Multi-stage loose sandstone sample and preparation method thereof, seepage experimental method and device

Abstract

The present application discloses a multi-section loose sandstone sample and its preparation method, seepage test method and device. The preparation device of the multi-section loose sandstone sample includes: a base, an annular sleeve and a pressure mold. The upper end surface of the base has a convex ring; the annular sleeve includes at least two sleeve monomers of equal height, and the at least two sleeve monomers of equal height are circumferentially surrounded to form an annular sleeve; wherein, one end of the annular sleeve is embedded in the convex ring; the pressure mold includes a cylindrical mold embedded in the inside of the annular sleeve, and the outer diameter of the cylindrical mold matches the inner diameter of the annular sleeve. Based on this preparation device, various types of loose sandstone can be effectively fixed to make multi-section loose sandstone samples, thereby improving the safety and reliability of seepage experiments of various rock bodies.

Description

Technical Field

[0001] The present application relates to the field of sandstone sample preparation, and specifically to a multi-segment loose sandstone sample and a preparation method thereof, and a seepage experimental method and device. Background Art

[0002] The study of the seepage characteristics of loose sandstone rock mass is a key research content in the field of energy storage development such as oil and gas extraction, in-situ leaching, and deep mining. The rock seepage experiment under multi-field coupling refers to the seepage experiment conducted on the rock mass under the joint action of multiple fields such as pressure field, hydraulic field, temperature field, and chemical field to obtain the changes in rock permeability, porosity, particle size distribution, strength and other characteristics.

[0003] Dense sandstone has a stable structure and can withstand high pressure, making the sample preparation and experimental process relatively simple. However, the sample preparation and experimental process for loose sandstone is particularly cumbersome. Loose sandstone is difficult to shape during sample preparation. If cementitious materials are used to fix the rock sample, the properties of the sandstone are directly changed, and the experimental results lack credibility. Loose sandstone has free surfaces at both ends of the flow during the experiment. Under the seepage pressure difference, the rock mass creeps, and its loose structure cannot withstand the confining pressure. Rock sample fragmentation often occurs, and particles are continuously lost during the seepage process. The lost sandstone particles accumulate in large quantities in the pipe network of the experimental equipment, which can damage the equipment at the least and cause pipe bursts or injuries to experimental personnel at the worst.

[0004] In addition, in engineering practice, we often encounter situations where rock types change rapidly within a small area, for example, the continuous change from surrounding rock to ore body. At this time, it is necessary to understand in advance the impact of injection operations on the seepage characteristics of multiple continuous rock masses, so as to guide engineering practice and improve production efficiency. Summary of the Invention

[0005] In view of this, the embodiments of the present application provide a multi-segment loose sandstone sample and its preparation method, seepage test method and device, which aim to effectively fix the loose sandstone and meet the seepage test requirements of the multi-segment loose sandstone sample.

[0006] The technical solution of the embodiment of the present application is implemented as follows:

[0007] In a first aspect, an embodiment of the present application provides a multi-stage loose sandstone sample preparation device, comprising:

[0008] A base, wherein the upper end surface of the base has a convex ring;

[0009] The annular sleeve comprises at least two sleeve units of equal height, wherein the at least two sleeve units of equal height are circumferentially combined to form the annular sleeve; wherein one end of the annular sleeve is embedded in the convex ring;

[0010] The pressure-applying mold comprises a cylindrical mold embedded in the annular sleeve, and the outer diameter of the cylindrical mold matches the inner diameter of the annular sleeve.

[0011] In the above solution, the pressure mold further includes:

[0012] The force applying part is connected to the cylindrical mold and is used to drive the cylindrical mold to move.

[0013] In the above solution, the lengths of the annular sleeve and the cylindrical mold are both greater than the total length of the multi-section loose sandstone sample.

[0014] In a second aspect, an embodiment of the present application provides a method for preparing a multi-stage loose sandstone sample, based on the preparation device described in the first aspect of the embodiment of the present application, the method comprising:

[0015] Sleeve a thermoplastic tube over the cylindrical mold of the pressure mold, with the lower end of the thermoplastic tube reserved for a set length to protrude from the cylindrical mold, and allow the thermoplastic tube to shrink under heat until the thermoplastic tube completely wraps the lower end of the cylindrical mold;

[0016] The thermoplastic tube after shaping is removed from the pressure mold, the at least two sleeve units of equal height are circumferentially embedded into the convex ring of the base to form the annular sleeve, and the thermoplastic tube is embedded into the annular sleeve;

[0017] placing a support mesh and a first filter screen into the thermoplastic tube in sequence, pouring a first aggregate of the first sandstone sample into the thermoplastic tube, and placing a second filter screen and a support mesh on top of the first aggregate in sequence;

[0018] Controlling the pressure mold to apply pressure to compact the first aggregate into a shape, removing the annular sleeve to expose the thermoplastic tube, and raising the pressure mold so that a set length of thermoplastic tube is left between the formed first sandstone sample and the pressure mold. The thermoplastic tube of the set length shrinks due to heat, pressing the supporting mesh on the upper end of the first sandstone sample, thereby completing the preparation of the first sandstone sample;

[0019] Re-embedding the at least two sleeve units of equal height into the convex ring of the base along the circumferential direction to enclose the annular sleeve, and placing the first section of sandstone sample into the annular sleeve;

[0020] The supporting mesh and the second filter are sequentially placed into the thermoplastic tube, the second aggregate of the middle sandstone sample is poured into the thermoplastic tube, and the second filter and the supporting mesh are sequentially placed on the second aggregate. The pressure mold is controlled to apply pressure to compact the second aggregate into shape. The annular sleeve is removed to expose the thermoplastic tube. The pressure mold is raised so that a set length of thermoplastic tube is left between the formed middle sandstone sample and the pressure mold. The thermoplastic tube of the set length shrinks due to heat, pressing the supporting mesh on the upper end of the middle sandstone sample, thereby completing the preparation of the middle sandstone sample.

[0021] Re-embedding the at least two sleeve units of equal height into the convex ring of the base along the circumferential direction to enclose the annular sleeve, and placing the first section sandstone sample and the middle section sandstone sample into the annular sleeve;

[0022] A supporting mesh and a second filter are sequentially placed into the thermoplastic tube, the third aggregate of the final sandstone sample is poured into the thermoplastic tube, and the first filter and the supporting mesh are sequentially placed on the third aggregate. The pressure mold is controlled to apply pressure to compact the third aggregate into shape, the annular sleeve is removed to expose the thermoplastic tube, and the pressure mold is raised so that a set length of thermoplastic tube is left between the formed final sandstone sample and the pressure mold. The thermoplastic tube of the set length shrinks due to heat, pressing the supporting mesh on the upper end of the final sandstone sample to complete the preparation of the final sandstone sample.

[0023] In the above solution, there are multiple middle-section sandstone samples, the preparation process of each middle-section sandstone sample is the same, and the second aggregates of different middle-section sandstone samples are different.

[0024] In the above scheme, the initial diameter of the thermoplastic tube is larger than the diameter of the multi-segment loose sandstone sample, and the diameter after complete contraction is smaller than the diameter of the multi-segment loose sandstone sample, so as to apply a certain pressure to the multi-segment loose sandstone sample, and the length of the thermoplastic tube is greater than the height of the multi-segment loose sandstone sample.

[0025] In the above solution, the supporting mesh is made of non-metallic material;

[0026] The first filter screen and the second filter screen are both made of non-metallic materials, wherein the mesh number of the first filter screen is greater than the mesh number of the second filter screen.

[0027] In a third aspect, an embodiment of the present application provides a multi-segment loose sandstone sample, which is a multi-segment loose sandstone sample prepared by the method described in the second aspect of the embodiment of the present application.

[0028] In a fourth aspect, an embodiment of the present application provides a seepage experiment method, comprising:

[0029] The multi-segment loose sandstone sample described in the third aspect of the embodiment of the present application is placed in a seepage experiment instrument to conduct a seepage experiment;

[0030] The multi-section loose sandstone sample after the seepage test is taken out, and the multi-section loose sandstone sample is cut along the interface between two adjacent sections of the sandstone sample. Each section of the cut sandstone sample is washed to collect the corresponding retained particles.

[0031] In the above solution, the method further includes:

[0032] A target test is performed on each of the sandstone samples after flushing, wherein the target test includes at least one of the following: a porosity test, a permeability test, and a particle size distribution test.

[0033] The technical solution provided in the embodiments of the present application is a device for preparing multi-segment loose sandstone samples, comprising: a base, an annular sleeve, and a pressure mold. The upper end surface of the base has a convex ring; the annular sleeve includes at least two sleeve monomers of equal height, and the at least two sleeve monomers of equal height are circumferentially enclosed to form an annular sleeve; wherein one end of the annular sleeve is embedded in the convex ring; the pressure mold includes a cylindrical mold embedded in the interior of the annular sleeve, and the outer diameter of the cylindrical mold matches the inner diameter of the annular sleeve. Based on this preparation device, various types of loose sandstone can be effectively fixed to produce multi-segment loose sandstone samples, thereby improving the safety and reliability of seepage experiments on various rock masses. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 This is a schematic structural diagram of a multi-stage loose sandstone sample preparation device according to an embodiment of the present application;

[0035] Figure 2 for Figure 1 Schematic diagram of the decomposition structure;

[0036] Figure 3 This is a schematic flow chart of a method for preparing a multi-stage loose sandstone sample according to an embodiment of the present application;

[0037] Figure 4 This is a schematic structural diagram of a multi-segment loose sandstone sample according to an embodiment of the present application;

[0038] Figure 5 for Figure 4 Schematic diagram of the decomposition structure;

[0039] Figure 6 This is a schematic structural diagram of a multi-segment loose sandstone sample in an application embodiment of the present application;

[0040] Figure 7 for Figure 6 The schematic diagram of the structure of each section of the multi-section loose sandstone sample after cutting is shown.

[0041] Description of reference numerals:

[0042] 1. Thermoplastic tube; 2. Support mesh; 3. Filter; 4. Rock sample; 5. Pressure mold;

[0043] 6. Annular sleeve; 7. Base. DETAILED DESCRIPTION

[0044] In order to make the purpose, technical solutions and advantages of this application clearer, the application will be further described in detail below with reference to the accompanying drawings. The described embodiments should not be regarded as limiting this application. All other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of this application.

[0045] In the description of this application, reference is made to “some embodiments”, which describe a subset of all possible embodiments, but it will be understood that “some embodiments” may be the same subset or different subsets of all possible embodiments and may be combined with each other without conflict.

[0046] In the description of this application, the terms "first," "second," etc., are used merely to distinguish similar objects and do not represent a specific ordering of the objects. It is understood that "first," "second," etc., may be interchanged with the specific order or precedence where permitted, so that the embodiments of the application described herein can be implemented in an order other than that illustrated or described herein. Unless otherwise specified, "plurality" means at least two.

[0047] In the description of this application, it should be noted that, unless otherwise expressly specified or limited, the terms "mounted," "connected," and "connected" should be understood in a broad sense. For example, they can refer to fixed connections, detachable connections, or integral connections; mechanical connections or electrical connections; direct connections or indirect connections through an intermediate medium; and internal connections between two components. Those skilled in the art will understand the specific meanings of the above terms in this application based on the specific circumstances.

[0048] In this application, unless otherwise expressly specified or limited, a first feature being "above" or "below" a second feature may include the first and second features being in direct contact, or may include the first and second features being in contact not directly but through another feature between them. Moreover, a first feature being "above," "above," and "above" a second feature may include the first feature being directly above or obliquely above the second feature, or may simply mean that the first feature is higher in level than the second feature. A first feature being "below," "below," and "below" a second feature may include the first feature being directly below or obliquely below the second feature, or may simply mean that the first feature is lower in level than the second feature.

[0049] The present application embodiment provides a multi-stage loose sandstone sample preparation device, such as Figure 1 and Figure 2 As shown, the preparation device includes: a base 7, an annular sleeve 6, and a pressure mold 5. The upper end surface of the base 7 has a convex ring; the annular sleeve 6 includes at least two sleeve units of equal height, which are circumferentially surrounded by the at least two sleeve units of equal height to form the annular sleeve 6; one end of the annular sleeve 6 is embedded in the convex ring; the pressure mold 5 includes a cylindrical mold embedded in the annular sleeve, and the outer diameter of the cylindrical mold matches the inner diameter of the annular sleeve 6.

[0050] It can be understood that based on this preparation device, it is possible to effectively fix various types of loose sandstone, make multi-segment loose sandstone samples, and improve the safety and reliability of seepage experiments of various rock masses. Specifically, the convex ring on the base 7 can install and fix each sleeve monomer, thereby forming an annular sleeve 6, which forms a sample preparation space for multiple sections of loose sandstone samples. The annular sleeve 6 adopts a detachable combination structure and can be assembled and disassembled according to needs during the preparation of the multi-segment loose sandstone sample. Based on the pressure mold 5, it is possible to apply pressure separately multiple times during the preparation of the multi-segment loose sandstone sample, thereby achieving segmented pressing and forming of each section of the rock sample, and combining to form a multi-segment loose sandstone sample.

[0051] For example, the pressure mold further includes: a force applying portion connected to the cylindrical mold and used to drive the cylindrical mold to move. Figure 2 As shown, in an application example, the top end of the cylindrical mold has a baffle with an outer diameter larger than the outer diameter of the annular sleeve 6, and a force-applying portion for easy gripping is provided on the baffle.

[0052] It can be understood that the lengths of the annular sleeve and the cylindrical mold are both greater than the total length of the multi-segment loose sandstone sample.

[0053] It should be noted that the lengths of each section of the multi-section loose sandstone sample may be equal or unequal, but the diameters are the same.

[0054] The present application also provides a method for preparing a multi-stage loose sandstone sample, based on the preparation device of the first aspect of the present application embodiment. Figure 3 As shown, the method includes:

[0055] In step 301 , a thermoplastic tube is placed on the cylindrical mold of the pressure mold, with the lower end of the thermoplastic tube being left exposed to a predetermined length from the cylindrical mold. The thermoplastic tube is heated to shrink until the thermoplastic tube completely covers the lower end of the cylindrical mold.

[0056] Step 302: remove the shaped thermoplastic tube from the pressure mold, circumferentially embed at least two sleeve units of equal height into the convex ring of the base to form an annular sleeve, and then embed the thermoplastic tube into the annular sleeve.

[0057] Step 303 , sequentially placing a support mesh and a first filter into the thermoplastic tube, pouring the first aggregate of the first sandstone sample into the thermoplastic tube, and sequentially placing a second filter and a support mesh on top of the first aggregate.

[0058] In step 304, the pressure mold is controlled to apply pressure to compact the first aggregate into shape. The annular sleeve is removed to expose the thermoplastic tube. The pressure mold is raised so that a set length of thermoplastic tube is left between the formed first sandstone sample and the pressure mold. The set length of thermoplastic tube shrinks due to heat, pressing the supporting mesh at the upper end of the first sandstone sample, thereby completing the preparation of the first sandstone sample.

[0059] Step 305 : Re-embed at least two casing units of equal height into the convex ring of the base along the circumferential direction to form an annular casing, and place the first section of sandstone sample into the annular casing.

[0060] Step 306: Place the support mesh and the second filter into the thermoplastic tube in sequence, pour the second aggregate of the middle sandstone sample into the thermoplastic tube, and place the second filter and the support mesh on top of the second aggregate in sequence. Control the pressure mold to apply pressure to compact the second aggregate into shape. Remove the annular sleeve to expose the thermoplastic tube. Raise the pressure mold so that a set length of thermoplastic tube is left between the formed middle sandstone sample and the pressure mold. The set length of thermoplastic tube shrinks due to heat, pressing the support mesh on the upper end of the middle sandstone sample, thereby completing the preparation of the middle sandstone sample.

[0061] Step 307 : Re-embed at least two casing units of equal height into the convex ring of the base along the circumferential direction to form an annular casing, and place the first section sandstone sample and the middle section sandstone sample into the annular casing.

[0062] In step 308, the supporting mesh and the second filter are sequentially placed into the thermoplastic tube, the third aggregate of the final sandstone sample is poured into the thermoplastic tube, and the first filter and the supporting mesh are sequentially placed on top of the third aggregate. The pressure mold is controlled to apply pressure to compact the third aggregate into shape, the annular sleeve is removed to expose the thermoplastic tube, and the pressure mold is raised so that a set length of thermoplastic tube is left between the formed final sandstone sample and the pressure mold. The set length of thermoplastic tube shrinks due to heat, pressing the supporting mesh on the upper end of the final sandstone sample, thereby completing the preparation of the final sandstone sample.

[0063] It should be noted that the multi-section loose sandstone sample prepared in the embodiment of the present application can achieve shaped protection for each section on the sides and at both ends, thereby effectively avoiding the creep of the loose sandstone during the seepage experiment; in addition, the multiple sections of the rock samples are interconnected, and the particles will not be lost into the experimental instrument during the seepage experiment. After the test, the escaped particles can be collected in sections; thirdly, after the seepage experiment, the multiple sections of the rock samples can be divided without affecting the shaped protection, and the shaped protection material does not affect experiments such as nuclear magnetic porosity testing.

[0064] For example, there are multiple intermediate sandstone samples, each prepared using the same process, and each having a different second aggregate. Thus, a multi-segment loose sandstone sample can have a structure of three or more segments, which is not limited in this embodiment of the present application.

[0065] Exemplarily, the initial diameter of the thermoplastic tube is larger than the diameter of the multi-segment loose sandstone sample, and the diameter after complete contraction is smaller than the diameter of the multi-segment loose sandstone sample, so as to apply a certain pressure to the multi-segment loose sandstone sample, and the length of the thermoplastic tube is greater than the height of the multi-segment loose sandstone sample.

[0066] It should be noted that after heating and shrinking, the thermoplastic tube can tightly wrap the rock sample laterally to make its shape stable. Its specifications are consistent with those of the rock sample. Its material does not react with the seepage fluid and does not affect the seepage and nuclear magnetic resonance experiments.

[0067] Exemplarily, the supporting mesh is made of non-metallic material; the first filter screen and the second filter screen are both made of non-metallic material, wherein the mesh number of the first filter screen is greater than the mesh number of the second filter screen.

[0068] It should be noted that the support mesh material is non-deformable, providing support for the rock sample at both ends, maintaining a stable shape. The mesh structure allows for the flow of liquid and particles, and its specifications are consistent with those of the rock sample. The material does not participate in the seepage fluid reaction, thus not affecting seepage and NMR experiments. For example, the support mesh can be made of rigid PVC board.

[0069] It should be noted that the mesh size of the filter screens at the ends of the multi-section loose sandstone sample (i.e., the first filter screen mentioned above) must be able to completely intercept all particles, and the mesh size of the filter screen in the middle section (i.e., the second filter screen mentioned above) must be able to retain the main particles of the rock sample to maintain the rock structure while allowing small particles to pass smoothly. For example, the mesh size of the filter screens at the ends is designed to be 500 mesh to intercept escaped particles larger than 0.04 mm, and the mesh size of the filter screen in the middle section is 100 mesh to intercept fine sandstone particles larger than 0.15 mm. The filter screen can be made of PP mesh, which does not participate in the seepage fluid reaction and does not affect the seepage and nuclear magnetic resonance experiments.

[0070] The following is an illustrative description of the preparation process of the multi-stage loose sandstone sample according to the embodiment of the present application in conjunction with an application example.

[0071] In this application example, a three-section loose sandstone sample consisting of three types of loose sandstone was designed. The sample diameter was 50 mm. The first section of the sample was a gray loose coarse sandstone with a length of 50 mm and a density of 1.6 g / cm 3 The minimum particle size is 0.1 mm; the middle section rock sample is 30 mm long black bulk fine sandstone with a density of 1.8 g / cm 3 The minimum particle size is 0.05 mm, and the final rock sample is a yellow medium sandstone with a length of 100 mm and a density of 1.7 g / cm 3 , minimum particle size 0.08mm.

[0072] According to the above experimental design requirements, the following device parameters are designed:

[0073] 1: Thermoplastic tube, its characteristics are: after heating and shrinking, it can tightly wrap the rock sample in the side to make its shape stable. Its specification is 55mm in diameter, 35mm in diameter after shrinking, and 240mm in total length. It can wrap three sections of rock samples. It is made of PVC and does not react with the seepage fluid, and does not affect the seepage and nuclear magnetic resonance experiments.

[0074] 2: Support mesh, its characteristics are: the material is not easy to deform, it can provide fixation at both ends of the rock sample to make its shape stable, and the mesh structure allows liquid and particles to flow. Its specifications are 1mm thickness, 50mm diameter, and mesh diameter 1mm. There are 6 pieces in total. It is made of hard PVC board and does not participate in the seepage fluid reaction, and does not affect the seepage and nuclear magnetic resonance experiments.

[0075] 3: Filter, its characteristics are: the mesh size of the filter at both ends of the multi-section rock sample must be able to completely intercept all particles, and the mesh size of the filter in the middle section must be able to retain the main particles of the rock sample to maintain the rock structure while allowing small particles to pass smoothly. Therefore, the mesh size of the filter at both ends is designed to be 500 mesh to intercept escaping particles larger than 0.04mm, and the mesh size of the filter in the middle section is 100 mesh to intercept fine sandstone particles larger than 0.15mm. Its specifications are 50mm in diameter, 2 pieces of 500 mesh, and 4 pieces of 100 mesh. It is made of PP mesh, does not participate in the seepage fluid reaction, and does not affect the seepage and nuclear magnetic resonance experiments.

[0076] 4: Rock sample, its characteristics are: the raw material of the rock sample can be loose and bulky, and after being compressed by the sample preparation device, wrapped with a thermoplastic tube and fixed with a hard mesh, a rock sample with a stable structure is formed. The core specifications are as follows: core diameter 50mm, the first section is gray loose coarse sandstone 50mm long, weighing 157g, the middle section is black loose fine sandstone 30mm long, weighing 106g, and the last section is yellow loose medium sandstone, weighing 334g.

[0077] 5: Pressure mold, its characteristics are: the diameter of the cylindrical part is 50mm, the length is 240mm, the material is stainless steel, and it can be used as a pressure device.

[0078] 6: Annular sleeve, its characteristics are: after splicing, the inner diameter is 50mm, the outer diameter is 60mm, its length is 240mm, it is made of stainless steel and can withstand high pressure.

[0079] 7: Base, its characteristics are: inner diameter is 60mm, material is stainless steel, can withstand high pressure.

[0080] See also Figure 4 and Figure 5 The preparation process of multi-stage rock samples is as follows:

[0081] 1) Take a 240mm thermoplastic tube 1 and put it on the pressure mold 5, with 1mm of the thermoplastic tube exposed at the lower end. Use a hot air gun to blow the thermoplastic tube until it completely wraps the pressure mold 5 and the 10mm exposed part at the lower end is completely shrunk. Take out the formed thermoplastic tube.

[0082] 2) Assemble the annular sleeve 6 and fix it with the base 7, embed the thermoplastic tube into the annular sleeve 6, place a support mesh 2 and a 500-mesh filter screen 3 into the bottom of the thermoplastic tube in turn, weigh 157g of gray loose coarse sand and pour it into the thermoplastic tube, then place a 100-mesh filter screen 3 and a support mesh 2 on the coarse sand in turn, use a pressure mold 5 to insert it into the thermoplastic tube, apply pressure to compact the sand body, then remove the annular sleeve to expose the thermoplastic tube, raise the pressure mold by 10mm, and leave a section of thermoplastic tube between the formed rock mass and the mold, use a hot air gun to heat the section of thermoplastic tube to shrink it and clamp the support mesh at the upper end of the rock mass, and the first section of rock sample 4 is prepared.

[0083] 3) Reassemble the annular casing and place the first section of rock sample 4 into the casing, place a supporting mesh and a 100-mesh filter in the thermoplastic tube in turn, and place them on the first section of rock sample 4. Weigh 106g of black loose fine sand and pour it into the thermoplastic tube. Then place a 100-mesh filter and a supporting mesh in turn on the fine sand. Use a pressure mold to insert it into the thermoplastic tube and apply pressure to compact the sand. Then remove the annular casing to expose the thermoplastic tube. Raise the pressure mold by 10mm to leave a section of thermoplastic tube between the formed rock and the mold. Use a hot air gun to heat the section of thermoplastic tube to shrink it and clamp the supporting mesh at the upper end of the rock. The middle section of the rock sample is prepared. Repeat this step to prepare the last section of the rock sample. The rock sample preparation is completed. Among them, for the end rock sample, after controlling the pressure mold to compact the aggregate into shape, the annular sleeve can be disassembled, the pressure mold can be removed, and a 10mm length of thermoplastic tube can be reserved. Use a hot air gun to heat this section of thermoplastic tube to shrink it and clamp the supporting mesh at the upper end of the rock mass. Cut off the excess thermoplastic tube to complete the rock sample preparation.

[0084] Figure 6 A schematic diagram of the physical structure of a multi-segment loose sandstone sample prepared in the above manner is shown.

[0085] The present invention also provides a flow test method, including:

[0086] The multi-segment loose sandstone sample according to the third embodiment of the present application is placed in a seepage experiment instrument to conduct a seepage experiment;

[0087] The multi-section loose sandstone sample after the seepage experiment is taken out, and the multi-section loose sandstone sample is cut along the interface between two adjacent sections of the sandstone sample. Each section of the cut sandstone sample is washed and the corresponding retained particles are collected.

[0088] For example, Figure 6 The segmented loose sandstone samples shown in the figure are cut along the interface between two adjacent segments of sandstone samples. Figure 7 Each section of sandstone sample can be flushed and the corresponding retained particles can be collected. The collected particles are convenient for studying the seepage characteristics and improving the accuracy of the seepage experiment.

[0089] It should be noted that the seepage experiment process is as follows:

[0090] 1) Prepare multiple cores of certain specifications (i.e., multi-section rock samples) as seepage test samples according to requirements and rock mass types;

[0091] 2) Place multiple core sections into the holder according to the experimental design, apply clamping pressure to tightly clamp the sides of the core so that the seepage liquid in the holder can only pass through the core;

[0092] 3) Liquid is injected from one end, passing through multiple core sections. The liquid enters the first core section and reacts physically and chemically with the core during the seepage process, carrying away particles in the core. At the same time, some particles are retained by the pores during the seepage process. The seepage liquid then enters the next core section and repeats the above reaction until it passes through all the core sections and flows out from the other end. This process causes the porosity, permeability, strength, etc. of the multiple core sections to gradually change.

[0093] It can be understood that the multi-section loose sandstone sample prepared in the embodiment of the present application can achieve the shape protection of the rock sample; in addition, the multiple sections of rock samples are connected to each other, and the particles will not be lost into the experimental instrument during the seepage experiment. After the test, the escaped particles can be collected in sections; thirdly, after the seepage experiment, the multiple sections of rock samples can be divided without affecting the shape protection, and the shape protection material does not affect experiments such as nuclear magnetic porosity testing.

[0094] Exemplarily, the seepage experimental method further includes:

[0095] A target test is performed on each of the sandstone samples after flushing, wherein the target test includes at least one of the following: a porosity test, a permeability test, and a particle size distribution test.

[0096] It is understandable that the porosity, permeability, and particle size distribution of each section of sandstone sample after flushing can be tested separately. Therefore, the multi-section loose sandstone sample of the embodiment of the present application can not only meet the need to connect multiple sections of rock samples in the seepage experiment, but also meet the need to be completely separated while maintaining the fixed protection after the seepage experiment.

[0097] It should be noted that the technical solutions described in the embodiments of this application can be combined arbitrarily without conflict.

[0098] The above are only specific embodiments of the present application, but the scope of protection of this application is not limited thereto. Any changes or substitutions that can be easily conceived by a person skilled in the art within the technical scope disclosed in this application should be included in the scope of protection of this application. Therefore, the scope of protection of this application should be based on the scope of protection of the claims.

Claims

1. A method for preparing a multi-stage loose sandstone sample, based on a device for preparing a multi-stage loose sandstone sample, characterized in that: The preparation device comprises: A base, wherein the upper end surface of the base has a convex ring; The annular sleeve comprises at least two sleeve units of equal height, wherein the at least two sleeve units of equal height are circumferentially combined to form the annular sleeve; wherein one end of the annular sleeve is embedded in the convex ring; A pressure die, wherein the pressure die comprises a cylindrical die embedded in the annular sleeve, and the outer diameter of the cylindrical die matches the inner diameter of the annular sleeve; The method comprises: Sleeve a thermoplastic tube over the cylindrical mold of the pressure mold, with the lower end of the thermoplastic tube reserved for a set length to protrude from the cylindrical mold, and allow the thermoplastic tube to shrink under heat until the thermoplastic tube completely wraps the lower end of the cylindrical mold; The thermoplastic tube after shaping is removed from the pressure mold, the at least two sleeve units of equal height are circumferentially embedded into the convex ring of the base to form the annular sleeve, and the thermoplastic tube is embedded into the annular sleeve; placing a support mesh and a first filter screen into the thermoplastic tube in sequence, pouring a first aggregate of the first sandstone sample into the thermoplastic tube, and placing a second filter screen and a support mesh on top of the first aggregate in sequence; Controlling the pressure mold to apply pressure to compact the first aggregate into a shape, removing the annular sleeve to expose the thermoplastic tube, and raising the pressure mold so that a set length of thermoplastic tube is left between the formed first sandstone sample and the pressure mold. The thermoplastic tube of the set length shrinks due to heat, pressing the supporting mesh on the upper end of the first sandstone sample, thereby completing the preparation of the first sandstone sample; Re-embedding the at least two sleeve units of equal height into the convex ring of the base along the circumferential direction to enclose the annular sleeve, and placing the first section of sandstone sample into the annular sleeve; The supporting mesh and the second filter are sequentially placed into the thermoplastic tube, the second aggregate of the middle sandstone sample is poured into the thermoplastic tube, and the second filter and the supporting mesh are sequentially placed on the second aggregate. The pressure mold is controlled to apply pressure to compact the second aggregate into shape. The annular sleeve is removed to expose the thermoplastic tube. The pressure mold is raised so that a set length of thermoplastic tube is left between the formed middle sandstone sample and the pressure mold. The thermoplastic tube of the set length shrinks due to heat, pressing the supporting mesh on the upper end of the middle sandstone sample, thereby completing the preparation of the middle sandstone sample. Re-embedding the at least two sleeve units of equal height into the convex ring of the base along the circumferential direction to enclose the annular sleeve, and placing the first section sandstone sample and the middle section sandstone sample into the annular sleeve; A supporting mesh and a second filter are sequentially placed into the thermoplastic tube, the third aggregate of the final sandstone sample is poured into the thermoplastic tube, and the first filter and the supporting mesh are sequentially placed on the third aggregate. The pressure mold is controlled to apply pressure to compact the third aggregate into shape, the annular sleeve is removed to expose the thermoplastic tube, and the pressure mold is raised so that a set length of thermoplastic tube is left between the formed final sandstone sample and the pressure mold. The thermoplastic tube of the set length shrinks due to heat, pressing the supporting mesh on the upper end of the final sandstone sample to complete the preparation of the final sandstone sample.

2. The method according to claim 1, characterized in that The pressure-applying mold further includes a force-applying portion connected to the cylindrical mold and configured to drive the cylindrical mold to move.

3. The method according to claim 1, characterized in that The lengths of the annular sleeve and the cylindrical mold are both greater than the total length of the multi-section loose sandstone sample.

4. The method according to claim 1, wherein There are multiple middle-section sandstone samples, each of which is prepared through the same process, and the second aggregates of different middle-section sandstone samples are different.

5. The method according to claim 1, characterized in that The initial diameter of the thermoplastic tube is larger than the diameter of the multi-segment loose sandstone sample, and the diameter after complete contraction is smaller than the diameter of the multi-segment loose sandstone sample, so as to apply a certain pressure to the multi-segment loose sandstone sample. The length of the thermoplastic tube is greater than the height of the multi-segment loose sandstone sample.

6. The method according to claim 1, characterized in that The supporting mesh is made of non-metallic material; The first filter screen and the second filter screen are both made of non-metallic materials, wherein the mesh number of the first filter screen is greater than the mesh number of the second filter screen.

7. A multi-segment loose sandstone sample, characterized in that: The multi-segment loose sandstone sample is prepared by the method according to any one of claims 1 to 6.

8. A seepage test method, characterized in that: include: Putting the multi-section loose sandstone sample as claimed in claim 7 into a seepage test instrument to conduct a seepage test; The multi-section loose sandstone sample after the seepage test is taken out, and the multi-section loose sandstone sample is cut along the interface between two adjacent sections of the sandstone sample. Each section of the cut sandstone sample is washed to collect the corresponding retained particles.

9. The method according to claim 8, characterized in that The method further comprises: A target test is performed on each of the sandstone samples after flushing, wherein the target test includes at least one of the following: a porosity test, a permeability test, and a particle size distribution test.

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