Excavation layouts, equipment, and related methods formed in the subsoil for geothermal installations

Abstract

This layout (12) comprises at least one heat exchange unit (24) having: - at least one central well (26) extending from the surface of the underlying soil (22); - at least one side well (28) extending from the surface of the underlying soil (22) and having an inclined lateral portion (48); - at least two separate drains (30) connecting the central well (26) and the inclined lateral portion (48) of the side well (28). For one or each heat exchange unit (24), the central well (26), the side well (28), and each drain (30) are installed in one and the same vertical plane, the intersections between the drain (30) and the central well (26), and between the drain and the inclined lateral portion (48) are spaced apart from each other, and the drain (30) opens with an inclination at an angle of less than 45° with respect to the inclined lateral portion (48).

Description

Technical Field

[0001] The present invention relates to an excavation layout formed in the underlying soil for geothermal facilities, as follows: - At least one central shaft extending from the surface of the underlying soil, - At least one side shaft extending from the surface of the underlying soil and having an inclined side portion, - At least two separate drains connecting the central shaft and the inclined side portion of the side shaft, and relates to an excavation layout comprising at least one heat exchange unit having the above.

Background Art

[0002] Such a layout is intended to be used, in particular, as a closed-loop heat exchanger within a non-invasive geothermal facility.

[0003] Such a layout does not require an underground location for producing high-temperature geothermal fluid, for example, from an aquifer. Such a layout has the advantage that it can be installed in various locations and depends only on the temperature gradient, rather than extracting fluid from the underlying soil.

[0004] Such a layout is configured to circulate a heat transfer fluid in a defined loop that passes through one of an inclined shaft or a vertical shaft, then through a drain excavated deep underground, and finally back into the other of the inclined shaft or the vertical shaft. When circulating, especially within the drain, the heat transfer fluid stores heat energy from the underlying soil mainly derived from the radiation of the earth's crust. The heated heat transfer fluid transported to the surface is supplied to a recovery facility for the distribution of heat energy and / or the conversion of the recovered heat energy into electrical energy. The heat transfer fluid can also transfer heat energy to the underlying soil and be cooled.

[0005] International Publication No. 2020 / 197511 describes a layout of the aforementioned type having a plurality of drains with inclined shafts and vertical shafts. The drains converge at a point (referred to as a diverter or manifold as described in the specification of European Patent Application Publication No. 3762663), which makes it possible to limit the number of holes to be drilled and balance the head loss in the drains, while at the same time having a large underground heat exchange surface. In its non-converging area, the drains are arranged with a certain spatial distance between each other in order to maximize the heat exchange through each drain by ensuring that the drains do not interfere with each other.

[0006] However, such a layout is not entirely satisfactory. Drilling at the angles and in the arrangements as described above is difficult and very costly. For example, an elbow joint is required for the connection between the inclined shaft and the drain, but the elbow joint may damage the drilling tool or even make it inoperable. Since there is a single convergence point between the drain and the vertical shaft, a very high drilling accuracy is required, which may slow down the drilling speed and / or induce the exclusion of non-converging drains.

Prior Art Documents

Patent Documents

[0007]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0008] An object of the present invention is therefore to obtain a drilling layout that enables efficient heat exchange between a heat transfer fluid and the underlying soil in which it is located, while providing an economical and simplified drilling trajectory for production and maintenance.

Means for Solving the Problems

[0009] For this purpose, the invention relates to an excavation layout of the aforementioned type, and for one or each heat exchange unit, the central shaft, the side shaft, and each drain are installed in one and the same vertical plane, and the intersections between the drain and the central shaft and between the drain and the inclined lateral part are spaced apart from each other, and the drain opens with an inclination at an angle of less than 45° with respect to the inclined lateral part.

[0010] The excavation layout according to the invention can have one or more of the following features, which are selected either alone or in any technically possible combination: - The central shaft is vertical, - The central shaft has at least one upper vertical part located above the drain, and the upper vertical part has a diameter larger than the diameter of each drain, - The side shaft and the central shaft each have at least one upper vertical part, - The side shaft has at least one upper vertical part and at least one slightly inclined part connected to the upper vertical part by a curved part, and the inclined lateral part extends downward from the slightly inclined part, - The drain is excavated in plutonic rock, in particular granite, or metamorphic rock, in particular gneiss, - The heat exchange unit has at least one settling leg that terminates at least one of the central shaft and the inclined lateral part, - The angle taken at the lateral intersection directed away from the central shaft, formed by the local axis of the central shaft directed downward at the central intersection and the local axis of the drain, is strictly less than 90°, in particular 45° to 70°, - The heat exchange unit has drains having straight parts that are spaced apart from each other by a maximum of 200 meters in the vertical direction, and the straight parts are preferably parallel to each other, and - The surface distance between the central shaft and the side shaft within the same heat exchange unit is 20 to 100 m. - The angle taken at the intersection between the downward local axis of the straight vertical portion of the side shaft and the downward local axis of the inclined lateral portion, formed by these two axes, is an acute angle, and the side shaft is concave.

[0011] The present invention also relates to a geothermal facility including an excavation layout as defined above, a system for pumping a heat transfer fluid to be heated or cooled into either the central shaft or the side shaft, a system for recovering the heated or cooled heat transfer fluid from the other of the central shaft and the side shaft, and an apparatus for distributing and / or converting energy from the heat transfer fluid.

[0012] The present invention also relates to a method for manufacturing an excavation layout in a subsoil, the following - Excavating a side shaft with an inclined lateral portion from the surface of the subsoil, - Excavating a central shaft from the surface of the subsoil, - Excavating at least two separate drains connecting the central shaft and the inclined lateral portion of the side shaft relates to a method including.

[0013] For one or each heat exchange unit, the central shaft, the side shaft, and each drain are excavated in one and the same vertical plane, the central intersection between the drain and the central shaft and the intersection between the drain and the inclined lateral portion are separated from each other, and the drain opens at an angle of less than 45° with respect to the inclined lateral portion.

[0014] The excavation method according to the present invention can have one or more of the following features selected alone or in any technically possible combination: - The excavation of the lateral well includes injecting the excavation fluid through the excavation tool and returning the excavation fluid through the lateral well in the annulus defined between the excavation tool and the wall of the lateral well; the excavation of the central well from the surface and at least the first drain is performed after the excavation of the lateral well, and the excavation fluid is kept under pressure in the lateral well at least during the formation of the lateral intersection between the first drain and the inclined lateral part. The excavation fluid under pressure in the inclined lateral part rises through the first drain towards the central well after the formation of the lateral intersection. - The excavation of at least two separate drains includes excavating a second drain above the first drain after the excavation of the first drain. The pressurized excavation fluid is kept circulating in the lateral well and through the first drain at least during the formation of the lateral intersection between the second drain and the inclined lateral part. The pressurized excavation fluid in the inclined lateral part rises through the second drain towards the central well after the formation of the lateral intersection. - The excavation tool (commonly known as the "drill string") includes a drill bit, a rotating drill string, and a rotating rod assembly between the rod assembly that can change the angular direction of the drill bit relative to the rod assembly and the drill bit.

[0015] The present invention will be better understood by reading the following description, given by way of example only, with reference to the accompanying drawings below.

Brief Description of the Drawings

[0016]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Mode for Carrying Out the Invention

[0017] A first geothermal facility 10 for producing heat according to the present invention is schematically shown in FIG. 1.

[0018] The facility 10 includes a drilling layout 12 according to the present invention, a system 14 for pumping a heat transfer fluid 16 into the drilling layout 12, a system 18 for recovering the heat transfer fluid 16 heated from the drilling layout 12, and a device 20 for distributing and / or converting energy from the heated heat transfer fluid 16.

[0019] The drilling layout 12 is cut into the underlying soil layer 22 through the underlying land layer 22. The drilling layout includes at least one heat exchange unit 24 located in a plane. The heat exchange unit 24 includes at least one central well 26, at least one side well 28, and at least two drains 30 connecting the central well 26 to the side well 28, and the wells 26, 28 and the drains 30 are in the same plane.

[0020] The heat exchange unit 24 is a set of underground pipes through which the same heat transfer fluid 16 supplied by the pumping system 14 and recovered by the recovery system 18 flows. The heat from the heat transfer fluid 16 recovered by the recovery system 18 is used by the energy distribution and / or conversion device 20, for example, to generate steam for driving a turbine.

[0021] The central shaft 26 and the side shafts 28 open onto the surface. These shafts 26, 28 are controlled at the surface of the subsoil by the shaft tops 32, 34.

[0022] The central shaft 26 has an upper vertical part 36 starting from the surface and piercing vertically into the subsoil 22, and a lower vertical or inclined part 38 located in the downward extension of the upper vertical part 36.

[0023] The inner diameter of the upper vertical part 36 is larger than the inner diameter of the lower part 38. Advantageously, the upper vertical part has a casing (in particular, a heat-insulating casing if a hot heat-transfer fluid is lifted through this shaft) fixed to the formation with cement.

[0024] The depth of the central shaft 26 is advantageously between 200 m and 5000 m in order to reach a metamorphic or plutonic rock that can withstand continuous erosion from the heat-transfer fluid for at least 50 years.

[0025] In this example, the side shaft 28 has a straight vertical part 44 opening at the surface level of the subsoil 22, a slightly inclined part 46 (for avoiding any risk of interference with the upper vertical part 36 of the central shaft 26) connected to the straight vertical part 44 by a curve, and an inclined lateral part 48 extending the slightly inclined part 46 downward. The side shaft 28 also defines a settling leg 49 terminating the inclined lateral part 48 at the bottom.

[0026] The angle defined by the downward local axis of the straight vertical part 44 and the downward local axis of the slightly inclined part 46 is advantageously between 2° and 10°.

[0027] The angle defined by the downward local axis of the straight vertical part 44 and the downward local axis of the inclined lateral part 48 is advantageously between 30° and 50°. This provides a heat-exchange unit with a large exchange surface while limiting the lateral extent of the partial inclination and the excavation layout 12 for ease of construction and maintenance.

[0028] The drain 30 is excavated from the central sump 26 and connects the central sump to the lateral sump 28. Each drain 30 has a central intersection 50 with the lower part 38 of the central sump 26, an angled part 52, a straight part 54, and a lateral intersection 56 with the inclined lateral part 48 of the lateral sump 28.

[0029] The central intersection 50 with the lower part 38 of the central sump 26 is positioned within the vertical plane of the heat exchange unit 24 and connects the lower part 38 of the central sump 26 to the angled part 52.

[0030] The angled part 52 is extended by the straight part 54. The straight part defines a preferred position for heat exchange between the heat transfer fluid 16 and the formation. The straight part 54 opens into the lateral sump 28 at the lateral intersection 56.

[0031] The angled part 52 of the drain 30 has a radius of curvature such that the angle taken at the lateral intersection 56, which is directed away from the central sump 26 and is formed by the local axis of the central sump 26 directed downward at the central intersection 50 and the local axis of the drain 30, is strictly less than 90°, and in particular is between 45° and 70°.

[0032] The straight part 54 is defined externally by non-insulated rock that allows heat flow to pass between the underlying soil 22 and the heat transfer fluid 16 present within the straight part 54 of the drain 30. The formation through which the drain passes is, for example, a metamorphic rock such as gneiss or an intrusive rock such as granite. The straight part 54 has no casing in order to maximize heat exchange between the formation and the heat transfer fluid 16 and to reduce the time, cost, and risk involved in the construction of the heat exchange unit 24.

[0033] The straight part 54 of the drain 30 is excavated vertically parallel in the vertical plane of the heat exchange unit.

[0034] The distance separating the straight part 54 in a direction perpendicular to the straight part 54 is, for example, between 50 and 500 m, and in particular between 80 and 200 m.

[0035] The straight portion 54 ends at a lateral intersection 56 with the inclined side portion 48 located above the settling leg 49.

[0036] The intersection between the drain 30 and the central shaft 26 and the intersection with the inclined side portion 48 are separated from each other. The drain 30 opening into the side shaft 28 is inclined at an angle of less than 45°, for example, an angle of 15° to 35°, with respect to the inclined side portion 48 at the lateral intersection 56.

[0037] The settling leg 49 is designed to receive any excavation debris or tool debris that is taken into the side shaft 28 or the drain 30 without clogging the portions 30, 36, 38, 44, 46, 48, 50, 52, 54, and 56.

[0038] The surface assembly 58 of the facility 10 houses the pumping system 14, the recovery system 18, and the energy distribution and / or conversion device 20. The surface assembly 58 is positioned on the surface of the subsoil 22 and houses the tops 32 and 34 of the shafts.

[0039] The surface distance between the top 32 of the central shaft 26 and the top 34 of the side shaft 28 within the same heat exchange unit is preferably 20 to 100 m.

[0040] The pumping system 14 for the heat transfer fluid 16 is connected to the shaft top 32 of the injection well, which is either the central shaft 26 or the side shaft 28, according to the desired flow direction within the excavation layout 12. The pumping system 14 pumps the heat transfer fluid 16 into the injection well at a pressure adapted to the proper flow of the fluid within the excavation layout 12.

[0041] The heat transfer fluid 16 is based on, for example, water, or other liquids such as alcohol, oil, refrigerant, or even CO2. The heat transfer fluid or gas circulates within a closed loop, which may be pressurized.

[0042] The recovery system 18 for the heat transfer fluid 16 is connected to the top of the production well formed by the other of the central shaft 26 or the side shaft 28. The recovery system 18 recovers the heated heat transfer fluid 16 and returns it to the energy distribution and / or conversion device 20. In the case of conversion to electricity, the energy conversion device 20 includes, for example, a turbine for expanding the steam generated from the heated heat transfer fluid 16, a generator, and a condenser for cooling the heat transfer fluid 16.

[0043] In the case of energy distribution, the heat transfer fluid is used directly or in heat exchange with a fluid, for example, to heat houses, factories, industrial processes, greenhouses, hotels, swimming pools, entertainment facilities, etc.

[0044] In another embodiment, the heat transfer fluid can also be used to cool them in the same way as water in thermal power plants (coal, oil, gas, nuclear power), and the consumption is reduced by replacing the cooling tower.

[0045] Next, a method for constructing the excavation layout 12 will be described with reference to FIG. 2. This method uses surface equipment including a directional drilling tool 64 to which a swivel system 65 is attached, means for rotating the directional drilling tool 64, preferably both at the bottom and at the surface, and means (not shown) for injecting drilling fluid into the drilling tool 64.

[0046] The drilling tool 64 (or "drill string") comprises a hollow rod assembly 66 disposed within the well to be drilled, a drill bit 67, and a swivel system 65 that supports the drill bit 67.

[0047] The swivel system 65 can continuously measure the inclination, azimuth, and mud pressure around the drilling tool 64. The system can also communicate with surface equipment and be guided by detecting an active beacon 68 installed in the inclined lateral portion 48 of the side shaft 28.

[0048] The drill bit 67 is provided with a rock breaking tool and is preferably rotated relative to the rod assembly 66 about the axis of the rod assembly 66 by a downhole motor.

[0049] The rock breaking tool uses, for example, polycrystalline diamond compact (PDC) or tricone bits, percussion systems, and / or pulse high pressure (PHP), plasma or millimeter electromagnetic wave excavation to drill metamorphic and plutonic rocks.

[0050] The rod assembly 66 is removably screwed onto the rotary swivel system 65. It consists of a number of hollow rods that are screwed vertically together as the shaft sinking progresses. The rod assembly 66 defines an internal circulation duct for the drilling fluid.

[0051] The rotary swivel system 65 defines a controlled joint between the body and the swivel housing and controls the drilling direction in real time. An example of the rotary swivel system 65 is described in International Publication No. WO 2007 / 110502.

[0052] The drilling fluid is preferably based on water and bentonite and is added as necessary to reduce the risk of investment and contamination.

[0053] In the first stage marked A in FIG. 2, the excavation of the layout 12 starts, for example, from the construction of an adit 28 from the surface.

[0054] A straight vertical portion 44, a slightly inclined portion 46, and an inclined lateral portion 48 are excavated in sequence, and the excavation tool 64 gradually inclines thanks to the rotary swivel system 65.

[0055] The drilling fluid is introduced at the surface and circulates through the inner tube of the rod assembly 66 to the drill bit 67. When the fluid comes out of the drill bit 67, it lubricates and cools the drill bit.

[0056] The drilling fluid then rises through the annular space defined between the drilling tool 64 or the rod assembly 66 and the formation defined by the wall of the lateral well 28 to wash the well and maintain its walls.

[0057] The excavation of the lateral well 28 is completed by providing a settling leg 49 at the bottom of the lateral well 28 so that waste that may occur during subsequent operations can be managed. The drilling tool 64 is withdrawn from the lateral well 28 via its well top 34.

[0058] Next, in a second stage represented by the letter B in FIG. 2, the central well 26 is drilled starting from the upper vertical portion 36, and the drilling fluid returns into the annular space defined between the drilling tool 64 and the formation defined by the wall of the central well 26.

[0059] Prior to a third drilling stage C, an active beacon 68 is placed at the lateral intersection 56A within the well 28 to guide the tool 65 to said point 56A with the possible aid of software guidance at the surface. A pressure sensor is associated with the active beacon 68 and continuously measures the pressure at the lateral intersection 56A. The active beacon 68 and the probe are lowered using an electric cable or, preferably, coiled tubing to which the electric cable is attached to supply power to the active beacon 68 and the probe and enable real-time communication with the surface.

[0060] In the third stage represented by the letter C in FIG. 2, the lower portion 38, the central intersection 50, the angled portion 52, and then the deepest drain 30A are then drilled down to the lateral intersection 56A with the lateral well 28, and upon receiving the installation of the production casing at the upper vertical portion 36 of the central well 26, the drilling diameter is decreasing. The drilling fluid rich in drilling cuttings is also returned via the annular space around the drilling tool 64 or the rod assembly 66.

[0061] During the entire stage C of excavating the drain 30A, the excavation fluid is advantageously injected into the cross - drift 28 through coiled tubing and maintained at a pressure at least equal to the pressure of the excavation fluid for the drain 30A. When the lateral intersection 56A between the cross - drift 28 and the drain 30A is formed, an overpressure is maintained with respect to the freshly excavated drain 30A.

[0062] In the fourth stage, represented by the letter D in FIG. 2, the drain 30B is excavated. The central intersection 50 between the lower part 38 and the first drain 30A has already been constructed, and the excavation tool 64 branches off using a rotary swivel system 65 to excavate the drain 30B.

[0063] At the same time, the active beacon 68 and the pressure sensor are pulled up to the next intersection 56B.

[0064] The excavation fluid thus returns to the surface through the annular space around the excavation tool 64, within the portions 52, 54 of the drain 30B, and then into the central shaft 26, even when the lateral intersection 56B is being prepared.

[0065] The overpressure maintained during the excavation at the lateral intersection 56B ensures that the excavation fluid returns to the annulus around the excavation tool 64 and prevents the cuttings from flowing into the cross - drift 28 and / or the drain 30A and clogging them.

[0066] The pressure of the excavation fluid in the cross - drift 28 is maintained by enabling the excavation fluid to be injected into the cross - drift 28 and circulate by rising through the previously excavated drain 30A(s) and through the vertical shaft 26.

[0067] The return of the drilling fluid into the annulus space of the drilling tool 64 or the rod assembly 66 within the central shaft 26 is a combination of the flow of the drilling fluid from the lateral shafts and the flow of the drilling fluid from the drilling of the new drain 30B. Since the diameter of the upper vertical portion 36 is larger than the diameter of the lower vertical portion 38 and in particular than the diameter of each drain, the cumulative flow of the drilling fluid from the different drains 30A, 30B is thus made possible.

[0068] Subsequently, each subsequent drain 30 is drilled in a similar manner to the stage represented by the letter D in FIG. 2. To do this, the drilling tool 64 retracts into the lower portion 38 of the central shaft 26 and starts drilling above the central intersection 50 between the previous drain 30 and the central shaft 26. The drains are drilled sequentially, starting from the deepest point and working upwards.

[0069] At the same time, the active beacon 68 and the pressure sensor are pulled up to the next intersection 56.

[0070] Once all the drains 30A, 30B have been drilled and the drilling tool 64 has been removed from the drilling layout 12, the drilling layout 12 is cleaned by injecting fluid through one of the shaft tops 32, 34 to ensure that there is no residue blocking one of the shafts 26, 28 or one of the drains 30.

[0071] The cleaning fluid will preferably be the drilling fluid that is gradually filtered at the surface so as to minimize the impact on the environment.

[0072] Next, the use for the heat production of the geothermal plant 10 will be briefly described.

[0073] The heat transfer fluid 16 is injected into the drilling layout 12 via one of the shaft tops 32, 34 by means of the pumping system 14. The heat transfer fluid 16 then flows through one of the central shaft 26 or the lateral shaft 28.

[0074] The heat transfer fluid 16 is then distributed into the drain 30 where, thanks to the non-insulated wall of the straight part 54 of the drain 30, the fluid 16 receives the heat flow from the hot rocks present in the subsoil 22.

[0075] A nozzle or flow restrictor is preferably installed in the drain 30 to adjust the flow distribution within said drain.

[0076] The heat transfer fluid 16 then exits via the top 32 or 34 of its shaft, via the other of the central shaft 26 or the side shaft 28, and is returned to the recovery system 18. Advantageously, after filtration, the heat transfer fluid then moves to the energy distribution and / or conversion device 20 where it transfers its heat energy so that it can be distributed to a heating system (residential, factory, industrial process, greenhouse, hotel, swimming pool, entertainment facility, etc.) and / or converted into mechanical energy and possibly electrical energy by a generator.

[0077] The heat transfer fluid 16 is then, if necessary, sent back to the condenser for regeneration or cooling. The fluid is then reinjected into the excavation layout 12 by the pumping system 14 and the circulation is started again.

[0078] The excavation layout 12 according to the invention is easy to excavate thanks to the simplified trajectory and at the same time enables an efficient heat exchange between the heat transfer fluid 16 and the subsoil 22. The angular deviation, which is the cause of risks and costs, is limited by the excavation in the same vertical plane. Furthermore, the excavation of such a layout 12 is facilitated by an excavation tool 64 having a rotary swivel system 65 as shown in WO 2007 / 110502.

[0079] In another embodiment, a plurality of heat exchange units 24 are drilled side by side. As shown in FIG. 3, two heat exchange units 24 are represented in the same plane and share the same surface assembly 58. Alternatively, "N" heat exchange units 24, each located in a plane, are not in the same plane as each other. In that case, they are distributed linearly in parallel exchange planes or around the vertical axis every 360 / N°.

[0080] These two heat exchange units 24 are also shown in another configuration having a common central shaft 26 for both units 24, as shown in FIG. 4. Alternatively, "N" heat exchange units 24 are evenly distributed around the axis of a central shaft 26 common to the "N" units 24.

[0081] A variant of the drilling method is shown in FIG. 5. In such a method, a drilling layout designed to utilize the geothermal fluid contained in the aquifer 70 is first drilled. This layout has several lateral drilling shafts 71, 72 that are standardly designed to recover and / or utilize the geothermal fluid.

[0082] If the production of geothermal fluid is not possible or the utilization of the aquifer 70 is not profitable enough, at least one central shaft 26 is drilled in the plane of each lateral shaft 71, 72, and then the drain 30 is drilled through the aquifer 70. The geothermal fluid used is then replaced by the heat transfer fluid 16 after installing an appropriate surface assembly 58.

[0083] This drilling method makes it possible to amortize the cost of drilling the lateral shafts 71, 72 when the utilization of the aquifer 70 is no longer desired or becomes infeasible.

[0084] In this application, "geothermal energy" refers to all technologies used to utilize the internal heat phenomena of the earth through heat exchange with the underlying soil. The geothermal facility 10 can thus be used as described above to heat the heat transfer fluid 16 by the natural transfer of heat energy from the high-temperature underlying soil 22 to the heat transfer fluid 16 that is cooler than the underlying soil. Alternatively, the geothermal facility 10 can be used to cool the heat transfer fluid 16 that is warmer than the underlying soil 22 by the natural transfer of heat from the heat transfer fluid 16 to the cooler underlying soil 22. Generally, this does not require any changes to the excavation layout 12 and only requires adapting the surface energy distribution and / or conversion device 20.

[0085] In one embodiment of the geothermal facility 10, as shown above, the surface distance between the central well 26 and the side well 28 within the same heat exchange unit is 20 - 100 m. The central well and the side well are thus in close proximity. Therefore, only one excavation location is required for the entire geothermal facility 10.

[0086] In the example shown in the figure, the central well 26 and one or each side well 28 are asymmetric, that is, there is no vertical symmetry plane other than where the central well 26, the side well 28, and the drain 30 are arranged between the central well 26 and one or each side well.

[0087] Excavation of the inclined lateral portion 48 of the side well 28 and the straight portion 54 of the drain 30 (referred to as "slant") of the excavation layout 12 can be carried out by an excavation device including a rotary excavation assembly (referred to as "rotary bottom hole assembly" or the acronym "rotary BHA"). This limits the excavation cost.

Description of Reference Numerals

[0088] 10 Geothermal facility 12 Excavation layout 22 Underlying soil 24 Heat exchange unit 26 Central well 28 Side well 30 Drain 48 Inclined side part

Claims

1. In an excavation layout (12) provided in the underlying soil (22) for a geothermal installation (10), - at least one central shaft (26) extending from the surface of the underlying soil (22), - at least one side shaft (28) extending from the surface of the underlying soil (22) and having an inclined lateral portion (48), - at least two separate drains (30A, 30B) connecting the central shaft (26) and the inclined lateral portion (48) of the side shaft (28), An excavation layout comprising at least one heat exchange unit (24) having, For one or each heat exchange unit (24), the central shaft (26), the side shaft (28), and each drain (30) are installed in one and the same vertical plane, the intersection between the drain (30) and the central shaft (26), and the intersection between the drain and the inclined lateral portion (48) are separated from each other, and the drain (30) opens with an inclination at an angle of less than 45° with respect to the inclined lateral portion (48). An excavation layout characterized by this.

2. The excavation layout (12) according to claim 1, wherein the central shaft (26) is vertical.

3. The excavation layout (12) according to claim 1 or 2, wherein the central shaft (26) has at least one upper vertical portion (36) located above the drain (30), and the upper vertical portion (36) has a diameter larger than the diameter of each drain (30).

4. The excavation layout (12) according to any one of claims 1 to 3, wherein the drain (30) is excavated in plutonic rock, particularly granite, or metamorphic rock, particularly gneiss.

5. The excavation layout (12) according to any one of claims 1 to 4, wherein the heat exchange unit (24) has at least one settling leg (49) terminating at least one of the central shaft (26) and the inclined lateral portion (28).

6. The angle taken at the lateral intersection (56) directed away from the central shaft (26), formed by the local axis of the central shaft (26) directed downward at the central intersection (50) and the local axis of the drain (30), is strictly less than 90°, particularly 45° to 70°. The excavation layout (12) according to any one of claims 1 to 5.

7. The excavation layout (12) according to any one of claims 1 to 6, wherein the heat exchange unit (24) has a drain (30) having straight portions (54) each spaced apart by a maximum of 200 meters in the vertical direction, and the straight portions (54) are preferably parallel to each other.

8. The excavation layout (12) according to any one of claims 1 to 7, wherein the surface distance between the central shaft (26) and the side shaft (28) within the same heat exchange unit is 20 to 100 m.

9. A geothermal facility (10) comprising the excavation layout (12) according to any one of claims 1 to 8, a system (14) for pumping a heat transfer fluid (16) to be heated into either the central shaft (26) or the side shaft (28), a system (18) for recovering the heated heat transfer fluid (16) from the other of the central shaft (26) and the side shaft (28), and a device (18) for distributing and / or converting energy from the heated heat transfer fluid (16).

10. In a method for manufacturing an excavation layout (12) in a subsoil (22), the following - a step of excavating a side shaft (28) having an inclined lateral portion (48) from the surface of the subsoil (22), - a step of excavating a central shaft (26) from the surface of the subsoil (22), - a step of excavating at least two separate drains (30A, 30B) connecting the central shaft (26) and the inclined lateral portion (48) of the side shaft (28), characterized in that for one or each heat exchange unit, the central shaft (26), the side shaft (28), and each drain (30) are excavated in one and the same vertical plane, the central intersection (50) between the drain (30) and the central shaft (26) and the intersection between the drain and the inclined lateral portion (48) are spaced apart from each other, and the drain (30) opens at an angle of less than 45° with respect to the inclined lateral portion (48).

11. The excavation of the lateral shaft (28) includes injecting the excavation fluid through the excavation tool (64) and returning the excavation fluid through the lateral shaft (28) in the annulus defined between the excavation tool (64) and the wall of the lateral shaft (28). The excavation of the central shaft (26) from the ground surface (22) and at least the first drain (30A) is carried out after the excavation of the lateral shaft (28). The excavation fluid is kept pressurized in the lateral shaft (28) at least during the formation of the lateral intersection (56) between the first drain (30A) and the inclined lateral portion (48). The excavation fluid under pressure in the inclined lateral portion (48) rises through the first drain (30A) towards the central shaft (26) after the formation of the lateral intersection (56). The method according to claim 10.

12. The excavation of at least two separate drains (30A, 30B) includes excavating a second drain (30B) above the first drain (30A) after the excavation of the first drain (30A). The pressurized excavation fluid is kept circulating in the lateral shaft (28) and through the first drain (30A) at least during the formation of the lateral intersection (56) between the second drain (30B) and the inclined lateral portion (48). The pressurized excavation fluid in the inclined lateral portion (48) rises through the second drain (30B) towards the central shaft (26) after the formation of the lateral intersection (56). The method according to claim 11.

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