Artificial large physical model shale core and preparation method thereof

Abstract

The invention provides an artificial large physical model shale core and a preparation method thereof. The preparation method comprises the following steps: determining core composition materials according to mineral composition data of reservoirs in a target area, and calculating the proportions of various materials forming a sand base in each reservoir; according to the material proportion, the adding amount of cement and water is adjusted, and an artificial shale core preparation formula meeting the property requirement of each reservoir in the target area is selected; the method comprises the following steps: respectively weighing solid materials and water required by each reservoir according to different formula amounts to prepare a mixture of core materials of each layer of artificial shale; sequentially filling the material mixture into a mold according to the multilayer distribution sequence of the shale gas reservoir, and applying a certain pressure; and performing water bath maintenance on the artificial shale core filled into the mold, and drying and demolding after maintenance to obtain the artificial large-physical-model shale core. The prepared artificial large-physical-model shale core meets the property of a shale gas reservoir in a target area, can meet the requirements of a multi-well three-dimensional development large-physical-model fracturing experiment, and provides support for three-dimensional development fracturing and multi-well fracturing experiment simulation.

Description

Technical Field

[0001] The present invention relates to the technical field of shale oil and gas development, and in particular to the field of multi-layer artificial large-scale model for simulating the properties of shale gas reservoirs in a target area, and specifically to an artificial large-scale model shale core and a preparation method thereof. Background Art

[0002] Hydraulic fracturing technology refers to a method of using hydraulic force to form cracks in oil and gas layers during oil or gas production. Hydraulic fracturing technology is widely used in the field of shale oil and gas production. Due to the low porosity and low permeability of shale gas, it is difficult for oil and gas to flow in the reservoir without fracturing measures, and the oil and gas migration distance is short. Therefore, it is necessary to use technical means such as horizontal wells and fracturing to change the seepage mechanism of oil and gas in the reservoir and increase the flow capacity of oil and gas in the reservoir, so as to improve the production efficiency of shale oil and gas.

[0003] Unconventional natural gas resources such as shale gas have become an important part of the world's energy supply. The industrial exploitation of these resources will be of great significance to alleviating the tense situation of energy supply and ensuring national energy security. As the proportion of shale gas exploration and development in the energy field increases year by year, the application of shale gas reservoir fracturing construction has become more extensive and common. The existing shale gas reservoir hydraulic fracturing production increase experiments generally use field simulations, which are slow, costly, and have reduced economic benefits. Indoor experiments for simulating shale gas reservoir hydraulic fracturing require the use of a large number of real reservoir cores. Using artificial shale cores for simulation comparison experiments is an important measure to reduce the cost of indoor experiments.

[0004] In addition, considering the characteristics of large-scale model fracturing experiments in three-dimensional development with multiple superimposed small layers, the use of core outcrops or conventional artificial sampling methods cannot understand the expansion rules of cracks within different small layers and between layers, nor can it meet the requirements of large-scale model fracturing experiments in multi-well three-dimensional development.

[0005] Therefore, it is of great significance to study the preparation method of multi-layered large-scale physical model shale rock samples based on the physical and mechanical properties of shale gas reservoirs in the target area to provide support for three-dimensional development fracturing and multi-well fracturing experimental simulation. Summary of the invention

[0006] The purpose of the present invention is to solve at least one of the above-mentioned deficiencies in the prior art. For example, one of the purposes of the present invention is to provide an artificial shale core that can understand the expansion law of cracks in different small layers and between layers, so as to meet the requirements of large-scale model fracturing experiments for multi-well three-dimensional development. The second purpose of the present invention is to provide a method for preparing a multi-layer artificial large-scale model shale core that simulates the properties of shale gas reservoirs in the target area.

[0007] In order to achieve the above object, the present invention provides a method for preparing an artificial large-scale shale core, the method comprising the following steps:

[0008] Determine the core composition materials based on the target area reservoir mineral composition data and calculate the proportion of various materials that make up the sand base of each reservoir;

[0009] According to the calculated proportion of each material in the sand matrix, by adjusting the amount of cement and water, the artificial shale core preparation formula that meets the requirements of each reservoir property in the target area is selected;

[0010] Weigh the solid materials and water required for each reservoir layer according to the different formula amounts of each reservoir layer, mix and stir the solid materials and water of each layer evenly, and prepare the mixture of artificial shale core materials of each layer;

[0011] The mixture of artificial shale core materials is sequentially filled into the mold according to the multi-layer distribution order of the shale gas reservoir, and a certain pressure is applied;

[0012] The artificial shale core filled into the mold is cured in a water bath, and after the curing is completed, it is dried and demoulded to obtain an artificial large-scale shale core that meets the reservoir properties of the target area.

[0013] Optionally, the core constituent material comprises a shale core cementing material.

[0014] Optionally, the shale core bonding material is cement.

[0015] Optionally, the cement is ordinary Portland cement, and the cement particle size is 600-800 meshes.

[0016] Optionally, the materials constituting the sand base include quartz sand powder, heavy calcium powder and illite powder.

[0017] Optionally, the particle size of the quartz sand powder is 100-200 meshes, the particle size of the heavy calcium powder is 600-800 meshes, and the particle size of the illite powder is 600-800 meshes.

[0018] Optionally, the calculated proportions of various materials constituting the sand matrix of each reservoir are based on parts by mass.

[0019] Optionally, the artificial shale core preparation formula that meets the property requirements of each reservoir in the target area is selected, and the selection basis includes the uniaxial compressive strength requirements and porosity requirements of different reservoirs.

[0020] Optionally, the selected result is a formula that is closest to the property requirements of the target area.

[0021] Optionally, the step of adjusting the amount of cement and water comprises the following steps:

[0022] Set an initial dosage range for cement and water addition for each reservoir;

[0023] Several small shale cores of a certain size are prepared from each formula, and the uniaxial compressive strength and porosity of the small shale cores are tested to verify whether the shale cores prepared from each formula meet the property requirements of the reservoir in the target area;

[0024] According to the uniaxial compressive strength and porosity test results, the cement addition and water addition ratio range that is closest to the reservoir property requirements of the target area is selected.

[0025] Optionally, the method of adjusting the amount of cement and water also includes the steps of: narrowing the ratio range, repeating the verification and selection operations, until the optimal amount of cement and water for the corresponding reservoir is selected.

[0026] Alternatively, the solid materials and water required for each reservoir are weighed according to different formula amounts for each reservoir, poured into a beaker container in sequence, mixed and stirred evenly, to obtain an artificial shale core material mixture.

[0027] Alternatively, the solid materials and water required for each reservoir are weighed separately according to the different formula amounts of each reservoir, the solid materials should be stirred evenly first, then the water is poured in, and then stirred and mixed.

[0028] Optionally, the pressure is 1-10 MPa, and continuous pressurization is not required.

[0029] Another aspect of the present invention provides an artificial large physical model shale core, which is prepared by the above-mentioned preparation method.

[0030] Compared with the prior art, the beneficial effects of the present invention include at least one of the following:

[0031] 1) The artificial large-scale shale core prepared by the present invention can understand the expansion law of shale gas reservoir cracks within different small layers and between layers.

[0032] 2) The artificial large-scale model shale core prepared by the present invention meets the physical and mechanical properties of the shale gas reservoir in the target area and can meet the requirements of large-scale model fracturing experiments for multi-well three-dimensional development.

[0033] 3) The present invention can provide support for three-dimensional development fracturing and multi-well fracturing experimental simulation. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] The above and other objects and / or features of the present invention will become more apparent through the following description in conjunction with the accompanying drawings, in which:

[0035] Figure 1AA longitudinal cross-sectional view of a mold for preparing an artificial small rock core with a size of 25×50 mm in exemplary embodiment 1 of the present invention is shown.

[0036] Figure 1B A side view of a mold for preparing an artificial small rock core of 25×50 mm in exemplary embodiment 1 of the present invention is shown.

[0037] Figure 1C A top view of a mold for preparing an artificial small rock core with a size of 25×50 mm in exemplary embodiment 1 of the present invention is shown.

[0038] Figure 1D A front view of a fixture for preparing a small artificial rock core having a size of 25×50 mm in exemplary embodiment 1 of the present invention is shown.

[0039] Figure 1E A side view of a fixture for preparing a small artificial rock core having a size of 25×50 mm in exemplary embodiment 1 of the present invention is shown.

[0040] Figure 1F A top view of a fixture for preparing a small artificial rock core having a size of 25×50 mm in exemplary embodiment 1 of the present invention is shown.

[0041] Figure 2A A front view of a real 25×50 mm artificial shale core prepared in exemplary embodiment 1 of the present invention is shown.

[0042] Figure 2B A side view of a physical object of preparing a 25×50 mm artificial shale core in exemplary embodiment 1 of the present invention is shown.

[0043] Figure 2C A top view of a real 25×50 mm artificial shale core prepared in exemplary embodiment 1 of the present invention is shown.

[0044] Figure 3A A front view of a large artificial object model rock core preparation mold with a size of 300 mm×300 mm×300 mm in exemplary embodiment 1 of the present invention is shown.

[0045] Figure 3B A side view of a large artificial object model rock core preparation mold with a size of 300 mm×300 mm×300 mm in exemplary embodiment 1 of the present invention is shown.

[0046] Figure 3C A top view of a large artificial object model rock core preparation mold with a size of 300 mm×300 mm×300 mm in exemplary embodiment 1 of the present invention is shown.

[0047] Figure 4A A front view of the actual multi-layer artificial large-scale shale core prepared and formed in exemplary embodiment 2 of the present invention is shown.

[0048] Figure 4B A side view of the actual multi-layered artificial large-scale shale core prepared and formed in exemplary embodiment 2 of the present invention is shown.

[0049] Figure 4C A top view of the actual multi-layer artificial large-scale shale core prepared and formed in exemplary embodiment 2 of the present invention is shown.

[0050] Description of main reference numerals:

[0051] 1-mold top cover; 2-mold base; 3-mold top cover handle; 4-mold outer wall; 5-screw hole; 6-front and rear plates; 7-left and right plates; 8-bottom plate; 9-screw hole; 10-fracturing simulation pipe string. DETAILED DESCRIPTION

[0052] Hereinafter, the artificial large-scale shale core and the preparation method thereof of the present invention will be described in detail in conjunction with exemplary embodiments.

[0053] Exemplary Embodiment 1

[0054] This exemplary embodiment provides a method for preparing an artificial large-scale shale core, comprising the following steps:

[0055] S10: Determine the core constituent materials based on the reservoir mineral composition data of the target area and calculate the proportion of various materials constituting the sand base of each reservoir.

[0056] In this embodiment, the materials constituting the shale core in the basic formula are selected according to the mineral composition data of the reservoir in the target area, including the cementing material and the material constituting the sand base. The cementing material for preparing the shale core can be cement, and the materials constituting the sand base can be quartz sand powder, heavy calcium powder and illite powder. Among them, the cement can be ordinary silicate cement, and the cement particle size can be 600-800 mesh; the particle size of the quartz sand powder can be 100-200 mesh, the heavy calcium powder can be 600-800 mesh, and the illite powder can be 600-800 mesh.

[0057] The mineral composition data of the reservoir contain the contents of calcite, chlorite, dolomite, feldspar, illite, quartz and clay. Heavy calcium powder is used to simulate the mineral components of calcite and dolomite in the reservoir, quartz sand powder is used to simulate the mineral components of quartz, and illite powder is used to simulate the mineral components of clay. The percentage of the three materials is normalized to obtain the proportion of various materials constituting the sand base of each reservoir, calculated by mass, for example:

[0058] Reservoir 1: 30-40 parts of heavy calcium powder, 40-50 parts of quartz sand powder, 20-30 parts of illite powder;

[0059] Reservoir 2: 10-20 parts of heavy calcium powder, 40-50 parts of quartz sand powder, 30-40 parts of illite powder;

[0060] Reservoir 3: 10-20 parts of heavy calcium powder, 50-60 parts of quartz sand powder, and 30-40 parts of illite powder.

[0061] S20: According to the calculated proportions of various materials in the sand matrix composition, by adjusting the amounts of cement and water added, an artificial shale core preparation formula that meets the requirements of each reservoir property in the target area is selected.

[0062] In this embodiment, after calculating the proportion of each material of the sand base, the cement addition amount and the water addition amount are continuously adjusted according to the uniaxial compressive strength requirements and porosity requirements of different reservoirs, and the artificial shale core preparation formula that meets the corresponding reservoir property requirements is selected according to the different mechanical properties of each shale gas reservoir in the target area; further, the best formula closest to the property requirements of the target area can be selected. The prepared artificial shale core must meet the uniaxial compressive strength and porosity requirements of the reservoir, and have different mechanical properties for different reservoirs.

[0063] In this embodiment, adjusting the amount of cement and water added includes the following steps:

[0064] S21: setting an initial dosage range for cement dosage and water dosage of each reservoir.

[0065] First, an initial range of cement and water additions for reservoirs 1, 2, and 3 should be set. For example, a formulation experiment is designed in which the initial cement addition for reservoir 1 is 40 to 80 parts and the initial water addition is 20 to 30 parts.

[0066] S22: Prepare a number of small shale cores of a certain size using each recipe, and test the uniaxial compressive strength and porosity of the small shale cores to verify whether the shale cores prepared by each recipe meet the property requirements of the reservoir in the target area.

[0067] In order to verify whether the artificial shale cores prepared by each formula meet the property requirements of the reservoir in the target area, 1 to 5 small shale cores of 25×50 mm can be prepared from each formula and their uniaxial compressive strength and porosity can be tested.

[0068] like Figure 1A-1F The figure shows the schematic diagram of preparing a 25×50 mm artificial small shale core mold. Figure 1A It is a longitudinal cross-sectional view of a small shale core mold. A space for preparing the core is formed between the mold top cover 1 and the mold base 2. The diameter of the mold top cover 1 is 25 mm. Figure 1B is the side view of the mold. Figure 1CIt is a top view of the mold, and it can be seen that the mold has a mold top cover handle 3, whose size can be 10 mm, and the thickness of the mold outer wall 4 can be 5 mm; Figure 1D This is a front view of the fixing device of the small shale core mold, the diameter of the screw hole 5 on it can be 7mm, Figure 1E This is a side view of the fixing device of the small shale core mold. Figure 1F A top view of the fixture for the small shale core mold.

[0069] The schematic diagram of the prepared small shale core is shown in Figure 2A-2C As shown, Figure 2A This is the front view of the small shale core. Figure 2B This is the side view of the small shale core. Figure 2C This is a top view of the small shale core.

[0070] S23: Select the cement addition and water addition ratio range that is closest to the reservoir property requirements of the target area based on the uniaxial compressive strength and porosity test results.

[0071] In this embodiment, the ratio range can be further narrowed, and the above verification and selection steps are repeated until the optimal cement addition amount and water addition amount corresponding to the reservoir are selected.

[0072] By repeatedly preparing cores and conducting testing experiments, the optimal preparation formula for artificial shale cores that meets the requirements of each reservoir property in the target area is finally selected.

[0073] The preparation formula of artificial shale core is calculated by weight. For example, the formula selected for different reservoirs can be:

[0074] Reservoir 1: 30-40 parts of heavy calcium powder, 40-50 parts of quartz sand powder, 20-30 parts of illite powder, 60-70 parts of cement, and 20-25 parts of water;

[0075] Reservoir 2: 10-20 parts of heavy calcium powder, 40-50 parts of quartz sand powder, 30-40 parts of illite powder, 60-70 parts of cement, and 20-25 parts of water;

[0076] Reservoir 3: 10-20 parts of heavy calcium powder, 50-60 parts of quartz sand powder, 30-40 parts of illite powder, 70-80 parts of cement, and 20-25 parts of water.

[0077] S30: solid materials and water required for each reservoir layer are weighed according to different formula amounts of each reservoir layer, and the solid materials and water of each layer are mixed and stirred evenly to obtain a mixture of artificial shale core materials for each layer.

[0078] In this embodiment, the weighed solid material and water are poured into a beaker container in sequence according to the formula amount and mixed and stirred evenly. The solid material should be stirred evenly first and then the water is poured in, and then stirred and mixed again to obtain an artificial shale core material mixture.

[0079] S40: Filling the artificial shale core material mixture into the mold in sequence according to the multi-layer distribution order of the shale gas reservoir, and applying a certain pressure.

[0080] In this embodiment, the obtained artificial shale core material mixture is sequentially filled into a large physical model mold according to the multi-layer distribution order of the shale gas reservoir, and a pressurizing device is used to apply an axial pressure of 1 to 10 MPa. Continuous pressurization is not required. For example, different pressures such as 1, 3, 5, and 7 MPa are selected to be applied to the artificial shale core material mixture in the mold. The compaction effect of the material mixture is enhanced by pressurization to improve the strength of the artificial shale core. The selection of applying different pressures can meet the different strength requirements of each reservoir of the artificial shale core.

[0081] In this embodiment, the mold size can be 300mm×300mm×300mm, and the artificial shale core produced by this mold size can meet the requirements of large-scale fracturing experiments for multi-well three-dimensional development. In addition, selecting this standard size for experimental research can not only more accurately and clearly show the morphological characteristics of reservoir fractures after fracturing, but also further weaken the impact of boundary effects on experimental results. Figure 3A-3C Schematic diagram of preparing a mold for a 300mm×300mm×300mm artificial large model rock core, where Figure 3A The front view of the mold shows that the lengths of the front and rear plates 6 can be 300 mm and 362 mm. Figure 3B The side view of the mold, the length of the left and right plates 7 can be 300mm, Figure 3C This is a top view of the mold. The length of the bottom plate 8 can be 320 mm and 362 mm, and the diameter of the screw hole 9 can be 12 mm.

[0082] S50: curing the artificial shale core filled into the mold in a water bath, drying and demoulding after the curing is completed, and obtaining an artificial large-scale shale core conforming to the reservoir properties of the target area.

[0083] The artificial shale core filled in the mold is water-bath cured for 1 to 7 days at room temperature and pressure. After the water-bath curing, it is naturally dried for 1 to 7 days at room temperature and pressure before demolding. After drying and demolding, it is trimmed and polished to finally obtain a multi-layer artificial large-scale shale core that meets the reservoir properties of the target area.

[0084] Exemplary Embodiment 2

[0085] This exemplary embodiment provides an artificial large physical model shale core, which is prepared by the method described in exemplary embodiment 1.

[0086] Figure 4A-4C This is a schematic diagram of the actual object of the multi-layer artificial large-scale shale core after preparation, where: Figure 4A This is the main view of the multi-layer artificial large-scale shale core after preparation. Figure 4B This is a side view of the actual multi-layer artificial large-scale shale core after preparation. Figure 4C The function of the fracturing simulation pipe string 10 in the figure is to pump the fracturing fluid into the large model shale core sample to simulate the process of the fracturing fluid passing through the wellbore perforation cluster to reach the reservoir in the target area of ​​fracturing during the fracturing process.

[0087] In order to better understand the above exemplary embodiments of the present invention, they are further described below with reference to specific examples.

[0088] Example 1

[0089] Calculated by weight in the formula, the multilayer artificial large-scale model shale core reservoir 3 provided in this embodiment includes 10 to 20 parts of 600-800 mesh heavy calcium powder, 50 to 60 parts of 100-200 mesh quartz sand powder, 30 to 40 parts of 600-800 mesh illite powder, 70 to 80 parts of 600-800 mesh cement, and 20 to 25 parts of water.

[0090] The reservoir 3 portion of the multi-layer artificial shale core was prepared as follows:

[0091] The heavy calcium powder, quartz sand powder, illite powder and cement weighed according to the formula are mixed and stirred evenly to obtain the artificial shale core solid material of reservoir 3. The weighed water is mixed and stirred evenly with the obtained solid material, and the solid material and water are mixed as evenly as possible to form a mixture of artificial shale core materials of reservoir 3 with a uniform texture.

[0092] The obtained artificial shale core material mixture is filled into the large material model core mold. During the filling process, the artificial shale core material mixture is continuously repaired, leveled and compacted to make the material evenly distributed. At this time, the reservoir 3 artificial shale core simulates the bottom reservoir of the entire multi-layer large material model shale core.

[0093] Calculated by weight in the formula, the multilayer artificial large-scale model shale core reservoir 2 provided in this embodiment includes the following components: 10 to 20 parts of 600-800 mesh heavy calcium powder, 40 to 50 parts of 100-200 mesh quartz sand powder, 30 to 40 parts of 600-800 mesh illite powder, 60 to 70 parts of 600-800 mesh cement, and 20 to 25 parts of water.

[0094] The reservoir 2 portion of the multi-layer artificial shale core was prepared as follows:

[0095] The heavy calcium powder, quartz sand powder, illite powder and cement weighed according to the formula are mixed and stirred evenly to obtain the artificial shale core solid material of reservoir 2. The weighed water is mixed and stirred evenly with the obtained solid material, and the solid material and water are mixed as evenly as possible to form a mixture of artificial shale core materials of reservoir 2 with a uniform texture.

[0096] The obtained artificial shale core material mixture is filled into the large material model core mold. During the filling process, the artificial shale core material mixture is continuously repaired, leveled and compacted to make the material evenly distributed. At this time, the reservoir 2 artificial shale core simulates the bottom reservoir of the entire multi-layer large material model shale core.

[0097] Calculated by weight in the formula, the reservoir 1 part of the multi-layer artificial large-scale model shale core provided in this embodiment includes the following components: 30 to 40 parts of 600-800 mesh heavy calcium powder, 40 to 50 parts of 100-200 mesh quartz sand powder, 20 to 30 parts of 600-800 mesh illite powder, 60 to 70 parts of 600-800 mesh cement, and 20 to 25 parts of water.

[0098] The reservoir 1 portion of the multi-layer artificial shale core was prepared as follows:

[0099] The heavy calcium powder, quartz sand powder, illite powder and cement weighed according to the formula are mixed and stirred evenly to obtain the artificial shale core solid material of reservoir 1. The weighed water is mixed and stirred evenly with the obtained solid material, and the solid material and water are mixed as evenly as possible to form a mixture of artificial shale core materials of reservoir 1 with a uniform texture.

[0100] The obtained artificial shale core material mixture is filled into the large material model core mold. During the filling process, the artificial shale core material mixture is continuously repaired, leveled and compacted to make the material evenly distributed. At this time, the reservoir 1 artificial shale core simulates the bottom reservoir of the entire multi-layer large material model shale core.

[0101] A pressure device is used to apply a pressure of 1 to 10 MPa to the artificial shale core material loaded into the mold. After reaching the specified pressure, the pressure is released and the mold with the core is removed.

[0102] The removed core mold is immersed in a water bath and cured for 1 to 7 days at room temperature and pressure to solidify the core in the mold. After the curing, the shale core needs to be dried for 1 to 7 days. After drying and forming, the mold is removed and the end face of the formed shale core is trimmed and polished with a grinding tool to finally obtain a multi-layer artificial large-scale shale core that meets the reservoir properties of a certain target area.

[0103] Example 2

[0104] According to the mechanical properties of each shale gas reservoir layer in a target area, an artificial shale core preparation formula that meets the property requirements of each layer in the target area is selected. The artificial shale core prepared by this formula must meet the requirements of uniaxial compressive strength and porosity of each reservoir.

[0105] The mixture of artificial shale core materials of reservoirs 1, 2, and 3 prepared in Example 1 was respectively filled into a mold for preparing a core with a diameter of 25 mm to prepare a φ25×50 mm small artificial shale core. One to five φ25×50 mm small shale cores were prepared for each reservoir recipe and their uniaxial compressive strength and porosity were tested. The results of the uniaxial compressive strength and porosity tests were used to determine whether the artificial shale core met the requirements of the mechanical properties of the natural shale gas reservoir in a certain target area. The test results of each uniaxial compressive strength and porosity are shown in Table 1 below.

[0106] Table 1 Experimental test results of artificial shale cores of φ25×50mm reservoirs 1, 2, and 3

[0107] Reservoir name Uniaxial compressive strength MPa Porosity, % Reservoir 1 100～120 6～7 Reservoir 2 100～120 6～7 Reservoir 3 140～160 6～7

[0108] As shown in the test results in Table 1, the uniaxial compressive strength and porosity test results of the three reservoirs are very close to the requirements of the target area reservoir. The specific target area reservoir performance is shown in Table 2. The multi-layer artificial large-scale model shale core prepared using the artificial shale core material can simulate the properties of the shale gas reservoir in the target area.

[0109] Table 2 Performance test results of reservoirs 1, 2, and 3 in the target area

[0110]

[0111]

[0112] Although the present invention has been described above in conjunction with the exemplary embodiments and the accompanying drawings, it should be apparent to those skilled in the art that various modifications may be made to the above-described embodiments without departing from the spirit and scope of the claims.

Claims

1. A method for preparing an artificial large-scale shale core, characterized in that: The preparation method comprises the following steps: Determine the core composition materials based on the target area reservoir mineral composition data and calculate the proportion of various materials that make up the sand base of each reservoir; According to the calculated proportion of each material in the sand matrix, by adjusting the amount of cement and water, the artificial shale core preparation formula that meets the requirements of each reservoir property in the target area is selected; Weigh the solid materials and water required for each reservoir layer according to the different formula amounts of each reservoir layer, mix and stir the solid materials and water of each layer evenly, and prepare the mixture of artificial shale core materials of each layer; The mixture of artificial shale core materials is sequentially filled into the mold according to the multi-layer distribution order of the shale gas reservoir, and a certain pressure is applied; The artificial shale core filled into the mold is cured in a water bath, and after the curing is completed, it is dried and demoulded to obtain an artificial large-scale shale core that meets the reservoir properties of the target area.

2. The preparation method according to claim 1, characterized in that: The core constituent material includes shale core cementing material.

3. The preparation method according to claim 2, characterized in that: The shale core cementing material is cement.

4. The preparation method according to claim 3, characterized in that: The cement is ordinary Portland cement, and the cement particle size is 600-800 meshes.

5. The preparation method according to claim 1, characterized in that: The materials constituting the sand base include quartz sand powder, heavy calcium powder and illite powder, wherein the particle size of the quartz sand powder is 100-200 meshes, the particle size of the heavy calcium powder is 600-800 meshes, and the particle size of the illite powder is 600-800 meshes.

6. The preparation method according to claim 1, characterized in that: The basis for selecting the artificial shale core preparation formula that meets the property requirements of each reservoir in the target area includes: the uniaxial compressive strength requirements and porosity requirements of different reservoirs.

7. The preparation method according to claim 1, characterized in that: The step of adjusting the amount of cement and water comprises the following steps: Set an initial dosage range for cement and water addition for each reservoir; Several small shale cores of a certain size are prepared according to each formula, and the uniaxial compressive strength and porosity of the small shale cores are tested to verify whether the shale cores prepared by each formula meet the property requirements of the reservoir in the target area; According to the uniaxial compressive strength and porosity test results, the cement addition and water addition ratio range that is closest to the reservoir property requirements of the target area is selected.

8. The preparation method according to claim 7, characterized in that: The method of adjusting the amount of cement and water also includes the steps of: narrowing the ratio range, repeating the verification and selection operations, until the optimal amount of cement and water for the corresponding reservoir is selected.

9. The preparation method according to claim 1, characterized in that: The solid materials and water required by each reservoir are weighed according to different formula amounts for each reservoir, poured into a beaker container in sequence, mixed and stirred evenly, and an artificial shale core material mixture is obtained.

10. The preparation method according to claim 9, characterized in that: The solid materials and water required for each reservoir are weighed separately according to the different formula amounts of each reservoir. The solid materials should be stirred evenly before pouring in the water, and then stirring and mixing.

11. The preparation method according to claim 1, characterized in that: The pressure is 1-10 MPa.

12. An artificial large-scale shale core, characterized in that: The artificial large-scale shale model core is prepared by the preparation method described in any one of claims 1-11.

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