Underground storage structures for storing fluids

Abstract

An underground storage system (1) for storing a fluid, comprising a hole (2) having a bottom (3), a support element (4) including at least one opening (7) capable of receiving a connecting element (18), at least one reservoir (10) having a longitudinal axis (1), a bottom end (14) and a top end (12), a first closure means (16) capable of closing the reservoir (10) at its bottom end (14), and a second closure means (17) capable of closing the reservoir (10) at its top end (12), said top end (12) being connectable to the support element (4) via the connecting element (18), said reservoir (10) being suspended within the hole (2) such that an axial clearance (G) remains between the first closure means (16) and the bottom (3) capable of accommodating axial thermal expansion of said reservoir (10).

Description

[Technical field]

[0001] The invention relates in particular to the field of underground storage for storing fluids. More particularly, the invention relates to the field of underground storage systems for storing gases, for example for storing hydrogen, or for storing oxygen. Even more particularly, the invention relates to the field of storing fluids at high pressure. "High pressure" is understood to be a pressure that may range from 100 bar to 1200 bar, more particularly from 200 bar to 500 bar.

[0002] The present invention also relates to an underground storage method for storing a fluid. [Background technology]

[0003] One of the new technologies to reduce the carbon footprint of industry is to use hydrogen produced by renewable processes such as wind or solar power processes. The electricity produced by these renewable processes can be used by power crackers to produce hydrogen and oxygen, in particular based on the power splitting of water.

[0004] This large amount of hydrogen produced by electrolysis needs to be compressed and stored so that it can then be used on demand to keep vehicles such as trucks or cars powered, or to power the grid during peak consumption times. To generate this electricity, the hydrogen can then be fed to either turbines or hydrogen fuel cells. As for oxygen, it may be advantageous to store it so that it can be used in areas such as agriculture or for medical purposes.

[0005] Certain gases, such as hydrogen, are known to be difficult gases to contain. For example, their low density requires them to be stored at high pressure, and their small size of the molecules and their low viscosity mean that they are prone to leaking. As a result, they must be stored in fully capable tight devices that can store large amounts of gas while still meeting stringent safety requirements, especially minimizing the risk of leakage. Underground storage is also advantageous for consumers and manufacturers, as it allows for a very effective reduction in the space used above ground for these storage facilities.

[0006] Such underground fluid storage systems are typically installed at depths ranging from 10 meters to 50 meters. These storage systems may be installed in earth of various geological nature, for example in solid rock such as granite or basalt, or in any other type of underground geological formation.

[0007] In this regard, the prior art patent US 10837601 includes a unit fixed to a single underground bore, the unit including a plurality of separate containers attached via at least one retainer, each of the plurality of separate containers including at least one inlet, outlet and central hole, the central hole being located away from the radial center of the upper surface of the cap, the unit being fixed to the single underground bore by a cement that extends continuously between the plurality of containers, surrounding the unit and contacting the side wall of the underground bore. Furthermore, the unit is attached to a fixing element near the bottom of the underground bore. A drawback of such an apparatus is that in order to hold the containers in place in the underground bore, said containers are fixed in cement and attached to an anchoring element at the bottom, which complicates maintenance operations, especially when one container needs to be extracted from the unit to make changes, since the cement and the anchoring element prevent such extraction. However, this type of operation may be necessary for control or maintenance operations, especially in case of leakage. Thus, the maintenance and safety of such an apparatus is not the best. Furthermore, by retaining the container in cement in this manner, the walls of the container are subjected to significant compressive loads, increasing the risk of leakage. Summary of the Invention [Problem to be solved by the invention]

[0008] In order to overcome the above mentioned drawbacks, a first object of the present invention is to make maintenance operations in underground storage systems for fluids such as gas easier. Furthermore, a second object of the present invention is to make it possible to store large volumes of fluids at high pressure while meeting stringent safety requirements. Finally, a third object of the present invention is to make it possible to store several different fluids underground in one and the same storage system, at different pressures in one and the same device. [Means for solving the problem]

[0009] As a result, the present invention provides an underground storage system for storing a fluid, said storage system comprising: a hole that can be formed in the ground, the hole having a bottom; and a support element having at least one opening capable of receiving a joining element; at least one reservoir, said reservoir having a longitudinal axis (l), a lower end and an upper end; a first closure means capable of closing the reservoir at its lower end and a second closure means capable of closing the reservoir at its upper end, said upper end being connectable to a support element via a connecting element such that the reservoir is suspended inside the bore and such that an axial gap remains between the first closure means of the reservoir and the bottom of the bore capable of accommodating an axial thermal expansion of said reservoir.

[0010] Thanks to these features, the integrity of the reservoir is not compromised by the mechanical stresses associated with the axial thermal expansion of the reservoir during fluid injection and withdrawal operations. In particular, the axial clearance makes it possible to prevent the axial thermal expansion during such operations from compressing the reservoir against the bottom of the bore. Such repeated stresses, particularly at the closure means, would weaken the fluid-tightness of the reservoir.

[0011] Moreover, in contrast to the systems of the prior art, such a system means that no cement is required to fix the reservoir. The reservoir is therefore only attached to the support element. The reservoir is therefore suspended in any fluid originating from the surrounding area in which the system is placed. For example, the reservoir is suspended in air or water originating from a nearby rock formation. It is therefore possible and easy to remove the reservoir from the system.

[0012] According to one embodiment, the reservoir is suspended substantially vertically.

[0013] According to one embodiment, the reservoir is made of at least one metal tube, said metal tube having at least one end provided with at least one thread.

[0014] According to one embodiment, the metal tube has two ends, each of said two ends comprising at least one thread.

[0015] According to one embodiment, the reservoir is composed of at least two metal tubes screwed together to form a tube column. The two metal tubes can be joined by an integral connection or via a connecting piece such as a sleeve.

[0016] According to one embodiment, the axial clearance satisfies the following inequality: G≧(L 2 *β*α)+[20*α*80*(1-e -0.11*L )] where G is the axial gap length in meters, L is the reservoir length in meters, β is the geothermal gradient in degrees Celsius per meter, and α is the gradient in degrees Celsius per meter. -1 represents the thermal expansion coefficient of metals.

[0017] The geothermal gradient β varies depending on the geological formation in which the storage system is located. Therefore, β is 0.02° / m≦β≦2° / m. α is the Celsius -1 represents the thermal expansion coefficient of metals. The thermal expansion coefficient α varies depending on the type of metal from which the tube used to form the reservoir is made. Thus, α is 8×10 -6 ℃ -1 ≦α≦18×10 -6 ℃ -1 It is.

[0018] The use of threaded tubes to manufacture the reservoirs makes them easier to install and remove, which is particularly advantageous when the tubes need to be replaced, thus making the reservoirs easier to service and improving the safety of the system.

[0019] According to one embodiment, the reservoir consists of a single tube.

[0020] According to one embodiment, the tubes used to manufacture the reservoir are metal tubes, preferably threaded metal tubes, for example they may be metal tubes made of titanium or steel tubes of the type used in the oil and gas industry, in particular tubes used to produce oil and / or gas producing wells.

[0021] According to one embodiment, the first closure means and / or the second closure means can close the reservoir by screw fastening. In this case, the thread of said closure means can be an external or internal thread. In addition to the thread, the first closure means and / or the second closure means can comprise a metal sheet. The presence of a metal sheet contributes to improving the fluid-tightness of the closure, which is particularly advantageous for storing gases, and in particular hydrogen, which is a gas that is prone to leaking.

[0022] According to one embodiment the first closure means and / or the second closure means are welds.

[0023] A closure that allows the reservoir to be closed by screwing is preferred over welding because a screwed closure does not significantly change the wall thickness of the reservoir at the closure. Thus, the mechanical properties of the reservoir at the closure are not changed with a screwed closure. Furthermore, when storing hydrogen, the potential problem of dihydrogen corrosion that can occur at the welds can be avoided.

[0024] According to one embodiment, the support element includes a top surface 54 and a bottom surface 56 .

[0025] According to one embodiment, the support element is laid on the ground or attached to a concrete or cement slab, said slab being poured onto the ground surface. The support element can be attached to the concrete or cement slab by any means known to a person skilled in the art.

[0026] According to one embodiment, the support element is a cylindrical plate or a plate with an angular geometric shape.

[0027] According to one embodiment, the support element has a length of at least 0.2 m 2 ~10m 2 , preferably 0.7m 2 ~4m 2 The surface area is in the range of

[0028] According to one embodiment, the support element may be a metal plate.

[0029] According to one embodiment, the at least one opening is a through hole made in the thickness of the support element.

[0030] According to one embodiment, at least one opening in the support element is a circular opening.

[0031] According to one embodiment, the interface element is attached to the upper end of the reservoir.

[0032] According to one embodiment, the interface element is welded or screwed to the upper end of the reservoir.

[0033] According to one embodiment, the interface element is tubular and has a flange which can be placed on a surface of the support element such that when the interface element is attached to the upper end of the reservoir, the reservoir is suspended from the support element via the interface element.

[0034] According to one embodiment, the system comprises a plurality of reservoirs, each reservoir having a longitudinal axis l, a lower end and an upper end, said upper end of each reservoir being capable of being joined to a support element via a joining element such that each reservoir is suspended inside the hole.

[0035] Such a system with multiple reservoirs makes it possible to have reservoirs of different lengths in one and the same storage system. This is particularly advantageous in order not to take unnecessarily high loads from the support elements. Furthermore, the length of the reservoirs can be adapted to make it easier to increase or decrease the pressure required depending on the fluid storage conditions. Thus, different fluids can be stored in the same system.

[0036] According to one embodiment, each reservoir is connected to a fluid supply line and to its own fluid withdrawal circuit, such that when the storage system comprises multiple reservoirs, said reservoirs may be independent of each other.

[0037] These features allow for larger volumes of fluid to be stored, particularly large volumes of gas at very high pressures in multiple reservoirs for the same bore depth. In addition, such systems allow for the storage of a variety of fluids, each of which can be stored at conditions, particularly temperature and pressure conditions, specific to the fluid and its intended use.

[0038] According to one embodiment, each reservoir can be fitted with a sensor such as a pressure gauge, a temperature gauge, a leak detector or a humidity detector. In this way, it is possible to control the pressure in each reservoir and the presence of leaks. This is advantageous both for the safety of the system and in the case that the reservoirs do not all store the same fluid. These sensors can also be placed directly in the bore.

[0039] According to one embodiment, the system comprises a single reservoir.

[0040] According to one embodiment, the length L of the reservoir ranges from 1 meter to 3000 meters, preferably from 10 meters to 2500 meters, more preferably even from 20 meters to 500 meters.

[0041] According to one embodiment, the storage system comprises 1 to 26 reservoirs, preferably 1 to 14 reservoirs, more preferably still 1 to 6 reservoirs.

[0042] According to one embodiment the hole has a depth in the range of 10 meters to 2500 meters, preferably 20 meters to 500 meters, said depth being measured between the ground and the bottom of the hole.

[0043] According to one embodiment, the hole has at least one casing.

[0044] According to one embodiment, the casing is made of concrete, cement, or steel plates.

[0045] According to one embodiment, the casing is a casing tube. The casing tube may be bonded.

[0046] According to one embodiment, the ground is made of solid rock, such as granite or basalt. The advantage of implementing the storage system in the ground made of solid rock is that it is possible to dispense with a casing, thereby simplifying the installation of the system. However, if the system is implemented in loose ground, a casing is necessary.

[0047] According to one embodiment, the holes may be formed by boring or drilling.

[0048] According to one embodiment, the holes have an average diameter in the range of 0.5 meters to 4.5 meters, preferably 1 meter to 3 meters.

[0049] The present invention also relates to an underground storage method for storing a fluid, said method comprising the steps of: creating a hole in the ground, said hole having a bottom; providing a support element with at least one opening capable of receiving a joining element; providing at least one reservoir, said reservoir having a longitudinal axis, a lower end, and an upper end; providing first closure means capable of closing said reservoir at its lower end and second closure means capable of closing the reservoir at its upper end; connecting said upper end to a support element via a connecting element such that the reservoir is suspended inside the bore and an axial gap remains between the first closing means of the reservoir and the bottom of the bore capable of accommodating axial thermal expansion of the reservoir.

[0050] (definition) The "lower end" of the reservoir is understood to be the end of the reservoir that is adjacent to the bottom of the hole. This "lower end" is defined in contrast to the end of the reservoir that is adjacent to the support element and therefore at the surface of the ground, which is called the "upper end" of the reservoir.

[0051] "Axial clearance" is understood to be the length extending along the longitudinal axis l of the reservoir and measured between the first closure means of the reservoir and the bottom of the hole. It should be noted that the position of the reservoir does not have to be perfectly vertical. In this case, the longitudinal axis l of the reservoir is at an angle to the vertical of the coordinate system (x; y). The maximum value of this angle is 15°. The axial clearance G is then measured by orthogonal projection onto the longitudinal axis through the point on the first closure means closest to the bottom of the hole. In other words, the axial clearance always corresponds to the shortest distance measured between the bottom of the hole and the first closure means.

[0052] A "threaded metal tube" is understood to be a tube having at least one end with at least one threaded portion, capable of joining to a threaded metal tube having at least one end with at least one complementary threaded portion. The thread may be male or female.

[0053] "Bottom of the hole" is understood to be the surface at the bottom of the hole. Thus, if the hole has a casing and said casing is cemented, the expression "bottom of the hole" means the surface of the cement layer at the bottom of the hole. If the casing is not cemented, the term "bottom of the hole" simply denotes the surface of the ground at the bottom of the hole.

[0054] BRIEF DESCRIPTION OF THE DRAWINGS The invention will be better understood and further objects, details, features and advantages thereof will become more apparent in the course of the following description of some particular embodiments of the invention, given by way of non-limiting example only with reference to the accompanying drawings, in which:

[0055] However, it should be understood that the application is not limited to the arrangement, structure, features, embodiments, and exact appearance shown. The drawings are not to scale and are not intended to limit the scope of the claims to the embodiments shown in these drawings.

[0056] Thus, where features recited in a claim follow by reference, it should be understood that said reference is provided solely to aid in the understanding of the claim and in no way limits the scope of said claim. [Brief description of the drawings]

[0057] [Figure 1] FIG. 1 is a cross-sectional view of a storage system according to an embodiment of the present invention. [Diagram 2] FIG. 2 is a three-dimensional view of the support element alone of the storage system shown in FIG. [Diagram 3] FIG. 3 is a three-dimensional view of an alternative support element by itself that may be used in one embodiment of the present invention. [Figure 4] FIG. 4 is a three-dimensional view of a contact element that can be used in the storage system shown in FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0058] 1 shows a cross-sectional view of a storage system 1 according to an embodiment of the present invention in a coordinate system (x;y), the axis x of which (x;y) is the horizontal axis and the axis y of which (x;y) is the vertical axis.

[0059] The storage system 1 comprises a hole 2 formed in the ground 40, a support element 4 disposed on a surface S of the ground 40, and six reservoirs 10 suspended in the hole 2 from the support element 4 (only four reservoirs are shown in FIG. 1).

[0060] The hole 2 has a bottom 3 and is provided with a casing 30. The hole 2 may be obtained by boring or drilling and has a depth of 500 metres measured between the earth's surface S and the bottom 3. The hole 2 is substantially cylindrical in shape and has an average diameter of 4 metres.

[0061] The casing is made of cement and extends vertically from the ground surface S to the bottom 3 of the hole 2.

[0062] As shown in figures 1 and 2, the support element 4 is a cylindrical plate having a central body 50 and a flange 52, said flange 52 having a bottom surface 56 resting on the ground surface S. The central body 50 has a first thickness E which may range from 10 mm to 500 mm. The flange 52 has a second thickness e which may range from 5 mm to 200 mm. In the embodiment shown in figures 1 and 2, the support element 4 is a metal plate with a first thickness E equal to 250 mm and a second thickness e equal to 100 mm.

[0063] The support element 4 also has an upper surface 54, said upper surface 54 being opposite a bottom surface 56 of the flange 52, said upper surface 54 being 8.6 mm 2 has a surface area equal to

[0064] As shown in Fig. 2, the support element 4 also comprises six openings 7. The openings 7 are through holes formed in the first thickness E of the body 50 of the support element 4. According to Fig. 3, which shows a support element 4 that can be used in one embodiment according to the invention, the support element 4 includes fourteen openings 7 formed in the first thickness E of the body 50.

[0065] Each reservoir 10 is suspended from the support element 4 via a connecting element 18. Thus, for each reservoir 10 of the storage device 1, an axial gap G remains between the first closing means 16, which closes the reservoir 10 at its lower end 14, and the bottom 3 of the bore 2. The purpose of this axial clearance G is to accommodate the axial thermal expansion of the reservoir 10, which occurs in particular during the filling and discharging operations. Thus, for each reservoir 10, the size of the axial clearance G, and in particular its length, directly depends on the conditions of the surrounding area of ​​the storage system 1, in particular the conditions regarding temperature, pressure and the ability of the reservoir 10 to expand when exposed to temperature and pressure fluctuations, in particular during the filling and discharging operations. The axial clearance G of any reservoir 10 of the storage system 1 therefore satisfies the following inequality: G≧(L 2 *β*α)+[20*α*80*(1-e -0.11*L )] where G is the length of the axial clearance in meters; L is the length of the reservoir 10 in meters; β is the geothermal gradient in degrees Celsius per meter. The geothermal gradient β varies depending on the geological formation in which the storage system 1 is located. Therefore, β is 0.02° / m≦β≦2° / m; and α is Celsius. -1 represents the thermal expansion coefficient of metals, expressed as α. The thermal expansion coefficient α varies depending on the type of metal from which the tube used to form the reservoir 10 is made. Thus, α is approximately 8×10 -6 ℃ -1 ≦α≦18×10 -6 ℃ -1 It is.

[0066] The reservoirs 10 are tubular with a circular cross-section and each have a longitudinal axis (l), a lower end 14, and an upper end 12.

[0067] Each reservoir is closed at its upper end 14 by a first closure means 16 and each reservoir 10 is closed at its lower end 12 by a second closure means 17. In the embodiment shown in Figure 1, the lower end 14 and the upper end 12 of each reservoir 10 are threaded ends, and the first closure means 16 and the second closure means 17 also have threads which are complementary to the threads of the lower end 14 and the upper end 12. Thus, the lower end 14 is liquid-tight closed by being threaded with the first closure means 16 and the upper end 12 is liquid-tight closed by being threaded with the second closure means 17.

[0068] The second closure means 17 is fitted with sensors 19 which are a pressure gauge, a temperature gauge and a leak detector. Of course, the first closure means 16 can also include a pressure gauge, a temperature gauge and a leak detector. Other types of sensors can be used depending on the purpose set.

[0069] Each reservoir 10 may be made up of several tubes A. In the embodiment shown in Figure 1, the reservoir 10 is made up of several threaded tubes A. The tubes A are thus screwed together to form a column C of tubes A. In this way, the assembly made up of the column C closed at its ends 12 and 14 by closure means 16 and 17 forms the reservoir 10. The reservoir 10 may also be made up of a single tube A closed at its ends 12 and 14 by closure means 16 and 17.

[0070] Each reservoir 10 is joined to a joining element 18. Each joining element 18 is inserted into an opening 7 and is held there by a flange 62 abutting the upper surface 54 of the support element 4. Each joining element 18 is thus suspended from the support element 4. In this way, each reservoir 10 is suspended from the support element 4 via the joining element 18 to which it is joined.

[0071] As shown in FIG. 4, the joining element 18 is a tubular metal section of circular cross section comprising a tubular body 60 and a flange 62 .

[0072] The body 60 of the interface element 18 is attached, preferably screwed, to the top end 12 of the reservoir 10. In an alternative embodiment, welding can be used. The body 60 of the interface element 18 has male or female threads (not shown) complementary to the threads of the top end 12 of the reservoir 10 to which said interface element 18 is to be joined. The flange 62 includes a top surface 64 and a bottom surface 66.

[0073] In the embodiment shown in Fig. 1, the tubular body 60 of each connecting element 18 is inserted into the opening 7 of the support element 4. Each connecting element 18 rests on the support element 4 via its bottom surface 66 which abuts against the upper surface 54 of the support element 4. In addition, each connecting element 18 is screwed onto the reservoir 10 at the upper end 12 of said reservoir 10.

[0074] Thus, the flange 62 of the interface element 18 allows the interface element to rest on the upper surface 54 of the support element 4. As a result, the interface element 18 does not have to be attached to the support element 4, for example by welding or screw fastening, thereby facilitating the assembly of the storage system 1, in particular for suspending the reservoir 10.

Claims

1. An underground storage system (1) for storing a fluid, said storage system (1) comprising: a hole (2) made in the ground (40), said hole (2) having a bottom (3); a support element (4) comprising at least one opening (7), a joining element (18) inserted into the opening (7) of the support element (4); at least one reservoir (10), said reservoir (10) having a longitudinal axis (1), a bottom end (14) closed by a first closure means (16) and a top end (12) closed by a second closure means (17); Including, said upper end (12) is connected to said support element (4) via said joining element (18), said reservoir (10) is suspended in said hole (2) and an axial clearance (G) capable of accommodating axial thermal expansion of said reservoir (10) remains between the first closing means (16) of said reservoir (10) and the bottom (3) of said hole (2); The storage system (1).

2. 2. The storage system (1) according to claim 1, characterized in that the reservoir (10) is made up of at least one metal tube (A), said metal tube (A) having at least one end provided with at least one threaded portion.

3. 3. A storage system (1) according to claim 2, characterized in that said reservoir (10) consists of at least two metal tubes (A) screwed together to form a column of tubes (C).

4. Storage system (1) according to any one of the preceding claims, characterized in that the axial clearance (G) satisfies the following inequality: G≧(L) ２ *β*α)+[20*α*80*(1-% －０．１１＊Ｌ )] where G is the axial clearance length in meters, L represents the reservoir length in meters (10), β represents the geothermal gradient in degrees Celsius per meter, and α represents the thermal expansion coefficient of the metal in meters per degree Celsius.

5. 10. Storage device (1) according to any one of the preceding claims, characterized in that the first closure means (16) and / or the second closure means (17) are capable of closing the reservoir by means of a screw fastening.

6. A storage device (1) according to any one of the preceding claims, characterized in that the system (1) comprises a plurality of reservoirs (10), each reservoir (10) having a longitudinal axis (l), a lower end (14) and an upper end (12), the upper end (12) of each reservoir (10) being capable of being joined to a support element (4) via a joining element (18) such that each reservoir (10) is suspended inside the hole (2).

7. A storage system (1) according to any one of the preceding claims, characterized in that said hole (2) has at least one casing (30).

8. 8. The storage system (1) according to claim 7, characterized in that the casing (30) is made of concrete, cement or steel plates.

9. 1. A method for underground storage for storing a fluid, comprising the steps of: creating a hole (2) in the ground (40), said hole (2) having a bottom (3); Providing a support element (4) with at least one opening (7) capable of receiving a joining element (18), providing at least one reservoir (10), said reservoir (10) having a longitudinal axis (1), a lower end (14) and an upper end (12); providing a first closure means (16) capable of closing said reservoir (10) at its lower end (14) and a second closure means (17) capable of closing said reservoir (10) at its upper end (12); joining the upper end (12) to the support element (4) via the joining element (18) so that the reservoir (10) is suspended in the hole (2) and an axial clearance (G) capable of accommodating axial thermal expansion of the reservoir (10) remains between the first closing means (16) of the reservoir (10) and the bottom (3) of the hole (2).

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