Gas storage cavern grouting confining pressure real-time monitoring system and method based on piezoresistive effect

Abstract

The invention relates to the technical field of underground energy storage, in particular to a gas storage cavern grouting confining pressure real-time monitoring system and method based on the piezoresistive effect, and the system comprises a grouting reinforcement module which is used for injecting grout into a target gas storage cavern and laying a lining to form a grouting reinforcement area; the resistance detection module is used for detecting resistivity distribution characteristics of the grouting reinforcement area in real time; the confining pressure monitoring module is used for analyzing the resistivity distribution characteristics based on a preset piezoresistive modified slurry resistivity-surrounding rock stress relation model to obtain the actual stress state of surrounding rock; and the early warning regulation and control module is used for triggering an early warning signal based on the actual stress state of the surrounding rock and releasing gas. According to the invention, continuous and non-contact measurement of the surrounding rock stress state of the gas storage cavern can be realized.

Description

Technical Field

[0001] This invention relates to the field of underground energy storage technology, and in particular to a real-time monitoring system and method for grouting confining pressure in gas storage caverns based on the piezoresistive effect. Background Technology

[0002] Lined rock caves (LRCs) are widely used for the large-scale storage of compressed gases and hydrogen due to their advantages such as large capacity and high sealing performance. However, existing lined gas storage rock cave systems still face the following technical bottlenecks:

[0003] 1. Lagging methods for monitoring surrounding rock stress: Traditional point sensors (such as optical fibers and strain gauges) can only acquire stress data at local discrete points, making it difficult to fully capture the stress field distribution in the grouting reinforcement area and surrounding rock, and there is a risk of equipment failure under long-term high pressure environment;

[0004] 2. The grouting effect cannot be dynamically verified: After conventional cement grout is injected into the surrounding rock fissures, there is a lack of effective means to verify its actual diffusion range and density. Defects in grout solidification can easily form gas leakage channels.

[0005] 3. Passive Overpressure Risk Prevention: Existing systems rely on periodic manual monitoring or delayed alarm mechanisms, which cannot provide real-time early warning of changes in surrounding rock stress. Once a sudden increase in cavern pressure leads to instability of the surrounding rock, it can easily induce a chain reaction of rock mass fractures or even cavern collapse. There is an urgent need to develop an innovative technology system that can monitor the stress state of the surrounding rock in gas storage caverns in real time and across the entire area, and has the capability for proactive safety control. Summary of the Invention

[0006] The purpose of this invention is to provide a real-time monitoring system and method for grouting confining pressure in gas storage caverns based on the piezoresistive effect, so as to realize continuous, non-contact measurement of the stress state of the surrounding rock in gas storage caverns.

[0007] To achieve the above objectives, the present invention provides the following solution:

[0008] A real-time monitoring system for confining pressure during grouting in a gas-storage cavern based on the piezoresistive effect includes:

[0009] The grouting reinforcement module is used to inject grout into the target gas storage cavern and lay the inner lining to form a grouting reinforcement zone.

[0010] The resistance detection module is used to detect the resistivity distribution characteristics of the grouting reinforcement zone in real time.

[0011] The confining pressure monitoring module is used to analyze the resistivity distribution characteristics based on a preset piezoresistive modified slurry resistivity-surrounding rock stress relationship model, and to obtain the actual stress state of the surrounding rock.

[0012] The early warning and control module is used to trigger an early warning signal and release gas based on the actual stress state of the surrounding rock.

[0013] Optionally, the grouting reinforcement module includes: an inner lining material, an asphalt buffer layer, a concrete lining, surrounding rock, and a pressure-resistance modified grout. The pressure-resistance modified grout is injected into the rock fissures of the surrounding rock, and after curing, a concrete lining, an asphalt buffer layer, and an inner lining material are sequentially constructed on the inner side of the surrounding rock to form the grouting reinforcement zone.

[0014] Optionally, the resistance detection module employs a geophysical electromagnetic detection device. The device emits electromagnetic waves into the ground and collects data on the attenuation constant, phase difference, and reflection intensity of the electromagnetic waves. Combined with the Maxwell electromagnetic field equation inversion algorithm, the resistivity distribution information of the underground medium is obtained, i.e., the resistivity distribution characteristics of the grouting reinforcement zone.

[0015] Optionally, the piezoresistive modified slurry resistivity-surrounding rock stress relationship model is constructed through axial loading tests, and the piezoresistive modified slurry resistivity-surrounding rock stress relationship model is as follows:

[0016] ρ = f(σ);

[0017] Where ρ is resistivity and σ is stress.

[0018] Optionally, the early warning and control module includes: an exhaust pipe, an expander, and a power grid. When the actual stress of the surrounding rock exceeds a preset safety threshold level, an early warning is triggered and the excess gas is controlled to be output to the ground through the exhaust pipe. The output gas drives the expander to do work and generate electricity, and the pressure potential energy is converted into electrical energy and then fed into the power grid.

[0019] To further achieve the above objectives, the present invention also provides a method for real-time monitoring of confining pressure during grouting in gas-storage caverns based on the piezoresistive effect, comprising:

[0020] Grout is injected into the target gas storage cavern and an inner lining is installed to form a grouting reinforcement zone;

[0021] Real-time detection of the resistivity distribution characteristics of the grouting reinforcement zone;

[0022] The resistivity distribution characteristics of the piezoresistive modified slurry are analyzed based on the preset piezoresistive modified slurry resistivity-surrounding rock stress relationship model to obtain the actual stress state of the surrounding rock.

[0023] An early warning signal is triggered based on the actual stress state of the surrounding rock, and gas is released.

[0024] The beneficial effects of this invention are as follows:

[0025] This invention replaces traditional cement grout with piezoresistive modified grout, significantly improving the mechanical strength and sealing performance of the grouting reinforcement zone. Simultaneously, it utilizes the conductivity of carbon nanotubes to form a visible tracer in electromagnetic monitoring, enabling precise positioning of the grout diffusion range. Furthermore, it innovatively leverages the physical characteristic of the piezoresistive modified grout's resistivity dynamically changing with surrounding rock stress (piezoresistive effect), and collaborates with a surface geophysical electromagnetic observation system to construct an in-situ real-time monitoring network. This achieves, for the first time, continuous, non-contact measurement of the stress state of the surrounding rock in gas-storage caverns, completely overcoming the technical limitations of traditional point sensors with limited coverage. When the monitoring system determines that the surrounding rock stress is approaching a safety threshold, it automatically triggers a gas release-power generation-pressure reduction control mechanism. By releasing excess gas to drive an expander to generate electricity, energy is recovered and utilized, simultaneously reducing the cavern gas pressure to a safe threshold. This eliminates the risk of surrounding rock instability and cavern collapse caused by excessive gas storage pressure at the source, significantly improving the system's safety margin. Attached Figure Description

[0026] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0027] Figure 1 This is a schematic diagram of the gas storage cavern structure according to an embodiment of the present invention;

[0028] Figure 2 This is a schematic diagram of a real-time monitoring system for grouting confining pressure in a gas-storage cavern based on the piezoresistive effect, according to an embodiment of the present invention.

[0029] Among them, 1-lining material, 2-asphalt buffer layer, 3-concrete lining, 4-surrounding rock, 5-piezoresistive modified grout, 6-gas pipeline, 7-lined gas storage cavern, 8-geophysical electromagnetic detection device, 9-electromagnetic wave, 10-gas outlet pipeline, 11-expander, 12-power grid, 13-compressor. Detailed Implementation

[0030] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0031] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0032] This embodiment provides a real-time monitoring system for confining pressure during grouting in gas-bearing caverns based on the piezoresistive effect, including:

[0033] The grouting reinforcement module is used to inject grout into the target gas storage cavern and lay the inner lining to form a grouting reinforcement zone.

[0034] The resistance detection module is used to detect the resistivity distribution characteristics of the grouting reinforcement zone in real time.

[0035] The confining pressure monitoring module is used to analyze the resistivity distribution characteristics based on a preset piezoresistive modified slurry resistivity-surrounding rock stress relationship model, and to obtain the actual stress state of the surrounding rock.

[0036] The early warning and control module is used to trigger an early warning signal and release gas based on the actual stress state of the surrounding rock.

[0037] Specifically, this embodiment uses piezoresistive modified grout instead of traditional cement grout, which not only significantly improves the mechanical strength and sealing performance of the grouting reinforcement zone, but also utilizes the conductivity of carbon nanotubes to form a visible tracer in electromagnetic monitoring, enabling precise positioning of the grout diffusion range. Based on this, it innovatively utilizes the physical characteristic of the piezoresistive modified grout resistivity dynamically changing with the surrounding rock stress (piezoresistive effect), and combines it with a surface geophysical electromagnetic observation system to construct an in-situ real-time monitoring network. This achieves, for the first time, continuous, non-contact measurement of the stress state of the surrounding rock in a gas-storage cavern, completely overcoming the technical shortcomings of traditional point sensors with limited coverage. When the monitoring system determines that the surrounding rock stress is approaching the safety threshold, it automatically triggers a gas release-power generation-pressure reduction control mechanism. By releasing excess gas to drive an expander to generate electricity, energy is recovered and utilized, simultaneously reducing the cavern gas pressure to the safety threshold. This eliminates the risk of surrounding rock instability and cavern collapse caused by excessive gas storage pressure at the source, significantly improving the system's safety margin.

[0038] Furthermore, the grouting reinforcement module includes: inner lining material 1, asphalt buffer layer 2, concrete lining 3, surrounding rock 4, and pressure resistance modified grout 5. The pressure resistance modified grout 5 is injected into the rock fissures of the surrounding rock 4, and after curing, the concrete lining 3, asphalt buffer layer 2 and inner lining material 1 are constructed sequentially on the inner side of the surrounding rock 4 to form the grouting reinforcement zone.

[0039] Specifically, such as Figure 1As shown, after the site selection and initial construction of the lined gas storage cavern 7 were completed, the surrounding rock 4 was first subjected to a tightness inspection to identify weak points with rock fissures. Subsequently, carbon nanotube modified cement grout (i.e., pressure-resistance modified grout 5) with a pressure-resistance effect was injected into the weak points to penetrate deep into and completely fill the fissures, forming the first line of defense against gas leakage. On the inner surface of the reinforced surrounding rock structure, the following were constructed in sequence: a concrete lining 3, which bears the gas pressure inside the cavern and evenly transmits the pressure to the surrounding rock area reinforced by the pressure-resistance grout; an asphalt buffer layer 2, which is set between the concrete lining 3 and the inner lining material 1, serving as a soft buffer layer to absorb the frictional stress between the two; and the inner lining material 1, which is set in the innermost layer of the cavern wall and has a sealing function to isolate the gas inside the gas storage cavern from the external environment.

[0040] Furthermore, the resistance detection module employs a geophysical electromagnetic detection device 8, which emits electromagnetic waves 9 into the ground and collects data on the attenuation constant, phase difference, and reflection intensity of the electromagnetic waves 9. Combined with the Maxwell electromagnetic field equation inversion algorithm, the resistivity three-dimensional distribution information of the underground medium is obtained, i.e., the resistivity distribution characteristics of the grouting reinforcement zone.

[0041] Specifically, such as Figure 2 As shown, in this embodiment, surplus electrical energy drives compressor 13 to compress gases such as air and hydrogen, which are then injected into the lined gas storage cavern 7 via gas pipeline 6 for non-peak charge storage. The injected gas compresses the cavern walls (especially the surrounding rock 4 and the grouting reinforcement area), causing changes in the stress state of the surrounding rock. Crucially, the resistivity characteristics of the piezoresistive modified grout 5 injected into the fissures and weak points of the surrounding rock are correlated with the stress it bears: as stress increases, resistivity decreases. Electromagnetic waves 9 are emitted underground using a geophysical electromagnetic detection device 8 (such as a transient electromagnetic device). By detecting the propagation characteristics of electromagnetic waves 9 in the rock strata (such as attenuation, reflection, and phase), the resistivity distribution information underground can be interpreted, especially the resistivity value of the piezoresistive modified grout 5 in the key monitoring area. Based on the pre-established piezoresistive modified grout resistivity-surrounding rock stress relationship model, the actual stress currently borne by the surrounding rock can be calculated backwards using the analyzed resistivity values.

[0042] Electromagnetic waves 9 are emitted into the ground using a geophysical electromagnetic detection device 8 (such as a transient electromagnetic device); by collecting data on the attenuation constant, phase difference, and reflection intensity of the electromagnetic waves, and combining this with the Maxwell electromagnetic field equation inversion algorithm, the three-dimensional resistivity distribution information of the underground medium is obtained.

[0043] Based on the pre-calibrated laboratory model of resistivity-surrounding rock stress relationship of piezoresistive modified slurry ρ=f(σ), this model was constructed through axial loading tests: a stepped stress of 0~20MPa was applied to the slurry sample, and the resistivity value was measured simultaneously. The quadratic polynomial relationship was then fitted and obtained: ρ=a·σ 2 The formula is: +b·σ+c, where ρ is resistivity, σ is stress, and a / b / c are material constants. The resistivity values ​​obtained from electromagnetic detection are iteratively optimized using the damped least squares method to eliminate background noise interference from the formation. Based on the inverted slurry resistivity change Δρ, a pre-calibrated piezoresistive modified slurry resistivity-surrounding rock stress relationship model ρ=f(σ) is used for inverse calculation. Utilizing its inverse function form σ=f⁻¹(Δρ), and combined with damped least squares optimization to suppress noise interference, a stable and high-precision inversion from resistivity to stress can be achieved. Finally, the stress state of the surrounding rock is determined based on the calculated stress value σ, providing crucial data support for the safe control of the gas storage facility.

[0044] Furthermore, the early warning and control module includes: an exhaust pipe 10, an expander 11, and a power grid 12. When the actual stress of the surrounding rock exceeds the preset safety threshold level, an early warning is triggered and the excess gas is controlled to be output to the ground through the exhaust pipe 10. The output gas drives the expander 11 to do work and generate electricity, and the pressure potential energy is converted into electrical energy and then fed into the power grid 12.

[0045] Specifically, when the monitoring system determines that the stress on the surrounding rock 4 exceeds the preset safety threshold, the system triggers an early warning and controls the output of excess gas (such as hydrogen) to the ground through the gas outlet pipe 10. The output high-pressure gas drives the expander 11 to generate electricity, converting the pressure potential energy of the gas into electrical energy, which is then fed into the power grid 12 to supplement energy demand during peak electricity consumption periods. This process not only realizes energy storage and reuse but also effectively avoids the risk of surrounding rock fracturing or collapse caused by excessive pressure inside the cave by actively releasing some of the gas pressure, ensuring the safe and stable operation of the gas storage facility.

[0046] To further optimize the technical solution, this embodiment also provides a method for real-time monitoring of confining pressure during grouting in gas-storage caverns based on the piezoresistive effect, including:

[0047] Grout is injected into the target gas storage cavern and an inner lining is installed to form a grouting reinforcement zone;

[0048] Real-time detection of the resistivity distribution characteristics of the grouting reinforcement zone;

[0049] The resistivity distribution characteristics of the piezoresistive modified slurry are analyzed based on the preset piezoresistive modified slurry resistivity-surrounding rock stress relationship model to obtain the actual stress state of the surrounding rock.

[0050] An early warning signal is triggered based on the actual stress state of the surrounding rock, and gas is released.

[0051] Specifically, the workflow includes the following:

[0052] 1. Excavation of underground cavern and grouting reinforcement of rock mass: Excavate underground gas storage cavern and inject cement grout containing carbon nanotubes (i.e., pressure resistance modified grout) into the surrounding fractured rock mass; the grout penetrates and fills the rock mass fractures, and forms a sealing barrier after solidification to prevent gas (such as hydrogen) from escaping from the fractures during gas storage.

[0053] 2. Construction of the tunnel lining structure: After the grout has completely cured, an asphalt buffer layer and an inner lining material are constructed sequentially on the inner side of the reinforced surrounding rock to form a double sealing system for the gas storage tunnel; the asphalt buffer layer is used to absorb the frictional stress between the inner lining and the lining layer, and the inner lining material mainly plays the role of gas sealing and isolation.

[0054] 3. Deployment of surface electromagnetic monitoring system: Deploy a geophysical electromagnetic real-time monitoring system (such as a transient electromagnetic device) on the surface; by transmitting electromagnetic waves into the ground, detect the resistivity distribution characteristics of the grouting reinforcement zone composed of piezoresistive modified grout; since the carbon nanotube grout has significant conductivity, it appears as a low-resistivity anomaly zone in the electromagnetic response data, and its spatial distribution and resistivity values ​​can be clearly analyzed.

[0055] 4. Real-time monitoring of surrounding rock stress based on piezoresistive effect: During gas storage operation, the stress of the surrounding rock in the cavern changes with the gas pressure; the resistivity of the piezoresistive modified grout changes negatively with the applied stress (i.e., piezoresistive effect). By periodically transmitting electromagnetic waves underground and analyzing the response data, the dynamic change value of the grout resistivity in the grouting area is obtained in real time; based on the pre-established grout resistivity-surrounding rock stress relationship model, the actual stress state of the surrounding rock is calculated by inversion.

[0056] 5. Stress Over-limit Early Warning and Active Control: When the surrounding rock stress is determined to exceed the preset safety threshold, an early warning signal is automatically triggered and a gas release program is started: excess gas (such as hydrogen) is controlled to be output to the ground surface through the gas outlet pipe, driving the expander to generate electricity and connecting the electricity to the grid to supplement peak demand; at the same time, the cavern gas pressure is reduced to relieve the risk of surrounding rock overload and effectively prevent rock mass instability or collapse accidents.

[0057] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made to the technical solutions of the present invention by those skilled in the art without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. A real-time monitoring system for confining pressure during grouting in a gas-storage cavern based on the piezoresistive effect, characterized in that, include: The grouting reinforcement module is used to inject grout into the target gas storage cavern and lay the inner lining to form a grouting reinforcement zone. The resistance detection module is used to detect the resistivity distribution characteristics of the grouting reinforcement zone in real time. The confining pressure monitoring module is used to analyze the resistivity distribution characteristics based on a preset piezoresistive modified slurry resistivity-surrounding rock stress relationship model, and to obtain the actual stress state of the surrounding rock. The early warning and control module is used to trigger an early warning signal and release gas based on the actual stress state of the surrounding rock.

2. The real-time monitoring system for confining pressure during grouting in a gas-storage cavern based on the piezoresistive effect according to claim 1, characterized in that, The grouting reinforcement module includes: inner lining material (1), asphalt buffer layer (2), concrete lining (3), surrounding rock (4), and pressure resistance modified grout (5). The pressure resistance modified grout (5) is injected into the rock fissures of the surrounding rock (4), and after curing, the concrete lining (3), asphalt buffer layer (2) and inner lining material (1) are constructed sequentially on the inner side of the surrounding rock (4) to form the grouting reinforcement zone.

3. The real-time monitoring system for confining pressure during grouting in a gas-storage cavern based on the piezoresistive effect according to claim 1, characterized in that, The resistance detection module uses a geophysical electromagnetic detection device (8). The geophysical electromagnetic detection device (8) emits electromagnetic waves (9) into the ground and collects the attenuation constant, phase difference and reflection intensity data of the electromagnetic waves (9). Combined with the Maxwell electromagnetic field equation inversion algorithm, the resistivity three-dimensional distribution information of the underground medium is obtained, that is, the resistivity distribution characteristics of the grouting reinforcement area.

4. The real-time monitoring system for confining pressure during grouting in gas-storage caverns based on piezoresistive effect according to claim 1, characterized in that, The piezoresistive modified slurry resistivity-surrounding rock stress relationship model was constructed through axial loading tests. The piezoresistive modified slurry resistivity-surrounding rock stress relationship model is as follows: ρ = f(σ); Where ρ is resistivity and σ is stress.

5. The real-time monitoring system for confining pressure during grouting in a gas-storage cavern based on the piezoresistive effect according to claim 1, characterized in that, The early warning and control module includes: an exhaust pipe (10), an expander (11), and a power grid (12). When the actual stress of the surrounding rock exceeds the preset safety threshold level, an early warning is triggered and the excess gas is controlled to be output to the ground through the exhaust pipe (10). The output gas drives the expander (11) to do work and generate electricity, and the pressure potential energy is converted into electrical energy and then connected to the power grid (12).

6. A method for real-time monitoring of confining pressure during grouting in a gas-storage cavern based on the piezoresistive effect, characterized in that, include: Grout is injected into the target gas storage cavern and an inner lining is installed to form a grouting reinforcement zone; Real-time detection of the resistivity distribution characteristics of the grouting reinforcement zone; The resistivity distribution characteristics of the piezoresistive modified slurry are analyzed based on the preset piezoresistive modified slurry resistivity-surrounding rock stress relationship model to obtain the actual stress state of the surrounding rock. An early warning signal is triggered based on the actual stress state of the surrounding rock, and gas is released.

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