Underground gas storage sealing structure and construction method

Abstract

The present invention relates to an underground gas storage sealing structure and a construction method. The structure comprises a sealing layer, a sliding layer, a lining structure, a filling layer and a drainage and gas leakage collection structure which are arranged in sequence from the inside to the outside. The filling layer is paved with compacted bentonite which is filled between the lining structure and the surrounding rock. The drainage and gas leakage collection structure is fixed on the surrounding rock. The drainage and gas leakage collection structure is composed of a plurality of pipes which are fixed on the inner side of the surrounding rock. The pipe walls of the pipes are provided with a plurality of openings. Compacted bentonite is filled between adjacent pipes. The compacted bentonite in the filling layer of the sealing structure absorbs water and expands to fill the expansion joints, surface cracks and pores of the lining structure, thereby enhancing the sealing performance of the lining structure, avoiding the use of large-area organic materials such as rubber, and reducing costs.

Description

Technical Field

[0001] The present invention relates to the technical field of underground gas storage, and in particular to a sealing structure and a construction method of an underground gas storage. Background Art

[0002] The statements herein merely provide background information related to the present invention and do not necessarily constitute prior art.

[0003] Compressed air energy storage (CAES) is an emerging large-scale energy storage technology with advantages such as long service life, large scale, low cost, and environmental friendliness. It enables large-scale energy storage and dispatch, optimizes power distribution, and improves the stability and reliability of power systems. Underground gas storage is a current development trend in compressed air energy storage.

[0004] In order to ensure the sealing of underground gas storage and the stability of the overlying rock mass, and to prevent air leakage and the impact of high air pressure on the ground, engineering measures must be taken on the underground chambers - sealing the structure.

[0005] In the existing chamber sealing structure design, the crack width of the chamber lining (conventional reinforced concrete lining, ring-anchor prestressed lining, etc.) under high gas pressure (10MPa and above) does not meet the crack limit design requirements. In addition, the large-scale use of organic materials such as rubber in some designs not only increases the project cost, but also brings environmental problems to a certain extent. Summary of the Invention

[0006] In view of the shortcomings of the existing technology, the purpose of the present invention is to provide an underground gas storage sealing structure and construction method, which can give full play to the performance advantages of the construction materials, while ensuring the sealing and stability of the gas storage, and being as green, economical and environmentally friendly as possible.

[0007] In order to achieve the above object, the present invention is implemented through the following technical solutions:

[0008] In a first aspect, an embodiment of the present invention provides an underground gas storage sealing structure, which includes a sealing layer, a sliding layer, a lining structure, a filling layer, and a drainage and gas leakage collection structure arranged in sequence from the inside to the outside.

[0009] The filling layer is formed by paving compacted bentonite between the lining structure and the surrounding rock.

[0010] The drainage and air leakage collection structure is fixed on the surrounding rock. The drainage and air leakage collection structure is composed of multiple pipes fixed on the inner side of the surrounding rock. The pipe wall is provided with multiple openings, and the space between adjacent pipes is filled with compacted bentonite.

[0011] Optionally, the lining structure is made of prestressed reinforced concrete or ultra-high performance concrete.

[0012] Optionally, the sliding layer is a bentonite waterproof blanket laid on the inner surface of the lining structure.

[0013] Optionally, the sealing layer is made of a low-carbon steel plate, and the surface of the low-carbon steel plate is coated with a waterproof coating.

[0014] Optionally, the sealing layer is composed of a plurality of low-carbon steel plates, and adjacent low-carbon steel plates are welded and fixed.

[0015] Optionally, the pipeline is laid in a direction parallel to the chamber, the pipeline is tied and fixed to the anchor rod inserted into the surrounding rock, one end of the pipeline is provided with a plug, and the other end is used to connect to the exhaust equipment through a connecting pipe.

[0016] Optionally, the outer surface of the pipe is sprayed with permeable concrete.

[0017] Optionally, a temperature detection element and a pressure detection element are installed in the pipeline.

[0018] In a second aspect, an embodiment of the present invention provides a construction method of the underground gas storage sealing structure according to the first aspect, comprising the following steps:

[0019] After fixing the pipeline to the surrounding rock outside the excavated underground rock chamber, fill and compact bentonite between adjacent pipelines to form a drainage and gas leakage collection structure;

[0020] Lay compacted bentonite on the inner side of the drainage and air leakage collection structure to form a filling layer;

[0021] Construct the lining structure on the inner side of the filling layer, and then construct the sliding layer and sealing layer in sequence;

[0022] Water is injected into the pipeline, and the water in the pipeline enters the filling layer, making the compacted bentonite in the filling layer saturated with water. The water inside is then discharged through the pipeline, completing the construction of the sealing structure.

[0023] The beneficial effects of the present invention are as follows:

[0024] 1. The sealing structure of the present invention has a filling layer filled with compacted bentonite, which has extremely low permeability and can ensure the sealing performance of the sealing structure; the compacted bentonite can expand after absorbing water, fill the cracks and pores in the surrounding rock, smooth the rough surface of the surrounding rock, provide a flat base surface for the lining structure, reduce the interlocking between the surrounding rock and the lining structure, and at the same time be able to transfer the force of the lining structure to the surrounding rock and evenly disperse the deformation; in addition, the compacted bentonite will fill the expansion joints, surface cracks and pores of the lining structure after absorbing water and expanding, thereby enhancing the sealing performance of the lining structure, avoiding the use of large-scale organic materials such as rubber, reducing costs, and avoiding environmental problems. At the same time, the compacted bentonite filled in the expansion joints will play a buffering role when the lining structure is subjected to force and deformation, thereby improving the mechanical properties of the lining structure.

[0025] 2. In the sealing structure of the present invention, the compacted bentonite filled in the filling layer absorbs water and expands, generating an expansion force of several to dozens of MPa, which applies pressure to the lining structure, causing the lining structure to bear an annular pre-pressure before gas injection into the gas storage reservoir. This is used to partially or even completely offset the annular stress generated in the sealing structure by the gas storage pressure, thereby increasing the tensile strain limit of the concrete in the lining structure, better exerting the material strength of the concrete, controlling the cracking of the gaps in the lining structure, and ensuring the sealing and stability of the underground gas storage reservoir.

[0026] 3. The sealing structure of the present invention fully utilizes the high expansibility, low permeability, and good self-healing properties of bentonite and the compressive resistance of concrete. While ensuring the sealing and stability of the underground gas storage, it also takes into account design requirements such as economy, environmental protection, and durability, and has good application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] The accompanying drawings, which constitute a part of the present invention, are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations on the present invention.

[0028] Figure 1 This is a schematic diagram of the overall structure of Example 1 of the present invention;

[0029] Among them, 1. Surrounding rock, 2. Drainage and air leakage collection structure, 3. Compacted bentonite, 4. Lining structure, 41. Expansion joint of lining structure, 42. Prestressed reinforced concrete, 43. Annular connecting steel bars, 5. Bentonite waterproofing blanket, 6. Low carbon steel plate. DETAILED DESCRIPTION

[0030] Example 1

[0031] This embodiment provides a sealing structure for an underground gas storage reservoir, such as Figure 1As shown, the sealing structure is distributed along the contour of the underground rock chamber, and from the inside to the outside, includes a sealing layer, a sliding layer, a lining structure, a filling layer and a drainage and gas leakage collection structure arranged in sequence. The drainage and gas leakage collection structure is fixed on the inner side of the surrounding rock 1.

[0032] In this embodiment, the direction from inside to outside refers to the direction from the middle of the chamber to the surrounding rock 1.

[0033] The sealing layer mainly plays a sealing role. In this embodiment, the sealing layer is formed by paving low-carbon steel plates 6. Preferably, the sealing layer is formed by paving multiple low-carbon steel plates 6, and adjacent low-carbon steel plates 6 are welded and fixed.

[0034] The low carbon steel plate 6 has good ductility and toughness and can resist the effect of fatigue load. In addition, the low carbon steel plate 6 has good weldability and is easy to construct.

[0035] The sliding layer mainly plays the role of reducing the wear of the sealing layer and protecting the sealing layer.

[0036] In this embodiment, the sliding layer adopts bentonite waterproof blanket 5, which is poured and laid on the inner surface of the lining structure, and the construction is simple and environmentally friendly.

[0037] The bentonite waterproof blanket 5 has good ductility and durability, can reduce the friction between the sealing layer and the lining structure, and reduce the wear of the sealing layer.

[0038] At the same time, the bentonite waterproof blanket 5 has good waterproof properties, can prevent water from seeping through the gaps in the lining structure, ensure the sealing layer is dry, and provide anti-corrosion protection for the steel plate.

[0039] Moreover, the bentonite in the bentonite waterproof blanket 5 can heal the cracks caused by the cracks in the lining structure 4 .

[0040] The lining structure 4 mainly plays the role of first bearing the stress of the stored gas and supporting the filling layer.

[0041] In this embodiment, the lining structure 4 is made of cast prestressed reinforced concrete 42 , with lining structure expansion joints 41 left between the prestressed reinforced concrete and connected by annular connecting steel bars 43 .

[0042] The provision of the annular connecting steel bars 43 ensures the integrity of the lining structure and, to a certain extent, increases the upper limit of the gas storage pressure required for the lining structure 4 to undergo significant deformation when the lining structure is subjected to load.

[0043] In this embodiment, the annular connecting steel bars 43 are first laid out, and then the prestressed reinforced concrete 42 is poured. The prestressed tendons in the prestressed reinforced concrete 42 are tensioned using the post-tensioning method. The construction can use existing technology and will not be described in detail here.

[0044] In some other embodiments, the lining structure 4 may also be made of ultra-high performance concrete, which will not be described in detail here.

[0045] The compacted bentonite 3 in the filling layer is formed by paving prefabricated compacted bentonite blocks.

[0046] The filling layer has the function of applying prestress to the lining structure 4 and sealing and healing the gaps in the lining structure 4 .

[0047] The concrete in the lining structure 4 is subjected to compressive stress under the action of the compacted bentonite 3 that absorbs water and expands in the filling layer and the prestressed steel bars in the lining structure. During the gas injection process of the gas storage reservoir, when the sealing structure is subjected to the tensile stress generated by the stored gas pressure, it will first offset the existing prestress in the concrete of the inner lining structure before gas injection. Then, as the gas storage pressure increases, the concrete deformation may exceed its ultimate tensile strain and cracks may appear, thereby increasing the upper limit of the ultimate tensile strain of the concrete, that is, increasing the upper limit of the gas storage pressure that the gas storage reservoir sealing structure can withstand, and better exerting the material strength of the concrete.

[0048] At the same time, after the compacted bentonite 3 of the filling layer absorbs water and expands, it can fill the gaps in the surrounding rock 1, smooth the rough surface of the surrounding rock 1, provide a flat base surface for the lining structure, reduce the interlocking between the surrounding rock 1 and the lining structure 4, and at the same time transfer the force of the lining structure to the surrounding rock 1, evenly disperse the deformation, and ensure the sealing and stability of the underground gas storage sealing structure.

[0049] The drainage and gas leakage collection structure 2 is the last safety barrier of the sealing structure. It is arranged on the inner surface of the surrounding rock 1 and plays the role of promptly discharging water seepage from the surrounding rock and gas leakage from the gas storage reservoir, avoiding the stress generated by water seepage and gas leakage from causing adverse effects on the overall stability of the structure. At the same time, it plays the role of monitoring the operating status of the gas storage reservoir and detecting leakage points.

[0050] In this embodiment, the drainage and gas leakage collection structure 2 is mainly composed of pipes arranged on the surface of the surrounding rock 1. The pipes are used for drainage and gas leakage collection. Multiple pipes on the same side are evenly spaced along the contour line of the chamber.

[0051] The pipe is fixed to the anchor rod inserted into the surrounding rock 1 by steel strands, and its outer surface is sprayed with low-strength permeable concrete to fix and protect the pipe. The permeable concrete can be made of existing materials and will not be described in detail here.

[0052] After spraying the permeable concrete, fill and compact bentonite between adjacent pipes.

[0053] Preferably, the pipes in the drainage and gas leakage collection structure 2 are made of high-temperature resistant polyethylene pipes, and a plurality of openings are provided on the pipe wall of the pipes for discharging water seepage from the surrounding rocks and collecting gas leakage from the chamber.

[0054] In this embodiment, the pipes in the drainage and air leakage collection structure 2 are arranged in a direction parallel to the chamber and are composed of multiple pipe sections. One end of the pipe is provided with a plug for sealing, and the other end is used to connect to the exhaust equipment through a connecting pipe. The exhaust equipment can use an existing exhaust pump, which will not be described in detail here.

[0055] The outer periphery of the pipeline in the drainage and gas leakage collection structure 2 is sprayed with low-strength permeable concrete. The low-strength permeable concrete has good water permeability and air permeability, which can ensure that water and gas can smoothly enter the pipeline through the through hole, and plays a role in protecting the pipeline and improving the hydraulic connection between the pipeline and the surrounding rock 1.

[0056] A plurality of temperature detection elements and pressure detection elements are also installed through through holes in the pipes of the drainage and gas leakage collection structure 2. The temperature detection elements use temperature sensors, and the pressure detection elements use pressure sensors. The temperature sensors and pressure sensors can monitor the operating status of the gas storage and detect leakage points.

[0057] Example 2

[0058] This embodiment provides a construction method for the underground gas storage sealing structure described in Example 1, comprising the following steps:

[0059] Step 1: Grouting reinforcement is performed on the surrounding rock 1 of the excavated underground rock chamber, cracks on the free surface are pre-treated, and anchor rods for tying pipes in the drainage and gas leakage collection structure 2 are fixed.

[0060] Step 2: Tie the pipes in the drainage and air leakage collection structure 2 with through holes to the anchor rods with steel wire ropes, place multiple pressure and temperature sensors in protective covers, and arrange them on the pipes through the through holes; seal one end of the pipe with a plug, and use the other end as the air outlet end, and connect the air outlet end of the pipe to the exhaust equipment through a connecting pipe.

[0061] Step 3: spray low-strength permeable concrete on the outer surface of the pipeline. After curing, form a drainage and air leakage collection structure 2, and fill and compact bentonite between adjacent pipelines.

[0062] Step 4: Use prefabricated compacted bentonite blocks to lay compacted bentonite 3 inside the drainage and air leakage collection structure 2 to form a filling layer. This layer is simple to construct and has a short construction period. During the construction process, necessary support structures must be built to ensure construction safety and prevent the compacted bentonite blocks from falling.

[0063] Step 5: Install formwork supports on the inner side of the filling layer, set up formwork and steel cages, and construct the lining structure 4 in sections. The lining structure uses prestressed reinforced concrete or existing ultra-high performance concrete. In this embodiment, prestressed reinforced concrete is used, and its construction method can use existing technology. During the construction of the lining structure, first, the annular connecting steel bars 43 are laid out, and then the prestressed reinforced concrete 42 is poured in sections. The lining structure expansion joints 41 are left between the prestressed reinforced concrete 42. The annular connecting steel bars 43 at the lining structure expansion joints 41 must be covered with protective sleeves to prevent them from being exposed to the outside. The prestressed bars are tensioned using the post-tensioning method. The prestressed bars of different sections are overlapped by connectors. Before pouring the latter section of concrete, the laitance, weak concrete layer, loose stones and surface dirt on the pouring surface need to be removed, and the coarse aggregate must be evenly exposed. The construction method of prestressed reinforced concrete 42 can adopt existing technology, and its further construction method details are not described in detail here. After the reinforced concrete of the lining structure 4 reaches the set strength, the bentonite waterproof blanket 5 is laid on its inner side and the bentonite waterproof blanket 5 is cast on the inner surface of the lining structure 4.

[0064] Step 6: Lay a plurality of low-carbon steel plates 6 on the inner surface of the bentonite waterproof blanket 5 , connect adjacent low-carbon steel plates 6 into a whole by welding, and coat the surface of the low-carbon steel plates 6 with a waterproof coating.

[0065] Step 7: Inject water into the pipes in the drainage and air leakage collection structure 2 to make the compacted bentonite 3 in the filling layer saturated with water, and monitor the saturation of the bentonite through the deployed temperature sensors and pressure sensors. After the bentonite is saturated with water, the water is discharged through the pipes, completing the construction of the sealing structure.

[0066] The construction method of this embodiment is simple and easy, with a short construction period. The formed gas storage sealing structure can be applied to the construction of underground rock chambers for compressed gas energy storage, and can realize gas leakage monitoring and treatment, and has good application prospects.

[0067] Before the gas storage reservoir is injected with gas, the concrete in the lining structure is subjected to circumferential compressive stress under the action of the compacted bentonite that absorbs water and expands in the filling layer; during the gas storage reservoir injection process, when the sealing structure is subjected to the tensile stress generated by the stored gas pressure, it will first offset the existing pre-stress in the concrete before gas injection, and then, as the gas storage pressure increases, the concrete deformation may exceed its ultimate tensile strain and cracks may appear, thereby increasing the upper limit of the ultimate tensile strain of the concrete, that is, increasing the upper limit of the gas storage pressure that the gas storage reservoir sealing structure can withstand. This means that when the designed gas storage pressure of the gas storage reservoir is constant, the sealing structure of this embodiment can reduce the overall deformation of the gas storage reservoir sealing structure to control the development of cracks in the lining structure. Moreover, the filling layer is filled with compacted bentonite, which has extremely low permeability and can ensure the sealing of the sealing structure; the compacted bentonite can expand after absorbing water, fill the cracks and pores in the surrounding rock, smooth the rough surface of the surrounding rock, provide a flat base surface for the lining structure, reduce the interlocking between the surrounding rock and the lining structure, and at the same time be able to transfer the force of the lining structure to the surrounding rock and evenly disperse the deformation; in addition, the compacted bentonite will fill the expansion joints, surface cracks and pores of the lining structure after absorbing water and expanding, thereby enhancing the sealing of the lining structure, avoiding the use of large areas of organic materials such as rubber, reducing costs, and avoiding environmental problems. At the same time, the compacted bentonite filled in the expansion joints will play a buffering role when the lining structure is subjected to force and deformation, thereby improving the mechanical properties of the lining structure.

[0068] The sealing structure and construction method of this embodiment can better utilize the high expansibility and low permeability of bentonite and the compressive strength of concrete, and can reduce the amount of material used. At the same time, the sealing structure of this embodiment is simple in structure and easy to construct. The materials used are economical and environmentally friendly. While ensuring the normal operation of the underground gas storage, it can greatly reduce construction costs while taking into account environmental protection requirements.

[0069] The above description is merely a preferred embodiment of the present application and is not intended to limit the present application. Various modifications and variations are possible for those skilled in the art. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present application shall be included within the scope of protection of the present application.

Claims

1. An underground gas storage sealing structure, characterized in that: From the inside to the outside, it includes a sealing layer, a sliding layer, a lining structure, a filling layer, and a drainage and air leakage collection structure arranged in sequence; The filling layer is formed by paving compacted bentonite between the lining structure and the surrounding rock; The drainage and air leakage collection structure is fixed on the surrounding rock. The drainage and air leakage collection structure is composed of a plurality of pipes fixed on the inner side of the surrounding rock. The pipe wall is provided with a plurality of openings. The space between adjacent pipes is filled with compacted bentonite. The sliding layer adopts a bentonite waterproof blanket laid on the inner surface of the lining structure; The lining structure is made of prestressed reinforced concrete or ultra-high performance concrete; Before the gas storage reservoir is injected with gas, water is injected into the water-absorbing and swollen compacted bentonite in the filling layer through the drainage and air leakage collection structure, so that the compacted bentonite in the filling layer is saturated with water, and then the water in the drainage and air leakage pipes is discharged; the concrete in the lining structure is subjected to circumferential compressive stress under the action of the water-absorbing and swollen compacted bentonite in the filling layer; during the gas storage reservoir injection process, when the sealing structure is subjected to the tensile stress generated by the stored gas pressure, it will first offset the existing pre-pressure in the concrete before gas injection, and as the gas storage pressure increases, the deformation of the concrete exceeds its ultimate tensile strain and cracks appear, thereby increasing the upper limit of the gas storage pressure that the gas storage sealing structure can withstand, and the sealing structure reduces the integrity of the gas storage sealing structure. The body shape changes to control the development of cracks in the lining structure; the filling layer is filled with compacted bentonite, which has extremely low permeability, ensuring the sealing of the sealing structure; the compacted bentonite can expand after absorbing water, filling the cracks and pores in the surrounding rock, smoothing the rough surrounding rock surface, providing a flat base surface for the lining structure, reducing the interlocking between the surrounding rock and the lining structure, transferring the force of the lining structure to the surrounding rock, and evenly dispersing the deformation; the compacted bentonite will fill the expansion joints, surface cracks and pores of the lining structure after absorbing water and expanding, enhancing the sealing of the lining structure. The compacted bentonite filled in the expansion joints plays a buffering role when the lining structure is subjected to force and deformation, thereby improving the mechanical properties of the lining structure; The pipeline is laid in a direction parallel to the chamber, and is tied and fixed to an anchor rod inserted into the surrounding rock. One end of the pipeline is provided with a plug, and the other end is used to connect to the exhaust equipment through a connecting pipe; The pipes in the drainage and air leakage collection structure are fixed to the anchor rods by steel wire ropes, and multiple pressure and temperature sensors are placed in protective sleeves and arranged on the pipes through the pipe through-holes; one end of the pipe is sealed with a plug, and the other end is used as the air outlet end, and the air outlet end of the pipe is connected to the air extraction equipment through a connecting pipe.

2. The underground gas storage sealing structure according to claim 1, characterized in that: The sealing layer is made of low-carbon steel plate, and the surface of the low-carbon steel plate is coated with waterproof paint.

3. The underground gas storage sealing structure according to claim 1, characterized in that: The sealing layer is composed of a plurality of low-carbon steel plates, and adjacent low-carbon steel plates are welded and fixed.

4. The underground gas storage sealing structure according to claim 1, characterized in that: The outer surface of the pipe is sprayed with permeable concrete.

5. A construction method for the underground gas storage sealing structure according to any one of claims 1 to 4, characterized in that: The following steps are involved: After fixing the pipeline to the surrounding rock outside the excavated underground rock chamber, fill and compact bentonite between adjacent pipelines to form a drainage and gas leakage collection structure; Lay compacted bentonite on the inner side of the drainage and air leakage collection structure to form a filling layer; Construct the lining structure on the inner side of the filling layer, and then construct the sliding layer and sealing layer in sequence; Water is injected into the pipeline, and the water in the pipeline enters the filling layer, making the compacted bentonite in the filling layer saturated with water. The water inside is then discharged through the pipeline, completing the construction of the sealing structure.

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