Pore structure modification device for porous rock and method for testing pore mechanical parameters thereof

Abstract

This invention discloses a device for modifying the pore structure of porous rocks and a method for testing its pore mechanical parameters. The method includes loading a columnar rock sample into the triaxial chamber of the device, applying confining pressure to the sample, opening a second input valve and a second output valve to inject a saturated first liquid into the pore structure, filling it with the liquid, closing the valves to lower the temperature, causing crystals to precipitate within the chamber, opening the first and first output valves to inject a second liquid into the crystallized pore structure, draining the first liquid and filling it with the second liquid, and then testing the pore parameters under multiple pressure conditions. This allows for precise analysis of the influence of rock pore structure on pore mechanical properties, enabling quantitative modification of the pore structure and alteration of its mechanical properties.

Description

Technical Field

[0001] This invention relates to the field of rock mechanical property testing technology, and in particular to a device for modifying the pore structure of porous rocks and a method for testing pore mechanical parameters. Background Technology

[0002] In geotechnical engineering, the combined effects of groundwater and cyclic loading / unloading are frequently encountered. This hydraulic coupling deteriorates the mechanical properties of the rock mass, reducing its actual bearing capacity and causing severe deformation. In practical engineering projects, this can lead to geological disasters such as collapses and landslides, severely impacting construction. The deformation of porous soil and rock materials is particularly pronounced. Current technologies modify the pore structure of rocks to alter their mechanical properties and improve engineering stability. This technology is cutting-edge; the challenge lies in how to alter the pore structure, including pore size distribution, pore connectivity, and porosity, without damaging the rock mass, while simultaneously accurately obtaining the impact of the rock strata's pore structure on pore mechanical properties. Furthermore, in many oil and gas fields and carbon dioxide sealing and storage projects, porous rock reservoirs often experience salt crystal precipitation during both displacement and pressurized injection processes. Salt crystal precipitation has a significant impact on the pore mechanical response of porous reservoirs; however, the extent and process of this impact are poorly understood. Obtaining quantitative laws governing pore mechanical parameters under different pore structure conditions through laboratory experiments is currently a technical challenge. In view of this, this application proposes a device for modifying the pore structure of porous rocks and an experimental method for accurately analyzing the influence of rock pore structure on pore mechanical properties. Summary of the Invention

[0003] The main objective of this invention is to propose a device for modifying the pore structure of porous rocks and a method for testing its pore mechanical parameters, so as to accurately analyze the influence of rock pore structure on pore mechanical properties, realize quantitative modification of pore structure, change pore mechanical properties, and improve engineering stability.

[0004] To achieve the above objectives, this invention provides a method for testing the pore mechanical parameters of porous rocks, based on a device for modifying the pore structure of porous rocks. The device includes a base, a pressure head, a loading pump, and an injection pump. The base has a first opening facing upwards. A first input pipe, a first output pipe, a second input pipe, and a second output pipe are disposed on the base. A first input valve is disposed on the first input pipe, and a second input valve is disposed on the second input pipe. One end of the first output pipe and one end of the second output pipe are both connected to the first opening. A first output valve is disposed on the first output pipe, and a second output valve is disposed on the second output pipe. The pressure head is positioned above the base and has a second opening facing downwards. The second opening is connected to one end of the first input pipe and one end of the second input pipe. The loading pump is connected to the other end of the first input pipe, and the injection pump is connected to the other end of the second input pipe. The method for testing the pore mechanical parameters of porous rocks includes the following steps:

[0005] The columnar rock sample is loaded into the triaxial chamber of the porous rock pore structure modification device, so that the pore structure of the columnar rock sample is connected to the first opening and the second opening in the vertical direction, respectively, and confining pressure is applied to the columnar rock sample.

[0006] To make the temperature of the triaxial chamber and the injection pump the same, the second input valve and the second output valve are opened, and the first liquid in a saturated state is injected into the pore structure of the columnar rock sample through the injection pump, so that the pore structure of the columnar rock sample is filled with the first liquid.

[0007] Close the second input valve and the second output valve, adjust the triaxial room temperature control system, and reduce the temperature of the triaxial chamber to cause crystals to precipitate in the pore structure of the columnar rock sample;

[0008] The temperature of the loading pump is made the same as the temperature of the cooled triaxial chamber. The first input valve and the first output valve are opened, and the second liquid is injected into the porous structure where crystals have precipitated through the loading pump to discharge the first liquid in the porous structure, so that the porous structure where crystals have precipitated is filled with the second liquid.

[0009] Pore ​​parameter tests were performed on the columnar rock sample under multiple pressure conditions when the first output valve and the first input valve were opened and closed, respectively.

[0010] Optionally, the step of testing the pore parameters of the columnar rock sample under multiple pressure conditions when the first output valve is opened and closed includes:

[0011] The first output valve and the first input valve are closed, lateral pressure is applied to the side of the columnar rock sample, and axial pressure is applied to the end of the columnar rock sample, wherein the lateral pressure and the axial pressure increase to a preset pressure value at the same rate.

[0012] Optionally, after the steps of closing the first output valve and the first input valve, applying lateral pressure to the side of the columnar rock sample, and applying axial pressure to the end of the columnar rock sample, wherein the lateral pressure and the axial pressure increase to a preset pressure value at the same rate, the method further includes:

[0013] Record the first evolution curves of pore fluid pressure and volumetric strain of columnar rock samples as a function of the lateral pressure and the axial pressure.

[0014] Optionally, the step of testing the pore parameters of the columnar rock sample under multiple pressure conditions when the first output valve is opened and closed includes:

[0015] Open the first output valve, close the first input valve, apply lateral pressure to the side of the columnar rock sample, and apply axial pressure to the end of the columnar rock sample, wherein the lateral pressure and the axial pressure increase to a preset pressure value at the same rate.

[0016] Optionally, after the steps of opening the first output valve, closing the first input valve, applying lateral pressure to the side of the columnar rock sample, and applying axial pressure to the end of the columnar rock sample, wherein the lateral pressure and the axial pressure increase to a preset pressure value at the same rate, the method further includes:

[0017] A second evolution curve recording the volumetric strain of the columnar rock sample as a function of the lateral pressure and the axial pressure.

[0018] Optionally, the step of testing the pore parameters of the columnar rock sample under multiple pressure conditions when the first output valve is opened and closed includes:

[0019] Close the first output valve, open the first input valve, apply lateral pressure to the side of the columnar rock sample, apply axial pressure to the end of the columnar rock sample, and apply pore water pressure to the columnar rock sample through the loading pump, wherein the pore water pressure, the lateral pressure and the axial pressure increase to a preset pressure value at the same rate.

[0020] Optionally, when the temperatures of the triaxial chamber and the injection pump are the same, the temperature is set to T1.

[0021] The first liquid includes a NaCl solution that is saturated at T1.

[0022] Optionally, the second liquid includes oil.

[0023] To achieve the above objectives, the present invention also provides a device for modifying the pore structure of porous rocks, employing the pore mechanical parameter testing method for the pore structure of porous rocks as described above. The device for modifying the pore structure of porous rocks includes:

[0024] The base has a first opening facing upwards. The base is provided with a first input pipe, a first output pipe, a second input pipe, and a second output pipe. A first input valve is provided on the first input pipe, and a second input valve is provided on the second input pipe. One end of the first output pipe and one end of the second output pipe are both connected to the first opening. A first output valve is provided on the first output pipe, and a second output valve is provided on the second output pipe.

[0025] A pressure head, disposed above the base, has a second opening facing downwards, the second opening being connected to one end of the first input pipe and one end of the second input pipe; and,

[0026] A loading pump is connected to the other end of the first input pipeline;

[0027] An injection pump is connected to the other end of the second input pipeline.

[0028] Optionally, the first input pipe, the first output pipe, the second input pipe, and the second output pipe are all configured as insulated pipes; and / or,

[0029] The porous rock pore structure modification device further includes a first temperature regulating component, which is used to regulate the temperature of the loading pump; and / or,

[0030] The porous rock pore structure modification device also includes a second temperature regulating component, which is used to regulate the temperature of the injection pump.

[0031] In the technical solution provided by this invention, a columnar rock sample is loaded into the triaxial chamber of a porous rock pore structure modification device, such that the pore structure of the columnar rock sample is connected vertically to the first opening and the second opening, respectively. A confining pressure is applied to the columnar rock sample to make the temperature of the triaxial chamber and the injection pump the same. The second input valve and the second output valve are opened, and a saturated first liquid is injected into the pore structure of the columnar rock sample through the injection pump, filling the pore structure with the first liquid. The second input valve and the second output valve are closed to lower the temperature of the triaxial chamber, causing crystals to precipitate within the pore structure of the columnar rock sample, thus aligning the temperature of the loading pump with that of the cooled triaxial chamber. With the temperature of the chamber constant, the first input valve and the first output valve are opened, and a second liquid is injected into the crystalline pore structure through the loading pump to discharge the first liquid in the pore structure, so that the crystalline pore structure is filled with the second liquid. When the first output valve and the first input valve are opened and closed respectively, the pore parameters of the columnar rock sample are tested under multiple pressure conditions to obtain the corresponding pore mechanical parameters. This allows for the determination of the pore water pressure response properties of porous rock layers based on the pore mechanical parameters, providing effective data support for evaluating formation deformation and instability. It also enables precise analysis of the influence of rock pore structure on pore mechanical properties, achieving quantitative modification of the pore structure and changing pore mechanical properties. Attached Figure Description

[0032] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the structures shown in these drawings without creative effort.

[0033] Figure 1 A three-dimensional structural schematic diagram of an embodiment of the porous rock pore structure modification device (partial structure) provided by the present invention;

[0034] Figure 2 A schematic flowchart of an embodiment of the method for testing the pore mechanical parameters of porous rocks provided by the present invention;

[0035] Figure 3 To close the first output valve and the first input valve, the pore structure of the columnar rock sample is modified by crystallization, and the pore fluid pressure is adjusted in both cases. With isotropic pressure Relationship curve;

[0036] Figure 4To close the first output valve and the first input valve, the volumetric strain of the columnar rock sample under two conditions—one with crystallization modification and the other without—was measured. With isotropic pressure Relationship curve;

[0037] Figure 5 When the first output valve is opened and the first input valve is closed, the volumetric strain of the columnar rock sample's pore structure is measured under two conditions: one where the pore structure is altered by crystallization, and the other where it is not. With isotropic pressure Relationship curve;

[0038] Figure 6 For columnar rock samples, when the lateral pressure, axial pressure, and pore water pressure increase at the same rate to a preset pressure value in both cases of crystallization modification and no modification, the volumetric strain is... With isotropic pressure The relationship curve.

[0039] Explanation of icon numbers:

[0040] label name label name 100 Pore ​​structure modification device for porous rocks 7 Injection pump 1 base 8 Second input pipeline 2 pressure head 9 Second output pipeline 3 Loading pump 10 Second input valve 4 First input pipe 11 First output valve 5 First output pipe 12 Second output valve 6 First input valve

[0041] The realization of the objective, functional features and advantages of the present invention will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0042] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0043] It should be noted that if the embodiments of the present invention involve directional indicators (such as up, down, left, right, front, back, etc.), the directional indicators are only used to explain the relative positional relationship and movement of the components in a certain specific posture (as shown in the figure). If the specific posture changes, the directional indicators will also change accordingly.

[0044] Furthermore, if the embodiments of this invention involve descriptions such as "first" or "second," these descriptions are for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined with "first" or "second" may explicitly or implicitly include at least one of those features. Additionally, the meaning of "and / or" throughout the text includes three parallel solutions; for example, "A and / or B" includes solution A, solution B, or a solution where both A and B are satisfied simultaneously. Furthermore, the technical solutions of the various embodiments can be combined with each other, but this must be based on the ability of those skilled in the art to implement them. When the combination of technical solutions is contradictory or impossible to implement, it should be considered that such a combination of technical solutions does not exist and is not within the scope of protection claimed by this invention.

[0045] In geotechnical engineering, the combined effects of groundwater and cyclic loading / unloading are frequently encountered. This hydraulic coupling deteriorates the mechanical properties of the rock mass, reducing its actual bearing capacity and causing severe deformation. In practical engineering projects, this can lead to geological disasters such as collapses and landslides, severely impacting construction. The deformation of porous soil and rock materials is particularly pronounced. Current technologies modify the pore structure of rocks to alter their mechanical properties and improve engineering stability. This technology is cutting-edge; the challenge lies in how to alter the pore structure, including pore size distribution, pore connectivity, and porosity, without damaging the rock mass, while simultaneously accurately obtaining the impact of the rock strata's pore structure on pore mechanical properties. Furthermore, in many oil and gas fields and carbon dioxide sealing and storage projects, porous rock reservoirs often experience salt crystal precipitation during both displacement and pressurized injection processes. Salt crystal precipitation has a significant impact on the pore mechanical response of porous reservoirs; however, the extent and process of this impact are poorly understood. Obtaining quantitative laws governing pore mechanical parameters under different pore structure conditions through laboratory experiments is currently a technical challenge. In view of this, this application proposes a device for modifying the pore structure of porous rocks and an experimental method for accurately analyzing the influence of rock pore structure on pore mechanical properties.

[0046] Reference Figure 1This invention provides a device 100 for modifying the pore structure of porous rocks. The device 100 includes a base 1, a pressure head 2, a loading pump 3, and an injection pump 7. The base 1 has a first opening facing upwards. The base 1 is provided with a first input pipe 4, a first output pipe 5, a second input pipe 8, and a second output pipe 9. A first input valve 6 is provided on the first input pipe 4, and a second input valve 10 is provided on the second input pipe 8. One end of the first output pipe 5 and one end of the second output pipe 9 are both connected to the first opening. A first output valve 11 is provided on the first output pipe 5, and a second output valve 12 is provided on the second output pipe 9. The pressure head 2 is located above the base 1 and has a second opening facing downwards. The second opening is connected to one end of the first input pipe 4 and one end of the second input pipe 8. The loading pump 3 is connected to the other end of the first input pipe 4, and the injection pump 7 is connected to the other end of the second input pipe 8.

[0047] In the technical solution provided by this invention, the base 1 has a first opening facing upwards. The base 1 is provided with a first input pipe 4, a first output pipe 5, a second input pipe 8, and a second output pipe 9. A first input valve 6 is provided on the first input pipe 4, and a second input valve 10 is provided on the second input pipe 8. One end of the first output pipe 5 and one end of the second output pipe 9 are both connected to the first opening. A first output valve 11 is provided on the first output pipe 5, and a second output valve 12 is provided on the second output pipe 9. The head 2 is positioned above the base 1. The pressure head 2 has a second opening facing downwards. The second opening is connected to one end of the first input pipe 4 and one end of the second input pipe 8. The loading pump 3 is connected to the other end of the first input pipe 4, and the injection pump 7 is connected to the other end of the second input pipe 8. This allows for the control of the opening or closing of the first input valve 6, the first output valve 11, the second input valve 10, and the second output valve 12 as needed, facilitating the experimental method for accurately analyzing the influence of rock pore structure on pore mechanical properties.

[0048] Specifically, the first input pipe 4, the first output pipe 5, the second input pipe 8, and the second output pipe 9 are all configured as heat-insulating pipes. This configuration avoids the liquid temperature from dropping during liquid transport, which could affect the test results.

[0049] Specifically, the porous rock pore structure modification device 100 also includes a first temperature regulating component, which regulates the temperature of the loading pump 3 so that the temperature of the loading pump 3 can always be maintained at a suitable temperature, thereby improving the accuracy of the test.

[0050] Specifically, the porous rock pore structure modification device 100 further includes a second temperature regulation component, which regulates the temperature of the injection pump 7 so that the temperature of the injection pump 7 can always be maintained at a suitable temperature, thereby improving the accuracy of the experiment.

[0051] It should be noted that the technology for temperature regulation using the first and second temperature regulation components is mature. For example, the first and second temperature regulation components may include a thermoelectric cooler, which regulates the temperature of the loading pump 3 and the injection pump 7, resulting in a simple structure. Of course, in other embodiments, the first and second temperature regulation components can be selected as needed.

[0052] In the above embodiments, the first input pipe 4, the first output pipe 5, the second input pipe 8, and the second output pipe 9 are all configured as heat-insulating pipes. The first temperature regulating component and the second temperature regulating component can be configured individually or simultaneously. When configured simultaneously, the effect is the best.

[0053] Based on the above hardware structure, an embodiment of the method for testing the pore mechanical parameters of porous rocks is proposed.

[0054] Reference Figure 2 , Figure 2 This is a schematic flowchart of an embodiment of the method for testing the pore mechanical parameters of porous rocks according to the present invention.

[0055] In this embodiment, the method for testing the pore mechanical parameters of the porous rock includes the following steps:

[0056] Step S10: Load the columnar rock sample into the triaxial chamber of the porous rock pore structure modification device 100, so that the pore structure of the columnar rock sample is connected to the first opening and the second opening in the vertical direction respectively, and apply confining pressure to the columnar rock sample.

[0057] Step S20: Make the temperature of the triaxial chamber and the injection pump 7 the same, open the second input valve 10 and the second output valve 12, and inject the first liquid in a saturated state into the pore structure of the columnar rock sample through the injection pump 7, so that the pore structure of the columnar rock sample is filled with the first liquid.

[0058] Step S30: Close the second input valve 10 and the second output valve 12, adjust the triaxial temperature control system to reduce the temperature of the triaxial chamber, so that crystals precipitate in the pore structure of the columnar rock sample;

[0059] It should be noted that when the temperatures of the triaxial chamber and the injection pump 7 are set to be the same (T1), the first liquid includes a NaCl solution that is saturated at T1. This setup ensures that, since the NaCl solution is saturated at T1, lowering the temperature of the triaxial chamber will cause crystals to precipitate within the pore structure of the columnar rock sample, thus guaranteeing the accuracy of the experiment. In other embodiments, the first liquid may also include a saturated solution of potassium nitrate. Of course, in other embodiments, the second liquid can be selected as needed, and this application does not limit its selection.

[0060] Specifically, in this application, 22℃≤T1≤26℃, so that the temperature is close to the ambient temperature and easy to control. In addition, in other embodiments, the temperature T1 can be set according to specific circumstances, and this application does not limit it.

[0061] Step S40: Make the temperature of the loading pump 3 the same as the temperature of the cooled triaxial chamber, open the first input valve 6 and the first output valve 11, and inject the second liquid into the pore structure with crystals precipitated through the loading pump 3 to discharge the first liquid in the pore structure, so that the pore structure with crystals precipitated is filled with the second liquid.

[0062] In addition, the second liquid should be a conductive liquid used to apply pore pressure. The second liquid cannot dissolve the solvent that crystallizes. Specifically, in this application, the second liquid includes oil. Of course, in other embodiments, the second liquid can be selected as needed, and this application does not limit it.

[0063] Step S50: When the first output valve 11 and the first input valve 6 are opened and closed respectively, the pore parameters of the columnar rock sample are tested under multiple pressure conditions.

[0064] In the technical solution provided by this invention, a columnar rock sample is loaded into the triaxial chamber of the porous rock pore structure modification device 100, so that the pore structure of the columnar rock sample is connected to the first opening and the second opening in the vertical direction, respectively. A confining pressure is applied to the columnar rock sample to make the temperature of the triaxial chamber and the injection pump 7 the same. The second input valve 10 and the second output valve 12 are opened, and a first liquid in a saturated state is injected into the pore structure of the columnar rock sample through the injection pump 7, so that the pore structure of the columnar rock sample is filled with the first liquid. The second input valve 10 and the second output valve 12 are closed to lower the temperature of the triaxial chamber, causing crystals to precipitate in the pore structure of the columnar rock sample, so that the temperature of the loading pump 3 is the same as that of the sample after cooling. With the triaxial chamber at the same temperature, the first input valve 6 and the first output valve 11 are opened. A second liquid is injected into the crystalline pore structure through the loading pump 3 to discharge the first liquid in the pore structure, so that the crystalline pore structure is filled with the second liquid. When the first output valve 11 and the first input valve 6 are opened and closed respectively, the pore parameters of the columnar rock sample are tested under multiple pressure conditions to obtain the corresponding pore mechanical parameters. This allows for the determination of the pore water pressure response properties of porous rock layers based on the pore mechanical parameters, providing effective data support for evaluating formation deformation and instability. It also enables precise analysis of the influence of rock pore structure on pore mechanical properties, achieving quantitative modification of the pore structure and changing pore mechanical properties.

[0065] Specifically, step S50, which involves testing the pore parameters of the columnar rock sample under multiple pressure conditions when the first output valve 11 is opened and closed, includes the following steps:

[0066] Step S501a: Close the first output valve 11 and the first input valve 6, apply lateral pressure to the side of the columnar rock sample, and apply axial pressure to the end of the columnar rock sample, wherein the lateral pressure and the axial pressure increase to a preset pressure value at the same rate.

[0067] In the above steps, the lateral pressure and the axial pressure increase to the preset pressure value at the same rate. This avoids uneven stress on the columnar rock sample, which could lead to deformation and affect the test results.

[0068] Further, step S501a involves closing the first output valve 11 and the first input valve 6, applying lateral pressure to the side of the columnar rock sample, and applying axial pressure to the end of the columnar rock sample. Following the step where the lateral pressure and the axial pressure increase at the same rate to a preset pressure value, the process further includes:

[0069] Step S502a: Record the first evolution curves of the pore fluid pressure and volumetric strain of the columnar rock sample as a function of the lateral pressure and the axial pressure.

[0070] It should be noted that, Figure 3 To close the first output valve 11 and the first input valve 6, the pore fluid pressure in the columnar rock sample under two conditions—one with crystallization modification and the other without—is... With isotropic pressure Relationship curve; Figure 4 To close the first output valve 11 and the first input valve 6, the volumetric strain of the columnar rock sample's pore structure under both crystallization-modified and unmodified conditions... With isotropic pressure The relationship curve; in the second embodiment, the first output valve 11 and the first input valve 6 are closed, that is, under non-drainage conditions, lateral pressure and axial pressure are applied to the columnar rock sample in two cases: one where the pore structure has been modified by crystallization and the other where it has not been modified. The lateral pressure and the axial pressure increase at the same rate to a preset pressure value. The second evolution curve of the pore fluid pressure and the volumetric strain of the columnar rock sample as a function of multiple pressures is recorded, such as... Figure 3 and Figure 4 The Skempton coefficients of columnar rock samples with altered pore structure and those without alteration are respectively... and The bulk moduli are respectively and Skempton coefficient can be obtained through... Received, among which Pore ​​water pressure, For isotropic pressure, For volumetric strain. Bulk modulus is obtained through... Since the conditions are undrained, the mass of the fluid within the pores remains unchanged. .

[0071] Specifically, step S50, which involves testing the pore parameters of the columnar rock sample under multiple pressure conditions when the first output valve 11 is opened and closed, includes the following steps:

[0072] Step S501b: Open the first output valve 11, close the first input valve 6, apply lateral pressure to the side of the columnar rock sample, and apply axial pressure to the end of the columnar rock sample, wherein the lateral pressure and the axial pressure increase to a preset pressure value at the same rate.

[0073] In the above steps, the lateral pressure and the axial pressure increase to the preset pressure value at the same rate. This avoids uneven stress on the columnar rock sample, which could lead to deformation and affect the test results.

[0074] Further, step S501b involves opening the first output valve 11, closing the first input valve 6, applying lateral pressure to the side of the columnar rock sample, and applying axial pressure to the end of the columnar rock sample. Following the step where the lateral pressure and the axial pressure increase at the same rate to a preset pressure value, the process further includes:

[0075] Step S502b: Record the second evolution curve of the volumetric strain of the columnar rock sample as a function of the lateral pressure and the axial pressure.

[0076] It should be noted that, in the first embodiment, Figure 5 When the first output valve 11 is opened and the first input valve 6 is closed, the volumetric strain of the columnar rock sample's pore structure is measured under two conditions: one where the pore structure is altered by crystallization and the other where it is not. With isotropic pressure The relationship curve, refer to Figure 5 When the first output valve 11 is opened and the first input valve 6 is closed, i.e., under drainage conditions, lateral and axial pressures are applied to the columnar rock sample. The lateral and axial pressures increase at the same rate to a preset pressure value. Under drainage conditions, the second liquid within the pore structure does not exert pressure on the framework of the columnar rock sample. The second evolution curve of the volumetric strain of the columnar rock sample as a function of multiple pressures is recorded during this process, such as... Figure 5 As shown. The drainage bulk modulus of the columnar rock sample with altered pore structure due to crystallization and the unaltered columnar rock sample are K´ and K, respectively. The drainage bulk modulus can be determined by... Obtain, among which, For isotropic pressure, For volumetric strain, This represents the pore water pressure. Since the pore fluid pressure increment is 0, that is... .

[0077] Specifically, step S50, which involves testing the pore parameters of the columnar rock sample under multiple pressure conditions when the first output valve 11 is opened and closed, includes the following steps:

[0078] Step S501c: Close the first output valve 11, open the first input valve 6, apply lateral pressure to the side of the columnar rock sample, apply axial pressure to the end of the columnar rock sample, and apply pore water pressure to the columnar rock sample through the loading pump 3, wherein the pore water pressure, the lateral pressure and the axial pressure increase to a preset pressure value at the same rate.

[0079] In the above steps, the pore water pressure, the lateral pressure, and the axial pressure increase to the preset pressure value at the same rate. This avoids uneven stress on the columnar rock sample, which could lead to deformation and affect the test results.

[0080] Figure 6 For columnar rock samples, when the lateral pressure, axial pressure, and pore water pressure increase at the same rate to a preset pressure value in both cases of crystallization modification and no modification, the volumetric strain is... With isotropic pressure In the third embodiment, regarding the relationship curve of the columnar rock sample, lateral pressure, axial pressure, and pore water pressure are applied to the columnar rock sample in two cases: one where the pore structure has been modified by crystallization and the other where it has not. The lateral pressure, axial pressure, and pore water pressure are increased at the same rate to a preset pressure value. The solid matrix compression modulus of the columnar rock sample containing crystals and the columnar rock sample without crystals are respectively... and Its solid matrix compressive modulus can be determined by... ,in, Pore ​​water pressure, For isotropic pressure, For volumetric strain, by Figure 6 The relationship curve between volumetric strain and isotropic pressure was obtained.

[0081] Specifically, pore parameter tests are performed on columnar rock samples under multiple pressure conditions to obtain their pore mechanical parameters. These parameters include the Skempton coefficient, bulk modulus, and matrix bulk modulus. When crystals are present within the pore structure of the columnar rock sample, the bulk modulus of the columnar rock sample with its pore structure altered by crystallization is defined as follows: The bulk modulus of the matrix is Skempton coefficient is When the pore structure of a columnar rock sample is filled with liquid, the bulk modulus of the columnar rock sample without altered pore structure is set as follows: The bulk modulus of the matrix is Skempton coefficient is ,in, > , > , < .

[0082] It should be noted that in the above embodiments, the preset pressure value is set to F1, where 9MPa≤F1≤15MPa. Furthermore, in other embodiments, the preset pressure value can be set according to specific circumstances, and this application does not limit this. Preferably, in the embodiments of this application, the preset pressure value F1=10MPa.

[0083] Specifically, in this application, the columnar rock sample is sandstone. Calculations show that when the pore structure of the columnar rock sample is altered by crystallization, =2256.62MPa; =0.2086; =1871.28MPa; =11365.21MPa; when the pore structure of the columnar rock sample is entirely composed of liquid, i.e., when the pore structure of the columnar rock sample has not been altered, =1970.29MPa; =0.2681; =1526.20MPa; =10151.30 MPa. This indicates that the pore structure of columnar sandstone samples exhibits different pore mechanical parameters depending on whether the sandstone has been altered by crystallization or not. When the pore structure of the columnar sandstone sample is altered by crystallization, all its pore mechanical parameters, except for the Skempton coefficient, are larger than those without alteration. This is because crystallization strengthens the cementation of the sandstone solid particles, making the sandstone skeleton more robust, increasing its bulk modulus, and making it more difficult to compress. The Skempton coefficient reflects the compressibility of the pore structure of the columnar sandstone sample. The degree of pore compressibility depends on the porosity and pore connectivity. The higher the porosity and the better the connectivity, the easier the pores are to compress, and the larger the Skempton coefficient. After crystallization, not only are the pores filled, but the sandstone particles are also cemented, reducing the porosity and weakening the pore connectivity; therefore, the Skempton coefficient is smaller.

[0084] The above are merely preferred embodiments of the present invention and do not limit the scope of the patent. Any equivalent structural or procedural transformations made based on the description and drawings of the present invention, or direct or indirect applications in other related technical fields, are similarly included within the scope of patent protection of the present invention.

Claims

1. A method for testing the pore mechanical parameters of porous rocks, based on a device for modifying the pore structure of porous rocks, characterized in that, The device for modifying the pore structure of porous rock includes a base, a pressure head, a loading pump, and an injection pump. The base has a first opening facing upwards. A first input pipe, a first output pipe, a second input pipe, and a second output pipe are installed on the base. A first input valve is installed on the first input pipe, and a second input valve is installed on the second input pipe. One end of the first output pipe and one end of the second output pipe are both connected to the first opening. A first output valve is installed on the first output pipe, and a second output valve is installed on the second output pipe. The pressure head is located above the base and has a second opening facing downwards. The second opening is connected to one end of the first input pipe and one end of the second input pipe. The loading pump is connected to the other end of the first input pipe, and the injection pump is connected to the other end of the second input pipe. The method for testing the pore mechanical parameters of the porous rock includes the following steps: The columnar rock sample is loaded into the triaxial chamber of the porous rock pore structure modification device, so that the pore structure of the columnar rock sample is connected to the first opening and the second opening in the vertical direction, respectively, and confining pressure is applied to the columnar rock sample. To make the temperature of the triaxial chamber and the injection pump the same, the second input valve and the second output valve are opened, and the first liquid in a saturated state is injected into the pore structure of the columnar rock sample through the injection pump, so that the pore structure of the columnar rock sample is filled with the first liquid. Close the second input valve and the second output valve, adjust the triaxial room temperature control system, and reduce the temperature of the triaxial chamber to cause crystals to precipitate in the pore structure of the columnar rock sample; The temperature of the loading pump is made the same as the temperature of the cooled triaxial chamber. The first input valve and the first output valve are opened, and the second liquid is injected into the porous structure where crystals have precipitated through the loading pump to discharge the first liquid in the porous structure, so that the porous structure where crystals have precipitated is filled with the second liquid. Pore ​​parameters of the columnar rock sample were tested under multiple pressure conditions when the first output valve and the first input valve were opened and closed, respectively. The step of testing the pore parameters of the columnar rock sample under multiple pressure conditions when the first output valve is opened and closed includes: Open the first output valve, close the first input valve, apply lateral pressure to the side of the columnar rock sample, and apply axial pressure to the end of the columnar rock sample, wherein the lateral pressure and the axial pressure increase to a preset pressure value at the same rate; The steps of opening the first output valve, closing the first input valve, applying lateral pressure to the side of the columnar rock sample, and applying axial pressure to the end of the columnar rock sample, wherein the lateral pressure and the axial pressure increase to a preset pressure value at the same rate, further include: A second evolution curve recording the volumetric strain of the columnar rock sample as a function of the lateral pressure and the axial pressure; When the temperatures of the triaxial chamber and the injection pump are the same, the temperature is defined as T1. The first liquid includes a NaCl solution that is saturated at T1; The second liquid includes oil.

2. The method for testing the pore mechanical parameters of porous rocks as described in claim 1, characterized in that, The step of testing the pore parameters of the columnar rock sample under multiple pressure conditions when the first output valve is opened and closed includes: The first output valve and the first input valve are closed, lateral pressure is applied to the side of the columnar rock sample, and axial pressure is applied to the end of the columnar rock sample, wherein the lateral pressure and the axial pressure increase to a preset pressure value at the same rate.

3. The method for testing the pore mechanical parameters of porous rocks as described in claim 2, characterized in that, The step of closing the first output valve and the first input valve, applying lateral pressure to the side of the columnar rock sample, and applying axial pressure to the end of the columnar rock sample, wherein the lateral pressure and the axial pressure increase to a preset pressure value at the same rate, further includes the following: Record the first evolution curves of pore fluid pressure and volumetric strain of columnar rock samples as a function of the lateral pressure and the axial pressure.

4. The method for testing the pore mechanical parameters of porous rocks as described in claim 1, characterized in that, The step of testing the pore parameters of the columnar rock sample under multiple pressure conditions when the first output valve is opened and closed includes: Close the first output valve, open the first input valve, apply lateral pressure to the side of the columnar rock sample, apply axial pressure to the end of the columnar rock sample, and apply pore water pressure to the columnar rock sample through the loading pump, wherein the pore water pressure, the lateral pressure and the axial pressure increase to a preset pressure value at the same rate.

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