Device for capturing CO2 residues under pore scale and multi-factor sensitivity analysis method

Abstract

The invention discloses a device for capturing CO2 residues under a pore scale, which can be used for carrying out CO2-displacement and imbibition tests under indoor and outdoor pressure conditions and generating effective CO2 residue capture. The invention further discloses a CO2 residue capture multi-factor sensitivity analysis method under the pore scale, a numerical simulation conclusion is verified through a test result, and the test result is taken as a reference, so that simulation setting conditions of numerical simulation sensitivity analysis are optimized, the reliability of the numerical simulation conclusion is ensured, and the detection accuracy is improved. And multi-factor sensitivity analysis which is difficult to carry out or high in consumption cost under some test conditions is carried out based on numerical simulation.

Description

Technical Field

[0001] The present invention relates to the technical field of CO2 geological storage, and in particular to a CO2 residual capture device at a pore scale, and also to a multi-factor sensitivity analysis method for CO2 residual capture at a pore scale. Background Art

[0002] CO2 residual capture is one of the important capture mechanisms in CO2 geological storage. It can greatly increase the CO2 storage capacity of deep saline layers and form effective capillary closed loops, thereby improving the safety and stability of CO2 geological storage. With the development of high-precision imaging technology, current research can examine the flow physics at the pore scale and fast time scale during displacement and imbibition. Frontier research mainly uses the real-time visualization advantages of microfluidic experiments and the high-precision imaging characteristics of CT scanning experiments to study the fluid interface evolution, local dynamic filling and two-phase fluid distribution under the influence of multiple factors during displacement and imbibition at the pore scale. Pore-scale numerical simulation has many advantages, such as easy parameterization analysis and easy acquisition of the spatial distribution of velocity field and pressure field in the seepage domain. It has become an important means to study the microscopic seepage mechanism of reservoirs after indoor physical experiments. Therefore, this method is widely used to study the detailed flow behavior in spontaneous imbibition under the influence of multiple factors. However, some key influencing factors cannot be studied under experimental conditions or the experimental cost is high, and numerical simulation cannot accurately control the boundary conditions and environmental settings of the model. Therefore, providing an analytical method that combines experiments and numerical simulations can effectively reduce the cost of CO2-brine displacement and imbibition experiments at the pore scale and improve the reliability of the conclusions of two-phase flow displacement and imbibition numerical simulations at the pore scale. Summary of the invention

[0003] In view of the difficulty in analyzing various influencing factors in the experiments of the prior art and the need to improve the reliability of numerical simulations, the present invention proposes a CO2 residual capture device at the pore scale and a multi-factor sensitivity analysis method for CO2 residual capture at the pore scale, thereby facilitating the research on CO2 residual capture at the pore scale.

[0004] In order to achieve the above-mentioned purpose, the present invention adopts the following technical measures:

[0005] A pore-scale CO2 residual capture device comprises a pump, wherein the piston of the pump is connected to the piston of a syringe; the water outlet of the syringe barrel is connected to a first pressure sensor through a hose, the first pressure sensor is connected to a first inlet and outlet on a chip through a hose and a hose connector in turn, the first inlet and outlet are connected to a second inlet and outlet on the chip through a pore network etched in the chip, the second inlet and outlet of the chip is connected to a second pressure sensor through a hose connector and a hose in turn, and the second pressure sensor is connected to a displaced fluid in a beaker through a hose; an imbibition pressure difference regulating device is arranged below the beaker; a high-speed camera is arranged above the chip, and the position of the high-speed camera is fixed by a camera clamp; the first pressure sensor, the second pressure sensor and the high-speed camera all transmit data to a computer through a data line.

[0006] As mentioned above, the chip is made of transparent material, and the chip is fixed on a hollow fixture. The light emitted by the fill light passes through the hollow area of ​​the fixture from the bottom of the fixture to illuminate the chip.

[0007] The multi-factor sensitivity analysis method for CO2 residual capture at the pore scale, using the CO2 residual capture device at the pore scale as described above, comprises the following steps:

[0008] S1. Build a CO2 residual capture device at the pore scale, draw the displaced fluid into the syringe, and drive the syringe to inject the displaced fluid into the chip at a set fluid injection speed, until the chip is saturated;

[0009] The high-speed camera collects the two-phase distribution diagram in the saturated chip;

[0010] S2. Replace a syringe filled with dry CO2 and conduct a displacement test:

[0011] The pump makes the syringe inject CO2 into the chip at a set displacement injection speed;

[0012] At the same time, the first pressure sensor detects the pressure change of the first inlet and outlet during the displacement test phase, the second pressure sensor detects the pressure change of the second inlet and outlet during the displacement test phase, and the high-speed camera collects the two-phase distribution diagram of the chip during the displacement test phase;

[0013] The computer draws the pressure change curve of the displacement test stage in real time according to the pressure change data detected by the first pressure sensor; draws the relationship curve between the initial saturation of CO2 and time in the displacement test according to the two-phase distribution diagram of the displacement test stage; and measures and statistics the contact angle between CO2 in the chip, the displaced fluid and the solid wall according to the two-phase distribution diagram of the displacement test stage;

[0014] S3. When the initial CO2 saturation reaches the preset CO2 initial saturation threshold, stop injecting CO2 and conduct an imbibition test:

[0015] The CO2 residual capture device at the pore scale is kept stationary; the displaced fluid in the beaker absorbs the CO2 in the displaced chip under the capillary pressure of the hose and produces CO2 residual;

[0016] At the same time, the first pressure sensor detects the pressure change of the first inlet and outlet during the imbibition test stage, and the second pressure sensor detects the pressure change of the second inlet and outlet during the imbibition test stage; the high-speed camera collects the two-phase distribution diagram of the chip during the imbibition test stage;

[0017] The computer draws the pressure change curve of the imbibition test stage in real time according to the pressure change data detected by the second pressure sensor; and draws the relationship curve between the residual saturation of CO2 and time in the imbibition test according to the two-phase distribution diagram of the imbibition test stage;

[0018] S4, processing the two-phase distribution map in the saturated chip in step S1 to obtain a pore network reference image, wherein the lines of the pore network in the pore network reference image are clear and consistent with the actual pore network;

[0019] S5. Using the pore network in the experimental reference image, numerical simulation is performed to reproduce the displacement test and the imbibition test under the same experimental conditions as in the displacement test and the imbibition test. The simulation setting conditions are adjusted until the pressure change curve and the two-phase distribution diagram of the displacement stage in the numerical simulation are respectively consistent with the pressure change curve and the two-phase distribution diagram in S2. Figure 1 The pressure change curve and two-phase distribution diagram of the numerical simulation in the infiltration stage are consistent with the pressure change curve and two-phase distribution diagram in S3. Figure 1 To;

[0020] S6, using the final simulation setting conditions of S5 as the simulation setting conditions for the numerical simulation sensitivity analysis;

[0021] Then, by changing one of the factors to be analyzed one by one while keeping the other factors unchanged, a numerical simulation sensitivity analysis under the same experimental conditions was carried out.

[0022] As mentioned above, the displaced fluid is a mixture of brine and pure water of different components.

[0023] As mentioned above, the factors to be analyzed in S6 include:

[0024] Fluid properties of the displaced fluid, displacement injection velocity, wettability of the porous medium, initial pressure inside the chip, static pressure at the first inlet and outlet during the imbibition phase, and static pressure at the second inlet and outlet;

[0025] Among them, fluid properties include viscosity and density, and the wettability of porous media is characterized by contact angle.

[0026] As mentioned above, the simulation setting conditions in S6 include simulation algorithm, initial step size, solver type and wall slip, and the wall slip is divided into no-slip and slip.

[0027] As mentioned above, the simulation algorithms in S6 include phase field method, level set method, moving mesh method and fluid volume method.

[0028] As described above, S1 further includes the following steps:

[0029] During the process of injecting the displaced fluid into the chip, observe and check the airtightness of the device. If there is no overflow of the displaced fluid at the hose connection, and the readings of the first pressure sensor and the second pressure sensor are stable and have no obvious fluctuations after being saturated with salt water, the device is airtight. If the device is airtight, adjust or rebuild the device before injecting the displaced fluid into the chip.

[0030] Compared with the prior art, the present invention can achieve the following beneficial effects:

[0031] First, the CO2 residual capture device at the pore scale proposed in the present invention can continuously carry out CO2-brine displacement and brine imbibition tests at room temperature and temperature pressure in the same closed system, thereby realizing effective research on CO2 residual capture at the pore scale; the CO2 residual capture device at the pore scale has a simple structure and is easy to use, and can carry out CO2 residual capture tests under room temperature and temperature pressure conditions and analyze its residual characteristics;

[0032] In addition, the present invention also proposes a multi-factor sensitivity analysis method for CO2 residual capture at the pore scale. Combining experiments with numerical simulation methods, it can perform sensitivity analysis on various influencing factors of two-phase flow problems at the pore scale; thereby solving the difficulties of being unable to study certain key influencing factors under experimental conditions or the high experimental costs, and improving the reliability of the conclusions of the numerical simulation method. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] The drawings described herein are used to provide further understanding of the present application and constitute a part of the present application. The illustrative embodiments of the present application and their descriptions are used to explain the present application and do not constitute improper limitations on the present application.

[0034] Figure 1 It is a schematic structural diagram of the CO2 residual capture device at the pore scale of the present invention;

[0035] Figure 2 It is a schematic diagram of the multi-factor sensitivity analysis method for CO2 residual capture at the pore scale of the present invention;

[0036] Figure 3The two-phase distribution diagram of CO2 breakthrough in the brine stage of CO2 displacement in the experiment and numerical simulation, where (a) is the two-phase distribution diagram of CO2 breakthrough in the brine stage of CO2 displacement in the experiment, and (b) is the two-phase distribution diagram of CO2 breakthrough in the brine stage of CO2 displacement in the numerical simulation;

[0037] Figure 4 The residual CO2 distribution diagrams in the experiment and numerical simulation, where (a) is the residual CO2 distribution diagram in the experiment, and (b) is the residual CO2 distribution diagram in the numerical simulation;

[0038] Figure 5 Figure 2 shows the relationship between initial CO2 saturation and contact angle under different contact angles in the numerical simulation of contact angle sensitivity analysis, as well as the variation curve of CO2 residual saturation under different contact angles. (a) is the relationship between initial CO2 saturation and contact angle under different contact angles with different injection times in numerical simulation, and (b) is the variation curve of CO2 residual saturation under different contact angles in hydrophilic media. The CO2 residual saturation is characterized by the CO2 residual volume fraction.

[0039] Among them, 1-pump, 2-syringe, 3-fill light, 4-fixer, 5-chip, 6-beaker, 7-high-speed camera, 8-camera fixture, 9-first pressure sensor, 10-second pressure sensor, 11-infiltration pressure difference regulating device. Specific implementation methods

[0041] The invention is further described in detail below in conjunction with the accompanying drawings so that those skilled in the art can implement it according to the description.

[0042] It should be understood that terms such as “having”, “including” and “comprising” used herein do not exclude the existence or addition of one or other elements or combinations thereof.

[0043] Embodiment 1:

[0044] Pore-scale CO2 residual capture devices, such as Figure 1 As shown, it includes a loading unit, a displacement unit, and a data recording unit, which are used to perform CO2-brine displacement tests at room temperature and room pressure and can produce CO2 residual capture through imbibition. Among them, the loading unit includes a pump 1 and a syringe 2, the displacement unit includes a chip 5, a fill light 3, a fixture 4, a beaker 6 and an imbibition pressure difference adjustment device 11, and the data recording unit includes a first pressure sensor 9, a second pressure sensor 10 and a high-speed camera 7. The advantage of this device is that it can continuously carry out two-phase flow displacement tests and imbibition tests in the same closed system.

[0045] The piston of the pump 1 is connected to the piston of the syringe 2, thereby driving the barrel of the syringe 2 to discharge CO2 or the displaced fluid; the water outlet of the barrel of the syringe 2 is connected to the first pressure sensor 9 through a hose, and the first pressure sensor 9 is connected to the first inlet and outlet on the chip 5 through a hose and a hose connector in turn, the first inlet and outlet are connected to the second inlet and outlet on the chip 5 through a pore network etched in the chip 5, and the second inlet and outlet of the chip 5 are connected to the second pressure sensor 10 through a hose connector and a hose in turn, and the second pressure sensor 10 is connected to the displaced fluid in the beaker 6 through a hose; an imbibition pressure difference regulating device 11 is arranged below the beaker 6, and the imbibition pressure difference regulating device 11 is used to adjust the placement height of the beaker 6, thereby adjusting the imbibition pressure difference; in this embodiment, the diameter of the hose is 1 mm; a high-speed camera 7 is arranged above the chip 5, and the high-speed camera 7 is fixed in position by a camera clamp 8, and the first pressure sensor 9, the second pressure sensor 10 and the high-speed camera 7 all transmit data to the computer through a data line.

[0046] The loading unit includes a pump 1 and a syringe 2. The syringe 2 is fixed on the pump 1. The pump 1 drives the syringe 2 to inject CO2 or a displaced fluid into the chip 5 at a set injection speed to achieve the purpose of displacement.

[0047] The displacement unit includes a chip 5, a fill light 3, a fixture 4, a beaker 6 and an imbibition pressure difference adjusting device 11. The depth of the pores in the pore network in the chip 5, the size of the pore throat, etc. can be etched according to the test requirements. The chip 5 is fixed on the hollow fixture 4, and the fixture 4 is used to fix and adjust the horizontal position of the chip 5. The chip 5 is made of transparent material, and a suitable light source is provided by the fill light 3 under the fixture 4. The light emitted by the fill light 3 passes through the hollow area of ​​the fixture 4 from the bottom of the fixture 4 to the chip 5; the imbibition pressure difference adjusting device 11 can change the invasion pressure (i.e., the imbibition pressure difference) of the displaced fluid in the imbibition stage by adjusting the vertical height of the beaker 6, thereby controlling the imbibition rate.

[0048] The data recording unit includes a first pressure sensor 9, a second pressure sensor 10 and a high-speed camera 7, and the first pressure sensor 9, the second pressure sensor 10 and the high-speed camera 7 all transmit data to the computer through a data line. When assembling the test equipment, the center of the chip 5 and the center of the imaging surface of the high-speed camera 7 are ensured to be on the same axis by fine-tuning the fixture 4, and the focal length of the high-speed camera 7 is adjusted to ensure that the imaging of the high-speed camera 7 is complete and clear, so that the fluid displacement process inside the chip 5 can be clearly captured.

[0049] In this embodiment, the chip 5 is made of glass, and the pore network in the chip 5 is etched based on the configuration of the pore network extracted from the real rock sample. The pore network in the chip 5 is connected to the outside of the chip 5 only through the first entrance and the second entrance. The etching depth of the pore network in the chip 5 can be selected from 7μm to 20μm, and the etching depth in this embodiment is 20μm. The shooting speed of the high-speed camera 7 can be set as needed, that is, to meet the detailed recording of the CO2 breakthrough and imbibition process. In the key stages of the experiment, such as the CO2 breakthrough stage and the imbibition reflux stage, the high-speed camera 7 can be set to collect 10-20 pictures per second; in other time periods when the distribution of the two phases changes slowly, the number of pictures collected can be reduced. In this embodiment, the displaced fluid is selected as brine.

[0050] Embodiment 2:

[0051] The multi-factor sensitivity analysis method for CO2 residual capture at the pore scale utilizes the CO2 residual capture device at the pore scale described in Example 1.

[0052] Factors affecting CO2 residual capture include: fluid properties of CO2 and displaced fluid, displacement injection rate (displacement injection rate affects displacement injection pressure), wettability of porous media (characterized by contact angle), initial pressure inside chip 5, static pressure of the first inlet and outlet during the imbibition stage, and static pressure of the second inlet and outlet, wherein fluid properties include viscosity and density. Except for the fixed fluid properties of CO2, other factors affecting CO2 residual capture are factors to be analyzed (i.e., fluid properties of displaced fluid, displacement injection rate, wettability of porous media, initial pressure inside chip 5, static pressure of the first inlet and outlet during the imbibition stage, and static pressure of the second inlet and outlet). Sensitivity analysis refers to studying the effects of the changed factors on fluid displacement and imbibition by changing one of the factors to be analyzed one by one in the two-phase flow displacement test and imbibition test, while keeping the other factors in the factors to be analyzed unchanged.

[0053] The method of the present invention specifically comprises the following steps:

[0054] S1. Build the CO2 residual capture device at the pore scale described in Example 1, draw the displaced fluid into the syringe 2, and the pump 1 drives the syringe 2 to inject the displaced fluid into the chip 5 at a set fluid injection speed until the chip 5 is in a saturated state; use the high-speed camera 7 to collect the two-phase distribution diagram in the saturated chip 5.

[0055] In this embodiment, 20 ml of saline is drawn into the syringe 2 as the displaced fluid, and the fluid injection speed of the pump 1 is set to 50 μl / min; the displaced fluid (in this embodiment, the displaced fluid is saline) is injected into the chip 5 until the pore network of the chip 5 is saturated with saline; during the process of injecting the displaced fluid into the chip 5, the airtightness of the device is observed and checked. If there is no overflow of the displaced fluid at the hose connection, and the readings of the first pressure sensor 9 and the second pressure sensor 10 are stable and have no obvious fluctuations after being saturated with saline, the airtightness of the device is good; if the airtightness of the device is poor, adjust or rebuild the device before injecting the displaced fluid into the chip 5.

[0056] S2. Replace a syringe 2 filled with dry CO2 and conduct a displacement test:

[0057] The pump 1 causes the syringe 2 to inject CO2 into the chip 5 at a set displacement injection speed;

[0058] At the same time, the first pressure sensor 9 detects the pressure change of the first inlet and outlet during the displacement test phase, the second pressure sensor 10 detects the pressure change of the second inlet and outlet during the displacement test phase, and the high-speed camera 7 collects the two-phase distribution diagram of the chip 5 during the displacement test phase;

[0059] The computer draws the pressure change curve of the displacement test stage in real time according to the pressure change data detected by the first pressure sensor 9; draws the relationship curve between the initial saturation of CO2 and time in the displacement test according to the two-phase distribution diagram of the displacement test stage; and measures and statistics the contact angle between CO2 in the chip 5, the displaced fluid and the solid wall according to the two-phase distribution diagram of the displacement test stage.

[0060] In this embodiment, the displacement injection speed set by the pump 1 is 10 μl / min, so that the syringe 2 injects CO2 into the chip 5; the first pressure sensor 9 records the CO2 entry pressure and breakthrough pressure of the first inlet and outlet; in this embodiment, the contact angle obtained is about 30°, and the contact angle is the angle between the tangent of the gas-liquid interface at the intersection of the gas, liquid and solid phases and the solid-liquid boundary line.

[0061] S3. When the initial CO2 saturation reaches the preset CO2 initial saturation threshold, stop injecting CO2 and conduct an imbibition test:

[0062] The CO2 residual capture device at the pore scale is kept stationary; the displaced fluid in the beaker 6 absorbs and displaces the CO2 in the chip 5 under the capillary pressure of the hose and generates CO2 residual;

[0063] At the same time, the first pressure sensor 9 detects the pressure change of the first inlet and outlet during the imbibition test phase, and the second pressure sensor 10 detects the pressure change of the second inlet and outlet during the imbibition test phase; the high-speed camera 7 collects the two-phase distribution diagram of the chip 5 during the imbibition test phase;

[0064] The computer draws the pressure change curve of the imbibition test stage in real time according to the pressure change data detected by the second pressure sensor 10; and draws the relationship curve between the residual saturation of CO2 and time in the imbibition test according to the two-phase distribution diagram of the imbibition test stage.

[0065] After the CO2 injection is completed, the pump 1 is turned off to ensure that the CO2 residual capture device at the pore scale is stationary; under the capillary pressure of the hose, the brine inside the beaker 6 spontaneously infiltrates into the chip 5, and the infiltration pressure difference can be adjusted by adjusting the height of the infiltration pressure difference adjustment device 11, thereby controlling the brine infiltration rate. The CO2 in the chip 5 is displaced and discharged by the displaced fluid from the beaker 6, and a card-breaking event occurs inside the pore network of the chip 5, and the continuous CO2 is divided into CO2 clusters to form residual capture.

[0066] S4, processing the two-phase distribution diagram of the chip 5 after saturation in step S1 to obtain a pore network reference image, wherein the lines of the pore network in the pore network reference image are clear and consistent with the actual pore network;

[0067] The two-phase distribution diagram of the saturated chip 5 obtained in step S1 is selected to extract the curve of the pore network and avoid the influence of the interface between CO2 and brine. In this embodiment, the two-phase distribution diagram in the saturated chip 5 is processed including: binarization, denoising, edge contour extraction, interface segmentation, de-coincidence of lines, and sharpening, so as to obtain a pore network reference image with clear lines of the pore network and consistent with the actual pore network, so as to perform subsequent numerical simulation.

[0068] S5, using the pore network in the pore network reference image, numerical simulation is repeated under the same experimental conditions as in the displacement test and the imbibition test, and the simulation setting conditions are adjusted until the pressure change curve and the two-phase distribution diagram of the displacement stage of the numerical simulation are respectively consistent with the pressure change curve and the two-phase distribution diagram in S2. Figure 1 The pressure change curve and two-phase distribution diagram of the numerical simulation in the infiltration stage are consistent with the pressure change curve and two-phase distribution diagram in S3. Figure 1 To.

[0069] The experimental conditions include: fluid properties of CO2 and displaced fluid, displacement injection rate, static pressure at the first inlet and outlet and static pressure at the second inlet and outlet during the imbibition stage, wettability of porous media (characterized by contact angle), and initial pressure inside the chip. The simulation setting conditions include simulation algorithm, initial step size, solver type, and the selection of wall slip in wall conditions, where wall slip is divided into no slip and slip;

[0070] Numerical simulations are performed by selecting different simulation algorithms, different initial step sizes, different solvers, and wall slip properties in turn until the pressure change curve and two-phase distribution diagram of the displacement stage of the numerical simulation are respectively consistent with the pressure change curve and two-phase distribution diagram in S2. Figure 1 The pressure change curve and two-phase distribution diagram of the numerical simulation in the imbibition stage are consistent with the pressure change curve and two-phase distribution diagram in S3. Figure 1 To.

[0071] In this case, the numerical simulation algorithm selected is the phase field method, and the CO2-brine displacement process is analyzed based on the Navier-Stokes equation coupled phase field equation. The model boundary condition is set to a no-slip wall, and the contact angle inside the pore network is set to the contact angle obtained in S2 (i.e., 30°); in the CO2 displacement brine stage, the simulation first inlet and outlet velocity is set to be equal to the displacement injection velocity in S2, i.e., 10μl / min, and the second inlet and outlet pressure is 0Pa; in the brine infiltration stage, the static pressure of the first inlet and outlet is set to 0Pa, and the static pressure of the second inlet and outlet is set to 0Pa; after the simulation, the pressure cloud map, CO2 flow rate distribution cloud map, CO2 volume fraction change curve, etc. in the chip pore network model can be viewed;

[0072] Comparing the pressure change curves of the first inlet and outlet obtained from the test and numerical simulation, both satisfy the rule that the pressure of the first inlet and outlet rises before CO2 breaks through, and the pressure of the first inlet and outlet gradually decreases after CO2 breaks through, and the pressure peaks are similar; at the moment of CO2 breakthrough, the two-phase distribution diagrams in the test and numerical simulation are close, and the dominant channel in the test and the dominant channel in the numerical simulation have a high degree of overlap;

[0073] During the brine infiltration stage, the CO2 residuals in the experiment and the numerical simulation both meet the characteristics of accumulation at the infiltration outlet (i.e., the first inlet and outlet), with more residuals at the pore edges and dead holes; generally speaking, the numerical simulation results obtained under the experimental conditions meet the objective laws and are reliable.

[0074] S6. Use the final simulation setting conditions of S5 (including simulation algorithm, initial step size, solver type, and wall slip in wall conditions) as the simulation setting conditions for numerical simulation sensitivity analysis; then perform numerical simulation sensitivity analysis under the same experimental conditions by changing one of the factors to be analyzed one by one while keeping the other factors unchanged.

[0075] This case takes the analysis of the effect of contact angle on CO2 residual capture as an example. Based on the final simulation setting conditions of S5, with contact angle as the changing factor, CO2 displacement brine simulation with contact angles of 30°, 45°, 60°, 90°, 120°, 135°, and 150° and brine imbibition simulation with contact angles of 30°, 45°, and 60° were carried out. The numerical simulation results show that in hydrophilic media, the initial CO2 saturation will increase with the decrease of contact angle, and in CO2-philic media, the initial CO2 saturation will increase with the increase of contact angle. In hydrophilic media, the decrease of contact angle will produce more snap-off events, increasing the amount of CO2 residual capture.

[0076] The displaced fluid in the above step S1 can be a mixture of brine and pure water with different components according to test requirements.

[0077] The above steps S2 and S3 are respectively the displacement of brine by CO2 and the spontaneous imbibition of brine. The initial saturation of CO2 and the residual saturation of CO2 can be calculated by image processing, and the CO2 capture rate at different displacement injection rates can be obtained.

[0078] In S6, boundary conditions need to be set for numerical simulation. The boundary conditions include, but are not limited to, adjusting the pressure of the first inlet and outlet, the pressure of the second inlet and outlet, the displacement injection velocity, and the wall conditions in the numerical simulation. The wall conditions include the contact angle and the wall slip property. Generally, a no-slip wall is selected. However, for microfluidic experiments, some pore throats are small, and the velocity field from the wall to the center of the pore throat changes little. In this case, a slip wall can be selected.

[0079] Improving numerical simulation algorithms includes but is not limited to using different simulation methods, such as phase field method, level set method, moving grid method, fluid volume method, etc.

[0080] The present invention is not limited to the above-mentioned implementation modes. The above-mentioned embodiments are only descriptions of the preferred embodiments of the present invention, and do not limit the concept of the present invention. The implementation schemes in the above-mentioned embodiments can be further combined or replaced. Various changes and improvements made to the technical solutions of the present invention by those skilled in the art all belong to the protection scope of the present invention.

Claims

1. A pore-scale CO2 residual capture device, characterized in that: The invention comprises a pump (1), wherein the piston of the pump (1) is connected to the piston of the syringe (2); the water outlet of the barrel of the syringe (2) is connected to a first pressure sensor (9) through a hose, the first pressure sensor (9) is connected to a first inlet and outlet on a chip (5) through a hose and a hose connector in turn, the first inlet and outlet are connected to a second inlet and outlet on the chip (5) through a pore network etched in the chip (5), the second inlet and outlet of the chip (5) is connected to a second pressure sensor (10) through a hose connector and a hose in turn, the second pressure sensor (10) is connected to the displaced fluid in a beaker (6) through a hose; an imbibition pressure difference regulating device (11) is arranged below the beaker (6); a high-speed camera (7) is arranged above the chip (5), the high-speed camera (7) is fixed in position by a camera fixture (8); the first pressure sensor (9), the second pressure sensor (10) and the high-speed camera (7) all transmit data to a computer through a data line.

2. The device for capturing residual CO2 at pore scale according to claim 1, characterized in that: The chip (5) is made of a transparent material and is fixed on a hollow fixture (4). The light emitted by the fill light (3) passes through the hollow area of ​​the fixture (4) from below the fixture (4) and irradiates the chip (5).

3. A multi-factor sensitivity analysis method for CO2 residual capture at the pore scale, using the CO2 residual capture device at the pore scale according to claim 2, characterized in that: The steps include: S1. A CO2 residual capture device is constructed at a pore scale. A displaced fluid is sucked into a syringe (2). A pump (1) drives the syringe (2) to inject the displaced fluid into a chip (5) at a set fluid injection speed until the chip (5) is in a saturated state. A high-speed camera (7) collects a two-phase distribution diagram in the saturated chip (5); S2. Replace a syringe (2) filled with dry CO2 and conduct a displacement test: The pump (1) causes the injector (2) to inject CO2 into the chip (5) at a set displacement injection speed; At the same time, the first pressure sensor (9) detects the pressure change of the first inlet and outlet during the displacement test phase, the second pressure sensor (10) detects the pressure change of the second inlet and outlet during the displacement test phase, and the high-speed camera (7) collects the two-phase distribution diagram of the chip (5) during the displacement test phase; The computer draws a pressure change curve in the displacement test phase in real time based on the pressure change data detected by the first pressure sensor (9); draws a curve of the relationship between the initial saturation of CO2 and time in the displacement test based on the two-phase distribution diagram in the displacement test phase; and measures and statistics the contact angles between CO2, the displaced fluid and the solid wall surface in the chip (5) based on the two-phase distribution diagram in the displacement test phase; S3. When the initial CO2 saturation reaches the preset CO2 initial saturation threshold, stop injecting CO2 and conduct an imbibition test: The CO2 residual capture device at the pore scale is kept stationary; the displaced fluid inside the beaker (6) absorbs the CO2 in the displaced chip (5) under the capillary pressure of the hose and generates CO2 residual; At the same time, the first pressure sensor (9) detects the pressure change of the first inlet and outlet during the imbibition test phase, and the second pressure sensor (10) detects the pressure change of the second inlet and outlet during the imbibition test phase; the high-speed camera (7) collects the two-phase distribution diagram of the chip (5) during the imbibition test phase; The computer draws a pressure change curve in the imbibition test stage in real time based on the pressure change data detected by the second pressure sensor (10); and draws a curve of the relationship between the residual saturation of CO2 and time in the imbibition test based on the two-phase distribution diagram of the imbibition test stage; S4, processing the two-phase distribution map in the chip (5) after saturation in step S1 to obtain a pore network reference image, wherein the lines of the pore network in the pore network reference image are clear and consistent with the actual pore network; S5, using the pore network in the experimental reference image, numerically simulate the displacement test and the imbibition test under the same experimental conditions as in the displacement test and the imbibition test, and adjust the simulation setting conditions until the pressure change curve and the two-phase distribution diagram of the numerical simulation displacement stage are consistent with the pressure change curve and the two-phase distribution diagram in S2, respectively, and the pressure change curve and the two-phase distribution diagram of the numerical simulation imbibition stage are consistent with the pressure change curve and the two-phase distribution diagram in S3; S6, using the final simulation setting conditions of S5 as the simulation setting conditions for the numerical simulation sensitivity analysis; Then, by changing one of the factors to be analyzed one by one while keeping the other factors unchanged, a numerical simulation sensitivity analysis under the same experimental conditions was carried out.

4. The multi-factor sensitivity analysis method for CO2 residual capture at pore scale according to claim 3 is characterized in that: The displaced fluid is a mixture of brine and pure water with different components.

5. The multi-factor sensitivity analysis method for CO2 residual capture at pore scale according to claim 3 is characterized in that: The factors to be analyzed in S6 include: The fluid properties of the displaced fluid, the displacement injection rate, the wettability of the porous medium, the initial pressure inside the chip (5), the static pressure at the first inlet and outlet and the static pressure at the second inlet and outlet during the imbibition stage; Among them, fluid properties include viscosity and density, and the wettability of porous media is characterized by contact angle.

6. The multi-factor sensitivity analysis method for CO2 residual capture at pore scale according to claim 3, characterized in that: The simulation setting conditions in S6 include simulation algorithm, initial step size, solver type and wall slip property, and the wall slip property is divided into no slip property and slip property.

7. The multi-factor sensitivity analysis method for CO2 residual capture at pore scale according to claim 6, characterized in that: The simulation algorithms in S6 include phase field method, level set method, moving grid method and fluid volume method.

8. The multi-factor sensitivity analysis method for CO2 residual capture at pore scale according to claim 3, characterized in that: The S1 further includes the following steps: During the process of injecting the displaced fluid into the chip (5), the airtightness of the device is observed and checked. If no displaced fluid overflows from the hose connection, and the readings of the first pressure sensor (9) and the second pressure sensor (10) are stable and have no obvious fluctuations after being saturated with salt water, the airtightness of the device is good. If the airtightness of the device is poor, the device is adjusted or rebuilt before injecting the displaced fluid into the chip (5).

Images