GEOTHERMAL HEAT EXCHANGE APPARATUS

Abstract

A heat exchange system and related method for retrofitting an existing bore with the said system, the system being adapted to be used within a bore formed within the ground, and being independent of formation fluids, the system comprising a first pipe and a second pipe together forming a fluid path, wherein substantially a lower end in use of each of the first pipe and the second pipe are in fluid communication with each other and with a sump, so that fluid can flow between the first pipe and the second pipe via the sump within the said bore, the system further comprising a pump adapted to drive heat exchange fluid through the said pipes and a heat exchange unit adapted to transfer thermal energy to or from the said heat exchange fluid.

Claims

1-15. (canceled)

16. A heat exchange system for geothermal heat extraction adapted to be used within a bore formed within the ground, and being independent of formation fluids, the system comprising a first pipe and a second pipe together forming a fluid path, wherein substantially a lower end in use of each of the first pipe and the second pipe are in fluid communication with each other and with a sump, so that fluid can flow between the first pipe and the second pipe via the sump within the said bore, the system further comprising a pump adapted to drive heat exchange fluid through the said pipes and a heat exchange unit adapted to transfer thermal energy to or from the said heat exchange fluid, and wherein the system further comprises an annular region of the said fluid path in which fluid may circulate, within which annular region is provided a convection centralizer.

17. A heat exchange system according to claim 16, wherein the system further comprises a production casing having a lower wall portion and a circumferential wall portion.

18. A heat exchange system according to claim 16, further comprises a cap.

19. A heat exchange system according to claim 16, further comprising one or more circulation shoes.

20. A heat exchange system according to claim 16, further comprising one or more landing nipples.

21. A heat exchange system according to claim 16, further comprising at least one cable.

22. A heat exchange system according to claim 16, wherein one or other of the first and/or second pipe are formed from a coiled tube.

23. A heat exchange system according to claim 16, wherein the pump forms part of a process plant.

24. A heat exchange system, wherein the bore has one or more further branches.

25. A heat exchange system according to 16, further comprising means adapted for extracting resources from the ground.

26. A heat exchange system according to claim 25, wherein the means adapted to extract resources from the ground comprises one or more extraction pipes.

27. A heat exchange system according to claim 26, wherein the said one or more extraction pipes are not in fluid communication with the said first and second pipes.

28. A heat exchange system according to any of claims 25, further adapted to be used with a secondary bore joined with the said bore, wherein the means adapted to extract resources from the ground are arranged within the secondary bore.

29. A method of adapting an existing bore to provide geothermal energy heat extraction, the method comprising the steps of: providing an existing bore with a first pipe and a second pipe together forming a fluid path, wherein substantially a lower end in use of each of the first pipe and the second pipe are in fluid communication with each other and with a sump, so that fluid can flow between the first pipe and the second pipe via the sump within the said bore, wherein an annular region is formed in which fluid may circulate, within which annular region of the said fluid path a convection centralizer is provided; providing a pump adapted to drive heat exchange fluid through the said pipes; and providing a heat exchange unit adapted to transfer thermal energy to or from the said heat exchange fluid.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0094] In these exemplary embodiments, respective features have been labelled with the same labels throughout; however the skilled reader will appreciate that features which have been labelled consistently across embodiments do not necessarily share every aspect with correspondingly labelled features in other embodiments. In other words, each embodiment should be understood to be independent from the others unless explicitly linked.

[0095] In FIG. 1, a horizontal cross-section through a main bore 1 is shown, with a first pipe 10 and second pipe 12 arranged within the bore 1. In the arrangement of FIG. 1, the first pipe 10 and second pipe 12 are arranged in parallel to one another and non-co-axially. In other words, the two pipes are arranged side by side within the bore 1 and with a gap between them. The first pipe 10 is of larger diameter than the second pipe 12. The first pipe 10 can be said to be a supply pipe and the second pipe 12 can be said to be a return pipe. In this arrangement, the second pipe 12 is also acting as a velocity string.

[0096] In FIG. 2, a horizontal cross-section through a main bore 1 is shown, with a first pipe 10 and second pipe 12 arranged within the bore 1. In the arrangement of FIG. 2, the first pipe 10 and the second pipe 12 are arranged in parallel and co-axially so that the relatively smaller diameter second pipe 12 is arranged within the relatively larger diameter first pipe 10. In this arrangement, the second pipe 12 is also acting as a velocity string.

[0097] In FIG. 3, a vertical cross section of an exemplary embodiment of a system having a bore 1 in which a first pipe 10 is arranged within the bore 1, and has arranged within it approximately co-axially a second pipe 12. A sump 14 is in fluid communication with the first pipe 10 and the second pipe 12 and together the first pipe 10, sump 14 and second pipe 12 form a fluid path. A pump (not shown in FIG. 3) drives heat exchange fluid (marked with various flow arrows in FIG. 3) through the system. Circulation of heat exchange fluid will also be driven by natural convection, such as via thermosiphon and/or density change.

[0098] The first pipe 10 forms the outer boundary of the sump 14, and the sump 14 is surrounded by a further annular region 20, i.e. between the first pipe 10 and a production casing 22 which is a lining of the bore 1 (which may be newly constructed or part of an existing well). Within the annular region 20 are arranged convection centralizers 21. As indicated by convection flow arrow FC, packer fluid convection occurs within the annular region 20 region.

[0099] At the top of the bore 1 a well head acts as a cap 16.

[0100] Below the production casing 22 is a portion of lower well construction 24. This may be newly constructed or part of an existing well.

[0101] Towards the lower end of the second pipe 12 is arranged a circulation shoe 26 which forms a narrowing of the second pipe 12.

[0102] Between the lower end and the upper end of the second pipe 12 — closer to the lower end in FIG. 3 — is arranged a landing nipple 28.

[0103] Arranged vertically within the first pipe 10 and the annular region 20 are fibre optic cables 30 (indicated by dashed lines) which provide distributed temperature sensing and data transfer.

[0104] The first pipe 10 and/or the second pipe 12 may be formed from a coiled tube.

[0105] Fluid flow arrows F1 (downwards) and F2 (upwards) show the approximate fluid flow within the first pipe 10 and the second pipe 12 in use. The second pipe 12 directs fluid to a heat exchange unit (not shown in FIG. 3).

[0106] FIG. 4 shows a further exemplary embodiment, similar to that of FIG. 3. The reader will appreciate that the description, features, labels etc. of FIG. 3 apply similarly to FIG. 4.

[0107] FIG. 5 shows a vertical cross section of a further exemplary embodiment. In FIG. 5, the bore 1 has arranged within it a first pipe 10 and a second pipe 12 substantially parallel to one another within the bore 1. First pipe 10 is much longer than second pipe 12. The lower ends of the first pipe 10 and second pipe 12 are each in fluid communication with a sump 14 and together the first pipe 10, sump 14 and second pipe 12 form a fluid path. A pump (not shown in FIG. 5) drives heat exchange fluid (labelled with various flow arrows in FIG. 5) through the system.

[0108] The first 10 and second 12 pipes convection centralizers 21 are arranged within the sump 14. As indicated by convection flow arrow FC, fluid convection occurs within the sump 14.

[0109] Below the production casing 22 is a portion of lower well construction 24. This may be newly constructed or part of an existing well. Forming a barrier at the upper end of the sump 14 is a packer forming a cap 16. The packer/cap 16 forms a pressure seal around the sump 14. Above the packer/cap packer fluid can circulate.

[0110] Towards a lower end and first pipe 12 is arranged a landing nipple 28.

[0111] Arranged vertically within the sump 14, attached to the outside of the first pipe 10, is a fibre optic cable 30 (indicated by a dashed line) which provides distributed temperature sensing and data transfer.

[0112] Fluid flow arrows F1 (downwards) and F2 (upwards) show the approximate fluid flow within the first pipe 10 and the second pipe 12 in use. The second pipe 12 directs fluid to a heat exchange unit (not shown in FIG. 5).

[0113] FIG. 6 shows a vertical cross section of a further exemplary embodiment. In FIG. 6, the bore 1 has arranged within it a first pipe 10 and a second pipe 12. The first pipe 10 is of larger diameter than the second pipe 12, and the second pipe 12 is arranged substantially coaxially within the first pipe 10. The lower ends of the first pipe 10 and the second pipe 12 are each at their lower ends in fluid communication with a sump 14. Together, the first pipe 10, second pipe 12 and sump 14 form a fluid path. A pump within a process plant 40 which is in fluid communication with the first pipe 10 drives heat exchange fluid (labelled with various flow arrows in FIG. 6) through the system.

[0114] The process plant 40 is adapted to monitor the temperature and pressure of the heat exchange fluid in the system, and sends information to a control unit 42 which is in turn adapted to control a choke valve 44. Thus the process plant 40 and the choke valve 44 act as an indirect cap, controlling the pressure of fluid within the system.

[0115] The first pipe 10 is surrounded by a further annular region 20, the sump 14 a production casing 22 which is a lining of the bore 1 (which may be newly constructed or part of an existing well). As indicated by flow arrow FC, fluid convection occurs within the annular region 20 region of the bore 1.

[0116] Within the annular region, convection centralizers 21 are arranged.

[0117] Below the production casing 22 is a portion of lower well construction 24. This may be newly constructed or part of an existing well.

[0118] Arranged vertically within the annular 20 region and within the second pipe 12, are fibre optic cables 30 (indicated by dashed lines) which provide distributed temperature sensing and data transfer.

[0119] Around the sump 14 is arranged a circulation shoe 26. The sump 14 is enveloped by a heat exchanger outer string 32. The lower part of the sump 14, within the circulation shoe 26 — which can also be referred to as a bottom hole assembly — can be provided with other devices.

[0120] The first pipe 10 and/or the second pipe 12 may be formed from a coiled tube.

[0121] Fluid flow arrows F1 (downwards) and F2 (upwards) show the approximate fluid flow within the first pipe 10 and the second pipe 12 in use. The second pipe 12 directs fluid to a heat exchange unit within the process plant 40.

[0122] FIG. 7 shows a vertical cross section of a further exemplary embodiment. In FIG. 7 the first pipe 10 and the second pipe 12 are arranged in parallel and side by side to one another and are approximately the same length within a sump 14. The lower ends of the first 10 and second 12 pipes are disposed within a circulation shoe 26 to form a bottom hole assembly. Sump 14 has a similar circulation shoe 26 arrangement to that of FIG. 6, and is enveloped by a heat exchanger. The circulation shoe 26 can also comprise further devices (not labelled).

[0123] The embodiment of FIG. 7 also has an annular region 20 with fluid convection indicated by arrow FC. Fibre optic cable 30 is arranged within the annular region 20, externally on the pipes 10, 12. Convection centralizers 21 are arranged within the annular region 20 attached to the pipes 10, 12 respectively.

[0124] At the top of the bore 1 a well head acts as a cap 16.

[0125] The first 10 and second 12 pipes are constructed from coil tubing, and the pipes are clamped in position by coil tubing pipe clamps 50.

[0126] Within the bore 1 is a production casing 22 which forms a lining of the bore 1 (which may be newly constructed or part of an existing well); below the production casing 22 is a portion of lower well construction 24 which may be newly constructed or part of an existing well.

[0127] FIG. 8 shows a vertical cross section of a further exemplary embodiment. In the arrangement of FIG. 8, the bore 1 has several further branches 100 (not all labelled to aid clarity). In this embodiment, the further branches are arranged radially away from the bore 1 at a downward angle thereto, and branch off from different points along the bore 1.

[0128] Within the bore 1 is arranged a first pipe 10 and a second pipe 12, both in fluid communication with a sump 14 to form a fluid path from the first pipe 10 to the second pipe 12. In this embodiment the second pipe 12 is arranged within and substantially coaxially with the first pipe 12.

[0129] The first pipe 10 is surrounded by a further region which acts as a convective annulus . Within the sump 14 are convection centralizers 21. The apparatus also has a production casing 22 which is a lining of the bore 1 (which may be newly constructed or part of an existing well). As indicated by flow arrow FC, fluid convection occurs within the sump 14 and also around the body of the heat exchanger in the bore 1 and in the radial branches.

[0130] Arranged vertically within the first pipe 10, is a fibre optic cable 30 (indicated by a dashed line) which provides distributed temperature sensing. Additional fibre optic cable can be connected to an outer pipe within each additional branch (lateral).

[0131] At each branch between the bore 1 and each further branch 100 is a valve 102 (only one is labelled in FIG. 8 to aid clarity). These valves allow switching between each branch to allow combined circulation from all branches into the main heat exchanger assembly of pipes 10 and 12 but also allows for selected circulation to the heat exchanger by one or more of the branches 100.

[0132] Below the production casing 22 is a portion of lower well construction 24. This may be newly constructed or part of an existing well.

[0133] Fluid flow arrows F1 (downwards) and F2 (upwards) show the approximate fluid flow within the first pipe 10 and the second pipe 12 in use. The second pipe 12 directs fluid to a heat exchange unit (not shown in FIG. 8).

[0134] FIG. 9 shows a vertical cross section of a further exemplary embodiment. In the arrangement of FIG. 9, the bore 1 has several further branches 100 (not all labelled for clarity). In this embodiment, the further branches are arranged radially away from the bore 1 at a downward angle thereto, and branch off from different points along the bore 1.

[0135] Within the bore 1 is arranged a first pipe 10 and a second pipe 12, both in fluid communication with a sump 14 to form a fluid path from the first pipe 10 to the second pipe 12. In this embodiment the second pipe 12 is arranged within and substantially coaxially with the first pipe 10.

[0136] The first pipe 10 is surrounded by a further annular region 20 which acts as a convective annulus enhanced by convection centralizers 21 between the first pipe 10 and a production casing 22 which is a lining of the bore 1 (which may be newly constructed or part of an existing well). As indicated by flow arrow FC, fluid convection occurs within the convection centralizer 20 region of the bore 1.

[0137] Arranged vertically within the annular region 20 and within the second pipe 12, is a fibre optic cable 30 (indicated by a dashed line) which provides distributed temperature sensing. Additional fibre optic cable can be connected to the outer pipe within each additional branch 100 (lateral).

[0138] Each lateral branch 100 acts as a heat source/heat sink allowing conduction and convection of heat to the bore 1.

[0139] FIG. 10 shows a vertical cross section of a further exemplary embodiment. In the arrangement of FIG. 10, the bore 1 has several further branches 100. In this embodiment, the further branches are arranged radially away from the bore 1 at a downward angle thereto, and branch off from different points along the bore 1. The branches are extending radially behind the lower production casing.

[0140] Within the bore 1 is arranged a first pipe 10 and a second pipe 12, both in fluid communication with a sump 14 to form a fluid path from the first pipe 10 to the second pipe 12. In this embodiment the second pipe 12 is arranged within and substantially coaxially with the first pipe 12.

[0141] The first pipe 10 is surrounded by a further annular region 20 which acts as a convective annulus enhanced by a convection centralizers 21 arranged within. The annular region 20 is between the first pipe 10 and a production casing 22 which is a lining of the bore 1 (which may be newly constructed or part of an existing well). As indicated by flow arrow FC, fluid convection occurs within the annular region 20 of the bore 1.

[0142] Arranged vertically within the annular region 20 and within the second pipe 12, is a fibre optic cable 30 (indicated by a dashed line) which provides distributed temperature sensing. Additional fibre optic cables will be connected to the outer pipe within the each additional branch 100 (lateral).

[0143] Each branch 100 acts as a heat source/heat sink allowing conduction and convection of heat to the main bore 1.

[0144] FIG. 11 shows a vertical cross section of a further exemplary embodiment. In the arrangement of FIG. 11, the bore 1 has several further branches 100. In this embodiment, the further branches are arranged radially away from the bore 1 at a downward angle thereto, and branch off from different points along the bore 1.

[0145] Within the bore 1 is arranged a first pipe 10 and a second pipe 12, both in fluid communication with a sump 14 to form a fluid path from the first pipe 10 to the second pipe 12. In this embodiment the firs pipe 10 and second pipe 12 are arranged side by side approximately in parallel with one another.

[0146] A packer acts as a cap 16 to isolate the sump 14 from the region above the sump 14 within the bore 1. Above the cap 16 is an annular region 20.

[0147] Within the sump 14 are arranged convection centralizers 21 (not all labelled for clarity).

[0148] As indicated by flow arrow FC, fluid convection occurs within the sump 14.

[0149] Arranged vertically along the outside of the first pipe 10, is a fibre optic cable 30 (indicated by a dashed line) which provides distributed temperature sensing and data transfer. Additional fibre optic cable an be connected to an outer pipe within the each additional branch 100 (lateral).

[0150] Each lateral branch 100 acts as a heat source/heat sink allowing conduction and convection of heat to the main bore.

[0151] FIG. 12 shows a vertical cross section of a further exemplary embodiment. In FIG. 12, the bore 1 has arranged within it a first pipe 10 and a second pipe 12 substantially parallel to one another within the bore 1. First pipe 10 is much longer than second pipe 12. The lower ends of the first pipe 10 and second pipe 12 are each in fluid communication with a sump 14 and together the first pipe 10, sump 14 and second pipe 12 form a fluid path. A pump (not shown in FIG. 12) drives heat exchange fluid (marked with various flow arrows in FIG. 12) through the system. The sump 14 is surrounded by a production casing 22 which is a lining of the bore 1 (which may be newly constructed or part of an existing well). This may or may not be cemented in place depending on the rock in which it is sited in order to maximise heat transfer from the rock.

[0152] Below the production casing 22 is a portion of lower well construction 24. This may be newly constructed or part of an existing well. A packer acts as a cap 16 to isolate the sump 14 from packer fluid above the cap 16. The cap 16 also forms a pressure seal around the sump 14.

[0153] Within the sump 14 there are convection centralizers 21 (not all labelled for clarity).

[0154] Towards a lower end and first pipe 12 is arranged a landing nipple 28.

[0155] Arranged vertically on the outside of the first pipe 10, is a fibre optic cable 30 (indicated by a dashed line) which provides distributed temperature sensing.

[0156] The first pipe 10 and/or the second pipe 12 may be formed from a coiled tube.

[0157] Fluid flow arrows F1 (downwards) and F2 (upwards) show the approximate fluid flow within the first pipe 10 and the second pipe 12 in use. The second pipe 12 directs fluid to a heat exchange unit (not shown in FIG. 9).

[0158] FIG. 13 shows a vertical cross section of a further exemplary embodiment. In FIG. 13, the bore 1 has a first pipe 10 and a second pipe 12 arranged in parallel with one another approximately vertically within the bore 1. A sump 14 is in fluid communication with the first pipe 10 and the second pipe 12 and together the first pipe 10, sump 14 and second pipe 12 form a fluid path. A pump (not shown in FIG. 10) drives heat exchange fluid (marked with various flow arrows in FIG. 10) through the system.

[0159] The first 10 and second 12 pipes are surrounded within the sump 14 by a further annular region 20 between the pipes (10, 12) and a production casing 22 which is a lining of the bore 1 (which may be newly constructed or part of an existing well). As indicated by convection flow arrow FC, fluid convection occurs within the sump 14. Within the annular region 20 are arranged convection centralizers 21.

[0160] Below the production casing 22 is a portion of lower well construction 24. This may be newly constructed or part of an existing well. A packer acts as a cap 16 to isolate the sump 14 from packer fluid above the cap 16.. The cap 16 also forms a pressure seal around the sump 14.

[0161] Arranged vertically on the outer part of the first pipe 10 is a fibre optic cable 30 (indicated by a dashed line) which provides distributed temperature sensing and data transfer.

[0162] The first pipe 10 and/or the second pipe 12 may be formed from a coiled tube.

[0163] Fluid flow arrows F1 (downwards) and F2 (upwards) show the approximate fluid flow within the first pipe 10 and the second pipe 12 in use. The second pipe 12 directs fluid to a heat exchange unit (not shown in FIG. 13).

[0164] FIG. 14 shows a vertical cross section of a further exemplary embodiment. In FIG. 14, the bore 1 has a first pipe 10 and a second pipe 12 arranged in parallel with one another approximately vertically within the bore 1. A sump 14 is in fluid communication with the first pipe 10 and the second pipe 12 and together the first pipe 10, sump 14 and second pipe 12 form a fluid path. A pump (not shown in FIG. 14) drives heat exchange fluid (marked with various flow arrows in FIG. 14) through the system.

[0165] The sump 14 is isolated at the top by a packer which forms a cap 16. The cap 16 also forms a pressure seal around the sump 14.

[0166] The first 10 and second 12 pipes are surrounded within the sump 14 by a further annular region 20 and subsequently by a production casing 22 which is a lining of the bore 1 (which may be newly constructed or part of an existing well). As indicated by convection flow arrow FC, fluid convection occurs within the annular region 20 region. Within the annular region 20 are arranged convection centralizers 21 (not all labelled to aid clarity).

[0167] Below the production casing 22 is a portion of lower well construction 24. This may be newly constructed or part of an existing well.

[0168] Arranged vertically on the outer part of the first pipe 10 is a fibre optic cable 30 (indicated by a dashed line) which provides distributed temperature sensing and data transfer.

[0169] The first pipe 10 and/or the second pipe 12 may be formed from a coiled tube.

[0170] Fluid flow arrows F1 (downwards) and F2 (upwards) show the approximate fluid flow within the first pipe 10 and the second pipe 12 in use. The second pipe 12 directs fluid to a heat exchange unit (not shown in FIG. 14).

[0171] FIG. 15 shows an exemplary embodiment of the system, in vertical cross section. This embodiment has a bore 1 within which are arranged a first pipe 10 and a second pipe 12 arranged approximately coaxially within the bore 1 — each of the first 10 and second 12 pipes being in fluid communication via a sump 14. A packer / cap 16 provides a pressure seal and isolation for that part of the system.

[0172] The embodiment of FIG. 15 also has a secondary bore 2 which branches off the bore 1 along its length; in this embodiment the branch of the secondary bore 2 from the bore 1 is above the region occupied by the sump 14 and cap 16. Within the secondary bore 2 a third pipe 3 is arranged. The third pipe 3 is adapted to extract mineral resources from underground regions connected to secondary bore 2.

[0173] An upper cap 160 provides a pressure seal and isolation for that part of the system including the secondary bore 2.

[0174] Fluid flow arrows F1 (downwards) and F2 (upwards) show the approximate fluid flow within the first pipe 10 and the second pipe 12 in use. Fluid arrows FC also show convection flow within the sump 14.

[0175] FIG. 16 shows an exemplary embodiment of the system, in vertical cross section. This embodiment has a bore 1 within which are arranged a first pipe 10 and a second pipe 12 arranged coaxially within one part of the bore 1 and side-by-side in a lower part of the bore 1. The lower ends of the first pipe 10 and the second pipe 12 are arranged in fluid communication with a sump 14. Packer / cap 16 forms a pressure seal and isolation for that part of the system in the sump 14 region.

[0176] The embodiment of FIG. 16 also has a secondary bore 2 which branches off the bore 1 along its length; in this embodiment the branch of the secondary bore 2 from the bore 1 is above the isolated region occupied by the sump 14 and cap 16. Within the secondary bore 2 a third pipe 3 is arranged. The third pipe 3 is adapted to extract mineral resources from underground regions connected to secondary bore 2.

[0177] An upper cap 160 provides a pressure seal for that part of the system including the secondary bore 2.

[0178] Fluid flow arrows F1 (downwards) and F2 (upwards) show the approximate fluid flow within the first pipe 10 and the second pipe 12 in use. Fluid arrows FC also show convection flow within the sump 14.