Regional scale coal mine goaf clustering CO2 storage simulation method

Abstract

The invention belongs to the technical field of CO2 sequestration, and provides a regional scale coal mine goaf clustered CO2 sequestration simulation method which comprises the following steps: building a regional scale coal mine goaf clustered CO2 sequestration simulation environment according to actual distribution characteristics of regional scale goaf clusters, and setting initial simulation conditions; filling a CO2 gas with a preset flow into the CO2 storage simulation environment; in the process of filling the CO2 gas with the preset flow into the CO2 storage simulation environment, acquiring pressure data of the CO2 storage simulation environment, and controlling and adjusting the flow of the CO2 gas according to the pressure data; and collecting and recording data of the whole simulation process, and generating a data curve and / or a data table. The goaf simulation cavity is arranged to be of a modular structure, clustered distribution and geological difference of a plurality of goaf areas can be reproduced, and the blank that the regional scale cannot be simulated in the prior art is filled.

Description

Technical Field

[0001] This invention belongs to the field of CO2 sequestration technology, and particularly relates to a regional-scale simulation method for clustered CO2 sequestration in coal mine goaf areas. Background Technology

[0002] CO2 geostorage is a key emission reduction technology that has attracted much attention. CO2 geostorage involves capturing CO2 generated by human activities and safely injecting it into suitable geological structures deep underground, thus isolating it from the atmosphere for a long period of time, thereby mitigating the greenhouse effect and global warming.

[0003] Goaf areas are widely distributed and have huge volumes, making them important carriers for CO2 geological sequestration, especially in coal mine goaf areas. However, at the regional scale, clustered sequestration systems composed of multiple goaf areas suffer from uneven flow distribution and mutual pressure interference, leading to technical bottlenecks such as poor sequestration stability.

[0004] Therefore, exploring and simulating the sequestration process and influencing factors through experimental simulation devices, and subsequently seeking stable sequestration control methods, is of great significance for CO2 geological sequestration. Currently, research focuses on simulating sequestration in single goaf areas, which leads to limitations in simulation and an inability to accurately reproduce the clustered distribution characteristics of multiple goaf areas at a regional scale. More importantly, at a regional scale, clustered goaf areas in coal mines are an interconnected whole. Even simply replicating a single goaf and connecting them together lacks simulation of the interactions between goaf areas in a real environment, resulting in significant discrepancies between simulation results and actual operations, making it difficult to apply to guiding the clustered CO2 sequestration of coal mine goaf areas at a regional scale. Summary of the Invention

[0005] This application addresses the shortcomings of existing methods that rely on simulating CO2 storage in single goaf areas. These methods fail to accurately reproduce the clustered distribution characteristics of multiple goaf areas at a regional scale. Furthermore, simply replicating a single goaf area and then connecting them together lacks simulation of the interactions between goaf areas in a real-world environment. This results in significant discrepancies between simulation results and actual operations, making it difficult to apply to guiding the clustered CO2 storage of coal mine goaf areas at a regional scale. This application proposes a simulation method for clustered CO2 storage in coal mine goaf areas at a regional scale, achieving a more accurate simulation and significantly contributing to the engineering application of CO2 clustered storage technology.

[0006] The specific technical solution is as follows:

[0007] A method for simulating clustered CO2 sequestration in coal mine goafs at a regional scale, comprising:

[0008] Based on the actual distribution characteristics of goaf clusters at the regional scale, a simulation environment for CO2 sequestration in goaf clusters at the regional scale was constructed, and initial simulation conditions were set. The CO2 sequestration simulation environment includes a goaf environment and a connecting environment, with the connecting environment connecting the goaf environments.

[0009] A preset flow rate of CO2 gas is introduced into the CO2 sequestration simulation environment;

[0010] During the process of introducing a preset flow rate of CO2 gas into the CO2 storage simulation environment, the pressure data of the CO2 storage simulation environment is acquired, and the flow rate of CO2 gas is controlled and adjusted based on the pressure data.

[0011] Collect and record data throughout the simulation process, and generate data curves and / or data tables.

[0012] In this invention, before filling the CO2 storage simulation environment with a preset flow rate of CO2 gas, a mixture of methane, nitrogen, oxygen and CO2 in a preset mixing ratio can also be filled into the simulation environment to simulate the gas in the closed old goaf of a coal mine.

[0013] According to the present invention, a regional-scale coal mine goaf clustered CO2 sequestration simulation method is provided, wherein the goaf environment includes the goaf coal drop environment, the goaf water-flooded residual coal environment, the residual coal pillar environment, the in-situ stress coal body or the coal body environment with different degrees of disturbance, and the goaf environment is simulated by a closed cavity and the coal and rock medium filled in the closed cavity.

[0014] According to the present invention, a regional-scale coal mine goaf clustered CO2 sequestration simulation method is provided, wherein the connecting environment includes a fault-connected cavity and a permeability-adjustable connecting cavity.

[0015] According to the present invention, a method for simulating clustered CO2 sequestration in coal mine goaf at a regional scale includes, in which the flow rate of CO2 gas is controlled and adjusted based on pressure data, the method comprises:

[0016] When the pressure difference exceeds the pressure balance threshold but is ≤1MPa, adjust the permeability of the connection environment, where the pressure difference is the pressure difference of the adjacent goaf environment components.

[0017] When the pressure difference exceeds 1 MPa or the environmental pressure in the goaf exceeds the safety limit, pressure relief begins and the flow rate of CO2 gas entering the goaf environment is adjusted.

[0018] When the pressure falls below the safe lower limit, begin replenishing the gas supply.

[0019] According to the present invention, a method for simulating clustered CO2 sequestration in coal mine goaf at a regional scale involves controlling and adjusting the flow rate of CO2 gas based on pressure data, while simultaneously recording the correspondence between the permeability adjustment data of the connected environment and pressure changes.

[0020] According to the present invention, a regional-scale coal mine goaf clustered CO2 sequestration simulation method is used to analyze the simulation results of flow distribution, pressure balance stability, CO2 sequestration efficiency, and permeability regulation response speed of the connecting channels based on the pressure and flow data of the entire simulation process.

[0021] According to the present invention, a regional-scale coal mine goaf clustered CO2 sequestration simulation method includes the following initial simulation conditions: the target total CO2 injection flow rate, the flow rate of CO2 distribution ratio in different goaf environments, the pressure balance threshold, the simulation temperature, the simulation period, and the connection environment permeability regulation response threshold.

[0022] The beneficial effects of this invention are as follows:

[0023] (1) Realize regional-scale clustered CO2 storage simulation: By setting the simulation cavity of the goaf as a modular structure, the clustered distribution and geological differences of several goafs can be reproduced, filling the gap that existing technologies cannot simulate regional scale.

[0024] (2) Realize CO2 sequestration simulation in goaf under specific environment: By controlling the goaf environment type simulation cavity unit individually, the sequestration simulation of goaf under different environment types can be reproduced;

[0025] (3) To achieve adjustment and adaptation of CO2 storage environment: Through direct connection of goaf cavity, the goaf area can be expanded, thereby adapting to different regional scale clustered goaf areas with different actual differences.

[0026] (4) Improve the realism of geological correlation simulation: By connecting the structural simulation cavity, the fault characteristics and permeability correlation of the goaf can be reproduced, adapting to different geological scenarios;

[0027] (5) It can carry out flow distribution-pressure balance simulation experiments: The flow distribution mechanism of “geological parameter change + monitoring feedback adjustment” is adopted, the flow control accuracy is ≤±1%, and differentiated flow distribution can be achieved according to the characteristics of each goaf.

[0028] (6) Dynamic control of pressure balance: Through the pressure sensor network and coupled control algorithm, the pressure of each goaf and the pressure difference between cavities are monitored and controlled in real time to avoid overpressure leakage or reservoir damage and improve the safety of sealing.

[0029] (7) Strong adaptability and convenient operation: The modular design of the device allows for flexible adjustment of the number of goaf areas, geological parameters, connection channel types and experimental conditions, adapting to sealing scenarios of different regional scales; the host computer software supports automated control and data visualization, making operation simple and experimental efficiency high.

[0030] (8) Significant engineering value: The simulation results can directly provide a scientific basis for optimizing injection parameters, formulating pressure control strategies, and assessing fault risks in regional-scale CO2 sequestration projects in goaf clusters, thereby reducing engineering risks and promoting the large-scale application of CCUS technology. Attached Figure Description

[0031] Figure 1 The diagram shows a schematic of a regional-scale CO2 sequestration simulation device for coal mine goaf clusters. Detailed Implementation

[0032] In the following description, certain specific details are set forth in order to provide a thorough understanding of various embodiments. However, those skilled in the art will understand that the invention can be practiced without these details. In other instances, well-known structures have not been shown or described in detail to avoid unnecessarily obscuring the description of the embodiments. Unless the context otherwise requires, throughout the specification and appended claims, the word "comprising" should be interpreted in an open-ended, inclusive sense, i.e., as "including but not limited to".

[0033] The technical problems that need to be overcome by the regional-scale coal mine goaf clustered CO2 sequestration simulation device of this invention include:

[0034] (1) How to reproduce the clustered distribution, geological parameter differences and spatial correlation of multiple goaf areas at the regional scale;

[0035] (2) How to achieve dynamic CO2 injection flow distribution based on the characteristics of each goaf area;

[0036] (3) How to regulate the pressure coupling effect during the injection process in multi-gap areas, maintain the overall pressure balance of the region, and avoid overpressure leakage or reservoir damage;

[0037] (4) How to establish a control mechanism for flow distribution and pressure balance to achieve long-term stable simulation of clustered storage system.

[0038] The following is combined Figure 1 The present invention provides an exemplary embodiment of a regional-scale coal mine goaf clustered CO2 sequestration simulation device.

[0039] The regional-scale coal mine goaf clustered CO2 storage simulation device provided in this embodiment of the invention includes: a gas supply system 100, a clustered goaf connection system, and a goaf environment type simulation cavity system 300, wherein the gas supply system 100, the clustered goaf connection system, and the goaf environment type simulation cavity system 300 are interconnected by pipelines.

[0040] In the regional-scale coal mine goaf clustered CO2 sealing simulation device provided in this embodiment of the invention, an insulation layer is also set outside the clustered goaf connection system, the goaf environment type simulation cavity system 300 and the pipeline to control the temperature of the device and thus simulate the formation temperature.

[0041] In the regional-scale coal mine goaf cluster CO2 sequestration simulation device provided in this embodiment of the invention, the gas supply system 100 includes a CO2 gas supply module 101a, a nitrogen gas supply module 101b, a methane gas supply module 101c, and an oxygen gas supply module 101d.

[0042] The CO2 supply module 101a, nitrogen supply module 101b, methane supply module 101c, and oxygen supply module 101d all use storage tanks to store gases. Specifically, the CO2 supply module 101a uses a storage tank to store CO2, the nitrogen supply module 101b uses a storage tank to store nitrogen, the methane supply module 101c uses a storage tank to store methane, and the oxygen supply module 101d uses a storage tank to store oxygen.

[0043] CO2 is injected as the storage gas, methane simulates the residual methane gas in the closed coal mine, and oxygen and nitrogen can be injected individually or in proportion.

[0044] Optionally, in the regional-scale coal mine goaf clustered CO2 sequestration simulation device provided in this embodiment of the invention, the volume of the storage tank is 10~50m³, and the working pressure is 6~30MPa.

[0045] Optionally, a pressure sensor and an emergency shut-off valve are also installed at the outlet of the gas supply system 100 to ensure the safety of the gas source; wherein the accuracy of the pressure sensor is ±0.1MPa.

[0046] Optionally, in the regional-scale coal mine goaf cluster CO2 sequestration simulation device provided in this embodiment of the invention, the gas supply system 100 further includes a gas source stabilization module. The gas source stabilization module includes a booster pump 102, an air compressor 103, a dryer 104, a preheater 105, a pressure reducing valve 106, and a constant pressure and constant speed pump 107. The gas source stabilization module is used to provide a stable, dry, and temperature-controllable gas source.

[0047] Optionally, in the regional-scale coal mine goaf cluster CO2 sequestration simulation device provided in this embodiment of the invention, the maximum outlet pressure of the booster pump 102 is 30 MPa; the dew point of the preheater 105 is -50℃, the temperature control range is 20~100℃, and the temperature control accuracy is ±1℃.

[0048] In the regional-scale coal mine goaf clustered CO2 sealing simulation device provided in this embodiment of the invention, the clustered goaf connection system is composed of several connection structure simulation cavities. Each connection structure simulation cavity is regarded as a separate connection structure. The clustered goaf connection system includes a simulated fault connection module 201 and an adjustable connection channel module 202. The simulated fault connection module 201 and the adjustable connection channel 202 are connected to the goaf environment type simulation cavity system 300 through pipelines.

[0049] The simulated fault connectivity module 201 is essentially a fault simulation cavity, used to simulate the filling medium system of the fault conduction cavity. The corresponding simulated medium is selected for filling based on the actual lithology of the fault in the target area. This includes simulating impermeable faults, permeable faults, and composite faults.

[0050] The fault simulation cavity simulates the fracture zone of coal seams or rock strata near a fault by loading materials. It changes porosity and permeability through unidirectional compressive stress. The internal materials include: using original pre-made coal or rock samples, cut along a pre-angle to form a fracture (the cross-section retains slight roughness or is coated with a small amount of quartz sand (simulating fault gouge or debris) to simulate normal or reverse faults with different dip angles (i.e., pre-made fault planes). Then, tensile or compressive stress is applied by an external triaxial apparatus. Its characteristic is that porosity and permeability are dynamically changed by loading in only one direction.

[0051] The simulated fault connectivity module 201 fills the medium according to the measured fault data, and then can be autonomously adjusted according to the preset medium configuration method.

[0052] Optionally, a seepage-proof fault simulation is performed by filling a clay-bentonite mixture, wherein the mass ratio of clay to bentonite is 3:1, the compaction density is 1.8~2.2 g / cm³, and the permeability can be as low as 1×10⁻¹. 6 ~1×10⁻¹ 5 m².

[0053] Optionally, the permeable fault simulation involves filling a quartz sand-gravel mixture with a gradation coefficient of 1.5 to 3.0, a particle size of 2 to 20 mm, a compaction density of 1.4 to 1.6 g / cm³, and a permeability of 1×10⁻¹³ to 1×10⁻¹² m².

[0054] Optionally, composite fault simulation: a layered filling structure is adopted, with the upper layer being a permeable fault and the lower layer being a permeable fault, to simulate the vertical permeability heterogeneity of the fault.

[0055] Optionally, in the regional-scale coal mine goaf cluster CO2 sealing simulation device provided in this embodiment of the invention, the simulated fault connectivity module 201 uses a closed tank filled with medium to simulate different faults, and a compaction device 201a is set on the top of the tank to control the permeability of the filling medium. Generally, the compaction pressure is negatively correlated with the permeability. For every 1 MPa increase in pressure, the permeability decreases by 1 to 2 orders of magnitude.

[0056] Optionally, in the regional-scale coal mine goaf cluster CO2 sealing simulation device provided in this embodiment of the invention, the compaction device 201a is a pressure plate driven by hydraulic or pneumatic pressure, with a maximum pressure of 50MPa and an adjustment accuracy of ±0.1MPa.

[0057] Optionally, in the regional-scale coal mine goaf clustered CO2 sequestration simulation device provided in this embodiment of the invention, the simulated fault connectivity module 201 further includes multiple pressure sensors and CO2 concentration sensors to monitor the pressure conduction and CO2 seepage characteristics inside the fault in real time.

[0058] Among them, at least two pressure sensors and two CO2 concentration sensors are provided, one pressure sensor and one CO2 concentration sensor are provided at the inlet and one outlet of the simulated fault connection module 201, respectively.

[0059] The adjustable connectivity channel module 202 is used to simulate the connectivity state of different goaf sections. In essence, it simulates the different permeabilities and different connection structures between different goaf sections. The cavity is filled with coal or rock to achieve the simulation effect, which is called the permeability diversity connectivity cavity.

[0060] The permeability-diverse connecting cavities include coal wall simulated connecting cavities, roof and floor rock wall simulated connecting cavities, roadway simulated connecting cavities, and triaxial stress dynamic simulated connecting cavities. The coal wall simulated connecting cavities, roof and floor rock wall simulated connecting cavities, and triaxial stress dynamic simulated connecting cavities require filling materials, while the roadway simulated connecting cavities do not require filling materials.

[0061] Among them, the simulated coal wall connection cavity simulates that there is no direct connection between goaf areas, but rather a weak connection through the residual coal body of the same coal seam with a certain degree of decompression (change in porosity and permeability). The connection is within the same coal seam, and the filling medium and its simulated degree of decompression (porosity and permeability) are static and preset.

[0062] The simulated connection cavity between the top and bottom rock walls is a weak connection between the rock layers through a certain degree of pressure relief (change in porosity and permeability), and the connection is with the adjacent coal seam.

[0063] The simulated tunnel connection cavity is a simulated goaf area directly connected by interconnected tunnels.

[0064] The triaxial stress dynamic simulation connection cavity integrates the coal wall simulation connection cavity and the roof and floor rock wall simulation connection cavity. Through triaxial loading control peripherals, it can control the changes in porosity and permeability during the experiment. It is dynamic and online, which is for research needs and can obtain dynamic and continuous data.

[0065] The connection method of coal wall / roof and floor rock wall under different stress states adopts a closed cavity, and the internal filling material is used to simulate the characteristics of coal wall / roof and floor rock wall between different goafs under real stress state, especially the porosity and permeability state. It can reflect the coal / rock structure under different stress states in coal mine goaf, and further simulate the non-direct connection state between different goafs, which can only be connected by coal walls, roof and floor rock walls or broken and piled coal and rock masses with different stress relief degrees.

[0066] The three-dimensional stress dynamic change connection method is based on the coal wall / roof and floor rock wall connection method under different stress states. It sets up a triaxial loading system to simulate the loading and unloading of the connecting channel under real environmental stress state, so as to realize the dynamic simulation and control of its physical structure, especially pore structure and permeability.

[0067] Optionally, in the regional-scale coal mine goaf clustered CO2 sealing simulation device provided in this embodiment of the invention, any module in the adjustable communication channel module 202 is designed to be detachable and has an inlet pipe and an outlet pipe. Control switches, pressure sensors and flow sensors are installed on the inlet pipe and the outlet pipe.

[0068] In the regional-scale coal mine goaf cluster CO2 sequestration simulation device provided in this embodiment of the invention, the goaf environment type simulation cavity system 300 adopts a sealed cavity to simulate the real geological permeability characteristics and realize dynamic permeability adjustment. Moreover, the sealed cavity adopted by the goaf environment type simulation cavity system 300 is the same as the closed cavity adopted by the coal wall / roof and floor rock wall connection method under different stress states.

[0069] In the regional-scale coal mine goaf clustered CO2 sequestration simulation device provided in this embodiment of the invention, the goaf environment type simulation chamber system 300 simulates the following environments: goaf coal fall environment, goaf water-flooded residual coal environment, residual coal pillar environment, in-situ stress coal body or coal body environment with different degrees of disturbance. Each simulated environment chamber adopts an independent modular chamber structure, is detachable, and has an inlet pipe and an outlet pipe. Control switches, pressure sensors, and flow sensors are installed on the inlet pipe and the outlet pipe.

[0070] The simulated environmental cavities of different types are all connected to the simulated fault connectivity module 201 and the adjustable connectivity channel module 202 through pipelines, thereby reproducing the spatial distribution and correlation of regional-scale goaf areas.

[0071] in:

[0072] Coal-bearing environment cavity in goaf: The cavity can be filled with simulated coal and rock media to a certain height according to the simulation settings. The particle size and stacking height of the coal and rock media are adjustable. Samples can be pre-prepared by manual or mechanical crushing.

[0073] The goaf water-flooded coal seam environment chamber: The chamber can be filled with simulated coal and rock media to a certain height, and water can be added, depending on the simulation requirements. The simulated coal and rock media can be pre-prepared raw coal or briquettes, or granular coal. The particle size and stacking height are adjustable. Samples can be pre-prepared through manual or mechanical crushing. Real mine water can also be used. The amount of water depends on the simulation requirements; it can wet the coal seam, overflow the coal seam to a set height, or expose part of the coal, simulating different flooding states of the coal seam by mine water in a closed coal mine.

[0074] The residual coal pillar environmental cavity: The cavity can be filled with simulated coal and rock media to a certain height, with or without water. The simulated coal and rock media can be pre-prepared raw coal or briquettes, and the water can be real mine water. The amount of water can be adjusted to a set height according to the simulation requirements to simulate different submersion states of the coal pillar under mine water in a closed coal mine, or the state without water. An external load needs to be applied to the top of the device; the load can be adjusted according to the simulation requirements to simulate the state of a residual coal pillar in a closed coal mine.

[0075] In-situ stress-induced coal seam or coal seam environment cavity with varying degrees of disturbance: Pre-prepared raw coal or briquettes are placed inside the cavity. This simulates the stress bearing state of coal seams at different locations after different abandonment times following mine closure. Stress bearing is controlled by setting true triaxial loading peripherals; triaxial stress settings are applied and unloaded according to simulated geological conditions to reproduce the stress conditions and coal seam structural damage after mining.

[0076] For the in-situ stress / disturbance coal body simulation environment chamber: a triaxial loading system is used in the rectangular inner wall rubber-sealed chamber to achieve dynamic control of permeability; axial / circumferential stress is applied through a hydraulic servo system to simulate the pressure changes at underground depth—the pore and fracture structure of the real rock core is consistent with the natural rock strata. The stress changes will cause the fractures to open and close and the pores to compress, thereby dynamically changing the permeability, thus reproducing the "stress-permeability" coupling relationship under real geological conditions.

[0077] All the cavity structures described above adopt a detachable modular structure, with both ends sealed to other pipelines or cavity structures via flanges. Fluororubber sealing rings are installed inside the flanges to adapt to the high temperature and high pressure environment of the system. The purpose is to simulate a goaf with a larger area by directly connecting the goaf cavity.

[0078] Each cavity structure and pipe has a detachable interface. Combined with the connection mode unit, it can realize the simulation of a closed underground coal mine environment or several identical / different simulation environments, either individually or in a cluster.

[0079] Optionally, the regional-scale coal mine goaf cluster CO2 sequestration simulation device provided in this embodiment of the invention also includes a control terminal 400. The control terminal 400 includes, but is not limited to, a mobile terminal (such as a mobile phone or a wearable watch), a computer, and software installed on the mobile terminal (such as a mobile phone or a wearable watch) or the computer.

[0080] Based on this, the triaxial loading system is connected to the control terminal 400. Axial and circumferential stresses can be applied according to the pressure difference data between the cavities, thereby changing the permeability and achieving dynamic adaptation of pressure balance. The pressure difference data between the cavities is obtained by a pressure sensor and acquired through the control terminal 400.

[0081] Optionally, in the regional-scale coal mine goaf clustered CO2 storage simulation device provided in this embodiment of the invention, the gas supply system 100, the clustered goaf connection system, and the goaf environment type simulation cavity system 300 are connected by a main pipeline, and the gas supply system 100, the clustered goaf connection system, and the goaf environment type simulation cavity system 300 are each connected by branch pipelines within their respective systems.

[0082] Optionally, the diameter of the main pipeline is DN50~DN100, and the diameter of the branch pipeline is DN10~DN30.

[0083] Optionally, the simulated different types of environmental cavities are all connected in series with electromagnetic flow meters and electric regulating valves. The electromagnetic flow meters collect the flow rate data and feed it back to the control terminal 400, and generate a control signal for the electric regulating valve to achieve closed-loop flow control.

[0084] Optionally, in the regional-scale coal mine goaf cluster CO2 sequestration simulation device provided in this embodiment of the invention, 3 to 5 pressure sensors are arranged inside each simulated different type of environmental cavity to monitor the pressure distribution in real time.

[0085] Optionally, the regional-scale coal mine goaf clustered CO2 sealing simulation device provided in this embodiment of the invention is also equipped with a centralized pressure control system, including a pressure relief device, a gas replenishment device and a pressure coupling control algorithm. Based on the pressure data and pressure difference threshold of each simulated environmental cavity of different types, the system dynamically initiates pressure relief or gas replenishment operations to maintain the overall pressure balance of the region.

[0086] In the regional-scale coal mine goaf cluster CO2 sealing simulation device provided in this embodiment of the invention, the centralized pressure control system, the adjustable connecting channel module 202, the pipeline, the electromagnetic flowmeter and the electric regulating valve are linked. When the pressure exceeds the threshold, the pressure is first balanced by adjusting the permeability of the connecting channel. If the permeability adjustment cannot meet the requirements, the injection flow rate of the corresponding goaf is then adjusted to achieve multi-level coupled control.

[0087] In summary, the data collected in the regional-scale coal mine goaf clustered CO2 sealing simulation device provided in this embodiment of the invention include CO2 injection flow rate in the environmental chambers, pressure in each environmental chamber, pressure difference between each environmental chamber, CO2 concentration in each chamber within the system, temperature in each chamber within the system, compaction pressure of the simulated fault module, applied stress, and adjustable permeability adjustment value of the connected channel.

[0088] Furthermore, embodiments of the present invention also provide a regional-scale coal mine goaf clustered CO2 sequestration simulation method, corresponding to the aforementioned regional-scale coal mine goaf clustered CO2 sequestration simulation device.

[0089] Embodiments of the present invention also provide a method for simulating clustered CO2 sequestration in coal mine goafs at a regional scale, comprising:

[0090] Step 101: Based on the actual distribution characteristics of regional-scale goaf clusters, construct a regional-scale coal mine goaf cluster CO2 sequestration simulation device.

[0091] Step 101 includes steps A1 to A4:

[0092] Step A1: Based on the actual distribution characteristics of goaf clusters at the regional scale, assemble a goaf environment type simulation cavity system:

[0093] If a fault exists in the target area, select the corresponding type of simulated environmental cavity;

[0094] If the target area has other connectivity methods, you can choose to simulate other connectivity units;

[0095] Step A2: Add and adjust the geological parameters of the simulation medium and preset conditions of each environmental type simulation cavity and goaf connecting cavity, including permeability, porosity and volume. Adjust them through preset or external loading and unloading devices to reproduce the geological conditions of the target area.

[0096] Step A3: Check the device's sealing performance by conducting an airtightness test. Maintain the pressure at 0.5 MPa, and ensure the pressure drop is ≤0.01 MPa after 30 minutes. Calibrate sensors for flow rate, pressure, temperature, CO2 concentration, and the compaction pressure sensor and loading / unloading stress sensor of the simulated fault module.

[0097] Step A4: Set the experimental parameters through the control terminal 400: target total injection flow rate, flow distribution ratio of each goaf, pressure balance threshold, experimental temperature, experimental cycle, permeability adjustment range and response threshold of the connected simulation unit, and the flow distribution ratio of each goaf is calculated based on geological parameters and goaf size.

[0098] Step 102: Allocate and control CO2 flow rate.

[0099] Step 102 includes steps B1 to B4:

[0100] Step B1: Start the gas supply system 100, and adjust the booster pump 102, dryer 104 and preheater 105 to make CO2 reach the preset temperature and preset pressure;

[0101] Step B2: Inject CO2 into the simulated environmental cavity according to the preset flow distribution ratio;

[0102] Step B3: Collect real-time flow data of each branch pipe connected to the simulated environmental cavity;

[0103] Step B4: Based on the actual flow data, the flow distribution algorithm is used to compare the deviation between the actual flow and the target flow, and the opening of the electric regulating valve is dynamically adjusted to ensure that the flow in each goaf reaches the preset value, with a flow control accuracy of ≤±1%. The flow distribution algorithm is based on PID control, with a proportional coefficient of 0.1~1.0, an integral time of 0.5~5s, and a derivative time of 0.1~2s.

[0104] Step 103: Balance and regulate pressure.

[0105] Step 103 includes steps C1 to C3:

[0106] Step C1: Pressure sensors collect pressure data of each goaf simulation cavity in the goaf environment type simulation cavity system 300 in real time, pressure difference sensors collect pressure difference data of the connecting channels between cavities, and data acquisition instruments upload the data to the control terminal 400.

[0107] Step C2: The control terminal 400 uses a pressure balance control algorithm to determine whether the pressure in each chamber is within a safe range and whether the pressure difference between chambers exceeds a preset threshold.

[0108] If the pressure difference does not exceed the threshold, maintain the current permeability and injection flow rate of the connecting channel;

[0109] If the pressure difference exceeds the threshold or the pressure in a certain cavity exceeds the safety limit, the pressure relief device is activated to slowly release the CO2 in that cavity, while the injection flow rate of the corresponding goaf is adjusted until the pressure or pressure difference returns to the safe range.

[0110] If the pressure in a certain chamber is lower than the safety limit, activate the gas replenishment device;

[0111] Step C3: During the pressure regulation process, the control terminal 400 records the correspondence between the permeability regulation data of the connecting channel and the pressure changes.

[0112] Step 104: Data Collection and Analysis.

[0113] Step 104 includes steps D1 to D3:

[0114] Step D1: The data acquisition instrument collects data such as flow rate, pressure, temperature, CO2 concentration, simulated fault compaction pressure, and permeability adjustment value of the connecting channel according to the preset sampling frequency, and stores them in the database of the control terminal 400;

[0115] Step D2: Control terminal 400 to draw data curves in real time and analyze the flow distribution size, pressure balance stability, CO2 storage efficiency, and response speed of permeability adjustment in connecting channels;

[0116] Step D3: After the experiment, generate an experimental report, including parameter settings, data recording tables, curve analysis charts, and optimization suggestions, including the permeability optimization range of connected channels and the flow distribution ratio adjustment scheme, to provide a reference for actual engineering.

[0117] Example 1

[0118] See Figure 1 The device in this embodiment simulates the clustered CO2 from five goaf areas in a coal mine.

[0119] Among them, the five goaf areas contain two seepage-conducting faults and three areas where normal rock strata are connected.

[0120] Among them, in the goaf environment type simulation cavity system 300, the permeability of the five goaf simulation cavities are 5×10⁻¹³m², 3×10⁻¹³m², 8×10⁻¹³m², 4×10⁻¹³m², and 6×10⁻¹³m², respectively, and the porosity is 25% for all of them.

[0121] The cavity of the simulated fault connectivity module 201 is filled with a quartz sand-gravel mixture (particle size 5-15mm), and the compaction pressure is set to 3MPa, corresponding to a permeability of 5×10⁻¹³m².

[0122] The adjustable connecting channel module 202 is filled with 1mm of quartz sand, corresponding to a permeability of 1×10⁻¹³m².

[0123] Experimental parameter settings:

[0124] The target total injection flow rate is 2 m³ / h, the flow rate distribution ratio according to the permeability ratio is 5:3:8:4:6, the pressure balance threshold is 0.3 MPa, the experimental temperature is 40℃, the experimental period is 7 days, and the permeability adjustment response threshold of the connecting channel is 0.3 MPa, that is, automatic adjustment when the pressure difference exceeds 0.3 MPa.

[0125] Traffic distribution control:

[0126] Start the gas supply system 100, adjust the booster pump 102 to make the outlet pressure reach 5MPa, the dew point of the dryer 104 drops to -50℃, and the preheater 105 heats the CO2 temperature to 40℃.

[0127] Based on the flow distribution ratio (5:3:8:4:6), the control terminal 400 calculates the target flow rates for each branch pipeline as 0.33 m³ / h, 0.20 m³ / h, 0.53 m³ / h, 0.27 m³ / h, and 0.47 m³ / h, respectively, and sends an initial opening command to the electric regulating valve to start CO2 injection.

[0128] The electromagnetic flowmeter collects flow data from each branch in real time and feeds it back to the control terminal 400. When the actual flow rate of a branch deviates from the target flow rate by more than ±1%, the control terminal 400 adjusts the opening of the electric regulating valve through a PID algorithm until the flow rate stabilizes at the target value.

[0129] Pressure balance regulation:

[0130] The pressure sensor collects pressure data from each cavity every 500ms, and the differential pressure sensor collects pressure difference data from the connecting channels between the cavities.

[0131] On the third day of the experiment, the pressure difference between the third chamber and the second chamber was monitored to reach 0.4 MPa, exceeding the threshold of 0.3 MPa. The third chamber and the second chamber were connected through the adjustable communication channel 202.

[0132] The control terminal 400 activates the stress loading and unloading device of the adjustable connecting channel 202, thereby increasing the permeability of the connecting channel from 1×10⁻¹³m² to 1.5×10⁻¹³m².

[0133] Continuously monitor the pressure difference data. After 10 minutes, the pressure difference drops to 0.28 MPa (within the threshold), maintaining the current permeability.

[0134] On the fifth day of the experiment, the pressure difference between the fourth and fifth chambers reached 0.6 MPa. The fourth and fifth chambers were connected by the simulated fault connection module 201. The control terminal 400 controlled the compaction device 201a to reduce the compaction pressure by 0.5 MPa (from 3 MPa to 2.5 MPa). The simulated fault permeability increased from 5 × 10⁻¹³ m² to 7 × 10⁻¹³ m². After 30 minutes, the pressure difference returned to 0.25 MPa.

[0135] Data collection and analysis:

[0136] The data acquisition instrument collects data such as flow rate, pressure, temperature, CO2 concentration, simulated fault compaction pressure, and displacement of connecting channels at a frequency of 5Hz, and stores them in the database of the control terminal 400.

[0137] The control terminal 400 plotted the curves of each parameter changing over time. The analysis showed that the flow distribution accuracy was stable within ±0.8%, the pressure balance accuracy was stable within ±0.008MPa, the permeability adjustment response time of the connecting channel was ≤30min, and the CO2 storage efficiency reached 85%.

[0138] After the experiment, an experimental report was generated, and optimization suggestions were made: the actual injection flow rate of the third goaf was adjusted to 0.45-0.50 m³ / h, and the initial compaction pressure of the simulated fault module was set to 2.8 MPa, which can further improve pressure stability.

[0139] Example Effect Verification

[0140] This embodiment verifies the effectiveness of the invention through simulation experiments:

[0141] Flow distribution accuracy: The deviation between the actual flow and the target flow in each goaf is ≤ ±0.8%, which meets the requirements for accurate flow distribution in regional-scale clustered storage.

[0142] Pressure balancing effect: The pressure in each goaf is stable within a safe range (0-7MPa), the pressure difference between cavities is ≤0.3MPa, and there is no risk of overpressure leakage;

[0143] Geological correlation simulation results: The permeability adjustment range of the simulated fault module covers 5×10⁻¹ 4 ~1×10⁻¹²m², with adjustable permeability adjustment accuracy of ±5% for the connected channels, which can truly reproduce the characteristics of goaf correlation under different geological conditions;

[0144] System stability: During the experimental period (7 days), the device operated continuously and stably, the connection channel adjustment responded promptly, there was no fault-free shutdown, and the data acquisition integrity rate was 100%.

[0145] Engineering reference value: The simulation results are highly consistent with the geological conditions and storage requirements of the target area, providing a reliable basis for optimizing injection parameters and assessing fault risks in actual engineering projects.

[0146] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it.

Claims

1. A method for simulating clustered CO2 sequestration in coal mine goaf at a regional scale, characterized in that, include: Based on the actual distribution characteristics of regional-scale goaf clusters, a regional-scale coal mine goaf cluster CO2 sequestration simulation environment was constructed, and initial simulation conditions were set. The CO2 sequestration simulation environment includes a goaf environment and a connecting environment, with the connecting environment connecting the goaf environments. A preset flow rate of CO2 gas is introduced into the CO2 sequestration simulation environment; During the process of introducing a preset flow rate of CO2 gas into the CO2 storage simulation environment, the pressure data of the CO2 storage simulation environment is acquired, and the flow rate of CO2 gas is controlled and adjusted based on the pressure data. Collect and record data throughout the simulation process, and generate data curves and / or data tables.

2. The method for simulating clustered CO2 sequestration in regional-scale coal mine goaf areas according to claim 1, characterized in that, The goaf environment includes the goaf coal drop environment, the goaf water-flooded residual coal environment, the residual coal pillar environment, the in-situ stress coal body or the coal body environment with different degrees of disturbance. The goaf environment is simulated by a closed cavity and the coal and rock medium filled in the closed cavity.

3. The method for simulating clustered CO2 sequestration in regional-scale coal mine goaf areas according to claim 1, characterized in that, The connection environment includes a fault-connected cavity and a permeability-adjustable connecting cavity.

4. The method for simulating clustered CO2 sequestration in regional-scale coal mine goaf areas according to claim 1, characterized in that, The method of controlling and adjusting the flow rate of CO2 gas based on pressure data includes: When the pressure difference exceeds the pressure balance threshold but is ≤1MPa, adjust the permeability of the connection environment, where the pressure difference is the pressure difference of the adjacent goaf environment components. When the pressure difference exceeds 1 MPa or the environmental pressure in the goaf exceeds the safety limit, pressure relief begins and the flow rate of CO2 gas entering the goaf environment is adjusted. When the pressure falls below the safe lower limit, begin replenishing the gas supply.

5. The method for simulating clustered CO2 sequestration in regional-scale coal mine goaf areas according to claim 4, characterized in that, The flow rate of CO2 gas is controlled and adjusted based on pressure data, while the correlation between the permeability adjustment data of the connected environment and pressure changes is recorded.

6. The method for simulating clustered CO2 sequestration in regional-scale coal mine goaf areas according to claim 1, characterized in that, Based on the pressure and flow data throughout the simulation process, simulation results were obtained regarding flow distribution magnitude, pressure balance stability, CO2 storage efficiency, and response speed of permeability regulation in connecting channels.

7. The method for simulating clustered CO2 sequestration in regional-scale coal mine goaf areas according to claim 1, characterized in that, The initial simulation conditions include: the target total CO2 injection flow rate, the flow rate of CO2 distribution ratio in different goaf environments, the pressure balance threshold, the simulation temperature, the simulation period, and the connection environment permeability regulation response threshold.

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