A device and method for preparing synthetic salt rock samples by brine percolation induced recrystallization

Abstract

The application provides a synthetic salt rock sample preparation device and method for brine infiltration induced recrystallization, and relates to the technical fields of rock mechanics, salt cavern gas storage and energy storage, underground salt rock engineering, physical simulation test and artificial rock sample preparation. The synthetic salt rock sample preparation device and method for brine infiltration induced recrystallization comprise a rack, a servo hydraulic cylinder, an upper porous seepage pressure head, a closed pressing mold assembly, a brine supply system, a vacuum replacement system, a heating and heat preservation sleeve and a multi-sensor closed-loop control system. The application solves the problems of lack of chemical cementation of salt particles, difficulty in discharging pore gas, dependence on empirical time for rock formation endpoint and difficulty in preparing layered samples in the existing dry pressing forming, and the microstructure and mechanical properties of the obtained synthetic salt rock sample are closer to natural salt rock, so that the synthetic salt rock sample is suitable for salt cavern gas storage and energy storage and salt rock engineering physical simulation test.

Description

Technical Field

[0001] This invention relates to the fields of rock mechanics, salt cavern gas storage and energy storage, underground salt rock engineering, physical simulation experiments and artificial rock sample preparation technology, specifically a device and method for preparing synthetic salt rock samples by brine filtration-induced recrystallization. Background Technology

[0002] Natural salt rock, due to its density, creep self-healing ability, and low permeability, is widely used as the surrounding rock medium for salt cavern gas, oil, hydrogen, compressed air energy storage, and underground energy reservoirs. The physical and mechanical parameters of salt rock (such as strength, creep rate, permeability, and damage evolution) are key input parameters for the long-term stability evaluation and design of reservoirs. However, sampling natural salt rock is difficult, especially coring from deep salt layers, which is costly. Furthermore, the mechanical parameters of natural salt rock are highly discrete due to factors such as sedimentary environment, bedding structure, impurity distribution, grain size, and post-diagenetic variations, exhibiting significant differences between different depths and layers within the same stratigraphic unit. This makes it difficult to meet the needs of large-scale, repeatable physical simulation experiments. Therefore, artificially synthesized salt rock samples have become an important supplementary means for salt rock mechanical testing. They enable controllable design of composition, structure, and mechanical properties, effectively improving the repeatability and comparability of experimental data.

[0003] Current methods for preparing artificial salt rock samples often employ cold pressing of dry salt powder, high-temperature and high-pressure dry pressing, or cold pressing followed by heat treatment. For example, dry NaCl salt powder is placed into a mold and directly compacted under axial pressure; or a heating and heat preservation process is introduced to promote recrystallization and grain boundary healing between salt particles. While these methods can achieve a certain degree of compaction, they have the following significant drawbacks: The lack of a brine-involved dissolution-precipitation-recrystallization cementation mechanism—existing methods mainly rely on dry pressing, where salt particles are physically bonded primarily through mechanical interlocking and a small amount of plastic deformation. This fails to simulate the chemical cementation mechanism of "brine dissolution-ion migration-saturated crystallization-crystal bridge growth" during the formation of natural salt rocks. Consequently, the particles in the sample lack crystal bridge connections, resulting in low cementation strength and a microstructure that differs significantly from that of natural salt rocks.

[0004] Pore ​​gas is difficult to expel effectively, resulting in insufficient density and uniformity. After the salt powder is filled, a large amount of air is trapped between the particles. When pressure is applied directly, the air is sealed in the pores, forming closed pores or local high-pressure air pockets. This leads to uneven density distribution inside the sample, with significant differences between the end and center areas, which seriously affects the homogeneity of the sample and the reliability of mechanical test data.

[0005] The endpoint of diagenesis relies on empirical time, and the process lacks real-time monitoring. Existing methods usually use preset heat and pressure holding times (such as empirical values ​​such as maintaining constant temperature and pressure for 24 hours) as the ending condition. There is a lack of quantitative means to determine the endpoint of diagenesis based on process parameters such as displacement, seepage, conductivity, resistivity, and temperature gradient. It is difficult to guarantee the consistency of samples between batches and cannot adapt to the personalized process requirements under different formulations, particle sizes, and temperature conditions.

[0006] The preparation of layered and heterogeneous salt rock samples is difficult. Natural salt rocks generally contain argillaceous interlayers, gypsum interlayers or bedding structures, while existing dry pressing methods are difficult to accurately control the bedding angle, interlayer thickness and component distribution during the molding process, which seriously limits the simulation ability of artificial salt rock samples under complex geological conditions.

[0007] In summary, existing dry pressing methods suffer from problems such as the lack of brine participation in diagenesis, difficulty in venting pore gases, lack of process monitoring, and difficulty in preparing layered samples, making it difficult to produce artificial samples with microstructures and mechanical properties close to natural salt rocks. This invention aims to provide a complete sample preparation device and method that completes vacuum degassing, brine replacement, axial and radial composite percolation, pulse loading, and heat- and pressure-maintaining recrystallization within the same sealed mold cavity, thereby solving the aforementioned problems. Summary of the Invention

[0008] To address the shortcomings of existing technologies, this invention provides a device and method for preparing synthetic salt rock samples by brine percolation-induced recrystallization, aiming to solve the problems of lack of crystal bridge cementation structure and low strength in existing dry-pressed samples.

[0009] To achieve the above objectives, the present invention is implemented through the following technical solution: a device and method for preparing synthetic salt rock samples by brine percolation-induced recrystallization.

[0010] Core technical solution for the lack of chemical bonding between salt particles The formation of natural salt rocks depends on the growth of crystal bridges caused by the dissolution of brine between grains, ion migration, and saturated crystallization during the diagenetic process. However, existing dry pressing methods rely solely on the physical bonding of mechanical compaction, making it difficult to simulate this chemical cementation mechanism. Therefore, this invention provides a sample preparation device that completes the entire process of vacuum degassing, brine replacement, loading and pressurization, and heat and pressure holding within the same sealed mold cavity.

[0011] The core of this device lies in the coordinated operation of the brine supply system and the multi-sensor closed-loop control system. Saturated or near-saturated brine is stored in a brine storage tank. A micro-metering pump injects brine through the axial inlet channel of the upper porous permeation head via an inlet control valve. After being dispersed in the pressure equalization chamber, the brine passes through a filter from top to bottom into the salt powder matrix. The bottom surface of the upper porous permeation head is equipped with replaceable porous filter plates, which both evenly distribute the brine and prevent salt powder particles from backflowing and clogging the channels. After the mold cavity is closed, the temperature control module controls the heating and insulation jacket to raise the temperature, bringing the molding cavity to the target temperature. A servo hydraulic cylinder applies axial pressure to the salt powder. Under the combined effects of high temperature, high pressure, and brine permeation, stress concentration occurs at the contact points of the salt particles, leading to localized dissolution. Ions migrate with the porous brine and recrystallize again due to supersaturation in the stress release zone, temperature gradient zone, and pore contraction zone, gradually forming crystal bridges and cemented structures between particles. This process can run continuously for several hours to tens of hours until recrystallization and cementation are fully completed.

[0012] The pulse loading control module can be used as a standalone unit or integrated into the central controller to control the servo hydraulic cylinders to apply constant pressure, graded loading, stepped loading, or cyclic pulse loading to the salt powder skeleton. Pulse loading includes cycles of pressurization, pressure holding, and micro-depressurization. The micro-depressurization stage facilitates the redistribution of brine to the not-yet-fully-compacted pore areas, while the pressurization stage promotes particle rearrangement and crystal bridge compaction, avoiding the problems of excessive end compaction and insufficient filtration in the central area caused by a single high-pressure loading.

[0013] Improved solutions for the difficulty in venting pore gas After salt powder is filled, a large amount of air is trapped between the particles. If this air is not removed beforehand, it will be trapped between the particles during subsequent high-pressure molding, forming closed pores or localized high-pressure air pockets, resulting in uneven density distribution inside the sample. To address this, the present invention integrates a vacuum displacement system into the mold cavity.

[0014] The vacuum pump is connected to the molding cavity via a vacuum switching valve. After loading and sealing the mold cavity, the liquid inlet control valve is closed first, and the vacuum switching valve is opened to start the vacuum pump, extracting air from between the salt powder particles and in the pores. During the vacuuming process, pulse-type evacuation can be performed through the cooperation of the vent valve and the vacuum switching valve to fully remove trapped gas in deep pores. After reaching the predetermined vacuum level and maintaining it for a set time, the vacuum switching valve is closed, and then the micro-metering pump is started to inject brine. Under the dual action of vacuum negative pressure and pumping pressure, the brine quickly penetrates into the pore channels between the salt powder particles, further displacing and expelling residual air.

[0015] A back pressure valve is installed on the outlet pipeline to maintain a predetermined pore back pressure during brine injection and pressurization. The injected brine can be discharged through the outlet / drainage channel of the lower porous pressure-bearing plate via the back pressure valve, forming an upward seepage path. Alternatively, the back pressure valve can be closed to allow the brine to fill the pores, creating static pore fluid pressure. This combination of vacuum extraction and brine replacement effectively reduces closed pores inside the sample, improving the density and uniformity of the molded sample.

[0016] Improvement scheme for addressing the dependence of diagenesis endpoint on empirical time Existing methods typically use preset heat and pressure holding times as the termination condition, which is difficult to adapt to the personalized process requirements under different formulations, particle sizes, and temperature conditions. Therefore, this invention introduces a multi-sensor closed-loop control system to achieve real-time monitoring of the diagenetic process and automatic determination of the endpoint.

[0017] Temperature sensors are positioned at different heights within the mold to detect the temperature distribution in the upper, middle, and lower areas of the molding cavity. When the temperature difference exceeds the allowable value, the temperature control module can reduce the heating rate or activate zoned compensation heating to ensure a uniform temperature field within the mold cavity. Mold cavity pressure sensors detect the pore fluid pressure, which, together with the loading pressure of the servo hydraulic cylinder, distinguishes between the effective stress of the skeleton and the pore pressure, preventing excessively high brine pressure from causing localized erosion of the channels or excessively low pressure from causing pore collapse. Axial displacement sensors record the compression displacement of the salt powder skeleton in real time during the pressurization process. When the rate of change of displacement per unit time drops below a set threshold, it indicates that the skeleton is stabilizing and particle rearrangement is essentially complete.

[0018] A conductivity sensor is installed on the drain pipe to monitor changes in the ion concentration of the discharged brine. In the initial stage of recrystallization, the salt powder dissolves at a high rate, resulting in continuous changes in the conductivity of the discharged brine. As crystal bridges grow and pores shrink, the dissolution-precipitation phase reaches a dynamic equilibrium, and the rate of change in conductivity gradually decreases until it stabilizes. A resistivity electrode assembly is embedded in the bottom surface of the upper porous permeation head and the top surface of the lower porous pressure plate to monitor changes in the interconnected pores and liquid state within the sample. As crystal bridge bonding progresses, the pore channels are gradually filled with newly formed crystals, and the sample resistivity tends to stabilize.

[0019] The central controller collects signals from the aforementioned sensors in real time. When the rate of change of axial displacement, the rate of change of liquid conductivity, the rate of change of sample resistivity, the temperature difference of the mold, and the pressure fluctuation of the mold cavity are all below their respective preset thresholds and remain below them for a set time, the central controller determines that recrystallization and cementation are complete. It then issues a command to stop heating and pressurization and proceed to the cooling, depressurization, and demolding process. The entire diagenesis process requires no manual intervention, and batch-to-batch consistency and repeatability are significantly improved.

[0020] Supplementary solutions to address the difficulties in preparing heterogeneous and layered salt rock samples Natural salt rocks commonly contain argillaceous interlayers, gypsum interlayers, or bedding structures, but existing dry pressing methods struggle to precisely control bedding angles, interlayer thicknesses, and component distribution during the molding process. This invention solves this technical problem through a layered and heterogeneous salt rock sample molding module.

[0021] The layered feeding guide cylinder is detachably installed above the sealed pressing mold assembly. Its interior has guide grooves for inserting pull-out layered partitions, which can be vertically inserted into the guide cylinder and extend into the molding cavity. During loading, the partitions are first inserted to the predetermined positions. Different components, particle sizes, or color-coded base mixtures, as well as interlayer materials such as clay powder, gypsum powder, or gypsum-salt mixture powder, are then added to both sides of the partitions. The partitions can be horizontal, inclined, or stepped. By adjusting the insertion angle and position of the partitions, precise control of horizontal, inclined, or stepped layering can be achieved.

[0022] The interlayer material is not limited to clay powder; gypsum powder, anhydrite powder, potassium-magnesium salt powder, or mixtures thereof with salt powder can also be selected according to simulation needs. The interlayer thickness can be precisely adjusted within millimeters by controlling the amount added. After each layer of material is filled, the partition is slowly and vertically extracted. A V-shaped scraper blade can be installed at the bottom of the partition to prevent mixing of materials on both sides during extraction. Subsequently, vacuum degassing, brine replacement, and high-temperature, high-pressure recrystallization are carried out according to conventional procedures. Ion exchange and recrystallization reactions occur at the interfaces between different material layers, forming a tightly bonded layered synthetic salt rock sample. The obtained sample can be used to study the effects of bedding dip angle, interlayer thickness, and interlayer composition on the mechanical anisotropy and permeability characteristics of salt rock.

[0023] This invention provides an apparatus and method for preparing synthetic salt rock samples by brine percolation-induced recrystallization. It has the following beneficial effects: Compared with existing technologies, this brine percolation-induced recrystallization synthetic salt rock sample preparation device and method introduces brine into the salt rock formation process, allowing salt powder to undergo dissolution, migration, and recrystallization precipitation in a high-temperature and high-pressure environment, forming a crystal bridge cementation structure between particles. This simulates the formation mechanism of natural salt rock, overcoming the shortcomings of dry pressing, where salt particles rely solely on mechanical interlocking and local plastic deformation for physical bonding, lacking chemical cementation. Simultaneously, the synergistic cooperation of the axial liquid inlet channel, the annular brine distribution chamber, and the radial percolation micropores achieves axial and radial composite percolation, ensuring uniform distribution of brine within the salt powder skeleton and eliminating end effects and the risk of localized channelization. Furthermore, the cyclic pressurization and micro-depressurization via pulse loading promote salt particle rearrangement and brine redistribution, further enhancing the sample's density and uniformity.

[0024] Compared with existing technologies, this apparatus and method for preparing synthetic salt rock samples by brine percolation-induced recrystallization uses a vacuum pump to pre-extract the air trapped between salt powder particles before injecting brine to replace pores, effectively reducing the formation of closed pores and improving the density and uniformity of the sample interior.

[0025] Compared with existing technologies, this synthetic salt rock sample preparation device and method for brine percolation-induced recrystallization uses temperature sensors, pressure sensors, displacement sensors, liquid conductivity sensors, and resistivity electrode sets to monitor temperature, pressure, displacement, conductivity, and resistivity during the recrystallization process in real time. The central controller automatically determines the diagenesis endpoint based on a comprehensive stability criterion of axial displacement change rate, liquid conductivity change rate, sample resistivity change rate, mold temperature difference, and mold cavity pressure fluctuation. This avoids the problem of poor batch-to-batch consistency caused by relying solely on empirical time control, and achieves monitorable, controllable, and repeatable diagenesis process.

[0026] Compared with existing technologies, this apparatus and method for preparing synthetic salt rock samples by brine percolation-induced recrystallization precisely separates salt-based mixtures and interlayer materials of different components or particle sizes during the loading process through a layered feeding guide cylinder and a removable layered partition. This allows for controllable bedding angles and interlayer thicknesses, enabling the preparation of layered, inclined bedding, and multi-component composite simulated natural salt rock samples. This overcomes the shortcomings of existing dry pressing methods in preparing heterogeneous salt rock samples. Attached Figure Description

[0027] Figure 1 This is a schematic diagram of the structure of the present invention; Figure 2 This is a partial cross-sectional schematic diagram of the sealed pressing mold assembly; Figure 3 for Figure 2 A magnified view of a section at point A in the middle; Figure 4 for Figure 2 A magnified view of a section at point B in the middle; Figure 5 This is a closed-loop control logic diagram; Figure 6 A schematic diagram of the molding structure of layered and mixed salt rock samples; Figure 7 This is a flowchart of the brine percolation-induced recrystallization method.

[0028] The components include: 1. Frame; 2. Servo hydraulic cylinder; 3. Insulated pressure transmission assembly; 4. Upper porous permeation head; 5. Sealed pressing mold assembly; 6. Split inner cylinder; 7. Outer sleeve; 8. Heating and insulation sleeve; 9. Forming cavity; 10. Salt powder or salt-based mixture; 11. Lower porous pressure bearing pad; 12. Mold base; 13. Axial liquid inlet channel; 14. Annular brine distribution cavity; 15. Radial permeation micropores / microgrooves; 16. Liquid outlet / drainage channel; 17. Brine storage tank; 18. Filtration, degassing, and preheating unit; 19. Micro-metering pump; 20. Liquid inlet control valve; 21. Vacuum pump; 22. Vacuum switching valve; 23. Gas-liquid separator; 24. 25. Back pressure valve; 26. Return liquid storage tank; 27. Temperature control module; 28. Temperature sensor; 29. ​​Mold cavity pressure sensor; 30. Axial displacement sensor; 31. Outlet conductivity sensor; 32. Resistivity electrode group; 33. Central controller; 34. Data acquisition module; 35. High temperature and high pressure sealing ring / sealing assembly; 36. Pull-out layered partition; 37. Layered feeding guide cylinder; 38. Sandwich material layer; 39. Pulse loading control module; 40. Acoustic wave detection probe; 41. Cooling channel; 42. Safety pressure relief valve; 43. Venting valve; 44. Pressure holding accumulator; 45. Replaceable porous filter; 46. Synthetic salt rock sample. Detailed Implementation

[0029] 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.

[0030] Example 1: Preparation of Standard Cylindrical Samples of Pure Salt Rock This embodiment uses the preparation of a pure salt rock cylindrical sample with a diameter of 50 mm and a height of 100 mm as an example to provide a detailed description of the apparatus and method of the present invention.

[0031] like Figures 1 to 7 As shown, the brine percolation-induced recrystallization synthesis salt rock sample preparation device used in this embodiment includes a frame 1, a servo hydraulic cylinder 2, a heat-insulated pressure-bearing transmission component 3, an upper porous percolation head 4, a sealed pressing mold assembly 5, a mold base 12, a brine storage tank 17, a filtration, degassing, and preheating unit 18, a micro-metering pump 19, an inlet control valve 20, a vacuum pump 21, a vacuum switching valve 22, a back pressure valve 24, a return liquid storage tank 25, a temperature control module 26, a temperature sensor 27, a mold cavity pressure sensor 28, an axial displacement sensor 29, an outlet conductivity sensor 30, a resistivity electrode group 31, a central controller 32, and a data acquisition module 33.

[0032] Frame 1 is a four-column hydraulic frame, consisting of a base worktable, four columns, a top crossbeam, and left and right side plates, providing overall load-bearing space and reaction force support. Servo hydraulic cylinder 2 is installed in the center of the top crossbeam of frame 1. The cylinder body passes through the crossbeam and is fixed to the upper surface of the crossbeam via a flange, with the piston rod extending downwards from the lower end of the cylinder body. The output pressure range of servo hydraulic cylinder 2 is 5 MPa to 300 MPa. It employs closed-loop servo control and is capable of performing constant pressure loading, graded loading, and cyclic pulse loading.

[0033] The heat-insulating pressure-bearing transmission assembly 3 is located between the lower end of the piston rod of the servo hydraulic cylinder 2 and the upper end of the upper porous permeation pressure head 4. It adopts a three-layer composite structure: the uppermost layer is an alloy steel pressure plate, the middle layer is a zirconia ceramic heat insulation plate, and the lowermost layer is an alloy steel pressure plate. The three layers are connected by bolts. The heat-insulating pressure-bearing transmission assembly 3 can both transmit high pressure and suppress the conduction of heat from the heating insulation jacket 8 to the servo hydraulic cylinder 2.

[0034] The sealed pressing mold assembly 5 includes a segmented inner cylinder 6, an outer sleeve 7, a heating and insulation sleeve 8, a high-temperature and high-pressure sealing ring 34, and a replaceable porous filter 44. The segmented inner cylinder 6 is composed of three arc-shaped inner cylinder segments joined together, with positioning tenons and sealing grooves on the joining surfaces, and the inner wall is coated with a salt corrosion resistant coating. The inner diameter of the segmented inner cylinder 6 is 50 mm, the wall thickness is 8 mm, and the height is 300 mm. It is used to limit the outer diameter of the synthetic salt rock sample 45 and facilitate demolding. The outer sleeve 7 is fitted outside the segmented inner cylinder 6, and an annular brine distribution cavity 14 is provided between the inner wall and the outer wall of the segmented inner cylinder 6. The outer sleeve 7 is an integral thick-walled cylinder with a wall thickness of 20 mm, used to withstand the radial expansion pressure generated during the salt powder compaction process and maintain the overall strength of the mold.

[0035] The heating and insulation jacket 8 is set around the outer sleeve 7 and consists of a resistance heating element, an insulation layer and a metal shell. The heating power is controlled by the temperature control module 26 and the heating rate is adjustable from 0.5 degrees Celsius to 5 degrees Celsius per minute.

[0036] The internal cavity of the segmented inner cylinder 6 is a forming cavity 9, used to contain salt powder or salt-based mixture 10. An annular groove is machined in the middle of the outer peripheral wall of the segmented inner cylinder 6, which, together with the inner wall of the outer sleeve 7, forms an annular brine distribution cavity 14. Multiple radial permeation micropores 15 are provided on the cylinder wall of the segmented inner cylinder 6, connecting the annular brine distribution cavity 14 and the forming cavity 9. The pores have a diameter of 0.5 mm and are evenly arranged circumferentially, allowing brine to enter the forming cavity 9 evenly from the circumference. The upper and lower outer walls of the segmented inner cylinder 6 and the inner wall of the outer sleeve 7 form a sealing mating surface, ensuring that the brine in the annular brine distribution cavity 14 does not leak from the ends.

[0037] The mold base 12, located below the outer sleeve 7 and the segmented inner sleeve 6, is made of alloy steel and has a positioning stop in the center of its upper surface to accommodate the lower porous pressure bearing plate 11. The mold base 12 has an annular cooling channel 40 inside, with its inlet and outlet ports extending from the front wall of the mold base 12 for controlled cooling water flow. A vertically penetrating liquid discharge channel 16 is located at the center of the mold base 12, aligned with the liquid outlet on the bottom surface of the lower porous pressure bearing plate 11.

[0038] The upper porous permeation head 4 is made of alloy steel and has a stepped cylindrical structure that is thicker at the top and thinner at the bottom. The outer diameter of the upper large-diameter section is the same as the inner diameter of the outer sleeve 7, and the outer diameter of the lower small-diameter section is the same as the inner diameter of the forming cavity 9. An axial liquid inlet channel 13 is provided in the center of the upper porous permeation head 4, which runs vertically from the center of the top surface of the large-diameter section to the bottom surface of the small-diameter section. A radial hole perpendicular to the axis is provided on the side wall of the large-diameter section of the upper porous permeation head 4, which communicates with the axial liquid inlet channel 13. A threaded pipe connector is provided at the outer end of the radial hole for connecting the brine supply pipeline. The lower end of the axial liquid inlet channel 13 diffuses into an inverted trapezoidal pressure equalization cavity at the bottom surface of the small-diameter section, and multiple liquid outlet micropores are provided on the bottom surface of the pressure equalization cavity. An annular step is provided on the outer edge of the bottom surface of the small-diameter section of the upper porous permeation head 4 to accommodate the resistivity electrode assembly 31. The annular step has a depth of 1 mm and a width of 3 mm. The resistivity electrode group 31 is a concentric double-ring electrode, with the inner ring being the excitation electrode and the outer ring being the measurement electrode. It is made of platinum-iridium alloy and embedded in the bottom surface of the annular step. The bottom surface of the small-diameter section of the upper porous permeation head 4 is covered with a replaceable porous filter 44. The replaceable porous filter 44 is a sintered metal porous disc with a pore size of 10 micrometers and a thickness of 0.5 mm, covering the entire bottom surface of the small-diameter section. It is used to evenly distribute brine and prevent salt particles from backflowing and clogging the channel.

[0039] The lower porous pressure bearing plate 11 is located at the bottom of the forming cavity 9, sitting on the top surface of the mold base 12. Its outer diameter is the same as the inner diameter of the forming cavity 9, and its thickness is 5 mm. The lower porous pressure bearing plate 11 is made of sintered metal porous material and has a three-dimensional interconnected pore network inside. This allows brine to pass through the salt powder skeleton and drain downwards through the plate, while also providing pressure resistance for the salt powder. The top surface of the lower porous pressure bearing plate 11 is also covered with a replaceable porous filter 44 with a pore size of 10 micrometers. The lower electrode of the resistivity electrode group 31 is embedded in the central area of ​​the top surface of the lower porous pressure bearing plate 11, corresponding to the position of the upper electrode on the bottom surface of the upper porous permeation head 4.

[0040] The high-temperature and high-pressure sealing ring 34 is set between the outer wall of the small-diameter section of the upper porous permeation pressure head 4 and the inner wall of the segmented inner cylinder 6. It is made of high-temperature resistant fluororubber, has a rectangular cross section, and is installed in the annular sealing groove of the outer wall of the small-diameter section to achieve sliding sealing between the pressure head and the inner cylinder.

[0041] The brine storage tank 17 is a stainless steel tank with a heating and insulation jacket, storing saturated sodium chloride brine. The outlet of the brine storage tank 17 is connected to the filtration, degassing, and preheating unit 18 via a pipeline. The filtration, degassing, and preheating unit 18 integrates a filter, a degassing chamber, and a preheating coil. The filter removes solid particles from the brine, the degassing chamber reduces the amount of dissolved gas entering the forming chamber 9, and the preheating coil preheats the brine to near the target temperature. The micro-metering pump 19 is a precision plunger pump with a flow rate range of 0.01 ml to 20 ml per minute. Its inlet is connected to the outlet of the filtration, degassing, and preheating unit 18, and its outlet is connected via an inlet control valve 20 to the radial orifice of the upper porous permeation head 4 and the inlet of the annular brine distribution chamber 14, respectively. The inlet control valve 20 is a three-way solenoid valve, which can control the on / off switching of axial and radial injection.

[0042] Vacuum pump 21 is a rotary vane vacuum pump, connected to the liquid outlet channel 16 of mold base 12 via vacuum switching valve 22. Gas-liquid separator 23 is connected in series between vacuum pump 21 and liquid outlet channel 16 to separate the extracted gas and liquid. Vent valve 42 is installed on the vacuum pipeline to release the negative pressure in the mold cavity after vacuum venting is completed.

[0043] The back pressure valve 24 is an adjustable pressure maintaining valve, installed on the outlet pipe of the liquid discharge channel 16, with a preset pressure range of 0.1 MPa to 30 MPa. The return liquid storage tank 25 is an atmospheric pressure collection tank, connected to the outlet of the back pressure valve 24, and is used to recover the discharged brine.

[0044] Temperature sensor 27 is an armored thermocouple, installed at three heights (top, middle, and bottom) of the heating insulation jacket 8, used to detect the temperature distribution in different areas of the molding cavity 9. Mold cavity pressure sensor 28 is installed on the side wall of the mold base 12 and connected to the liquid outlet channel 16, used to detect the pressure of the pore brine. Axial displacement sensor 29 is a grating ruler, installed between the top crossbeam of the frame 1 and the piston rod of the servo hydraulic cylinder 2, used to measure axial compression displacement in real time. Liquid outlet conductivity sensor 30 is a flow-through conductivity electrode, installed on the liquid outlet pipe upstream of the back pressure valve 24, used to monitor changes in the ion concentration of the discharged brine.

[0045] The central controller 32 is a programmable logic controller (PLC) and is connected to the data acquisition module 33 via signal lines. Temperature sensor 27, mold cavity pressure sensor 28, axial displacement sensor 29, outlet conductivity sensor 30, and resistivity electrode group 31 are all connected to the data acquisition module 33 via signal lines. The control output terminals of the central controller 32 are respectively connected to the servo hydraulic cylinder 2, micro-metering pump 19, inlet control valve 20, vacuum switching valve 22, back pressure valve 24, and temperature control module 26. The pulse loading control module 38, built into the central controller 32, is used to control the servo hydraulic cylinder 2 to perform cyclic pulse loading of pressure increase, pressure holding, and micro-pressure release.

[0046] The preparation method of this embodiment includes the following steps: S1: Raw material drying and gradation mixing. Weigh out sodium chloride salt powder with a purity of not less than 99.5% as the base mixture 10. Use a standard sieve to separate the salt powder into three grades: coarse particles (300-800 micrometers), medium particles (100-300 micrometers), and fine particles (20-100 micrometers). Mix them evenly with the following mass ratio: coarse particles to medium particles to fine particles = 3:4:3. Place the mixed salt powder in a constant temperature drying oven and dry it at 105 degrees Celsius for 12 hours until the moisture content is reduced to below 0.3%.

[0047] S2: Mold Assembly and Loading. Assemble and install the three arc-shaped segments of the split inner cylinder 6 onto the mold base 12, then insert the outer sleeve 7 and heating insulation sleeve 8. Place the lower porous pressure bearing pad 11 at the bottom of the forming cavity 9, and lay replaceable porous filter sheets 44 on the top surface of the pad. Add the dried salt powder to the forming cavity 9 in batches, smoothing the surface with a flat scraper after each addition, and gently vibrating with a vibrating table to naturally compact the salt powder. After loading, slowly press the upper porous permeation head 4 into the upper end of the forming cavity 9, allowing the smaller diameter section to enter the split inner cylinder 6, with the stepped surface of the larger diameter section approaching the top surface of the split inner cylinder 6. Simultaneously, install the high-temperature, high-pressure sealing ring 34.

[0048] S3: Sealing and Vacuuming. Close the liquid inlet control valve 20, open the vacuum switching valve 22, and start the vacuum pump 21 to extract the air between the salt powder particles in the molding chamber 9. During the vacuuming process, three pulse-type evacuations are performed through the cooperation of the vent valve 42 and the vacuum switching valve 22 to fully remove the gas trapped in the deep pores. Maintain the vacuum for 30 minutes until the vacuum level reaches below -0.095 MPa.

[0049] S4: Brine Injection and Pore Displacement. Close the vacuum switching valve 22, open the liquid inlet control valve 20, and start the micro-metering pump 19. The saturated sodium chloride brine in the brine storage tank 17 is heated to 60 degrees Celsius after being treated by the filtration, degassing, and preheating unit 18. The brine is injected into the axial liquid inlet channel 13 of the upper porous permeation pressure head 4 at a flow rate of 2 ml per minute. The brine enters the forming chamber 9 evenly through the pressure equalization chamber and the replaceable porous filter 44, passes through the salt powder skeleton from top to bottom, and is discharged from the lower porous pressure bearing plate 11 and the liquid outlet channel 16. After the liquid outlet channel 16 continuously discharges liquid without bubbles, close the back pressure valve 24 to the preset back pressure of 2 MPa.

[0050] S5: Pre-compression and establishment of pore back pressure. Activate servo hydraulic cylinder 2 to apply pre-compression up to 10 MPa at a rate of 1 MPa per minute, initially compacting the salt powder and forming a load-bearing skeleton. Back pressure valve 24 maintains the pore back pressure at 2 MPa.

[0051] S6: Pulse loading and shaft-diameter composite percolation. The central controller 32 activates the pulse loading control module 38, controlling the servo hydraulic cylinder 2 to execute the pulse loading program: increasing the pressure from 10 MPa to 50 MPa within 10 minutes, holding the pressure for 5 minutes; slightly depressurizing to 40 MPa, holding the pressure for 3 minutes; then increasing the pressure again to 60 MPa, holding the pressure for 5 minutes. The pressure increase amplitude for each cycle is 10 MPa to 15 MPa, the cycle is 15 minutes to 20 minutes, and a total of 3 cycles are performed. Simultaneously with pulse loading, in addition to percolating from top to bottom through the axial inlet channel 13, the brine also enters the forming cavity 9 circumferentially through the annular brine distribution chamber 14 and the radial percolation micropores 15, achieving composite percolation of axial and radial directions. The micro-metering pump 19 maintains a micro-flow rate of 0.5 ml of brine per minute to ensure that the pores are always filled with brine.

[0052] S7: Constant Temperature and Pressure Recrystallization and Cementation. The temperature control module 26 controls the heating insulation jacket 8 to heat to 120 degrees Celsius at a rate of 1 degree Celsius per minute. When the temperature reaches 120 degrees Celsius and the pressure reaches 100 MPa, it enters the constant temperature and pressure maintenance stage. In this stage, the liquid inlet control valve 20 and the back pressure valve 24 are closed, making the molding cavity 9 a closed system. The servo hydraulic cylinder 2 maintains an axial pressure of 100 MPa, and the temperature control module 26 maintains a constant temperature of 120 degrees Celsius ± 2 degrees Celsius. The micro-metering pump 19 only performs pulsed liquid replenishment when the mold cavity pressure sensor 28 detects a pressure drop, with a replenishment volume of 0.5 ml each time. The valve is closed immediately after replenishment. Under the combined action of high temperature, high pressure and brine, the salt powder undergoes local dissolution at the particle contact points. Ions migrate with the pore brine and recrystallize and precipitate in the stress concentration area and temperature gradient area, gradually forming a crystal bridge cemented structure.

[0053] S8: Diagenesis endpoint closed-loop determination. The central controller 32 collects signals from various sensors in real time for comprehensive determination. When the axial displacement change rate is less than 0.01 mm per hour for 2 consecutive hours, the liquid conductivity change rate is less than 0.5 microSiemens per centimeter per minute for 2 consecutive hours, the sample resistivity change rate is less than 0.1 ohm-meters per hour for 2 consecutive hours, the maximum temperature difference between the upper, middle and lower points of the mold is less than 3 degrees Celsius for 2 consecutive hours, and the mold cavity pressure fluctuation is less than ±0.5 MPa for 2 consecutive hours, the central controller 32 determines that recrystallization and cementation have been completed and proceeds to step S9. If the stability conditions are not met, it returns to step S6, adjusts the pressure pulse parameters, brine flow rate and temperature, and continues the cycle until all criteria meet the stability conditions.

[0054] S9: Cooling, pressure relief, and demolding. The central controller 32 issues a command to stop the micro-metering pump 19 and heating, and slowly releases the pore pressure to atmospheric pressure at a rate of 0.5 MPa per minute through the back pressure valve 24. The temperature control module 26 shuts off the heating and starts the cooling channel 40 to introduce cooling water, cooling the temperature to below 60 degrees Celsius at a rate of 1 degree Celsius per minute. The outer sleeve 7 is disassembled, the segmented inner cylinder 6 is taken out, and the three arc-shaped segments of the segmented inner cylinder 6 are removed one by one to take out the synthetic salt rock sample 45.

[0055] The synthetic salt rock sample obtained in this embodiment is a cylinder with a diameter of 50 mm and a height of 100 mm, with a density of about 2.15 g per cubic centimeter. It has a uniform internal structure and well-developed crystal bridge cementation, and can be used for uniaxial compression, triaxial compression and creep tests.

[0056] Example 2: Preparation of Salt Rock Samples with Horizontal Muddy Thin Interlayers The main difference between this embodiment and Embodiment 1 is that a layered salt rock sample containing a horizontal argillaceous thin interlayer was prepared.

[0057] Before loading, the layered feeding guide cylinder 36 is installed above the outer sleeve 7. The layered feeding guide cylinder 36 is a stepped cylinder that is larger at the top and smaller at the bottom, and the upper opening is provided with a vertical guide groove for inserting a pull-out layered partition 35. The pull-out layered partition 35 is vertically inserted into the layered feeding guide cylinder 36 and extends into the forming cavity 9, with the bottom of the partition close to the top surface of the lower porous pressure bearing pad 11.

[0058] Sodium chloride powder was prepared as the salt layer material according to the gradation ratio and drying method of Example 1. Additionally, clay powder was prepared as interlayer material layer 37. The clay powder was composed of kaolin, illite, and quartz powder mixed in a mass ratio of 5:3:2, with a particle size less than 50 micrometers and a moisture content not exceeding one percent.

[0059] Add a first layer of sodium chloride powder to the left side of the partition, about 30 mm thick, smooth it with a scraper and gently tamp it down with a tamping rod. Add mud-like powder to the right side of the partition, about 2 mm thick, and spread it evenly with a scraper. Slowly and vertically pull out the pull-out layered partition 35. The bottom of the partition has a V-shaped scraper blade to prevent the materials on both sides from mixing during the removal process. Add a second layer of sodium chloride powder above the interlayer formed after the partition is removed, about 35 mm thick.

[0060] After loading is completed, the layered feeding guide cylinder 36 is removed, and the porous seepage head 4 and the heat-insulating pressure-bearing transmission component 3 are installed. The subsequent vacuuming and degassing, brine injection and pore replacement, pre-compression and establishment of pore back pressure, pulse loading and shaft diameter composite seepage, constant temperature and pressure recrystallization and cementation, diagenesis endpoint closed-loop determination, and cooling, pressure relief and demolding steps are the same as steps S3 to S9 in Example 1. Since the permeability of the mud interlayer is lower than that of the salt layer, the injection flow rate of the micro-metering pump 19 is adjusted to 0.3 ml per minute, and the maximum pressure of pulse loading is set to 80 MPa to avoid over-compacting or dispersing of the interlayer.

[0061] The synthetic salt rock sample obtained in this embodiment is a cylindrical sample containing a horizontal thin argillaceous interlayer with a thickness of about 1.8 mm. The interface between the interlayer and the salt layer is well bonded with no obvious debonding or cracks, and can be used to study the influence of the argillaceous interlayer on the mechanical strength and deformation characteristics of the salt rock.

[0062] Example 3: Preparation of Salt Rock Samples Containing Inclined Frames and Composite Brine The main difference between this embodiment and Embodiment 1 is that a salt rock sample with inclined bedding was prepared and a composite brine was used.

[0063] Before loading, the layered feeding guide cylinder 36 is installed above the outer sleeve 7. The removable layered partition 35 is inserted into the inclined guide groove of the layered feeding guide cylinder 36 at a 30-degree angle, with the partition extending into the forming cavity 9. Sodium chloride salt powder with different particle size distributions is added to both sides of the partition, with coarse-grained powder added to the left and fine-grained powder added to the right. After loading, the partition is slowly and vertically pulled out, forming a 30-degree inclined layered interface.

[0064] The brine storage tank 17 is filled with compound brine, the composition of which is: saturated sodium chloride, 0.5 mol / L potassium chloride, 0.2 mol / L magnesium chloride, and 0.05 mol / L calcium sulfate, to simulate the composition of natural salt layer brine containing potassium and magnesium salts.

[0065] After vacuuming and venting, the composite brine is simultaneously injected into the axial inlet channel 13 and the annular brine distribution chamber 14 via a micro-metering pump 19, forming axial and radial composite percolation. The pulse loading program is set as follows: the axial pressure is increased from 5 MPa to 70 MPa in steps within 30 minutes, and held for 10 minutes; the pressure is slightly depressurized to 50 MPa and held for 5 minutes; then increased to 90 MPa and held for 10 minutes; then decreased to 70 MPa and held for 15 minutes, and this cycle is repeated 3 times before the final pressure is increased to 100 MPa and held. The temperature control module 26 heats the water to 140 degrees Celsius at a rate of 0.8 degrees Celsius per minute. The threshold for determining the diagenetic endpoint is relaxed by 10% to 15% compared to Example 1 to account for the complex influence of potassium and magnesium salt components on dissolution and precipitation kinetics. The remaining steps S3 to S9 are the same as in Example 1.

[0066] The synthetic salt rock sample obtained in this embodiment is a simulated natural salt rock sample with a 30-degree inclined bedding. The crystal bridges at the bedding interface are well cemented, and potassium and magnesium ions locally form potassium-magnesium salt-containing cements. It can be used to study the influence of bedding dip angle on the mechanical anisotropy and permeability of salt rock.

[0067] Example 4: Preparation of salt rock samples containing gypsum interlayers and long-term recrystallization The main difference between this embodiment and Embodiment 1 is that it involves preparing a large-sized salt rock sample containing a thin gypsum interlayer.

[0068] The salt powder used is sodium chloride salt powder with a particle size of 100 to 500 micrometers. The interlayer material layer 37 is a gypsum dihydrate powder mixed with salt powder in a mass ratio of 6:4.

[0069] Using a layered filling method similar to that in Example 2, three layers of salt powder and two layers of paste salt interlayer are sequentially filled into the molding cavity 9. The interlayer thickness is approximately 3 mm, and the layer spacing is approximately 25 mm. After filling, the porous permeation head 4 is installed and sealed.

[0070] The process parameters for this embodiment are as follows: vacuum degree -0.098 MPa, vacuuming time 60 minutes; injection flow rate 1 ml / min, brine using composite brine containing 0.03 mol / L calcium sulfate; pre-pressure 5 MPa; pulse loading program increasing from 5 MPa to 150 MPa in 8 steps, each holding pressure for 10 minutes, pulse amplitude 15% to 20% of the target pressure; synthesis temperature 160 degrees Celsius; pore back pressure 10 MPa; holding time automatically determined by closed-loop criteria. In addition to using five criteria—displacement, conductivity, resistivity, temperature, and pressure—to determine the diagenetic endpoint, acoustic wave velocity changes are monitored by acoustic wave detection probe 39. When the acoustic wave velocity stabilizes, it assists in determining the completion of recrystallization. The remaining steps S3 to S9 are the same as in Embodiment 1.

[0071] The specimen obtained after demolding is a synthetic salt rock specimen containing two gypsum interlayers. The interface between the interlayer and the salt layer is tightly bonded and can be used to study the deformation and failure characteristics of gypsum-bearing salt rock under triaxial compression.

[0072] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A synthetic salt rock sample preparation device for brine percolation-induced recrystallization, comprising a frame (1), a servo hydraulic cylinder (2) mounted on the frame (1), an upper porous percolation head (4) mounted below the servo hydraulic cylinder (2), a sealed pressing mold assembly (5) mounted below the upper porous percolation head (4), and a mold base (12) mounted below the sealed pressing mold assembly (5), characterized in that, The device further includes: The brine supply system includes a brine storage tank (17), a micro-metering pump (19), and an inlet control valve (20). The inlet of the micro-metering pump (19) is connected to the brine storage tank (17), and the outlet is connected to the axial inlet channel (13) of the upper porous permeation head (4) through the inlet control valve (20) for injecting brine into the forming cavity (9). The vacuum displacement system includes a vacuum pump (21) and a vacuum switching valve (22), wherein the vacuum pump (21) is connected to the forming chamber (9) through the vacuum switching valve (22) and is used to extract the air between the salt powder particles before the brine is injected; A heating insulation sleeve (8) is fitted around the sealed pressing mold assembly (5) to heat the molding cavity (9) to the target temperature; The multi-sensor closed-loop control system includes a central controller (32) and a temperature sensor (27), a mold cavity pressure sensor (28), and an axial displacement sensor (29) connected to the central controller (32). The central controller (32) is connected to a servo hydraulic cylinder (2), a micro-metering pump (19), an inlet control valve (20), and a temperature control module (26) for adjusting the loading pressure, brine flow rate, and heating power according to the sensor signals. The device completes the entire process of vacuum degassing, brine replacement, loading and pressurization, and heat and pressure recrystallization in the same sealed mold cavity.

2. The apparatus for preparing synthetic salt rock samples by brine percolation-induced recrystallization according to claim 1, characterized in that, The sealed pressing mold assembly (5) also includes a split inner cylinder (6) and an outer cylinder (7). The split inner cylinder (6) is fitted inside the outer cylinder (7). The internal cavity of the split inner cylinder (6) is a forming cavity (9). An annular brine distribution cavity (14) is provided between the outer peripheral wall of the split inner cylinder (6) and the inner wall of the outer cylinder (7). The cylinder wall of the split inner cylinder (6) is provided with a plurality of radial permeation micropores or microgrooves (15) for connecting the annular brine distribution cavity (14) and the forming cavity (9). The annular brine distribution cavity (14) is connected to the brine supply system and is used to evenly distribute brine from the circumference into the forming cavity (9).

3. The apparatus for preparing synthetic salt rock samples by brine percolation-induced recrystallization according to claim 1, characterized in that, The multi-sensor closed-loop control system also includes an outlet conductivity sensor (30) installed on the outlet pipeline and a resistivity electrode group (31) installed on the bottom surface of the upper porous permeation head (4) and the top surface of the lower porous pressure bearing pad (11). The outlet conductivity sensor (30) and the resistivity electrode group (31) are both connected to the central controller (32) via signal. The central controller (32) automatically determines the diagenesis endpoint based on the comprehensive stability criteria of axial displacement change rate, outlet conductivity change rate, sample resistivity change rate, mold temperature difference and mold cavity pressure fluctuation.

4. The apparatus for preparing synthetic salt rock samples by brine percolation-induced recrystallization according to claim 1, characterized in that, The lower end of the upper porous permeation pressure head (4) is provided with an annular step for embedding resistivity electrode group (31), and the bottom surface of the upper porous permeation pressure head (4) and the top surface of the lower porous pressure bearing pad (11) are respectively provided with replaceable porous filter (44).

5. The apparatus for preparing synthetic salt rock samples by brine percolation-induced recrystallization according to claim 1, characterized in that, The servo hydraulic cylinder (2) is equipped with a pulse loading control module (38), which is connected to the central controller (32) for controlling the servo hydraulic cylinder (2) to perform a cyclic pulse loading of pressure increase-pressure holding-micro pressure release; a heat-insulating pressure-bearing transmission component (3) is provided between the upper porous seepage pressure head (4) and the servo hydraulic cylinder (2).

6. The apparatus for preparing synthetic salt rock samples by brine percolation-induced recrystallization according to claim 1, characterized in that, The mold base (12) is provided with a cooling channel (40) inside. The side wall of the mold base (12) is provided with a water inlet and a water outlet that are connected to the cooling channel (40). The center of the mold base (12) is provided with a vertically penetrating liquid outlet / drainage channel (16). The outlet pipe of the liquid outlet / drainage channel (16) is provided with a liquid outlet conductivity sensor (30) and a back pressure valve (24) in sequence.

7. The apparatus for preparing synthetic salt rock samples by brine percolation-induced recrystallization according to claim 1, characterized in that, It also includes a layered and heterogeneous salt rock sample forming module, which includes a pull-out layered partition (35) and a layered feeding guide cylinder (36). The layered feeding guide cylinder (36) is detachably installed above the sealed pressing mold assembly (5). The pull-out layered partition (35) is vertically inserted into the layered feeding guide cylinder (36) and extends into the forming cavity (9) to separate salt-based mixtures and interlayer material layers (37) of different components or different particle sizes on both sides of the partition during the loading process.

8. A method for preparing synthetic salt rock samples using the apparatus according to any one of claims 1 to 7, characterized in that, Includes the following steps: S1: Dry and grade NaCl salt powder or base mixture (10); S2: Install the split inner cylinder (6) on the mold base (12), put on the outer sleeve (7) and the heating and heat preservation sleeve (8), place the lower porous pressure bearing pad (11) at the bottom of the molding cavity (9), fill in the salt powder or salt-based mixture (10), and install the upper porous permeation pressure head (4) and the heat insulation and pressure transmission assembly (3). S3: Close the liquid inlet control valve (20), open the vacuum switching valve (22), and start the vacuum pump (21) to extract the air between the salt powder particles; S4: Close the vacuum switching valve (22), open the liquid inlet control valve (20), and the micro metering pump (19) injects the filtered, degassed and preheated brine into the axial liquid inlet channel (13) and / or the annular brine distribution chamber (14) so ​​that the brine replaces the gas in the pores; S5: Start the servo hydraulic cylinder (2) to apply pre-pressure, so that the salt powder is initially compacted and forms a load-bearing skeleton, and the back pressure valve (24) maintains the predetermined pore back pressure; S6: The central controller (32) starts the pulse loading control module (38), so that the servo hydraulic cylinder (2) performs multi-stage pulse loading, and the brine passes through the salt powder skeleton through axial percolation, radial percolation or axial-radial composite percolation. S7: Temperature control module (26) controls heating insulation jacket (8) to stabilize mold temperature, servo hydraulic cylinder (2) maintains set pressure, micro metering pump (19) maintains micro flow or intermittent flow, promotes dissolution, migration and recrystallization of salt powder skeleton; S8: The central controller (32) determines whether the axial displacement change rate, the liquid conductivity change rate, the sample resistivity change rate, the temperature gradient, and the pressure fluctuation have entered the stable range; if the stable conditions have not been met, return to S6 to adjust the pressure pulse, brine flow rate, and temperature; S9: Stop the brine injection, release the pore pressure through the back pressure valve (24), the temperature control module (26) shuts off the heating or starts the cooling channel (40) for controlled cooling, disassemble the outer sleeve (7) and the split inner cylinder (6), and take out the synthetic salt rock sample (45).

9. The manufacturing method according to claim 8, characterized in that, In step S2, when preparing layered or heterogeneous salt rock samples, salt-based mixtures of different components or particle sizes and interlayer material layers (37) are added layer by layer with the help of layered feeding guide cylinder (36) and removable layered partition (35). After filling, the removable layered partition (35) is removed.

10. The manufacturing method according to claim 8, characterized in that, In step S8, the determination of the diagenesis endpoint adopts a comprehensive stability criterion: when the axial displacement change rate, the liquid conductivity change rate, the sample resistivity change rate, the mold temperature difference and the mold cavity pressure fluctuation are all lower than the preset threshold and continue for more than the set time, the central controller (32) determines that the sample has completed recrystallization and cementation.

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