Comprehensive testing device and method suitable for CO2 geological storage cover layer valve pressure and breakthrough pressure

Abstract

The invention discloses a comprehensive testing device and method suitable for CO2 geological storage cover layer valve pressure and breakthrough pressure. The device comprises a stress application module, an environment simulation module, a fluid control module, a sensing monitoring module, an auxiliary execution module and a control and display module. The environment simulation module constructs a stratum in-situ temperature and pressure environment through a reaction kettle with temperature controlled by a resistance wire and oil-filled confining pressure. The stress applying module reproduces a mining-induced stress path through a mining-induced stress servo press; the fluid control module realizes water-CO2 multiphase flow regulation and control by virtue of a double-phase injection pump and an external tempered glass sleeve, and is matched with a gas-liquid separation structure to guarantee data accuracy; the sensing monitoring module synchronously collects temperature, pressure and strain data. The testing method comprises the steps of sample loading, environment simulation, stress application, hydraulic seepage simulation, valve pressure measurement, breakthrough pressure measurement and sample unloading maintenance. According to the method, the environment reproduction degree and the test precision are improved, the test period is shortened, complex lithology and load scenes are adapted, and reliable support is provided for cover layer sealing capacity evaluation.

Description

Technical Field

[0001] This invention relates to the field of CO2 geological storage technology, and in particular to a comprehensive testing device and method for valve pressure and breakthrough pressure of CO2 geological storage caprock. Background Technology

[0002] Driven by global carbon emission reduction goals, CO2 geological storage technology has become a key approach. Deep mining spaces, such as abandoned mine goafs, possess ample storage capacity and represent a highly promising carbon storage medium. The ability of the caprock to seal CO2 is crucial to the safety of CO2 storage projects, and its valve pressure and breakthrough pressure are key indicators for assessing this capability, requiring precise testing. However, current testing devices for CO2 geological storage caprock valve pressure and breakthrough pressure have significant shortcomings in terms of simulation realism, functional completeness, and testing reliability, making it difficult to meet practical engineering needs.

[0003] Existing equipment has weak in-situ formation environment simulation capabilities, poor reactor sealing, weak resistance to CO2 corrosion, low precision and lack of coordination in temperature and pressure control, and rigid clamping of rock samples easily leads to stress concentration, making it impossible to reproduce the actual occurrence conditions and causing distortion in the testing of rock sample mechanical properties. At the same time, simulation of mining-induced stress disturbance is lacking. Most equipment can only apply constant axial pressure and cannot reproduce dynamic stress changes in the field. Even some equipment with stress control functions suffer from unreasonable pressure transmission structure design, resulting in uneven pressure transmission and low control precision, making it difficult to accurately characterize the mechanical response of the caprock after mining disturbance.

[0004] In the treatment of multiphase fluids, existing devices have significant shortcomings. Most use single-medium injection, which cannot simulate the multiphase coexistence environment of water-CO2 and the CO2 phase transition. Incomplete gas-liquid separation interferes with pressure monitoring, and there is no means to visualize the fluid state, which restricts the understanding of the caprock sealing mechanism. In addition, valve pressure and breakthrough pressure need to be measured by separate devices, resulting in long test cycles, poor parameter correlation, and significant error superposition. The devices have a narrow range of applications, which can only test single lithologies. Sample loading is cumbersome, and the control and data acquisition systems are scattered, making operation inconvenient and prone to errors.

[0005] Based on the existing technologies mentioned above, there is an urgent need to design a comprehensive testing device that can accurately construct the in-situ temperature and pressure environment of the formation, reproduce the stress path disturbance caused by mining, realize the visualized control and efficient separation of water-CO2 multiphase fluid, and uniformly measure the caprock valve pressure and breakthrough pressure in the same test process, while being adaptable to complex lithology and easy to operate. Summary of the Invention

[0006] To address the aforementioned technical problems, this invention provides a comprehensive testing device and method for the valve pressure and breakthrough pressure of the caprock in CO2 geological storage. This device can accurately construct the in-situ temperature and pressure environment of the formation, reproduce the stress path disturbance caused by mining, realize the visualized control and efficient separation of water-CO2 multiphase fluids, and uniformly measure the caprock valve pressure and breakthrough pressure in the same test process.

[0007] The technical solution adopted by the present invention to solve its technical problem is: a comprehensive testing device for valve pressure and breakthrough pressure of CO2 geological sealing caprock, including a stress application module, an environmental simulation module, a fluid control module, a sensing and monitoring module and an auxiliary execution module;

[0008] The environmental simulation module is used to construct a temperature and pressure environment that matches the in-situ formation, providing an experimental basis for rock samples that conforms to actual occurrence conditions. The environmental simulation module includes a reaction vessel, in which the rock sample is installed. The reaction vessel is equipped with a resistance wire to regulate the internal temperature. The reaction vessel is filled with oil to form a confining pressure environment. Together with the temperature control of the resistance wire, the in-situ temperature and pressure occurrence environment of the rock sample is simulated.

[0009] The reaction vessel is equipped with a rock sample fixing assembly, which includes a rubber sleeve, a water-permeable gasket, and an air-permeable gasket. The rubber sleeve is made of high-temperature resistant rubber and is used to wrap the rock sample to ensure uniform application of confining pressure. The water-permeable gasket and the air-permeable gasket are respectively set at the top and bottom of the rock sample.

[0010] The stress application module is used to apply axial pressure to the caprock sample and control the stress-strain state of the sample to simulate the stress path disturbance during mining. The stress application module is located at the top of the reactor and includes a mining stress servo press, a pressure plate, and a pressure probe. The mining stress servo press is driven and connected to the pressure plate. One end of the pressure probe is connected to the pressure plate, and the other end is used to abut against the rock sample. Through the force transmission between the pressure plate and the pressure probe, the axial pressure is applied to the rock sample and the stress-strain is controlled.

[0011] The fluid control module is used to realize the injection, seepage and state regulation of multiphase fluids of water and CO2, and can simulate the seepage process of multiphase CO2 in rock samples. The fluid control module includes an external tempered glass sleeve, a fluid pressure controller, a fluid piston, a two-phase injection pump, an oil inlet pump, an oil outlet pump, an air collection pump, a water collection pump, an air outlet pipe and a water outlet pipe.

[0012] The outer tempered glass sleeve is located at the bottom of the rock sample and is sealed against the bottom of the reactor. This sleeve receives fluid and presses it into the rock sample, and provides a visual representation of the fluid state. The fluid pressure controller is located at the bottom of the outer tempered glass sleeve and is connected to a fluid piston drive, used to push the piston to pump the fluid from the outer tempered glass sleeve into the rock sample. The two-phase injection pump is used to pump water or CO2 into the outer tempered glass sleeve. The oil inlet pump is used to fill the reactor with oil to apply confining pressure, and the oil outlet pump is used to pump out the oil from the reactor. The gas collection pump is connected to the rock sample via an outlet pipe to collect CO2 that has permeated through the rock sample, and the water collection pump is connected to the rock sample via a water outlet pipe to collect water that has permeated through the rock sample. The outer tempered glass sleeve has a two-phase outlet to discharge any remaining fluid that did not permeate into the rock sample after the test.

[0013] The sensing and monitoring module is used to collect temperature, pressure, and strain data of rock samples and fluids in real time.

[0014] The auxiliary execution module is used to complete rock sample loading and unloading, fluid collection and discharge, and equipment operation assistance. The modules work together to achieve unified measurement of caprock valve pressure and breakthrough pressure.

[0015] Furthermore, a lifting guide rail mechanism is provided between the fluid pressure control machine and the mining stress servo press. The reaction vessel can be vertically lifted and lowered via the lifting guide rail mechanism to accommodate rock sample loading and unloading. The lifting guide rail mechanism includes four screws and a drive motor. The screws are located at the four corners of the mining stress servo press, and both ends of the screws are rotatably connected to the outer casing of the mining stress servo press and the fluid pressure control machine. The drive motor is used to drive the screws to rotate. Four connecting rods corresponding to each screw are fixed to the outside of the reaction vessel. A nut is fixed to the end of each connecting rod away from the reaction vessel. The nut is sleeved on the corresponding screw and threadedly connected to the screw.

[0016] Furthermore, the air outlet pipe is equipped with a sponge to absorb the water that has permeated through the rock sample; the water outlet pipe is filled with activated carbon to separate the CO2 that has infiltrated during the permeation process.

[0017] Furthermore, the permeable pad is designed with three structures: a cylindrical structure, a combination of a cylinder and a cone, or a combination of a cylinder and an irregular shape, which respectively represent continuous uniform load, point load, and non-uniform load.

[0018] Furthermore, the pressure probe is provided with a flow channel, and one end of the air outlet pipe and water outlet pipe passes through the pressure steel plate and is connected to the flow channel.

[0019] Furthermore, the outer contour dimensions of the pressure steel plate are adapted to the size of the top opening of the reactor, which can seal the top opening of the reactor, and a sealing ring is provided on the outer ring of the pressure steel plate.

[0020] Furthermore, the sensing and monitoring module includes a temperature and pressure sensor, a fluid temperature and pressure sensor, a radial strain sensor, and an axial strain sensor. The temperature and pressure sensor is installed inside the reactor to collect temperature and pressure data within the reactor. The fluid temperature and pressure sensor is installed inside an external tempered glass sleeve to collect temperature and pressure data of the fluid inside the sleeve. The radial strain sensor is installed outside the rock sample to collect the radial strain of the rock sample. Two axial strain sensors are provided and symmetrically arranged on both sides of the rock sample. One end of each axial strain sensor is connected to a pressure probe, and the other end is connected to a breathable gasket to collect the axial strain of the rock sample.

[0021] Furthermore, it also includes a control and display module, which includes a pressure control interface, a pump pressure control interface, and a data acquisition and display interface; the pressure control interface is used to adjust the application method and threshold of mining stress; the pump pressure control interface is used to regulate the pressure of the two-phase injection pump, oil inlet pump, air collection pump, water collection pump, and oil outlet pump; the data acquisition and display interface is used to receive and display all data acquired by the sensing and monitoring module.

[0022] This invention also provides a comprehensive testing method for the valve pressure and breakthrough pressure of CO2 geological storage caprock, using the aforementioned comprehensive testing device suitable for the valve pressure and breakthrough pressure of CO2 geological storage caprock, including the following steps:

[0023] S1: Sample loading: Check the connectivity of each pump and pipeline, load the rock sample into the rubber sleeve and place it on the venting gasket, install the radial strain sensor and axial strain sensor, assemble the water-permeable gasket and pressure probe, close the operating door and lower the reactor to match the venting gasket.

[0024] S2: Environmental simulation: The target temperature is heated to and stabilized by resistance wire in the reactor, and oil is injected into the reactor by oil pump to make the oil temperature reach the specified temperature for the test, thus constructing an in-situ temperature and pressure environment for the rock sample;

[0025] S3: Stress application: Axial pressure is applied to the rock sample by a stress servo press, and axial and radial strain data of the rock sample are collected simultaneously by axial strain sensors and radial strain sensors to determine the stress state and related mechanical properties of the rock at this stage.

[0026] S4: Hydraulic seepage simulation: Water is injected into the outer tempered glass sleeve through a two-phase injection pump. The pump pressure is controlled to allow the water to seep into the rock sample until the water flows into the water collection pump at a constant rate. Then, the fluid piston is used to force all the water in the outer tempered glass sleeve into the rock sample. After completion, the fluid of the two-phase injection pump is replaced.

[0027] S5: Valve pressure measurement: CO2 is injected into the external tempered glass sleeve through a two-phase injection pump. After the valve is closed, the CO2 is compressed to a supercritical state by a fluid piston. The fluid piston is continued to be pushed until the pressure drops. The pressure value of the fluid temperature and pressure sensor at this time is recorded, which is the valve pressure.

[0028] S6: Breakthrough pressure measurement: Keep the fluid piston position fixed, continue to push CO2 into the external tempered glass sleeve through the two-phase injection pump, and at the same time turn on the gas collection pump. After the pressure inside the gas collection pump and the pressure of the fluid temperature and pressure sensor are stable, record the pressure value of the fluid temperature and pressure sensor, which is the breakthrough pressure.

[0029] S7: Sample unloading and maintenance: Turn off the two-phase injection pump, discharge the remaining fluid through the two-phase outlet, pump out the oil in the reactor through the oil pump, turn off the resistance wire and wait for the temperature to cool to room temperature, remove the sensor and lift the reactor to take out the rock sample.

[0030] The beneficial effects of this invention are:

[0031] 1. The device of this invention can construct a temperature and pressure environment that matches the formation in situ through the synergistic effect of resistance wire temperature control and oil-filled confining pressure in the reactor. The reactor is made of high-strength nickel-plated steel to resist CO2 corrosion, solving the problems of poor sealing and lagging temperature and pressure control in traditional devices. In the rock sample fixing assembly, the high-temperature resistant rubber sleeve ensures uniform application of confining pressure, and the special design of the water-permeable gasket and air-permeable gasket adapts to different load simulations, effectively avoiding stress concentration and greatly improving the reproducibility of the rock sample occurrence environment, providing a test basis that fits the actual field conditions for subsequent pressure testing.

[0032] 2. The stress application module of this invention, through the synergy of a mining-induced stress servo press, a pressure plate, and a pressure probe, can precisely control the axial pressure application method and threshold, and reproduce the mining-induced stress path disturbance under different mining methods. The pressure probe is made of high-strength corrosion-resistant material, and the pressure plate is compatible with the opening of the reaction vessel and equipped with a sealing ring to ensure uniform and stable pressure transmission, avoid premature damage to rock samples, and accurately capture the stress-strain response of the overburden rock mass after mining disturbance, providing a reliable mechanical state basis for pressure parameter determination.

[0033] 3. The fluid control module of this invention achieves selective injection of water and CO2 through a two-phase injection pump. The external tempered glass sleeve allows visualization of the fluid state, and the fluid piston precisely controls the fluid seepage. The gas outlet pipe has a built-in sponge for dehydration, and the water outlet pipe is filled with activated carbon to separate CO2, solving the problem of incomplete gas-liquid separation in traditional methods. The fluid temperature and pressure sensor monitors the fluid state in real time, ensuring that the multiphase fluid seepage simulation closely matches the actual situation, significantly reducing the error of gas-liquid mixing in pressure measurement, and improving the accuracy of valve pressure and breakthrough pressure testing.

[0034] 4. The sensing and monitoring module of this invention integrates temperature and pressure sensors, fluid temperature and pressure sensors, and radial and axial strain sensors to achieve synchronous and high-precision acquisition of rock sample temperature and pressure, strain, and fluid parameters. The same device can complete valve pressure and breakthrough pressure measurements in a continuous test process without changing equipment or repeating sample loading, shortening the test cycle. At the same time, it ensures that the two core pressure parameters are based on the same rock sample stress history and environmental conditions, resulting in stronger parameter correlation and avoiding the error superposition and data disconnect caused by traditional separate device testing.

[0035] 5. The permeable pad of this invention is designed with three structures to simulate continuous uniform, point and non-uniform loads, adapting to different mining load scenarios. The device can test single lithology and complex lithological caprocks such as sand-mud interlayers. The lifting guide rail mechanism realizes the vertical lifting of the reactor, the quick-opening operating door and rock sample positioning structure simplify the sample loading process, and the control and display module integrates pressure regulation, pump pressure control and data acquisition functions, which can be completed by a single person, reducing human operation error. Attached Figure Description

[0036] Figure 1 This is a schematic diagram of the overall structure of the present invention.

[0037] Figure 2 This is an isometric view of the structure of the present invention.

[0038] Figure 3 This is a partial cross-sectional view of the present invention.

[0039] Figure 4 yes Figure 3 A magnified view of part A in the middle.

[0040] Figure 5 This is a partial structural diagram used in this invention to illustrate the internal structure of the reactor.

[0041] In the diagram: 1. Reactor; 11. Rubber sleeve; 12. Water-permeable gasket; 13. Air-permeable gasket; 14. Operating door; 2. Dynamic stress servo press; 21. Pressurized steel plate; 211. Oil inlet; 212. Oil outlet; 22. Pressure probe; 221. Flow channel; 3. Fluid pressure controller; 31. Fluid piston; 32. External tempered glass sleeve; 321. Fixed baffle; 322. Two-phase outlet; 33. Air outlet pipe; 34. Water outlet pipe; 35. Two-phase injection pump; 36. Oil outlet pump; 37. Oil inlet pump; 38. Air collection pump; 39. Water collection pump; 4. Lifting guide rail mechanism; 41. Screw; 42. Connecting rod; 43. Nut; 5. Temperature and pressure sensor; 6. Fluid temperature and pressure sensor; 7. Radial strain sensor; 8. Axial strain sensor. Detailed Implementation

[0042] The present invention will now be described in further detail with reference to the accompanying drawings. These drawings are simplified schematic diagrams, illustrating only the basic structure of the invention, and therefore only show the components relevant to the invention.

[0043] This invention discloses a comprehensive testing device for valve pressure and breakthrough pressure in CO2 geological sealing caprock.

[0044] Reference Figure 1 and Figure 2 This integrated testing device includes an environmental simulation module, a stress application module, a fluid control module, a sensing and monitoring module, and an auxiliary execution module. The stress application module applies axial pressure to the caprock sample and controls its stress-strain state to simulate mining-induced stress path disturbances, overcoming the technical deficiency of traditional devices in being unable to reproduce deep mining-induced stress disturbances. The environmental simulation module constructs a temperature and pressure environment that matches the in-situ formation, providing a test basis for the rock sample that conforms to actual occurrence conditions, thus overcoming the problem of single environmental simulation in traditional devices. The fluid control module realizes the injection, seepage, and state control of multiphase fluids such as water and CO2, simulating the seepage process of multiphase CO2 in the rock sample. The sensing and monitoring module collects real-time temperature, pressure, and strain data of the rock sample and fluids, achieving precise quantification of the test process. The auxiliary execution module completes the loading and unloading of rock samples, fluid collection and discharge, and equipment operation assistance. All modules work together to achieve unified measurement of caprock valve pressure and breakthrough pressure, improving the consistency between test results and actual field conditions, and solving the core problem of large experimental deviations in traditional evaluation devices.

[0045] Reference Figure 2 and Figure 3 The environmental simulation module includes a reactor 1; the rock sample is installed inside the reactor 1, which is made of high-strength nickel-plated steel to resist CO2 corrosion. The reactor 1 is equipped with a resistance wire inside to regulate the temperature, and the temperature control accuracy can reach ±0.5℃, which solves the problems of poor sealing and lag in temperature control of traditional reactor 1. The reactor 1 is equipped with a resistance wire inside to regulate the internal temperature. The reactor 1 is filled with oil to form a confined pressure environment. Together with the temperature control of the resistance wire, it simulates the in-situ temperature and pressure environment of the rock sample in the formation. The temperature and pressure sensor 5 monitors the temperature and pressure parameters inside the cavity in real time, realizing the accurate simulation of the high temperature and high pressure environment, and significantly improving the environmental reproduction of traditional devices.

[0046] Reference Figures 3 to 5The reaction vessel 1 is equipped with a rock sample fixing assembly, which includes a rubber sleeve 11, a water-permeable gasket 12, and a ventilated gasket 13. The rubber sleeve 11 is made of high-temperature resistant rubber and can withstand temperatures up to 150°C. It is used to wrap the rock sample to ensure uniform application of confining pressure, solving the stress concentration problem caused by traditional rock sample fixing. The water-permeable gasket 12 and the ventilated gasket 13 are respectively set at the top and bottom of the rock sample. The water-permeable gasket 12 has three structural designs: a cylindrical structure, a combination of a cylinder and a cone, and a combination of a cylinder and an irregular shape. The cylindrical structure corresponds to continuous uniform loads. The combination of a cylinder and a cone is a structure with a cylinder at the top and a cone at the bottom, solid in the middle and permeable around the edges, corresponding to point loads. The combination of a cylinder and an irregular shape is a structure with a cylinder at the top and an irregular shape at the bottom, corresponding to non-uniform loads.

[0047] This single component enables the simulation of multiple load modes, reducing the cost of load simulation. The venting pad 13 is a structure of interlocking cylinders with unequal diameters, with the lower cylinder having a larger diameter and internal venting holes. The lower cylinder is fully coupled with the axial strain sensor 8 to transmit strain signals. This rock sample fixing component improves the consistency of rock sample stress and deformation monitoring, reducing repeatability errors in experimental data.

[0048] The stress application module includes a mining-driven stress servo press 2, a pressure plate 21, and a pressure probe 22. The mining-driven stress servo press 2 is driven and connected to the pressure plate 21. The stress application method and threshold can be adjusted through the pressure control interface to accurately reproduce the stress path under different mining methods, making the simulation effect closer to the actual site. The pressure probe 22 is made of high-strength nickel-plated steel. One end of it is in direct contact with the pressure plate 21, and the other end is used to abut against the permeable pad 12 of the rock sample. Its nickel-plated steel material can effectively resist CO2 corrosion.

[0049] The upper end cap of the pressure plate 21 has an oil inlet hole 211 and an oil outlet hole 212, which are used to connect the pipelines of the oil inlet pump 37 and the oil outlet pump 36, respectively. Axial pressure is applied and stress-strain control is achieved through the force transmission between the pressure plate 21 and the pressure probe 22, ensuring the uniformity and stability of pressure transmission and avoiding premature destruction of rock samples due to stress concentration. The outer contour dimensions of the pressure plate 21 are adapted to the top opening size of the reactor 1, which can seal the top opening of the reactor 1. A sealing ring is provided on the outer ring of the pressure plate 21 to ensure the sealing effect inside the reactor 1.

[0050] Reference Figures 3 to 5The fluid control module includes a fluid pressure controller 3, an external tempered glass sleeve 32, a fluid piston 31, a two-phase injection pump 35, an oil inlet pump 37, an oil outlet pump 36, an air collection pump 38, a water collection pump 39, an air outlet pipe 33, a water outlet pipe 34, and a fixed baffle 321. The fixed baffle 321 is fixedly installed on the inner top of the external tempered glass sleeve 32. The external tempered glass sleeve 32 is located at the bottom of the rock sample and is sealed against the bottom of the reactor 1. The external tempered glass sleeve 32 is connected and fixed to the venting gasket 13 through the fixed baffle 321. It is used to receive the fluid and press it into the rock sample from bottom to top. It can also visualize the fluid state and directly capture the CO2 phase change and seepage path through visual observation.

[0051] The fluid pressure controller 3 is located at the bottom of the outer tempered glass sleeve 32 and is driven and connected to the fluid piston 31. The fluid pressure controller 3 drives the fluid piston 31 to pump the fluid inside the outer tempered glass sleeve 32 into the rock sample. The two-phase injection pump 35 is used to selectively inject water or CO2 into the outer tempered glass sleeve 32. The oil inlet pump 37 is used to fill the reactor 1 with oil to apply confining pressure, and the oil outlet pump 36 is used to pump out the oil in the reactor 1. The pressure probe 22 is provided with a flow channel 221. One end of the gas outlet pipe 33 and the water outlet pipe 34 passes through the pressure plate 21 and is connected to the flow channel 221. The gas collection pump 38 is connected to the rock sample through the gas outlet pipe 33 and is used to collect CO2 that has permeated the rock sample. The water collection pump 39 is connected to the rock sample through the water outlet pipe 34 and is used to collect water that has permeated the rock sample. The outer tempered glass sleeve 32 is provided with a two-phase discharge port 322 to discharge the remaining water or CO2 that has not permeated into the rock sample after the test. This module realizes the precise control and efficient separation of multiphase fluids.

[0052] The outlet pipe 33 is filled with sponge to absorb moisture entrained in the permeated gas; the water outlet pipe 34 has activated carbon inside to separate CO2 mixed in the water, solving the data interference problem caused by incomplete gas-liquid separation in traditional methods; the connecting pipes between the gas collection pump 38 and the outlet pipe 33, and between the water collection pump 39 and the water outlet pipe 34 are all made of corrosion-resistant materials to ensure fluid separation and collection efficiency, thereby significantly reducing the impact of gas-liquid mixing on pressure measurement errors and improving pressure test accuracy.

[0053] The fluid pressure control machine 3 and the mining stress servo press 2 are connected by a lifting guide rail mechanism 4. The reactor 1 can be vertically lifted and lowered through the lifting guide rail mechanism 4 to accommodate the loading and unloading of rock samples. The lifting guide rail mechanism 4 includes four screws 41 and a drive motor. The screws 41 are located at the four corners of the mining stress press, and both ends of the screws 41 are rotatably connected to the outer shell of the mining stress servo press 2 and the fluid pressure control machine 3. The drive motor is used to drive the screws 41 to rotate. Four connecting rods 42 corresponding to each screw 41 are fixed to the outside of the reactor 1. A nut 43 is fixed to the end of the connecting rod 42 away from the reactor 1. The nut 43 is sleeved on the corresponding screw 41 and threadedly connected to the screw 41.

[0054] The sensing and monitoring module includes a temperature and pressure sensor 5, a fluid temperature and pressure sensor 6, a radial strain sensor 7, and an axial strain sensor 8. The temperature and pressure sensor 5 is located inside the reactor 1 to collect the temperature and pressure inside the cavity to ensure that it meets the in-situ environment. The fluid temperature and pressure sensor 6 is located on the external tempered glass sleeve 32 to monitor whether the fluid temperature and pressure meet the test settings. The radial strain sensor 7 is fitted and sleeved on the outer wall of the rock sample to collect radial strain. Two axial strain sensors 8 are provided and symmetrically arranged on both sides of the rock sample. One end of the axial strain sensor 8 is connected to the pressure probe 22, and the other end is coupled to the venting pad 13 to collect axial strain. This symmetrical design can offset the measurement deviation of a single sensor. The entire sensing module realizes synchronous high-precision acquisition of multiple parameters, providing comprehensive data support for the analysis of the mechanical behavior of the caprock.

[0055] The control and display module includes a pressure control interface, a pump pressure control interface, and a data acquisition and display interface. The pressure control interface adjusts the dynamic stress parameters and supports preset stress path programming. The pump pressure control interface regulates the pressure of five types of pumps, including the dual-phase injection pump 35 and the oil inlet pump 37, and has a pressure closed-loop feedback function. The data acquisition and display interface receives and displays all monitoring data from the temperature and pressure sensor 5, strain sensor, etc. in real time, realizing visual monitoring of the test process. This module simplifies the operation process, enabling a single person to complete the test control, and reduces human error through automated control.

[0056] The auxiliary execution module includes an operating door 14 and a positioning structure. The operating door 14 is located on the side of the reactor 1 and adopts a quick-opening design to facilitate the loading and unloading of rock samples. The positioning structure includes a limiting protrusion on the inner wall of the rubber sleeve 11 and a groove on the surface of the venting gasket 13 to ensure that the rock sample maintains the preset position during the test, avoids displacement affecting the test accuracy, shortens the sample loading time, improves the test efficiency, and ensures the consistency of different batches of tests.

[0057] A comprehensive testing method for valve pressure and breakthrough pressure in CO2 geological storage caprock, employing the aforementioned comprehensive testing device suitable for valve pressure and breakthrough pressure in CO2 geological storage caprock, includes the following steps:

[0058] S1: Sample loading: Check the connectivity of the two-phase injection pump 35, oil inlet pump 37, air collection pump 38, water collection pump 39, oil outlet pump 36 and each connecting pipeline to ensure that the five pumps and the core part of the instrument are unobstructed, and complete the sample loading preparation; load the rock sample into the rubber sleeve 11, and select the permeable pad 12 with the corresponding structure according to the simulated load type: cylindrical structure corresponds to continuous uniform load, cylindrical and conical combination structure corresponds to point load, and cylindrical and irregular shape combination structure corresponds to non-uniform load.

[0059] Open the operating door 14 and place the rock sample wrapped in the rubber sleeve 11 on the ventilated pad 13. The relative position is fixed by the matching of the limiting protrusion on the inner wall of the rubber sleeve 11 and the positioning groove on the surface of the ventilated pad 13. Install the radial strain sensor 7 against the side of the rock sample and the axial strain sensor 8 symmetrically assembled on the upper part of the rock sample. Precisely align the water-permeable pad 12 with the pressure probe 22. Close the operating door 14 and control the reactor 1 to descend to the lowest point along the external slide rail, so that its bottom fits tightly with the ventilated pad 13 to form a closed space.

[0060] S2: Environmental Simulation: The internal resistance wire of reactor 1 is activated to heat the chamber to the preset target temperature and maintain it stable. The bottom is automatically sealed by utilizing the thermal expansion and contraction characteristics of the reactor 1 material. The oil pump 37 is turned on to slowly fill the chamber of reactor 1 with oil. The oil filling rate is controlled to gradually raise the oil temperature to the specified test temperature. The temperature and pressure sensor 5 monitors in real time to ensure that the temperature and pressure parameters in the chamber meet the requirements of the in-situ rock storage environment simulation. The simulation of the in-situ rock storage environment is completed, and the coordinated stability of temperature and confining pressure is achieved, avoiding the changes in the physical properties of the rock sample caused by temperature and pressure fluctuations in traditional devices.

[0061] S3: Stress Application: Adjust the stress application method and threshold parameters of the mining-driven stress servo press 2 through the pressure control interface; start the mining-driven stress servo press 2 to apply axial pressure to the rock sample, and simultaneously collect the axial and radial strain data of the rock sample in real time through the axial strain sensor 8 and the radial strain sensor 7. By analyzing the strain data, determine the stress state of the rock at this stage and its mechanical properties such as elastic modulus and Poisson's ratio, thereby simulating the stress disturbance process of the overburden rock mass affected by mining before CO2 injection; this process reproduces the on-site geological stress environment, making the subsequent seepage test closer to the actual working conditions;

[0062] S4: Hydraulic seepage simulation: Turn on the dual-phase injection pump 35 to inject water into the outer tempered glass sleeve 32; open the valve of the pipeline connecting the dual-phase injection pump 35 and the outer tempered glass sleeve 32, and adjust the pump pressure through the pump pressure control interface to allow water to seep into the rock sample along a preset path. Continuously monitor the water flow status of the water collection pump 39 until the water flows into the water collection pump 39 at a constant rate and remains stable, thus proving that the seepage channels inside the rock have been completely opened; turn off the dual-phase injection pump 35, and drive the fluid piston 31 upward through the fluid pressure controller 3 to force all the remaining water in the outer tempered glass sleeve 32 into the rock sample; control the fluid piston 31 to pull it down to reset, and after confirming that the water has completely entered the rock sample, switch the fluid of the dual-phase injection pump 35 to CO2 to prepare for the subsequent gas injection test. This step opens up the natural pore channels of the rock sample, provides a real path for CO2 seepage, and solves the problem of the disconnect between traditional dry rock sample tests and the on-site water-bearing environment;

[0063] S5: Valve Pressure Measurement: Turn on the dual-phase injection pump 35 to inject CO2 into the external tempered glass sleeve 32 to the preset volume, then close the valve; turn on the fluid temperature and pressure sensor 6 to monitor the temperature and pressure changes of CO2 inside the external tempered glass sleeve 32 in real time; slowly push the fluid piston 31 to compress CO2 through the fluid pressure controller 3, and visually observe the changes in the state of CO2 through the external tempered glass sleeve 32. When the fluid temperature and pressure sensor 6 shows that CO2 has reached the supercritical state, it is confirmed that the valve pressure measurement conditions have been met; turn off the dual-phase injection pump 35, and continue to push the fluid piston 31 to allow the supercritical CO2 to slowly penetrate into the rock sample. When the fluid temperature and pressure sensor 6 detects the pressure starting to drop, immediately keep the fluid piston 31 in a fixed position and record the pressure measurement value of the fluid temperature and pressure sensor 6 at this time. This value is the valve pressure of the caprock. This measurement method, through the combination of visual observation and pressure monitoring, accurately captures the valve pressure critical point, effectively reducing measurement errors.

[0064] S6: Breakthrough Pressure Measurement: Keep the fluid piston 31 in a fixed position, turn on the two-phase injection pump 35, and continuously push CO2 into the external tempered glass sleeve 32 at a preset rate, while simultaneously turning on the gas collection pump 38; observe the gas pressure change curve in the gas collection pump 38 and the pressure change curve of the fluid temperature and pressure sensor 6 in real time. When both pressures enter a stable fluctuation state and remain so for a preset time, record the pressure value of the fluid temperature and pressure sensor 6 at this time. This value is the breakthrough pressure of the CO2 capping layer; through the above steps, the valve pressure and breakthrough pressure are continuously measured in the same test process.

[0065] S7: Sample unloading and maintenance: After the test is completed, turn off the two-phase injection pump 35, open the two-phase outlet 322, and discharge all the remaining un-seeped fluid in the outer tempered glass sleeve 32; turn on the oil pump 36 to pump the oil in the chamber of reactor 1 into the pump for recovery; turn off the resistance wire in reactor 1, and after the chamber temperature cools to room temperature, open the operating door 14; remove the radial strain sensor 7 and the axial strain sensor 8 in sequence, control reactor 1 to lift upward along the slide rail, take out the rock sample and observe its external morphology to provide a basis for subsequent analysis of the test results.

[0066] The above method, through a continuous test process of stress disturbance, hydraulic seepage, and gas-driven breakthrough, achieves unified measurement of valve pressure and breakthrough pressure on the same device. The experimental test results are highly correlated and the test cycle is effectively shortened, providing an efficient and reliable solution for assessing the sealing capacity of the cap layer.

[0067] Based on the above-described preferred embodiments of the present invention, and through the foregoing description, those skilled in the art can make various changes and modifications without departing from the inventive concept. The technical scope of this invention is not limited to the contents of the specification, but must be determined according to the scope of the claims.

Claims

1. A comprehensive testing device for valve pressure and breakthrough pressure in CO2 geological storage caprock, characterized in that: It includes a stress application module, an environmental simulation module, a fluid control module, a sensing and monitoring module, and an auxiliary execution module; The environmental simulation module is used to construct a temperature and pressure environment that matches the in-situ formation, providing a test basis for rock samples that conforms to actual occurrence conditions. The environmental simulation module includes a reactor (1), in which the rock sample is installed. The reactor (1) is equipped with a resistance wire to regulate the internal temperature. The reactor (1) is filled with oil to form a confining pressure environment. Together with the temperature control of the resistance wire, the in-situ temperature and pressure occurrence environment of the rock sample is simulated. The reaction vessel (1) is equipped with a rock sample fixing assembly, which includes a rubber sleeve (11), a water-permeable gasket (12), and an air-permeable gasket (13). The rubber sleeve (11) is made of high-temperature resistant rubber and is used to wrap the rock sample to ensure uniform application of confining pressure. The water-permeable gasket (12) and the air-permeable gasket (13) are respectively set at the top and bottom of the rock sample. The stress application module is used to apply axial pressure to the caprock sample and control the stress-strain state of the rock sample to simulate the stress path disturbance during mining. The stress application module is located at the top of the reactor (1) and includes a mining stress servo press (2), a pressure plate (21) and a pressure probe (22). The mining stress servo press (2) is driven to the pressure plate (21). One end of the pressure probe (22) is connected to the pressure plate (21), and the other end is used to abut against the rock sample. Through the force transmission between the pressure plate (21) and the pressure probe (22), the axial pressure application and stress-strain control of the rock sample are realized. The fluid control module is used to realize the injection, seepage and state regulation of multiphase fluids of water and CO2, and can simulate the seepage process of multiphase CO2 in rock samples. The fluid control module includes an external tempered glass sleeve (32), a fluid pressure controller (3), a fluid piston (31), a two-phase injection pump (35), an oil inlet pump (37), an oil outlet pump (36), an air collection pump (38), a water collection pump (39), an air outlet pipe (33), and a water outlet pipe (34). The outer tempered glass sleeve (32) is located at the bottom of the rock sample and is sealed against the bottom of the reaction vessel (1). The outer tempered glass sleeve (32) is used to receive fluid and press it into the rock sample, and has a fluid state visualization function. The fluid pressure controller (3) is located at the bottom of the outer tempered glass sleeve (32) and is driven by the fluid piston (31). It is used to push the fluid piston (31) to pump the fluid in the outer tempered glass sleeve (32) into the rock sample. The two-phase injection pump (35) is used to inject fluid into the outer tempered glass sleeve (32). 2) Pump in water or CO2; the oil inlet pump (37) is used to fill the reactor (1) with oil to apply confining pressure, and the oil outlet pump (36) is used to pump out the oil in the reactor (1); the gas collection pump (38) is connected to the rock sample through the gas outlet pipe (33) to collect CO2 that has permeated through the rock sample, and the water collection pump (39) is connected to the rock sample through the water outlet pipe (34) to collect water that has permeated through the rock sample; the external tempered glass sleeve (32) is provided with a two-phase discharge port (322) to discharge the remaining fluid that has not permeated into the rock sample after the test; The sensing and monitoring module is used to collect temperature, pressure, and strain data of rock samples and fluids in real time. The auxiliary execution module is used to complete rock sample loading and unloading, fluid collection and discharge, and equipment operation assistance. The modules work together to achieve unified measurement of caprock valve pressure and breakthrough pressure.

2. The comprehensive testing device for valve pressure and breakthrough pressure of CO2 geological storage caprock as described in claim 1, characterized in that: The fluid pressure control machine (3) and the mining stress servo press (2) are connected by a lifting guide rail mechanism (4). The reactor (1) can be lifted vertically through the lifting guide rail mechanism (4) to accommodate the loading and unloading of rock samples. The lifting guide rail mechanism (4) includes four screws (41) and a drive motor. The screws (41) are located at the four corners of the mining stress servo press (2), and the two ends of the screws (41) are rotatably connected to the outer shell of the mining stress servo press (2) and the fluid pressure control machine (3). The drive motor is used to drive the screws (41) to rotate. The reactor (1) is fixed with four connecting rods (42) corresponding to each screw (41). The end of the connecting rod (42) away from the reactor (1) is fixed with a nut (43). The nut (43) is sleeved on the corresponding screw (41) and threadedly connected to the screw (41).

3. The comprehensive testing device for valve pressure and breakthrough pressure of CO2 geological storage caprock as described in claim 1, characterized in that: The air outlet pipe (33) is equipped with a sponge inside to absorb the water that has permeated through the rock sample; the water outlet pipe (34) is filled with activated carbon inside to separate the CO2 that has permeated along with the rock sample during the permeation process.

4. The comprehensive testing device for valve pressure and breakthrough pressure of CO2 geological storage caprock as described in claim 1, characterized in that: The permeable pad (12) is designed with three structures: cylindrical structure, cylindrical and conical combination structure, or cylindrical and irregular shape combination structure, which respectively represent continuous uniform load, point load and non-uniform load.

5. A comprehensive testing device for valve pressure and breakthrough pressure in CO2 geological storage caprock as described in claim 1, characterized in that: The pressure probe (22) is provided with a flow channel (221), and one end of the air outlet pipe (33) and water outlet pipe (34) passes through the pressure plate (21) and is connected to the flow channel (221).

6. The comprehensive testing device for valve pressure and breakthrough pressure of CO2 geological storage caprock as described in claim 1, characterized in that: The outer contour dimensions of the pressure plate (21) are adapted to the top opening dimensions of the reactor (1), and the top opening of the reactor (1) can be sealed. The outer ring of the pressure plate (21) is provided with a sealing ring.

7. The comprehensive testing device for valve pressure and breakthrough pressure of CO2 geological storage caprock as described in claim 1, characterized in that: The sensing and monitoring module includes a temperature and pressure sensor (5), a fluid temperature and pressure sensor (6), a radial strain sensor (7), and an axial strain sensor (8). The temperature and pressure sensor (5) is installed inside the reactor (1) to collect temperature and pressure data inside the reactor (1). The fluid temperature and pressure sensor (6) is installed inside an external tempered glass sleeve (32) to collect temperature and pressure data of the fluid inside the sleeve. The radial strain sensor (7) is installed outside the rock sample to collect radial strain of the rock sample. Two axial strain sensors (8) are installed symmetrically on both sides of the rock sample. One end of the axial strain sensor (8) is connected to a pressure probe (22), and the other end is connected to a breathable gasket (13) to collect axial strain of the rock sample.

8. The comprehensive testing device for valve pressure and breakthrough pressure of CO2 geological storage caprock as described in claim 1, characterized in that: It also includes a control and display module, which includes a pressure control interface, a pump pressure control interface, and a data acquisition and display interface; the pressure control interface is used to adjust the application method and threshold of mining stress; the pump pressure control interface is used to regulate the pressure of the two-phase injection pump (35), the oil inlet pump (37), the air collection pump (38), the water collection pump (39), and the oil outlet pump (36); the data acquisition and display interface is used to receive and display all data collected by the sensing and monitoring module.

9. A comprehensive testing method for valve pressure and breakthrough pressure in CO2 geological storage caprock, characterized in that: The comprehensive testing device for valve pressure and breakthrough pressure of CO2 geological storage caprock as described in claim 7 includes the following steps: S1: Sample loading: Check the connectivity of each pump and pipeline, load the rock sample into the rubber sleeve (11) and place it on the venting pad (13), install the radial strain sensor (7) and axial strain sensor (8), assemble the water-permeable pad (12) and pressure probe (22), close the operating door (14) and lower the reactor (1) to match the venting pad (13); S2: Environmental simulation: The target temperature is heated to and stabilized by resistance wire in the reactor (1), and oil is injected into the reactor (1) by oil pump (37) to make the oil temperature reach the specified temperature of the test, thus constructing the in-situ temperature and pressure environment of the rock sample; S3: Stress application: Axial pressure is applied to the rock sample by the stress servo press (2), and the axial and radial strain data of the rock sample are collected simultaneously by the axial strain sensor (8) and the radial strain sensor (7) to determine the stress state and related mechanical properties of the rock at this stage; S4: Hydraulic seepage simulation: Water is injected into the outer tempered glass sleeve (32) through a two-phase injection pump (35), and the pump pressure is controlled to allow water to seep into the rock sample until the water flows into the water collection pump (39) at a constant rate. Then, the water in the outer tempered glass sleeve (32) is completely forced into the rock sample through the fluid piston (31). After completion, the fluid of the two-phase injection pump (35) is replaced. S5: Valve pressure measurement: CO2 is injected into the external tempered glass sleeve (32) through the two-phase injection pump (35). After the valve is closed, CO2 is compressed to the supercritical state through the fluid piston (31). The fluid piston (31) is pushed until the pressure drops. The pressure value of the fluid temperature and pressure sensor (6) at this time is recorded, which is the valve pressure. S6: Breakthrough pressure measurement: Keep the fluid piston (31) in a fixed position, continue to push CO2 into the external tempered glass sleeve (32) through the two-phase injection pump (35), and at the same time turn on the gas collection pump (38). After the pressure inside the gas collection pump (38) and the pressure of the fluid temperature and pressure sensor (6) are stable, record the pressure value of the fluid temperature and pressure sensor (6), which is the breakthrough pressure. S7: Sample unloading and maintenance: Turn off the two-phase injection pump (35), discharge the remaining fluid through the two-phase outlet (322), pump out the oil in the reactor (1) through the oil pump (36), turn off the resistance wire and wait for the temperature to cool to room temperature, remove the sensor and lift the reactor (1) to take out the rock sample.

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