Orienting and Supporting a Casing of a Coaxial Geothermal Borehole

Abstract

A casing support of a geothermal borehole heat exchanger having an outer casing, the casing support comprising a base support element incorporating an aperture therethrough, the base support element being arranged to be supported by a ground surface around a borehole, an annular orientation guide element at an upper surface of the base support element and having a central conduit communicating with the aperture, the orientation guide element having an upper surface at a selected angle relative to a lower support surface of the base support element, and a casing support ring fitted around an outer casing of a geothermal borehole heat exchanger, the casing support ring being coupled to the orientation guide element to support the casing in the borehole, the outer casing extending through the ring, the conduit and the aperture.

1 . A geothermal borehole heat exchanger supported in a borehole by a casing support, the casing support being fitted around an outer casing of the geothermal borehole heat exchanger and suspending the borehole heat exchanger within a borehole extending downwardly from the casing support, the casing support defining a predetermined angle of an upper end of the borehole heat exchanger within the borehole. 
     
     
         2 . A geothermal borehole heat exchanger according to  claim 1  wherein the casing support suspends the entire weight of the borehole heat exchanger within the borehole. 
     
     
         3 . A geothermal borehole heat exchanger according to  claim 1  or  claim 2  wherein the casing support has an inner annular surface engaging an outer cylindrical surface of an upper end of the outer casing. 
     
     
         4 . A geothermal borehole heat exchanger according to  claim 3  wherein the inner annular surface of the casing support threadably engages the outer cylindrical surface of an upper end of the outer casing. 
     
     
         5 . A geothermal borehole heat exchanger according to any foregoing claim wherein the casing support comprises an inner element mounted around the upper end of the borehole heat exchanger and an outer landing guide mounted on an orientation guide element located in a chamber, the inner element being fitted in the outer landing guide. 
     
     
         6 . A geothermal borehole heat exchanger according to  claim 5  wherein the inner element and the landing guide have complementary outer and inner tapered fitting surfaces to permit the inner element to be downwardly fitted into the landing guide. 
     
     
         7 . A geothermal borehole heat exchanger according to any foregoing claim further comprising a borehole surface casing surrounding an upper portion of the borehole heat exchanger within the borehole and fitted to the casing support. 
     
     
         8 . A geothermal borehole heat exchanger according to  claim 7  when appendant on  claim 5  wherein the borehole surface casing is threadably fitted to an inner annular surface of the landing guide. 
     
     
         9 . A geothermal borehole heat exchanger according to any foregoing claim wherein the borehole heat exchanger extends downwardly to a depth of greater than 100 metres. 
     
     
         10 . A chamber comprising a plurality of geothermal borehole heat exchangers according to any foregoing claim, each casing support having a respective borehole heat exchanger extending downwardly therefrom at a respective orientation. 
     
     
         11 . A chamber according to  claim 10  when appendant on  claim 5  wherein the orientations of at least some of the borehole heat exchangers are different, each orientation being provided by a corresponding selected orientation of the respective orientation guide element. 
     
     
         12 . A method of installing a geothermal borehole heat exchanger, the method including the steps of:
 (a) providing a first casing support portion which is supported by a ground surface and defines a predetermined drilling angle for a borehole;   (b) drilling a borehole through the first casing support portion, the first casing support portion defining a predetermined angle of an upper end of the borehole; and   (c) suspending, from the first casing support portion, a borehole heat exchanger within the borehole extending downwardly from the first casing support portion, the first casing support portion defining a predetermined angle of an upper end of the borehole heat exchanger within the borehole.   
     
     
         13 . A method according to  claim 12 , further including the steps, between steps (b) and (c), of:
 (d) fitting a second casing support portion around an outer casing of the geothermal borehole heat exchanger; and   (e) coupling together the first and second casing support portions to form a combined casing support fitted to the borehole heat exchanger and adapted to suspend the borehole heat exchanger within the borehole.   
     
     
         14 . A method according to  claim 13  wherein the casing support suspends the entire weight of the borehole heat exchanger within the borehole. 
     
     
         15 . A method according to  claim 13  or  claim 14  wherein the second casing support portion supports an outer casing of the borehole heat exchanger in the borehole, the outer casing extending through the casing support, the second casing support portion having an inner annular surface engaging an outer cylindrical surface of an upper end of the outer casing. 
     
     
         16 . A method according to  claim 15  wherein the inner annular surface of the second casing support portion threadably engages the outer cylindrical surface of the upper end of the outer casing. 
     
     
         17 . A method according to  claim 15  or  claim 16  wherein the second casing support portion comprises an inner element mounted around the upper end of the borehole heat exchanger and an outer landing guide mounted on the first casing support portion, the inner element being fitted in the outer landing guide. 
     
     
         18 . A method according to  claim 17  wherein the inner element and the landing guide have complementary outer and inner tapered fitting surfaces and the inner element is downwardly fitted into the landing guide. 
     
     
         19 . A method according to any one of  claims 12  to  18  further comprising fitting a borehole surface casing to surround an upper portion of the borehole heat exchanger within the borehole and fitted to the casing support. 
     
     
         20 . A method according to  claim 19  when appendant on  claim 17  wherein the borehole surface casing is threadably fitted to an inner annular surface of the landing guide. 
     
     
         21 . A method according to any one of  claims 12  to  20  wherein the borehole heat exchanger extends downwardly to a depth of greater than 100 metres. 
     
     
         22 . A method according to any one of  claims 12  to  21  of installing a plurality of casing supports, each casing support having a respective borehole heat exchanger extending downwardly therefrom at a respective orientation. 
     
     
         23 . A method according to  claim 22  when appendant on  claim 15  wherein the orientations of at least some of the borehole heat exchangers are different, each orientation being provided by a corresponding selected orientation of the respective casing support. 
     
     
         24 . A method according to  claim 22  or  claim 23  wherein the upper end of the borehole heat exchanger is installed at a preset height above the casing support, and further comprising fitting a well head to the upper end of the borehole heat exchanger. 
     
     
         25 . A casing support of a geothermal borehole heat exchanger having an outer casing, the casing support comprising a base support element incorporating an aperture therethrough, the base support element being arranged to be supported by a ground surface around a borehole, an annular orientation guide element at an upper surface of the base support element and having a central conduit communicating with the aperture, the orientation guide element having an upper surface at a selected angle relative to a lower support surface of the base support element, and a casing support ring fitted around an outer casing of a geothermal borehole heat exchanger, the casing support ring being coupled to the orientation guide element to support the casing in the borehole, the outer casing extending through the ring, the conduit and the aperture. 
     
     
         26 . A casing support according to  claim 25  wherein the base support element and the orientation guide element are integral. 
     
     
         27 . A casing support according to  claim 26  wherein the base support element and the orientation guide element are composed of precast concrete. 
     
     
         28 . A casing support according to any one of  claims 25  to  27  wherein the orientation guide element is located at a preset rotational position, with respect to a longitudinal axis of the aperture, relative to the base support element. 
     
     
         29 . A casing support according to any one of  claims 25  to  28  wherein the upper surface of the orientation guide element is inclined at an angle to a lower surface of the base support element. 
     
     
         30 . A casing support according to  claim 29  wherein the angle is from 5 to 45 degrees. 
     
     
         31 . A casing support according to  claim 25  wherein the annular orientation guide element is adapted to be fitted onto the upper surface of the base support element. 
     
     
         32 . A casing support according to  claim 31  wherein the base support element comprises a plate. 
     
     
         33 . A casing support according to  claim 32  wherein the base support element is composed of precast concrete. 
     
     
         34 . A casing support according to any one of  claims 31  to  33  wherein the base support element and the orientation guide element are provided with interlocking elements which mutually fit together to locate the orientation guide element at a preset rotational position, with respect to a longitudinal axis of the aperture, relative to the base support element. 
     
     
         35 . A casing support according to  claim 34  wherein the interlocking elements comprise male and female elements. 
     
     
         36 . A casing support according to any one of  claims 31  to  35  wherein the upper surface of the orientation guide element is parallel to, or inclined at an angle to, a lower surface of the orientation guide element. 
     
     
         37 . A casing support according to  claim 36  wherein the upper and lower surfaces of the orientation guide element are mutually inclined at an angle of from 5 to 45 degrees. 
     
     
         38 . A casing support according to any one of  claims 25  to  37  wherein the casing support ring has an inner annular surface engaging an outer cylindrical surface of an upper end of the outer casing. 
     
     
         39 . A casing support according to  claim 38  wherein the inner annular surface of the casing support ring threadably engages the outer cylindrical surface of an upper end of the outer casing. 
     
     
         40 . A casing support according to  claim 38  or  claim 39  wherein the casing support ring comprises an inner element mounted around the upper end of the coaxial borehole heat exchanger and an outer landing guide mounted on the orientation guide element, the inner element being fitted in the outer landing guide. 
     
     
         41 . A casing support according to  claim 40  wherein the inner element and the landing guide have complementary outer and inner tapered fitting surfaces to permit the inner element to be downwardly fitted into the landing guide. 
     
     
         42 . A casing support according to any one of  claims 25  to  41  further comprising a borehole surface casing surrounding an upper portion of the borehole heat exchanger within the borehole and fitted to the casing support ring. 
     
     
         43 . A casing support according to  claim 42  when appendant on  claim 40  wherein the borehole surface casing is threadably fitted to an inner annular surface of the landing guide. 
     
     
         44 . A casing support according to any one of  claims 25  to  43  wherein the borehole heat exchanger extends downwardly to a depth of greater than 100 metres. 
     
     
         45 . A chamber comprising a plurality of casing supports according to any one of  claims 25  to  44 , each casing support having a respective borehole heat exchanger extending downwardly therefrom at a respective orientation. 
     
     
         46 . A chamber according to  claim 45  wherein the orientations of at least some of the borehole heat exchangers are different, each orientation being provided by a corresponding selected orientation of the respective orientation guide element. 
     
     
         47 . A method of installing a casing support of a geothermal borehole heat exchanger having an outer casing, the method including the steps of:
 (a) providing a base support element incorporating an aperture therethrough, the base support element being supported by a ground surface, and an annular orientation guide element at an upper surface of the base support element and having a central conduit communicating with the aperture, the orientation guide element having an upper surface at a selected angle relative to a lower support surface of the base support element; and   (b) drilling a borehole through the central conduit and the aperture at an orientation preset by the orientation guide element.   
     
     
         48 . A method according to  claim 47  wherein the base support element and the orientation guide element are integral. 
     
     
         49 . A method according to  claim 48  wherein the base support element and the orientation guide element are composed of precast concrete. 
     
     
         50 . A method according to any one of  claims 47  to  49  wherein the orientation guide element is located at a preset rotational position, with respect to a longitudinal axis of the aperture, relative to the base support element. 
     
     
         51 . A method according to any one of  claims 47  to  50  wherein the upper surface of the orientation guide element is inclined at an angle to a lower surface of the base support element. 
     
     
         52 . A method according to  claim 51  wherein the angle is from 5 to 45 degrees. 
     
     
         53 . A method according to  claim 47 , the method including the steps of:
 (a) providing a base support element incorporating an aperture therethrough, the base support element being supported by a ground surface;   (b) fitting an annular orientation guide element onto the upper surface of the base support element, the orientation guide element having a central conduit communicating with the aperture, the orientation guide element having an upper surface at a selected angle relative to a lower support surface of the base support element; and   (c) drilling a borehole through the central conduit and the aperture at an orientation preset by the orientation guide element.   
     
     
         54 . A method according to  claim 53  wherein the base support element comprises a plate. 
     
     
         55 . A method according to  claim 54  wherein the base support element is composed of precast concrete. 
     
     
         56 . A method according to any one of  claims 53  to  55  wherein the base support element and the orientation guide element are provided with interlocking elements which mutually fit together to locate the orientation guide element at a preset rotational position, with respect to a longitudinal axis of the aperture, relative to the base support element. 
     
     
         57 . A method according to  claim 56  wherein the interlocking elements comprise male and female elements. 
     
     
         58 . A method according to any one of  claims 53  to  57  wherein the upper surface of the orientation guide element is parallel to, or inclined at an angle to, a lower surface of the orientation guide element. 
     
     
         59 . A method according to  claim 58  wherein the upper and lower surfaces of the orientation guide element are mutually inclined at an angle of from 5 to 45 degrees. 
     
     
         60 . A method according to any one of  claims 47  to  59  further comprising installing a casing support ring fitted around an outer casing of a geothermal borehole heat exchanger and coupling the casing support ring to the orientation guide element to support the casing in the borehole, the outer casing extending through the ring, the conduit and the aperture, the casing support ring having an inner annular surface engaging an outer cylindrical surface of an upper end of the outer casing. 
     
     
         61 . A method according to  claim 60  wherein the inner annular surface of the casing support ring threadably engages the outer cylindrical surface of an upper end of the outer casing. 
     
     
         62 . A method according to  claim 60  or  claim 61  wherein the casing support ring comprises an inner element mounted around the upper end of the coaxial borehole heat exchanger and an outer landing guide mounted on the orientation guide element, the inner element being fitted in the outer landing guide. 
     
     
         63 . A method according to  claim 62  wherein the inner element and the landing guide have complementary outer and inner tapered fitting surfaces and the inner element is downwardly fitted into the landing guide. 
     
     
         64 . A method according to any one of  claims 60  to  64  further comprising fitting a borehole surface casing to surround an upper portion of the borehole heat exchanger within the borehole and fitted to the casing support ring. 
     
     
         65 . A method according to  claim 64  when appendant on  claim 62  wherein the borehole surface casing is threadably fitted to an inner annular surface of the landing guide. 
     
     
         66 . A method according to any one of  claims 60  to  65  wherein the borehole heat exchanger extends downwardly to a depth of greater than 100 metres. 
     
     
         67 . A method according to any one of  claims 60  to  66  of installing a plurality of casing supports, each casing support having a respective borehole heat exchanger extending downwardly therefrom at a respective orientation. 
     
     
         68 . A method according to  claim 67  wherein the orientations of at least some of the borehole heat exchangers are different, each orientation being provided by a corresponding selected orientation of the respective orientation guide element. 
     
     
         69 . A method according to  claim 67  or  claim 68  wherein the upper end of the borehole heat exchanger is installed at a preset height above the base support element, and further comprising fitting a well head to the upper end of the borehole heat exchanger.