chamfer 53, and the free end of the extension 30. As shown in alternative embodiments of the invention, the first tubular housing 50 may be at a non-zero axial length of the annular bridge 26, as shown in Figure 1b, or supporting such annular bridge 56 without covering the annular bridge 26, as shown in Figure 1e. Figure 1b represents the extension 30 before the pin 33 is turned thereon. The first tubular housing 50 may have concentrically shaped inner and outer walls before the turning step. In Figure 1b, the walls of the first tubular housing 50 are not yet turned. In Figure 1e, the first tubular housing 50 does not have a first chamfer to accommodate the tubular bridge 26. The first tubular housing of Figure 1e has a second chamfer 53 extending to the first distal end 54. In this way, the first portion 50a and the transition portion 50b are a single portion according to Figure 1e. For all modalities of the first tubular housing, an outside diameter at the first distal end 54 is preferably less than an outside diameter at the second distal end 55 of such first tubular housing 50, opposite the first distal end 54. In accordance with an alternative process of isolating an isolated tubular assembly of the invention, the first tubular housing 50 is held in that axial position after being forcefully adjusted. In accordance with another alternative process of isolating an isolated tubular assembly of the invention, the first tubular housing 50 is held in that axial position after being welded at the second distal end 55 to the outer tube 22. In that case, as in Figure 10d, the first tubular housing 50 comprises an outer metal sleeve 57 and a polymer core 58. The metal sleeve 57 is welded to the outer tube 22 or the annular bridge 26. The polymer core 58 is preferably expanded and fitted into the metal sleeve 57 before welding, with liquid nitrogen used for the expanded fitting process. As shown in Figure 10d, a radial gap ε can be defined between an outer diameter of the unthreaded portion 36 of the extension 30 and an inner surface of the polymer core 58. Alternatively, the polymer core 58 can be force-fitted between the unthreaded portion 36 and the inner surface of the polymer core 58. PQC7 ίη / 77Π7 / E / YΙΛΙ of the extension 30 and the outer metal sleeve. The polymer core 58 is longer than the metal sleeve 57 so that the polymer core is defining only the first distal end 54. In accordance with this alternative process, the polymer core 58 is turned with the same tool used to turn the pin 33 in the extension 30, such that the first distal end 54 and outer diameter of the polymer core are in a predetermined position relative to the free end 34 of the extension 30. If the polymer core 58 is shorter than the metal sleeve 57 before turning, then the same tool is also capable of turning the metal sleeve 57 so that the polymer core 58 defines only the first distal end 54. The polymer core 58 is provided with a first portion 50a up to the second bevel 53, the second bevel being a radial shoulder. Before preparing an assembly in accordance with the invention, a protector, not shown, is threaded onto pin 33 in order to protect pin 33 before it is prepared at the equipment site. In Figure 2, the outer surface 37 of the extension 31 of the second insulated pipe segment 16 is covered by a second pipe shell 50. The second pipe shell 50 is cylindrical with a first distal end 64 extending beyond the free end 35 of the extension 31. Opposite the first distal end 64, the second pipe shell comprises an opposite distal end 65 near the annular bridge 27. According to this embodiment, the second pipe shell overlaps at least partially with this annular bridge 27. To increase the reliability and effectiveness of the insulation, the second pipe shell 60 can extend beyond the connection to substantially overlap the annular space 25 with the second insulated pipe segment 16. However, within the scope of the invention, the opposite distal end 65 can also be at a non-zero axial distance from the annular bridge 27.But in order to reduce heat loss, it is preferable to have an interior space between the second tubular shell 60 and that annular bridge 27, even preferably that the second tubular shell 60 overlaps completely with the annular bridge 27 and also covers part of the outer tube 23. Preferably, the outside diameter of the second tubular shell 60 is less than the outside diameter of the outer tube 23, and within a tolerance of + / -5% of the nominal accepted outside diameter dimension for those outer tubes 20, 22. An inside diameter of such a second tubular shell 60 is such that it is preferably greater than or equal to the outside diameter of the first portion 50a. Alternatively, an interference fit between the first and second tubular shoulders 50, 60 may be acceptable when they are made of polymeric material. When pin 33 and box 34 are made in order to obtain a threaded joint, the free end 35 of the extension 31 remains away from the first distal end 54 of the first PQC7 ίη / 77P7 / E / YILI tubular housing 50, but the portion of the second tubular housing 60 overlaps at least with the first portion 50a and the second bevel 53. At the time of preparation, the second tubular segment 16 is vertical, and the housing 33 is oriented upwards, while the first tubular segment 14 is also vertical but with the pin 32 oriented downwards; the second tubular housing 60 is already around the extension 31, either resting on the annular bridge 27 under gravity forces, or fixed in some axial location. The assembly process includes the step of reducing and riveting the first tubular segment in the direction of the second tubular segment 16, and threading the pin and housing together. While being prepared, the first tubular housing 50 is partially and progressively fitted into the annular volume provided by the second tubular housing 60. In this way, the insulating sleeve of the invention comprising such a tubular casing 50 and a second tubular casing 60 provides continuous thermal insulation. Figure 3 shows a slight variation of the assembly in Figure 2, where the extension 30, the unthreaded portion 36, the first tubular casing 50, and especially the transition portion 50b are longer than those in Figure 2, for example, approximately 50 mm longer than 130 mm. With an insulated first tubular segment 14 in Figure 3, service life is improved, as this assembly can be used in a well for some time. Then, when it is removed from the well for maintenance, the joints are broken, and the extension 30 provides sufficient length to cut a new pin 32 and a new free end 34. While the first tubular casing is still around the unthreaded portion 36, it will be possible to shorten the length and reshape the first tubular casing 50 to the required distance with the cut free end 34.Without any need to adjust the shape of the second tubular housing 60, it will be possible to provide a new assembly with the first tubular segment cut off 14. The first tubular housing 50 can also be reduced in length if the housing 33 is also cut off at the second tubular segment 31. Alternatively and / or in addition, the second tubular housing 60 could also be shortened in length with a turning tool at the time of trimming the box 33, but this would require preventing the second tubular housing from having any non-rotating axial movement around the outer surface 37. The second tubular housing 60 may be provided with a radial gap from the outer surface 37 or be shrink-fitted around the outer surface 37. When the second tubular housing 60 is fitted around the outer surface 37 with a radial gap, a female protector provided at the free end 35 will retain the second tubular housing 60 around the extension 31 to an equipment site, where the female protector will be removed to allow preparation for assembly in accordance with the invention. Alternatively, the second tubular housing may be provided separately and positioned in PQC7 ίη / 77Π7 / E / YΙΛΙ the free end 35 only on the equipment site. Figures 4 to 7 illustrate other embodiments of the tubular assembly 110 having a T&C connection 112. As pipe segments 14, 16 of the tubular assembly 10, pipe segments 114, 116 have inner tubes 120, 121, outer tubes 122, 123, and annular spaces 124, 125 between them to maintain a vacuum and / or contain an insulating material. Annular bridges in the form of frustoconical impulse rings 126, 127 connect, by welding at both ends, the inner tubes 120, 121 with their respective outer tubes 122, 123, to close the annular space to the atmosphere. Pipe segments 114, 116 have extensions 130, 131 at at least one end of each pipe segment 114, 116. The extensions 130, 131 can be portions of the inner pipes 120, 121 that extend beyond the bridges 126, 127. Contrary to the versions shown in Figures 2 and 3, both extensions 130 and 131 in Figures 4 to 7 are provided with a male threaded connection with pins 132 and 133 respectively. Extensions 130 and 131 preferably have the same male threaded portion on them. The connection 112 of the tubular assembly 110 comprises a tubular coupling 180 for receiving extensions 130, 131 of pipe segments 114, 116. The tubular coupling 180 has threaded box ends 187 and 188, which engage with respective pin threads 132 and 133, for joining pipe segments 114, 116. Like the tubular assembly 10 in Figure 2, the tubular assembly 110 in Figures 4 to 6 includes an insulating sleeve 118 for insulating the connection 112. The sleeve 118 comprises a first tubular housing 150 in the first extension 130, a second tubular housing 160 covering the coupling 180, and a third tubular housing 170, identical to the tubular housing 150, in the second extension 131. The sleeve 118 surrounds the connection 112 to isolate the connection 112 and to isolate both joints between the pin 132 and a first box end 187 of the coupling and the second joint between the pin 133 and second box end 188 of the same coupling 180. The sleeve of a tubular assembly preferably extends across an entire connection so that the insulation of the tubular assembly can be substantially continuous along the length of the tubular assembly, i.e., from one insulated pipe segment, across a connection, to the next pipe segment. The second tubular sleeve 160 extends beyond both free ends of the coupling 180 so that the second tubular sleeve 180 overlaps externally to both of the first and third tubular housings 150 and 170. Preferably, each tubular shell 150, 160, and 170 has a rigid, one-piece construction. In Figure 4, each tubular shell is a one-piece construction made of a single material, for example, all of the same material. In Figure 4, the second tubular shell 160 is PQC7 iη / 77P7 / E / YILI fits by shrinkage or force fit around coupling 160. Alternatively, the second tubular housing 160 can be free to rotate around coupling 180. In accordance with this alternative solution, the second tubular housing 160 can also be free to slide longitudinally between the first and third tubular housings, to the extent of a longitudinal tolerance that permits such sliding movement. Alternatively, this unitary tubular housing may have a separate inner core as 58 and an outer metallic sleeve as 57. Figure 5, tubular housings 150 and 170 are identical to those described in connection with Figure 1d. For the embodiment of Figure 5, the second tubular housing 150 comprises a metallic sleeve 168 and a polymeric core 167, such that the polymeric core extends axially beyond the metallic sleeve 168 at both ends, and the polymeric core 167 overlaps with the polymeric cores 157 in both the first and third tubular housings 150 and 170. As a slight difference from Figure 1d, the metallic sleeve 157 is welded to the annular thrust rings 126 and 127, respectively. The second tubular housing 160 can alternatively be slidably mounted around the coupling 180 with an acceptable radial gap between an outer surface of the coupling and an inner diameter of the second tubular housing. Figure 6 is an alternative to Figure 5 in that the metal sleeves 157 and 167 are incorporated into their respective polymer cores 105 and 168, in order to reduce the outside diameter of the insulation sleeve formed by the first, second, and third overlapping tubular shells. Furthermore, the maximum outside diameter provided by the polymer cores 158 and 168 is also provided. The metal sleeves 157 and 167 are leveled with the maximum outside diameter provided by the polymer cores 158 and 168. Figure 7 is an alternative embodiment of Figures 4 to 6, with extensions 130 and 131 provided by outer tubes 122 and 123. Extensions 130 and 131 are still provided with pins 132 and 133 thereon for joining the box ends of a coupling 180. However, in accordance with this embodiment, the insulating sleeve comprises a first inner tubular shell 250 and a second inner tubular shell 260. The first inner tubular shell 250 is inserted along an inner surface of the extension 130, and the second inner tubular shell is provided along an inner surface of the extension 131, such that when joints are prepared, one of the inner tubular shells 250 and 260 overlaps the other. Preferably, a maximum inside diameter of those inner tubular casings 250 and 260 is greater than an inside diameter of the inner tubes 120, 121.The maximum inside diameters of those inner tubular casings 250 and 260 can be equal. A string can be assembled, as needed, from a plurality of individual pipe segments to reach the earth's surface or a reservoir. PQC7 iη / 77P7 / E / YILI underground. Each insulated pipe segment may have an extension at each of the two opposite ends, so that a connection may be formed at each end of the pipe segment. An insulating sleeve may be installed at each connection, so that the pipe assembly is continuously insulated along its length, without interruption at each connection. Those skilled in the art shall understand that the embodiment shown and described in illustrative and various other modifications can be made in the practice of the invention. Accordingly, the scope of the invention shall be understood to include such modifications that are within the spirit of the invention.

Claims

1. An insulated tubular assembly characterized in that it comprises two joined insulated pipe segments, a first insulated pipe segment and a second insulated pipe segment, each insulated pipe segment comprising an inner tube defining an inner passage adapted for conveying fluids; an outer tube concentrically arranged around and defining an annular space with said inner tube; an annular bridge at each opposite end of the insulated pipe segment, each annular bridge connecting said inner tube to said outer tube such that one of the inner and outer tubes is longer than the other;the longer one forming an outwardly extending extension at one end of the first insulated pipe segment such that a pin member having an external male thread is formed thereon to thread-engage a female thread of a box member provided on either the second insulated pipe segment or a coupling attached to such second insulated pipe segment, pin member and box joined together to form a threaded joint between said first and second insulated pipe segments; and an insulating sleeve, wherein the insulating sleeve comprises a first tubular shell adapted to cover at least part of the extension of the first insulated tubular segment and a second tubular shell overlapping either internally or externally part of the first tubular shell, such that the second tubular shell extends axially around the threaded joint.

2. The insulated tubular assembly according to claim 1, further characterized in that said first tubular casing is adapted to cover at least part of the annular bridge of the first insulated tubular segment.

3. The insulated tubular assembly according to claim 2, further characterized in that said first tubular shell comprises a first bevel adapted to expand over the annular bridge of the first insulated tubular segment, and preferably the first tubular shell can axially cover, from any axial side of that annular bridge, parts of both the inner and outer tube of the first insulated pipe segment.

4. The insulated tubular assembly according to claim 1, further characterized in that said first tubular housing is adjacent to the pin member.

5. The insulated tubular assembly according to claim 1, further characterized in that said second tubular housing expands over the box member, so that it is longer than the box member.

6. The insulated tubular assembly according to claim 1, PQC7 ίη / 77Π7 / E / YΙΛΙ further characterized in that said insulating sleeve expands from at least part of the annular bridge of the first tubular segment and to at least part of an annular bridge of the second tubular segment.

7. The insulated tubular assembly according to claim 1, further characterized in that the female thread of a box member is provided on the second insulated pipe segment and the second tubular housing extends partially around the first tubular housing and to an outer surface of an extension of the second insulated pipe segment.

8. The insulated tubular assembly according to claim 1, further characterized in that the female thread of a box member is provided on a coupling attached to such second insulated pipe segment, the second insulated tubular segment comprising a second extension with a second pin member thereon, for the purpose of threading onto such second pin member on another box member of the coupling forming another threaded joint, and the insulating sleeve comprising a third tubular shell such that the third tubular shell is adapted to cover at least part of the second extension, the second tubular shell overlapping either internally or externally on part of the first tubular shell and also part of that third tubular shell, such that the second tubular shell extends axially around both threaded joints,The second tubular shell extends from the first tubular shell to the third tubular shell.

9. The insulated tubular assembly according to the preceding claim, further characterized in that the first and third tubular housings are identical.

10. The insulated tubular assembly according to claim 8 or 9, further characterized in that the first and second insulated pipe segments are provided with a pin member at both ends, such that prior to preparation of such assembly, the first tubular shell is held at one end by a protector, to be removed at the time of preparation, and the coupling and second and third tubular shells are provided at one end of the second insulated tubular assembly; the second and third tubular shells being held by another coupling protector, to be removed at the time of preparation.

11. The insulated tubular assembly according to claim 1, further characterized in that each tubular housing comprises: a rigid material selected from the group consisting of plastics and metals, for example, preferably selected from polymeric materials, expanded or particulate inorganic materials, expanded graphite and mixtures thereof.

12. The insulated tubular assembly according to claim 11, further characterized in that the first and / or second tubular casing comprises an outer metal sleeve PQC7 ίη / 77Π7 / E / YΙΛΙ welded to one of the first and second insulated pipe segments, preferably welded to the outer tube and / or the annular bridge connecting said inner tube to said outer tube.

13. - The insulated tubular assembly according to claim 1, further characterized in that each tubular housing is respectively a unitary tubular body.

14. - The insulated tubular assembly according to claim 1, further characterized in that the second tubular housing comprises a substantially uniform wall thickness such that the first tubular housing further comprises a second bevel to allow overlapping of the second tubular housing over the second bevel.

15. The insulated tubular assembly according to claim 1, further characterized in that the insulating sleeve defines an outside diameter with + or -5% of the nominal outside diameter of the first or second insulated pipe segment.

16. The insulated tubular assembly according to claim 1, further characterized in that the first tubular shell is fixed in an axial position relative to the annular bridge of the first insulated pipe segment, either by shrink-fitting around the first insulated tubular segment as the first tubular shell is made of a softer material than the first insulated tubular segment or welded at some point of the first insulated tubular segment.

17. A first insulated tubular segment adapted to be part of an insulated tubular assembly of claim 1, comprising a protector fitted at one end to retain a first tubular housing around an extension of that first insulated tubular segment, the protector being removed at the time of preparation.

18. A process for isolating an insulated tubular assembly of claim 1, wherein prior to preparation of the first insulated pipe segment with the second insulated pipe segment, the first tubular shell is inserted through a first end of the first insulated pipe segment, and the first tubular shell is fitted into a longitudinal position of the extension of the first insulated pipe segment, and is then turned with a specific pattern determined as a function of a distance from a free end of that first end.

19. A process for isolating an insulated tubular assembly of claim 1, wherein prior to preparation of the first insulated pipe segment with the second insulated pipe segment, the second tubular shell is inserted through a free end of either the second insulated pipe segment or the coupling attached to such second insulated pipe segment, and the second tubular shell is turned with a specific pattern determined as a function of a distance from the free end.

20. A method of assembling an insulated tubular assembly of claim 1, wherein prior to preparation, the first insulated pipe segment is vertical, the first tubular housing PQC7 ίη / 77Π7 / E / YΙΛΙ retained around the annular bridge even when oriented towards the ground in order to be threaded to the same second insulated pipe or coupling attached to such second insulated coupling already vertical.

21. A process for isolating an isolated tubular assembly of claim 1, wherein - the thread coupling of the pin member with the housing member is broken, - the pin member is trimmed, and another external male thread is turned into the trimmed pin member, such that the first tubular housing is also turned with a specific pattern determined as a function of a distance from the newly trimmed free end.

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