Preparation method and device of salt rock-mudstone interface model sample

Abstract

The invention discloses a preparation method and device of a salt rock-mudstone interface model sample. The preparation method comprises the following steps: pre-pressing and splicing a salt rock block body and a mudstone block body to form a sample assembly; placing the spliced sample assembly with the pre-compressive stress in a preset high-humidity air environment and / or a high-humidity-low-humidity circulating air environment, so that the surface of the salt rock block deliquesces to generate a saturated salt solution, and the saturated salt solution is filled in an interface gap between the salt rock block and the mudstone block; activating a gap self-healing mechanism of a salt rock block on one side of the interface to realize interface stitching, and preparing a salt rock-mudstone interface model sample matched with an actual rock structure; according to the application, the salt rock-mudstone interface can be simulated more truly, so that more accurate mechanical and permeability characteristic experimental data of the salt rock-mudstone interface can be obtained, and the evaluation precision of the long-term operation reliability of the underground layered salt rock-salt cavern energy storage system is improved.

Description

Technical Field

[0001] The present application relates to the field of geotechnical engineering technology, and in particular to a method and device for preparing a salt rock-mudstone interface model sample. Background Art

[0002] At present, underground salt caverns are widely used in compressed air energy storage, hydrogen energy storage and crude oil storage as a key energy storage facility. Salt caverns are built in salt rock layers with sodium chloride as the main component, and have excellent sealing and long-term stability. However, most of the salt rocks in China are layered salt rocks deposited in the lacustrine phase. These salt rock layers are interspersed with mudstone layers, resulting in a large number of salt rock-mudstone interfaces in the surrounding rocks of the salt caverns. The tensile and shear strengths of these interfaces are weak, and they are prone to slippage when uncoordinated displacement occurs between the two rocks. In this way, the anchoring effect of the interlayer used to suppress the creep of the surrounding rock will fail, resulting in a reduction in the available volume of the salt cavern, and will also affect the mechanical stability of the salt cavern. In addition, after the interface of the two rocks is damaged or even slipped, cracks will be generated between them. When the interlayer crack network is fully developed, it will become a leakage channel for the stored medium, affecting the energy storage economy of the salt cavern. The leaked energy storage medium may also cause accidents such as groundwater pollution and surface fires.

[0003] Therefore, conducting mechanical and permeability experiments on the salt rock-mudstone interface is critical for evaluating the energy storage reliability of salt caverns. However, due to the poor mechanical properties of the interface, the interface is often damaged by drilling mechanical forces, stress release, etc. during the process of drilling and coring, making it difficult to obtain complete and sufficient interface rock samples. To solve this problem, the most commonly used method in academia is to artificially prepare salt rock-mudstone interface model samples, using cement slurry or cement mortar as an alternative material. After the cement slurry or cement mortar is layered and cast into shape, it is pressed using positive stress to achieve bonding between the interfaces. This method utilizes the plasticity of cement slurry and cement mortar, has the advantages of convenient preparation and homogeneous finished products, and can achieve batch preparation of model samples. However, this method has many defects:

[0004] 1. Material mismatch: The mechanical and permeability properties of cement paste and cement mortar are quite different from those of natural salt rock and mudstone. The experimental data obtained based on the interface model specimens do not fully represent the characteristics of the real salt rock-mudstone interface, resulting in distortion of the experimental data.

[0005] 2. Inaccurate simulation of the diagenetic process: Existing methods fail to accurately simulate the diagenetic mechanism during the deposition of layered salt rocks, and therefore the simulated interface characteristics are not convincing enough.

[0006] From the above analysis, it can be seen that the existing layered rock preparation technology has many shortcomings in simulating the mechanical and permeability properties of the layered salt rock-mudstone interface. The present application provides a method and device for preparing a salt rock-mudstone interface model sample, aiming to solve the defects of the above-mentioned prior art. Summary of the invention

[0007] In order to solve the above problems, the present application provides a method and device for preparing a salt rock-mudstone interface model sample, which can more realistically simulate the salt rock-mudstone interface, thereby obtaining more accurate experimental data on the mechanical and permeability characteristics of the salt rock-mudstone interface, thereby improving the evaluation accuracy of the long-term operation reliability of the underground layered salt rock salt cavern energy storage system. The technical solution is as follows:

[0008] The first aspect of the present application provides a method for preparing a salt rock-mudstone interface model sample, comprising the following steps: pre-pressing and splicing a salt rock block and a mudstone block to form a sample assembly; placing the spliced ​​and pre-stressed sample assembly in a preset high-humidity air environment and / or a high-humidity-low-humidity cyclic air environment, so that the surface of the salt rock block deliquesces to generate a saturated salt solution and fills the interface gaps between the salt rock block and the mudstone block, and by controlling the environmental humidity and the cycle frequency and amplitude, the gap self-healing mechanism of the salt rock block on one side of the interface is activated to achieve interface suture, thereby preparing a salt rock-mudstone interface model sample that matches the actual rock structure.

[0009] For example, in the method for preparing the salt rock-mudstone interface model sample provided in one embodiment, the humidity of the high humidity air environment is greater than 75%.

[0010] For example, in the method for preparing the salt rock-mudstone interface model sample provided in one embodiment, the upper limit of the air environment humidity of the high humidity-low humidity cycle is greater than 75%.

[0011] For example, in the method for preparing the salt rock-mudstone interface model sample provided in one embodiment, the salt rock block and the mudstone block are distributed up and down, the salt rock block is located on the mudstone block, or the mudstone block is located on the salt rock block.

[0012] For example, in the method for preparing the salt rock-mudstone interface model sample provided in one embodiment, the salt rock block and the mudstone block are columns, which are formed by selecting natural salt rock and mudstone and cutting and grinding them into columns respectively.

[0013] A second aspect of the present application provides a device for preparing a salt rock-mudstone interface model sample, comprising a pre-pressing device and a sample preparation box, wherein the pre-pressing device is used to load salt rock blocks and mudstone blocks, and pre-press and splice the salt rock blocks and mudstone blocks together; the sample preparation box is used to place the pre-pressing device loaded with salt rock blocks and mudstone blocks, and apply a high-humidity air environment and / or a high-humidity-low-humidity cycle air environment.

[0014] For example, in a preparation device for the salt rock-mudstone interface model sample provided in one embodiment, the prestressing device includes two relatively arranged prestressing plates and a connecting plate connecting the two prestressing plates, the connecting plate is connected to the sides of the two prestressing plates so that the two prestressing plates and the connecting plate form an open prestressing space, the salt rock block and the mudstone block are located in the prestressing space, and the surfaces of the salt rock block and the mudstone block facing away from each other are respectively abutted against the two prestressing plates to apply prestressing stress to the salt rock block and the mudstone block.

[0015] For example, in the salt rock-mudstone interface model sample preparation device provided in one embodiment, a humidity sensor is provided in the sample preparation box to monitor the air humidity in the sample preparation box in real time.

[0016] For example, in the salt rock-mudstone interface model sample preparation device provided in one embodiment, a fan is provided in the sample preparation box to achieve uniform distribution of air humidity in space.

[0017] For example, in the salt rock-mudstone interface model sample preparation device provided in one embodiment, a humidity program control system is provided on the sample preparation box, and the humidity sensor and the fan are electrically connected to the humidity program control system to control the ambient humidity, high humidity-low humidity cycle frequency and amplitude in the sample preparation box.

[0018] The beneficial effects of a method and device for preparing a salt rock-mudstone interface model sample provided in some embodiments of the present application are as follows: the present application mechanically splices the natural salt rock sample and the mudstone sample by applying pre-compressive stress, and places them in a humid environment, and uses mechanical compression and the self-healing effect of salt rock in a wet environment to sew the interface, thereby fully enhancing its mechanical strength and anti-permeability properties. Compared with traditional methods, the present application has the following obvious advantages:

[0019] (1) High material similarity: The salt rock-mudstone interface was prepared by using natural salt rock and mudstone, ensuring the similarity between the sample and the actual geological conditions.

[0020] (2) Simulation of interface healing mechanism: Under the conditions of humidity and mechanical compression, the self-healing properties of salt rock are utilized to restore the mechanical and permeability properties of the interface. The sample preparation process is also closer to the actual diagenetic process (i.e., static geostress and groundwater environment).

[0021] (3) Improved accuracy of experimental results: Based on similar main materials and more realistic interface forming mechanisms, the experimental data obtained will more realistically reflect the characteristics of the salt rock-mudstone interface and provide an experimental basis for evaluating the safety and reliability of long-term energy storage in salt caverns. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to more clearly illustrate the embodiments of this specification or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0023] Figure 1 This is a schematic diagram of the overall structure of the salt rock-mudstone interface model sample preparation device of the present application;

[0024] Figure 2 This is a schematic diagram of the structure of the pre-pressing device of the salt rock-mudstone interface model sample preparation device of the present application. DETAILED DESCRIPTION

[0025] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0026] Unless otherwise defined, the technical terms or scientific terms used in the present disclosure should be understood by people with ordinary skills in the field to which the present disclosure belongs. The "first", "second" and similar words used in the present disclosure do not indicate any order, quantity or importance, but are only used to distinguish different components. "Include" or "comprise" and similar words mean that the elements or objects appearing before the word cover the elements or objects listed after the word and their equivalents, without excluding other elements or objects. "Connect" or "connected" and similar words are not limited to physical or mechanical connections, but can include electrical connections, whether direct or indirect. "Up", "down", "left", "right" and the like are only used to indicate relative positional relationships. When the absolute position of the described object changes, the relative positional relationship may also change accordingly.

[0027] In response to the problems of material mismatch and inaccurate simulation of the diagenetic process in traditional artificially prepared interface models, the present application provides a model sample preparation method and device that can more realistically simulate the salt rock-mudstone interface, so as to obtain more accurate experimental data on the mechanical and permeability properties of the salt rock-mudstone interface, thereby improving the assessment accuracy of the long-term operation reliability of underground layered salt rock salt cavern energy storage systems.

[0028] The salt rock-mudstone interface model sample preparation device of the present application is as follows Figure 1-2As shown, it includes a pre-pressing device 1 and a sample preparation box 4, wherein the pre-pressing device 1 is used to load salt rock blocks 2 and mudstone blocks 3, and pre-press and assemble the salt rock blocks 2 and mudstone blocks 3; the sample preparation box 4 is used to place the pre-pressing device 1 loaded with salt rock blocks 2 and mudstone blocks 3, and apply a high-humidity air environment and / or a high-humidity-low-humidity cycle air environment.

[0029] Among them, Figure 2 As shown, the prestressing device 1 includes two relatively arranged prestressing plates 11 and a connecting plate 12 connecting the two prestressing plates 11, and the connecting plate 12 is connected to the sides of the two prestressing plates 11 so that the two prestressing plates 11 and the connecting plate 12 form an open prestressing space, and the salt rock block 2 and the mudstone block 3 are located in the prestressing space, and the surfaces of the salt rock block 2 and the mudstone block 3 that are away from each other are respectively abutted against the two prestressing plates 11 to apply prestressing stress to the salt rock block 2 and the mudstone block 3.

[0030] like Figure 1 As shown, a humidity sensor 6 is provided in the sample preparation box 4 to monitor the air humidity in the sample preparation box 4 in real time; a fan 5 is provided in the sample preparation box 4 to achieve uniform distribution of air humidity in space; a humidity program control system 7 is provided on the sample preparation box 4, and the humidity sensor 6 and the fan 5 are electrically connected to the humidity program control system 7 to control the ambient humidity, high humidity-low humidity cycle frequency and amplitude in the sample preparation box 4.

[0031] The method for preparing a salt rock-mudstone interface model sample using the salt rock-mudstone interface model sample preparation device of the present application is as follows:

[0032] 1. Material preparation

[0033] Natural salt rock and mudstone are selected and cut and ground into columns to form salt rock blocks 2 and mudstone blocks 3 respectively.

[0034] 2. Material loading

[0035] 2.1 The prepared salt rock block 2 and mudstone block 3 are assembled up and down. The salt rock block 2 can be located on the mudstone block 3, or the mudstone block 3 is located on the salt rock block 2. The assembled salt rock block 2 and mudstone block 3 are placed in the preloading space of the preloading device 1, so that the surfaces of the salt rock block 2 and the mudstone block 3 facing away from each other are respectively in contact with the two preloading plates 11, so as to apply preloading stress to the salt rock block 2 and the mudstone block 3, ensure the close contact of the interface between the salt rock block 2 and the mudstone block 3, and simulate the effect of the static geostatic pressure at the salt rock-mudstone interface by mechanical pressing.

[0036] 2.2 Place the pre-pressing device 1 loaded with the salt rock block 2 and the mudstone block 3 into a sample preparation box 4 with a preset high humidity air environment and / or a high humidity-low humidity circulating air environment.

[0037] The humidity of the high humidity air environment is greater than 75%, and the upper limit of the humidity of the air environment in the high humidity-low humidity cycle is greater than 75%.

[0038] In the air environment, when the humidity exceeds 75%, the surface of the salt rock block 2 will undergo extensive deliquescence, generating a saturated salt solution, which will infiltrate into the crack structure at the interface of the salt rock block 2 and the mudstone block 3 under the action of capillary force. Therefore, in a high-humidity air environment and / or a high-humidity-low-humidity circulating air environment, the interface gaps will be filled with saturated salt solution, i.e., liquid brine, providing the necessary salt solution environment to trigger the self-healing mechanism of the salt rock on one side of the interface, activating the gap self-healing mechanism of the salt rock block on one side of the interface, and realizing the suture of the interface. The interface gap self-healing mechanism is mainly realized through the following two physical-chemical processes:

[0039] Diffusion mass transfer: After the salt rock on one side of the interface comes into contact with the liquid brine in the voids, driven by the surface potential, the crack space in the interface is gradually isolated and closed through the mechanism of dissolution-diffusion to the crack tip-crystallization to construct a geometric structure with the lowest surface potential energy. This process realizes the discontinuity and alienation of the crack voids in the interface, and the recrystallized salt structure at the junction of the two types of rocks will increase the cementation strength of the interface.

[0040] Recrystallization: After the distorted crystals on the surface of the salt rock come into contact with the liquid brine in the interfacial voids, they are gradually dissolved by the distortion potential energy, and new self-shaped crystals are formed in the interfacial cracks, further filling the interfacial voids and cementing the interface. This process is driven by the ambient humidity and saturated salt solution, and works in synergy with the diffusion mass transfer process to further enhance the mechanical properties of the interface.

[0041] By placing the sample assembly in a high-humidity-low-humidity cycling air environment, the drying stage in the low-humidity state will also cause the evaporation of the salt solution in the cracks, especially in the mesoscopic and microscopic cracks. The local supersaturated state of the salt solution produced by the evaporation of water further accelerates the diffusion and precipitation of salt, providing additional power for the recrystallization process, and further enhancing the self-healing effect of the cracks.

[0042] This application sets specific humidity conditions, activates the self-healing mechanism of the salt rock on one side of the interface, and sews the interface to achieve mechanical and permeability properties close to those of the natural layered rock interface. It can more accurately simulate the diagenetic mechanism of layered salt rock, especially the diffusion and recrystallization behavior under pre-stress and humidity control, and provide a more realistic experimental basis for the long-term reliability of the salt cavern energy storage system.

[0043] The method for preparing the salt rock-mudstone interface model sample of the present application effectively simulates the physical and chemical conditions in the natural formation process of salt rock, especially the process of combining salt rock self-healing with positive compressive stress. By preparing samples closer to the real geological environment, the present application makes the mechanical and permeability characteristics of the obtained model rock closer to the conditions of the surrounding rock of the actual salt rock reservoir, and adjusts the control parameters of the humidity environment, such as changing the air humidity level and the cycle frequency and amplitude, so as to finely control the interface self-healing behavior.

[0044] Although the implementation scheme of the present application has been disclosed as above, it is not limited to the applications listed in the specification and implementation modes, and it can be fully applicable to various fields suitable for the present application. For those familiar with the art, additional modifications can be easily implemented. Therefore, without departing from the general concept defined by the claims and the scope of equivalents, the present application is not limited to the specific details and the illustrations shown and described herein.

Claims

1. A method for preparing a salt rock-mudstone interface model sample, characterized in that: The following steps are involved: Pre-pressing and splicing salt rock blocks and mudstone blocks to form a sample assembly; The assembled and pre-stressed sample assembly is placed in a preset high-humidity air environment and / or a high-humidity-low-humidity cyclic air environment, so that the surface of the salt rock block is deliquesced to generate a saturated salt solution and fills the interface gaps between the salt rock block and the mudstone block. By controlling the environmental humidity and the cycle frequency and amplitude, the self-healing mechanism of the gaps in the salt rock block on one side of the interface is activated, the interface is sutured, and a salt rock-mudstone interface model sample matching the actual rock structure is prepared.

2. The method for preparing the salt rock-mudstone interface model sample according to claim 1, characterized in that: The humidity of the high humidity air environment is greater than 75%.

3. The method for preparing the salt rock-mudstone interface model sample according to claim 1, characterized in that: The upper limit of the air environment humidity of the high humidity-low humidity cycle is greater than 75%.

4. The method for preparing the salt rock-mudstone interface model sample according to claim 1, characterized in that: The salt rock block and the mudstone block are distributed up and down, the salt rock block is located on the mudstone block, or the mudstone block is located on the salt rock block.

5. The method for preparing the salt rock-mudstone interface model sample according to claim 1, characterized in that: The salt rock block and the mudstone block are columns, which are formed by selecting natural salt rock and mudstone and cutting and grinding them respectively.

6. A device for preparing a salt rock-mudstone interface model sample, characterized in that: include: A pre-pressing device, used for loading salt rock blocks and mudstone blocks, and pre-pressing and splicing the salt rock blocks and mudstone blocks together; The sample preparation box is used for placing a pre-pressing device loaded with salt rock blocks and mudstone blocks, and applying a high-humidity air environment and / or a high-humidity-low-humidity cycle air environment.

7. The device for preparing the salt rock-mudstone interface model sample according to claim 6, characterized in that: The prestressing device includes two relatively arranged prestressing plates and a connecting plate connecting the two prestressing plates, wherein the connecting plate is connected to the sides of the two prestressing plates so that the two prestressing plates and the connecting plate form an open prestressing space, wherein the salt rock block and the mudstone block are located in the prestressing space, and the surfaces of the salt rock block and the mudstone block facing away from each other are respectively in contact with the two prestressing plates so as to apply prestressing stress to the salt rock block and the mudstone block.

8. The device for preparing the salt rock-mudstone interface model sample according to claim 6, characterized in that: A humidity sensor is provided in the sample preparation box to monitor the air humidity in the sample preparation box in real time.

9. The device for preparing the salt rock-mudstone interface model sample according to claim 8, characterized in that: A fan is arranged in the sample preparation box to achieve uniform distribution of air humidity in the space.

10. The device for preparing the salt rock-mudstone interface model sample according to claim 9, characterized in that: A humidity program control system is provided on the sample preparation box, and the humidity sensor and the fan are electrically connected to the humidity program control system to control the ambient humidity, high humidity-low humidity cycle frequency and amplitude in the sample preparation box.

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