A layered salt rock stratum physical model and a preparation method thereof

Abstract

The application discloses a layered salt rock stratum physical model and a preparation method thereof. The method comprises the following steps: material preparation, interlayer pouring frame preparation, model stacking and preliminary sealing, interlayer slurry filling and hardening, pipe column arrangement and final sealing. By means of staggered stacking of salt rock blocks and interlayer pouring frames, and in combination with geological material slurries such as mudstone powder, gypsum powder and salt powder with adjustable proportions, the structural features and mechanical properties of salt rock and interbedded interlayers can be accurately simulated. The application has the advantages of simple operation and low cost. By using transparent acrylic frames, epoxy resin adhesives and other easily available materials, the preparation of models with different sizes, layers, interlayer types and interlayer distributions can be realized, and the application is suitable for salt cavern water dissolution cavity simulation tests, and can truly reflect the diversity of interlayer strength, permeability and collapse behavior.

Description

Technical Field

[0001] This invention belongs to the technical field of deep salt cavern energy storage construction and geotechnical engineering physical simulation test, and in particular relates to a layered salt rock strata physical model and its preparation method. Background Technology

[0002] Salt caverns, especially underground salt caverns used for strategic energy reserves such as oil and natural gas, are crucial infrastructure for ensuring national energy security. These caverns are typically constructed deep underground within target salt deposits using water-soluble cavity-forming technology. This technology involves injecting fresh water into salt rock layers and gradually dissolving the salt layer by controlling the combination of fresh water injection and brine discharge, ultimately forming underground cavities that meet specific shape, size, and stability requirements for energy or other material storage.

[0003] However, unlike the high-purity, thick salt domes or salt arches commonly found abroad, the salt strata suitable for reservoir construction in my country are mostly layered salt rock strata. A significant characteristic of these strata is the alternating layering of salt layers with non-salt rock interlayers (such as mudstone and gypsum rock). During the water-soluble cavity construction process, these insoluble or poorly soluble interlayers become unstable and collapse due to the dissolution of the underlying salt rock. The collapsed material easily accumulates at the bottom of the cavity or adheres to the cavity walls, not only disrupting the dissolution flow field and altering the cavity expansion morphology, making precise control of the cavity shape difficult, but also potentially burying the oil cushion layer or damaging the tubing, seriously threatening the efficiency and safety of salt cavern construction. Therefore, in-depth research into the cavity morphology evolution and control techniques of water-soluble cavity construction in layered salt rock strata is crucial for the efficient construction of salt cavern reservoirs in my country.

[0004] Physical simulation experiments are one of the most intuitive and effective methods for studying the expansion law of cavity morphology during water-soluble cavity formation. To achieve effective simulation, the key lies in creating physical model specimens that can realistically reflect the actual stratigraphic structure and material properties. For layered salt rock formations, the physical model needs to simulate the interlayered stacking structure of salt layers and interlayers, and to a certain extent reproduce the collapse behavior of the interlayers during water-soluble cavity formation.

[0005] Currently, in the physical simulation research of water-soluble salt cavern construction, there are two main methods for preparing model samples. The first method uses a single large-sized, high-purity natural salt brick as the simulation object of the salt rock strata, as shown in the paper "Physical simulation of flow field and construction process of horizontal salt cavern for natural gas storage" (Jie Yang et al., Journal of Natural Gas Science and Engineering, Vol. 82, October 2020).Figure 3 , Figure 10 As shown, while this method is simple, it cannot simulate the characteristics of salt rock strata containing complex interlayer structures, especially the impact of the interlayers on cavity morphology development and collapse behavior, resulting in limited accuracy and guiding significance of the simulation results. The second method involves layering salt rock powder, calcium sulfate, and clay, then fusing them into salt blocks under high temperature and pressure, as illustrated in the content of a large-size interlayered salt cavity construction test method (CN102011579A). This method has a complex production process, long cycle, and high cost, making it difficult to meet the experimental requirements for interlayer collapse tracking simulation, and also unable to flexibly change the thickness of the interlayers and salt layers to simulate complex strata structures.

[0006] Therefore, there is an urgent need to propose a method that can accurately and efficiently produce physical model specimens of layered salt rock formations to simulate the interlayered structure of salt layers and interlayers, as well as the diverse collapse behaviors of interlayers, so as to meet the requirements of high-fidelity model specimens for engineering physical simulation tests of layered salt rock water-soluble cavity formation. Summary of the Invention

[0007] The purpose of this invention is to provide a physical model of layered salt rock formations and its preparation method, which solves the problems in the prior art that it cannot simulate interlayer structures and collapse behavior, and that the model structure differs significantly from the actual layered salt rock formations, so as to improve the authenticity and reliability of physical simulation test results.

[0008] The technical solution adopted in this invention is a layered salt rock strata physical model, comprising a layered structure composed of salt rock blocks, a layered casting frame, and hardened interlayers stacked alternately; the layered casting frame is a U-shaped hollow frame with an open front; the hardened interlayers are surrounded by three sides of the layered casting frame; the layered casting frame and the hardened interlayers form a single-layer structure located between two adjacent salt rock blocks; a linear groove is provided on the outer front of the model, and a metal pipe one and a metal pipe two are installed in the groove; the metal pipe one is nested inside the metal pipe two, and the top end of the metal pipe one extends to the outside of the metal pipe two; it also includes a water distribution valve, which is a tee fitting, the upper surface interface of which is sealed and fixedly connected to the metal pipe one; the lower surface interface of the water distribution valve is sealed and fixedly connected to the metal pipe two; and the lateral interface of the water distribution valve is sealed and connected to the water guide pipe.

[0009] Furthermore, the hardened interlayer is formed by solidifying the slurry filled within the interlayer casting frame, and the thickness of the hardened interlayer is equal to the thickness of the interlayer casting frame.

[0010] Furthermore, the gap between the outer wall of the metal tube and the inner wall of the model groove is filled with fine-grained industrial salt powder.

[0011] Furthermore, a rubber plug is fitted to the second outlet end of the metal tube; the contact edge between the rubber plug and the salt rock block is sealed with epoxy resin adhesive.

[0012] Furthermore, at least one model observation surface is fixed by adhesive sealing through a visually sealed transparent plate.

[0013] The above-mentioned method for preparing a physical model of layered salt rock strata includes the following steps:

[0014] Step S1: Material preparation and fabrication of the sandwich casting frame: Prepare pre-treated salt rock blocks that have been cut and ground, as well as metal pipe one, metal pipe two, water pipe, rubber stopper, transparent sealing plate, geological material powder, sealant, saturated brine, industrial salt powder and water distribution valve; use transparent plexiglass or equivalent material resistant to salt and brine corrosion to make a hollow frame with a concave cross section as the sandwich casting frame;

[0015] Step S2: Model stacking and preliminary sealing: According to the preset layered salt rock stratum structure scheme, the salt rock blocks and the interlayer casting frame are stacked alternately to form a layered structure. A sealant is applied to the contact interface, the side of the model and the back of the model to form a sealing layer. Pressure is applied to make each layer fit tightly and then left to stand until the sealing layer is cured.

[0016] Step S3: Preparation, filling and compaction of interlayer slurry: After the sealing layer has cured in step S2, mudstone powder, gypsum powder and salt rock powder are mixed according to the preset interlayer material ratio scheme. Saturated brine is added and stirred to form a flowing interlayer slurry, which is then filled into the reserved concave area of ​​the interlayer casting frame. After filling, the model is placed on a vibrating table to compact it, and then transferred to a constant temperature drying oven to dehydrate and harden, forming a hardened interlayer.

[0017] Step S4: Installation and final sealing of the tubular simulation system: After the model hardens, a groove 40-50mm from the bottom surface is chiseled at a preset position on the top surface; metal tube one is inserted into metal tube two and embedded in the groove, with the end of metal tube one protruding; a rubber plug is installed at the outlet end of metal tube two, and epoxy resin adhesive is applied to the interface between the rubber plug and the salt rock block for sealing; industrial salt powder is filled into the gap between the outer wall of the tube and the groove; epoxy resin adhesive is applied to the edge of the model observation surface, a transparent visual sealing plate is covered and pressure is applied to ensure tight contact, and the system is left to stand at room temperature for ≥24 hours or until the adhesive cures.

[0018] Furthermore, both metal tube one and metal tube two are made of stainless steel, with metal tube one having a diameter of 3-4 mm and metal tube two having a diameter of 5-7 mm; the rubber stopper is matched to the outer diameter of metal tube two; the transparent sealing plate is made of acrylic glass; the geological material powder includes mudstone powder, gypsum powder, and salt rock powder; the sealant is a transparent epoxy resin adhesive; and the saturated brine is used to mix with the geological material powder to prepare the interlayer slurry.

[0019] Furthermore, in step S1, the outer contour dimensions of the interlayer casting frame are consistent with the planar dimensions of the salt rock block, and the thickness of the interlayer casting frame is 5-20mm and determined according to the simulated interlayer thickness. Its central area is provided with a through hole to form the interlayer slurry filling space, and the size of the hole is set according to the simulated interlayer geological extensibility.

[0020] Furthermore, in step S3, the mass ratio of mudstone powder to gypsum powder used in the interlayer material is 3:1 to 6:1, and the mass of salt rock powder is 10% to 30% of the total mass of mudstone powder and gypsum powder; the mass ratio of geological material powder composed of mudstone powder, gypsum powder and salt rock powder to saturated brine is 8:2.

[0021] Furthermore, in step S3, the vibration compaction process uses a vibration frequency of 50-100Hz and lasts for 30-50 seconds; the drying and dehydration process continues at 60°C for 48 hours or until the interlayer slurry is completely hardened.

[0022] The beneficial effects of this invention are:

[0023] 1. This invention has a high degree of structural simulation. By stacking salt rock blocks and interlayer casting frames in an alternating manner, it can accurately simulate the structural characteristics of salt layers and interlayers in layered salt rock strata, including the thickness of each layer, the sequence of layers, and the contact relationship between interlayers and salt layers. Moreover, the mechanical properties of the interlayers are controllable. By selecting different geological materials (such as mudstone powder, gypsum powder, salt rock powder, etc.) and their proportions, as well as the amount of saturated brine, simulated interlayers with differentiated physical and mechanical properties (such as strength and permeability) and collapse characteristics (such as ease of collapse) can be prepared, which more realistically reflects the diversity of physical and mechanical behavior of interlayers in actual strata.

[0024] 2. The method of the present invention is relatively simple, with clear production steps and easy operation. The materials used (such as salt rock blocks, geological material powders, acrylic glass plates, epoxy resin adhesives, etc.) are easy to obtain, and the overall preparation cost is low. Moreover, the method is flexible in production and has a wide range of applications. It can be used to prepare layered salt rock physical model samples of different sizes, number of layers, layer thickness, interlayer types and interlayer distributions, which can meet the needs of physical simulation tests of salt cavern water dissolution cavity formation under various geological conditions. Attached Figure Description

[0025] 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 these drawings without creative effort.

[0026] Figure 1These are actual images of the mudstone powder, gypsum powder, and salt rock powder used in the model samples of this invention.

[0027] Figure 2 This is a physical image of the salt rock block used for the model sample.

[0028] Figure 3 This is a physical image of the sandwich-cast frame used in the model specimen.

[0029] Figure 4 This is a structural diagram of the unfilled interlayer of the model specimen.

[0030] Figure 5 This is a schematic diagram of the final structure of the model specimen.

[0031] Figure 6 This is a schematic diagram of the forward and reverse cyclic process of the model specimen.

[0032] Figure 7 This is a schematic diagram of the model tubular closed system.

[0033] Figure 8 These are actual images of hardened interlayers when the mass ratio of salt rock powder to non-salt rock powder is 1:3, 1:4, 1:5, and 1:6, respectively.

[0034] Figure 9 The strength diagrams are for hardened interlayer samples with a non-salt rock powder to salt rock powder mass ratio of 3, 4, 5 and 6.

[0035] Figure 10 The graph shows the dissolution time of hardened interlayers when the mass ratio of non-salt rock powder to salt rock powder is 3, 4, 5, and 6.

[0036] Figure 11 The graph shows the permeability coefficient of the hardened interlayer when the mass ratio of non-salt rock powder to salt rock powder is 3, 4, 5, and 6.

[0037] In the diagram, 1-1. Metal pipe one, 1-2. Metal pipe two, 1-3. Water pipe, 2. Rubber stopper, 3. Salt rock block, 4. Interlayer casting frame, 5. Hardened interlayer, 6. Visual sealing transparent plate, 7. Industrial salt powder, 8. Water distribution valve. Detailed Implementation

[0038] 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 some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0039] Unless otherwise stated, all materials used in the following examples and comparative examples are commercially available products. Specifically: Himalayan salt rock blocks were purchased from Hebei Yanxin Minerals Co., Ltd.; industrial salt powder was purchased from Shandong Yanda Chemical Co., Ltd.; mudstone powder and gypsum powder were purchased from Lingshou Shengfeng Mineral Products Processing Plant; PO425 cement was purchased from Jiangxi Wannianqing Cement Co., Ltd.; transparent epoxy resin was purchased from Zhongshan Jiecheng Organosilicon Co., Ltd.; stainless steel metal tubes were purchased from Dongguan Meite Metal Materials Factory; acrylic glass sheets were purchased from Jingtai Acrylic Plastic Products Factory; and rubber stoppers were purchased from Huadong Glass Instruments.

[0040] like Figure 1-7 As shown, a layered salt rock strata physical model includes a layered structure composed of salt rock blocks 3, interlayer casting frames 4, and hardened interlayers 5 stacked alternately. The interlayer casting frames 4 are hollow "U"-shaped frames with their openings facing the front, and the interlayer casting frames 4 surround the three sides of the hardened interlayers 5. The interlayer casting frames 4 and the hardened interlayers 5 together form a single-layer structure located between adjacent salt rock blocks 3. A linear groove is provided on the outer front of the model, and metal pipe 1-1 and metal pipe 1-2 are installed in the groove. Metal pipe 1-1 The metal tube 1-1 is nested inside the metal tube 2-2, and the top of the metal tube 1-1 extends to the outside of the metal tube 2-2; the outlet end of the metal tube 2-2 is fixedly fitted with a rubber plug 2; the water distribution valve 8 is a three-way fitting, the upper surface interface of the water distribution valve 8 is sealed and fixedly connected to the metal tube 1-1 and the channel passes through the valve body; the lower surface interface of the water distribution valve 8 is sealed and fixedly connected to the metal tube 2-2 but the channel does not pass through the valve body; the side interface of the water distribution valve 8 is sealed and connected to the water guide pipe 1-3; the model observation surface is sealed and fixed by adhesive through the visualization sealing transparent plate 6.

[0041] Furthermore, the hardened interlayer 5 is formed by filling the interlayer casting frame 4 with interlayer slurry. Its thickness is limited by the structural dimensions of the interlayer casting frame 4. By adjusting the material composition and ratio of the slurry, the hardened interlayer 5 can have differentiated physical and mechanical properties and dissolution and collapse characteristics. The sleeve pipe column composed of metal pipe 1-1 and metal pipe 2-2, together with water pipe 1-3 and water distribution valve 8, forms a water-soluble cavity-forming pipe column simulation system. The contact edge between the rubber plug 2 and the salt rock block 3 is sealed with epoxy resin adhesive. The gap between the outer wall of metal pipe 2-2 and the inner wall of the model groove is filled with fine-grained industrial salt powder 7. At least one model observation surface is sealed with a visual sealing transparent plate 6 for direct observation of cavity formation, expansion and interlayer collapse behavior.

[0042] In this embodiment, a method for preparing a physical model of layered salt rock strata includes the following steps:

[0043] Step S1: Material preparation: Himalayan salt rock blocks are preferred as salt rock blocks 3. After cutting and grinding pretreatment, the plane size is 200mm×200mm and the thickness is 25~50mm; and the following are prepared: metal pipe 1-1, metal pipe 2-2, water pipe 1-3, rubber stopper 2, transparent visual sealing plate 6, geological material powder, sealant, saturated brine and industrial salt powder 7, and water distribution valve 8.

[0044] Furthermore, both metal tube 1-1 and metal tube 2-2 are stainless steel tubes, with metal tube 1-1 preferably having a diameter of 3-4 mm and metal tube 2-2 preferably having a diameter of 5-7 mm; the rubber stopper 2 is selected to match the outer diameter of metal tube 2-2; the transparent sealing plate 6 is preferably an acrylic glass plate; the geological material powder includes mudstone powder, gypsum powder and salt rock powder; the sealant is preferably a transparent epoxy resin adhesive; and saturated brine is used to mix with the geological material powder to prepare the interlayer slurry.

[0045] Step S2: Preparation of the interlayer casting frame: Prepare an interlayer casting frame 4 to define the shape and thickness of the interlayer. The frame is made of materials that do not easily react with salt or brine, such as transparent plexiglass (acrylic). The thickness of the plate is 5-20mm, determined according to the required interlayer thickness. The plate is processed into a hollow frame with a U-shaped structure. Its outer contour dimensions (e.g., 200mm long × 200mm wide) are consistent with the planar dimensions of the salt rock block 3. The frame thickness corresponds to the design thickness of the interlayer being simulated. The central area is designed as a through-hole structure. The size of the opening is set according to the geological extensibility of the simulated interlayer to ensure that the interlayer is continuously distributed in the model. The opening area is the space for filling the interlayer slurry, and the geometry of the concave part is designed to reserve enough space for subsequent filling operations.

[0046] Step S3: Model Stacking and Preliminary Sealing: The treated salt rock blocks 3 and the interlayer casting frame 4 are stacked alternately according to the pre-designed layered salt rock stratum structure scheme (such as determined according to the actual geological profile or test scheme); during the stacking of each layer, transparent epoxy resin is evenly applied as a sealant at the contact interface between the salt rock blocks 3 and the interlayer casting frame 4, as well as on the sides and back of the model structure, to achieve bonding and initial sealing between the layers; after stacking, the entire structure is placed on a horizontal operating platform and uniform and moderate pressure is applied (such as using heavy objects or special clamps) to ensure that each layer is tightly attached and firmly connected; then, the assembled model structure is placed in a suitable environment (such as a dry environment at 25°C) for a period of time (such as 1 to 3 days, or according to the curing time recommended in the instructions of the epoxy resin used) until the sealant is fully cured, forming a stable preliminary model structure.

[0047] Furthermore, in this embodiment, the layered structure scheme is as follows: from top to bottom, a 50mm thick salt rock block 3, a 5mm thick interlayer casting frame 4, a 30mm thick salt rock block 3, a 7mm thick interlayer casting frame 4, a 30mm thick salt rock block 3, a 15mm thick interlayer casting frame 4, a 30mm thick salt rock block 3, a 15mm thick interlayer casting frame 4, a 35mm thick salt rock block 3, a 5mm thick interlayer casting frame 4, and a 50mm thick salt rock block 3 are stacked sequentially.

[0048] Step S4: Preparation and filling of interlayer slurry: After the sealant of the preliminary model structure has fully cured, accurately weigh the mudstone powder, gypsum powder, salt rock powder and saturated brine according to the preset interlayer material ratio scheme; then, mix the specific weight parts of mudstone powder, gypsum powder and salt rock powder evenly in a dry state, and add the predetermined weight parts of saturated brine; continue stirring during this process until a uniform, non-lumpy and fluid interlayer slurry is formed; then, fill this slurry evenly into the model structure made in step S3, within the reserved concave area defined by the interlayer casting frame 4, until it is completely filled.

[0049] Furthermore, in this embodiment, the ratio of mudstone powder to gypsum powder in the interlayer material is 3:1 to 6:1, and the mass of salt rock powder is 10% to 30% of the total mass of mudstone powder and gypsum powder; the mass ratio of geological material powder composed of mudstone powder, gypsum powder and salt rock powder to saturated brine is 8:2.

[0050] Step S5: Compaction and Hardening of the Interlayer: To ensure the compaction and uniformity of the filling slurry and eliminate internal air bubbles, the filled model structure is placed on a vibrating device (such as a vibrating table) and subjected to moderate vibration (such as continuous vibration for 30-50 seconds at a frequency of 50-100 Hz) to improve the compaction of the interlayer slurry. After vibration, the model is transferred to a constant temperature drying device (such as a constant temperature drying oven) and continuously dried at 60°C for 48 hours, or until the interlayer slurry has completely lost its free moisture and reached the expected degree of hardening, as determined by observation or weighing, to form a stable hardened interlayer 5.

[0051] Step S6: Installation of the tube simulation system: After the model structure has been completely dried and hardened, according to the experimental design requirements, a groove for installing metal tubes is chiseled from a predetermined position on the top surface of the model; the predetermined position is the centerline in the width direction, and the bottom of the groove is 40-50mm from the bottom surface of the model; the width and depth of the groove are determined according to the requirements for metal tube installation; insert the inner metal tube 1-1 into the outer metal tube 2-2, keeping the end of the inner metal tube 1-1 protruding; process a flared groove at the outlet end of the outer metal tube 2-2 for the installation of the seal; embed the assembled metal tube assembly into the groove; then install a rubber plug 2 at the outlet end of the outer metal tube 2-2 to ensure a tight fit or sleeve with the outer metal tube 2-2; apply epoxy resin adhesive to the contact interface between the rubber plug 2 and the salt rock block 3 to achieve effective sealing; finally, fill the gap between the outer wall of the outer metal tube 2-2 and the inner wall of the groove with industrial salt powder 7, and compact it tightly with tools to fix the outer metal tube 2-2 and remove air to the maximum extent.

[0052] Furthermore, this embodiment employs a tubular system consisting of metal pipe 1-1 and metal pipe 1-2, combined with water pipe 1-3 and water distribution valve 8, to form a water-soluble cavity-forming tubular system simulation system. During the positive circulation cavity-forming process, fresh water is injected into the model through metal pipe 1-1, and the dissolved brine is discharged through the annular channel between metal pipe 1-1 and metal pipe 1-2. This annular channel is connected to water distribution valve 8 and the brine is discharged through water pipe 1-3. During the reverse circulation cavity-forming process, fresh water is injected through water pipe 1-3 and diverted to the annular channel for injection into the model through water distribution valve 8, while the dissolved brine is discharged through metal pipe 1-1. By switching the injection / discharge direction of the fluid through external circulation equipment, water distribution valve 8 achieves the flow channel distribution of the positive and negative circulation modes in a passive flow guiding manner, fully simulating the function of the on-site tubular system.

[0053] Step S7: Final sealing: Apply epoxy resin adhesive evenly to the four edges of the model observation surface; precisely cover the adhesive-coated observation surface with the pre-prepared visualization sealing transparent plate 6, whose size matches the observation surface, ensuring edge alignment; apply uniform pressure (e.g., using clamps or placing weights) to ensure that the visualization sealing transparent plate 6 is in close contact with the model structure body; maintain the applied pressure and let the entire structure stand at room temperature for at least 24 hours, or until the epoxy resin adhesive is completely cured, to complete the final sealing of the entire model specimen.

[0054] After completing all the above steps, a physical model specimen of layered salt rock strata with a complete structure and clearly visible internal sequence and simulated tubular system can be obtained. This model specimen is ready for subsequent physical simulation tests of water-soluble cavity formation.

[0055] Comparative Example 1

[0056] A physical model of layered salt rock strata and its preparation method, comprising the following steps:

[0057] Except that the geological material powder in step 1 is replaced with cement powder; in step 4, the cement powder accounts for 80% of the mass of the interlayer material and the saturated brine accounts for 20% of the mass.

[0058] Everything else is the same as in the example.

[0059] Comparative Example 2

[0060] A physical model of layered salt rock strata and its preparation method, comprising the following steps:

[0061] In addition to the geological material powders in step 1, which include mudstone powder and gypsum powder, and salt-free rock powder, the mudstone powder to gypsum powder ratio selected for the interlayer material in step 4 is 3:1 to 6:1 by mass. The total mass of mudstone powder and gypsum powder accounts for 80%, and the mass of saturated brine accounts for 20%.

[0062] Everything else is the same as in the example.

[0063] Comparative Example 3

[0064] A physical model of layered salt rock strata and its preparation method, comprising the following steps:

[0065] Except that the salt rock block 3 in step 1 is replaced with artificially synthesized salt blocks.

[0066] Everything else is the same as in the example.

[0067] A water-soluble cavity-forming physical simulation experiment was conducted on the physical simulation samples prepared in Examples 1, 2, and 3. The experimental results are shown in Table 1.

[0068] Table 1 Results of water-soluble cavity-making test using physical model of layered salt rock strata

[0069]

[0070] As shown in Table 1, although the methods of Comparative Examples 1 and 2 can achieve a short model preparation cycle, they cannot simulate the interlayer collapse process. In addition, although Comparative Example 3 can simulate the interlayer collapse process, the artificial rock block production cycle is too long. Therefore, the models prepared by Comparative Examples 1-3 are difficult to meet the requirements of rapid and efficient testing. However, the physical model preparation method in the embodiments can not only meet the requirements of short-term and efficient preparation, but also effectively simulate the behavior of interlayer collapse in the field, thus meeting the requirements of physical simulation experiments for efficiency and functionality.

[0071] The physical model of this invention possesses high structural simulation fidelity and precise controllability of mechanical properties. Through the interlayered stacking of salt rock blocks 3 and the interlayer casting frame 4, and with full visualization throughout the process, it accurately reproduces the structural characteristics of salt layers and interlayers in layered salt rock strata. Compared with existing technologies, it significantly improves the simulation effect and model preparation efficiency of interlayer structures. The mechanical properties of the interlayers are controlled by adjusting the proportions of geological materials such as mudstone powder, gypsum powder, and salt rock powder, as well as the amount of saturated brine, to prepare simulated interlayers with differentiated strength, permeability, and collapse characteristics (characterized by dissolution time). Figure 8-11 As shown, the control basis is derived from the uniaxial compressive mechanical properties, permeability and solubility test results of hardened interlayer 5 under different salt rock powder and non-salt rock powder ratios. The results show that the mechanical strength and permeability change significantly with the ratio, and the collapse difficulty can be precisely controlled by the dissolution time.

[0072] The physical model of this invention can flexibly prepare layered salt rock samples of different sizes, numbers of layers, layer thicknesses, interlayer types, and interlayer distributions. The interlayer type is achieved by adjusting the ratio of mudstone powder, gypsum powder, and salt rock powder to reflect differentiated strength and collapse behavior. The model's planar dimensions are adjusted by selecting salt rock blocks 3 of different specifications; however, due to limitations in the commercially available size of high-purity salt blocks, the maximum currently achievable model is 30cm × 20cm × 50cm (length × width × height). The number of stacked layers and the thickness of a single layer can be adjusted according to the characteristics of the target salt mine strata, but the overall structural stability must be ensured (total height not exceeding 50cm, single salt layer height not exceeding 5cm). This satisfies the physical simulation requirements for water-soluble cavity formation in salt caverns under various geological conditions. In this embodiment, through the interlayered structure of salt rock blocks 3 and the interlayer casting frame 4, the typical occurrence characteristics of layered interlayers in Chinese salt mine strata are realistically reproduced while considering both operability and geological similarity.

[0073] The various embodiments in this specification are described in a related manner. Similar or identical parts between embodiments can be referred to mutually. Each embodiment focuses on describing the differences from other embodiments. In particular, the system embodiments are basically similar to the method embodiments, so the description is relatively simple; relevant parts can be referred to the descriptions of the method embodiments.

[0074] The above description is merely a preferred embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention are included within the scope of protection of the present invention.

Claims

1. A physical model of layered salt rock strata, characterized in that, The model comprises a layered structure consisting of staggered stacked salt rock blocks (3), interlayer casting frame (4), and hardened interlayer (5); the interlayer casting frame (4) is a U-shaped hollow frame with an open front; the hardened interlayer (5) is surrounded by three sides of the interlayer casting frame (4); the interlayer casting frame (4) and the hardened interlayer (5) form a single-layer structure located between two adjacent salt rock blocks (3); a linear groove is provided on the outer front of the model, and a metal tube (1-1) is installed in the groove. The system includes a metal pipe 1 (1-1) nested inside the metal pipe 2 (1-2), with the top end of the metal pipe 1 (1-1) extending to the outside of the metal pipe 2 (1-2); it also includes a water distribution valve (8), which is a three-way fitting, with its upper surface interface sealed and fixedly connected to the metal pipe 1 (1-1); the lower surface interface of the water distribution valve (8) is sealed and fixedly connected to the metal pipe 2 (1-2); and the lateral interface of the water distribution valve (8) is sealed and connected to the water guide pipe (1-3). The salt rock block (3) is a natural salt rock block; the hardened interlayer (5) is formed by solidifying geological material powder containing mudstone powder, gypsum powder and salt rock powder with saturated brine.

2. The physical model of layered salt rock strata according to claim 1, characterized in that, The hardened interlayer (5) is formed by the curing of slurry filled in the interlayer casting frame (4), and the thickness of the hardened interlayer (5) is equal to the thickness of the interlayer casting frame (4).

3. The physical model of layered salt rock strata according to claim 1, characterized in that, The gap between the outer wall of the metal tube 2 (1-2) and the inner wall of the model groove is filled with fine-grained industrial salt powder (7).

4. The physical model of layered salt rock strata according to claim 1, characterized in that, The outlet end of the metal tube 2 (1-2) is fitted with a rubber plug (2); the contact edge between the rubber plug (2) and the salt rock block (3) is sealed with epoxy resin adhesive.

5. A physical model of layered salt rock strata according to claim 1, characterized in that, At least one model observation surface is fixed by adhesive sealing through a visual sealing transparent plate (6).

6. A method for preparing a physical model of layered salt rock strata as described in any one of claims 1-5, characterized in that, Includes the following steps: Step S1: Material preparation and preparation of the sandwich casting frame: Prepare the pre-treated salt rock block (3) after cutting and grinding, as well as metal pipe one (1-1), metal pipe two (1-2), water pipe (1-3), rubber stopper (2), transparent visual sealing plate (6), geological material powder, sealant, saturated brine, industrial salt powder (7) and water distribution valve (8); use transparent plexiglass or equivalent material resistant to salt and brine corrosion to make a hollow frame with a concave cross section as the sandwich casting frame (4); Step S2: Model stacking and preliminary sealing: According to the preset layered salt rock stratum structure scheme, the salt rock blocks and the interlayer casting frame are stacked alternately to form a layered structure. A sealant is applied to the contact interface, the side of the model and the back of the model to form a sealing layer. Pressure is applied to make each layer fit tightly and then left to stand until the sealing layer is cured. Step S3: Preparation, filling and compaction of interlayer slurry: After the sealing layer is cured in step S2, mudstone powder, gypsum powder and salt rock powder are mixed according to the preset interlayer material ratio scheme. Saturated brine is added and stirred to form a flowing interlayer slurry, which is then filled into the reserved concave area of ​​the interlayer casting frame (4). After filling, the model is placed on a vibrating table for compaction and then moved into a constant temperature drying oven for dehydration and hardening to form a hardened interlayer (5). Among them, the mass ratio of mudstone powder to gypsum powder selected for the interlayer material ratio is 3:1 to 6:1, and the mass of salt rock powder is 10% to 30% of the total mass of mudstone powder and gypsum powder. The mass ratio of geological material powder composed of mudstone powder, gypsum powder and salt rock powder to saturated brine is 8:

2. Step S4: Installation and final sealing of the tube simulation system: After the model hardens, a groove 40-50mm from the bottom surface is chiseled at a preset position on the top surface; metal tube one (1-1) is inserted into metal tube two (1-2) and embedded in the groove, so that the end of metal tube one (1-1) protrudes; rubber plug (2) is installed at the outlet end of metal tube two (1-2), and epoxy resin adhesive is applied to the contact interface between the rubber plug (2) and the salt rock block (3) for sealing; industrial salt powder (7) is used to fill the gap between the outer wall of the tube and the groove; epoxy resin adhesive is applied to the edge of the model observation surface, and a transparent visual sealing plate (6) is covered and pressure is applied to make it in close contact. It is left to stand at room temperature for ≥24 hours or until the adhesive cures.

7. The method for preparing a physical model of layered salt rock strata according to claim 6, characterized in that, Both metal tube one (1-1) and metal tube two (1-2) are made of stainless steel. The diameter of metal tube one (1-1) is 3~4mm and the diameter of metal tube two (1-2) is 5~7mm. The rubber stopper (2) is matched with the outer diameter of metal tube two (1-2). The transparent sealing plate (6) is an acrylic glass plate. The geological material powder includes mudstone powder, gypsum powder and salt rock powder. The sealant is a transparent epoxy resin adhesive. The saturated brine is used to mix with the geological material powder to prepare the interlayer slurry.

8. The method for preparing a physical model of layered salt rock strata according to claim 6, characterized in that, In step S1, the outer contour dimensions of the interlayer casting frame (4) are consistent with the plane dimensions of the salt rock block, and the thickness of the interlayer casting frame (4) is 5~20mm and determined according to the simulated interlayer thickness. Its central area is provided with a through hole to form the interlayer slurry filling space, and the hole size is set according to the simulated interlayer geological extensibility.

9. The method for preparing a physical model of layered salt rock strata according to claim 6, characterized in that, In step S3, the vibration compaction process uses a vibration frequency of 50~100Hz and lasts for 30~50s; the drying and dehydration process is carried out at 60°C for 48 hours or until the interlayer slurry is completely hardened.

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