Shale physical model, preparation method and device of saturated oil shale core sample

Abstract

The present application provides a kind of shale physical model, saturated oil shale core sample preparation method and device, shale physical model includes sand, cementing agent and solid phase cementing material with water absorption, the shale physical model is that sand and solid phase cementing material are mixed uniformly and are pressed after being sprayed with water-diluted cementing agent;Saturated oil shale core sample preparation method includes: sand and solid phase cementing material with water absorption are mixed uniformly;Cementing agent is diluted with water;Solid phase raw material is sprayed with cementing agent solution and is mixed uniformly;To be pressed raw material is soaked in oil liquid and is pressed.The shale physical model of the present application is assisted with solid phase cementing material with water absorption, under the double action of cementing agent and solid phase cementing material, not only guarantee the cementing quality, and form the pore structure with shale characteristics, by pressing saturated oil shale core sample in oil phase environment, completely simulate the distribution of oil phase in pore in actual shale oil reservoir.

Description

Technical Field

[0001] This invention relates to the field of oilfield development technology, and in particular to a shale physical model, a method and apparatus for preparing saturated oil shale core samples. Background Technology

[0002] As the scale of shale oil reservoir development gradually expands, research on the seepage mechanism of shale oil is becoming increasingly in-depth. Displacement experiments are one of the most fundamental research areas, and naturally, researchers are using existing reservoir development technologies for shale oil development. Core displacement technology has evolved from high-permeability (permeability greater than 100 mD) reservoirs to medium- and low-permeability reservoirs, and is gradually being extended to ultra-low-permeability reservoirs. As reservoir permeability decreases, the technical difficulty of displacement experiments gradually increases. When permeability drops below 0.1 mD (such as the permeability of shale), existing displacement experiment techniques face more and more challenges.

[0003] Key challenges include: difficulty in obtaining core samples with reservoir characteristics, and difficulty in saturating cores with water / oil. When permeability is high, the rock's pore structure has little impact on seepage conditions. However, when permeability is low to ultra-low permeability (permeability greater than 1 mD), even when sampling from reservoir rocks, pressure drop and stress changes alter the pore structure. This change has a significant impact on seepage when the pore diameter is less than 1 micrometer. Due to the narrow pores, the fluid injection pressure is significantly increased. Although high pressure can be provided, the effect of saturating cores with water / oil is still poor, with over 30% of the pores being micropores that are difficult for fluid to penetrate. These problems significantly deviate from the initial conditions of shale oil reservoirs; the basic experimental conditions are severely deviated, and the application of experimental results obtained on this basis will also be problematic. Summary of the Invention

[0004] The purpose of this invention is to provide a shale physical model, a method and apparatus for preparing saturated oil shale core samples, in order to solve the problems of difficulty in obtaining core samples with oil reservoir characteristics and difficulty in saturating cores with oil.

[0005] To achieve the above objectives, the present invention provides a shale physical model comprising sand grains, a cementing agent, and a water-absorbing solid binder, wherein the particle size of the solid binder is smaller than that of the sand grains.

[0006] The shale physical model described above, wherein the solid phase binder comprises, by weight percentage, the following components: aqueous calcium carbonate: 80%–90%; clay: 10%–15%; gypsum: 5%–10%.

[0007] In the shale physical model described above, the sand grains and the solid phase cementing material constitute the solid phase raw material of the shale physical model, wherein the content of the sand grains accounts for 85% to 90% of the total weight of the solid phase raw material, and the content of the solid phase cementing material accounts for 10% to 15% of the total weight of the solid phase raw material.

[0008] In the shale physical model described above, the particle size of the sand grains is less than 100 μm, and the particle size of the solid phase binder is 15 μm to 25 μm.

[0009] The shale physical model described above, wherein the binder is an aqueous epoxy resin.

[0010] The present invention also provides a method for preparing a saturated oil shale core sample, comprising: mixing sand grains and a water-absorbing solid binder uniformly to obtain a solid raw material, wherein the particle size of the solid binder is smaller than that of the sand grains; diluting a binder with water to obtain a binder solution; spraying the binder solution onto the solid raw material and mixing it uniformly to obtain a raw material to be pressed; and immersing the raw material to be pressed in oil for pressing to obtain a saturated oil shale core sample.

[0011] The method for preparing saturated oil shale core samples as described above, wherein the solid phase cement comprises, by weight percentage: aqueous calcium carbonate: 80%–90%; clay: 10%–15%; gypsum: 5%–10%.

[0012] In the method for preparing saturated oil shale core samples as described above, the content of sand grains accounts for 85% to 90% of the total weight of the solid raw materials, and the content of solid cementitious material accounts for 10% to 15% of the total weight of the solid raw materials.

[0013] In the method for preparing saturated oil shale core samples as described above, the particle size of the sand grains is less than 100 μm, and the particle size of the solid phase binder is 15 μm to 25 μm.

[0014] The method for preparing saturated oil shale core samples as described above, wherein the binder is an aqueous epoxy resin.

[0015] This invention also provides a preparation apparatus for saturated oil shale core samples, which is a preparation apparatus used in the preparation method of saturated oil shale core samples for preparing shale physical models. The preparation apparatus includes: a pressing cylinder, including a cylinder body, an upper end cap and a lower end cap respectively disposed at the upper and lower ends of the cylinder body, and an upper piston and a lower piston disposed within the cylinder body. The upper piston and the lower piston are respectively slidably and sealingly connected to the cylinder body. A pressing cavity is formed between the upper piston and the lower piston. A cavity for accommodating the sand particles, the solid phase binder, the binder solution, and... is formed between the upper piston and the upper end cap. The system includes an upper pressurizing chamber for the oil, a lower pressurizing chamber formed between the lower piston and the lower end cap; an upper pressurizing pipe passing through the upper end cap and communicating with the upper pressurizing chamber; a lower pressurizing pipe passing through the lower end cap and communicating with the lower pressurizing chamber; an upper connecting pipe passing through the upper end cap and the upper piston and communicating with the compression chamber; a lower connecting pipe passing through the lower end cap and the lower piston and communicating with the compression chamber; a pressurizing container for containing pressurizing fluid, connected to the upper pressurizing pipe and the lower pressurizing pipe; and a pressurizing pump connected to the pressurizing container and capable of pumping the pressurizing fluid in the pressurizing container into the upper pressurizing chamber and the lower pressurizing chamber.

[0016] The apparatus for preparing saturated oil shale core samples as described above includes an inner wall of a cylinder comprising an upper cylindrical section, an upper conical section, a lower conical section, and a lower cylindrical section connected sequentially from top to bottom. An upper piston is disposed in the upper cylindrical section, and a lower piston is disposed in the lower cylindrical section. The inner diameter of the upper conical section gradually decreases from top to bottom, and the inner diameter of the lower conical section gradually decreases from bottom to top.

[0017] The apparatus for preparing saturated oil shale core samples as described above includes a first switching valve on the upper pressurization pipe, a second switching valve on the lower pressurization pipe, a third switching valve on the upper connecting pipe, and a fourth switching valve on the lower connecting pipe.

[0018] The apparatus for preparing saturated oil shale core samples as described above further includes a displacement container for containing displacement fluid. The displacement container is connected to the upper connecting pipe or the lower connecting pipe and is connected to the pressure pump, which pumps the displacement fluid in the displacement container into the pressure chamber.

[0019] The apparatus for preparing saturated oil shale core samples as described above further includes a back pressure controller connected to the upper connecting pipe and the lower connecting pipe.

[0020] The apparatus for preparing saturated oil shale core samples as described above further includes a fluid metering device connected to the upper connecting pipe and the lower connecting pipe.

[0021] The apparatus for preparing saturated oil shale core samples as described above further includes: a first multi-way valve, through which the upper pressurization pipe and the lower pressurization pipe are connected to the pressurization container; a second multi-way valve, through which the upper connecting pipe is connected to the fluid metering device, the displacement container, and the back pressure controller; and a third multi-way valve, through which the lower connecting pipe is connected to the fluid metering device, the displacement container, and the back pressure controller.

[0022] The apparatus for preparing saturated oil shale core samples as described above, wherein the first multi-way valve is connected to the pressurization vessel and the displacement vessel via an inlet pipeline, and the second multi-way valve and the third multi-way valve are respectively connected to the displacement vessel via the first multi-way valve and the inlet pipeline.

[0023] In the apparatus for preparing saturated oil shale core samples as described above, the first multi-way valve is connected to a main gas pipe, the main gas pipe is connected to the second multi-way valve through a first gas branch pipe, the main gas pipe is connected to the third multi-way valve through a second gas branch pipe, the main gas pipe is equipped with a fifth switching valve, the first gas branch pipe is equipped with a sixth switching valve, and the second gas branch pipe is equipped with a seventh switching valve.

[0024] The apparatus for preparing saturated oil shale core samples as described above includes a second multi-way valve connected to a first liquid guide pipe, a third multi-way valve connected to a second liquid guide pipe, an eighth switching valve on the first liquid guide pipe, a ninth switching valve on the second liquid guide pipe, the second multi-way valve connected to the fluid metering device and the back pressure controller via the first liquid guide pipe, and the third multi-way valve connected to the fluid metering device and the back pressure controller via the second liquid guide pipe.

[0025] The apparatus for preparing saturated oil shale core samples as described above, wherein the pressurizing pump is a high-pressure plunger pump.

[0026] The apparatus for preparing saturated oil shale core samples as described above further includes a rotating support for supporting the pressing cylinder, wherein the cylinder is rotatably connected to the rotating support.

[0027] The features and advantages of the shale physical model, the method and apparatus for preparing saturated oil shale core samples of the present invention are as follows:

[0028] 1. The shale physical model of the present invention utilizes a water-absorbing solid-phase cementitious material. During pressing, the water-absorbing solid-phase cementitious material can absorb water from the cementing agent droplets in the form of molecularly bound water. The higher the pressure, the better the absorption effect. The solid-phase cementitious material after absorbing a certain amount of water also has a cementing effect, that is, the local surface of the solid-phase cementitious material that is not covered by the cementing agent also has cementing ability. Since some cementing agent is adsorbed on the particle surface of the solid-phase cementitious material, the contact area between the cementing agent and the surface of the sandstone particles is significantly reduced. Under the dual action of the cementing agent and the solid-phase cementitious material, not only is the cementing quality guaranteed, but also the effective pore space is guaranteed, forming a pore structure with shale characteristics, which solves the problem of difficulty in obtaining shale core samples in the prior art.

[0029] 2. Based on the formation mechanism of shale oil, this invention employs a pressing method in an oil phase environment. After the rock is shaped and solidified, the oil phase is naturally sealed in the pores, completing the oil saturation step. Mechanistically, this invention completely simulates the distribution of the oil phase in the pores of actual shale oil reservoirs, ensuring that pores at all levels are filled with the oil phase and achieving a maximum oil saturation of 100%. Compared with existing methods that inject fluid into shale core samples, this invention avoids the problem of fluid difficulty entering micropores, resulting in better oil saturation and solving the problem of difficulty in saturating cores with oil in existing technologies.

[0030] 3. The preparation apparatus of the present invention has the functions of preparing core samples and conducting oil displacement experiments, realizing continuous operation of core preparation, saturation oil and displacement / development steps. Attached Figure Description

[0031] The following figures are intended only to illustrate and explain the present invention and do not limit the scope of the invention. Wherein:

[0032] Figure 1 This is a schematic diagram illustrating the cementation effect of existing technologies in preparing physical models of shale.

[0033] Figure 2 This is a schematic diagram of the cementation effect of the shale physical model prepared by the present invention;

[0034] Figure 3 This is a schematic diagram of a preparation apparatus according to an embodiment of the present invention;

[0035] Figure 4 This is a cross-sectional view of the cylindrical body in this invention;

[0036] Figure 5 This is a schematic diagram of the fit between the cover and the plug in this invention;

[0037] Figure 6 This is a schematic diagram of the cover body in this invention;

[0038] Figure 7 This is a schematic diagram of the plug in this invention.

[0039] Explanation of key component designations:

[0040] 100. Sand; 200. Solid binder; 300. Cementing agent; 400. Oil;

[0041] 1. Cylinder body; 101. Upper cylindrical section; 102. Upper conical section; 103. Lower conical section; 104. Lower cylindrical section;

[0042] 2. Upper end cap; 3. Lower end cap; 4. Upper piston; 401. Piston through hole;

[0043] 5. Lower piston; 501. Piston through hole; 6. Pressing chamber; 7. Upper pressurizing chamber; 8. Lower pressurizing chamber;

[0044] 9. Upper pressurization pipe; 10. Lower pressurization pipe; 11. Upper connecting pipe; 12. Lower connecting pipe; 13. Pressurization container;

[0045] 14. Pressure pump; 15. Cover; 151. Large hole; 152. Small hole; 153. Annular insertion hole;

[0046] 16. Plug; 161. Large diameter section; 162. Small diameter section; 163. Sealing through hole; 164. Injection through hole;

[0047] 17. First switching valve; 18. Second switching valve; 19. Third switching valve; 20. Fourth switching valve;

[0048] 21. Displacement container; 22. Back pressure controller; 23. Fluid metering device; 24. First multi-way valve;

[0049] 25. Second multi-way valve; 26. Third multi-way valve; 27. Inlet pipeline; 28. Main vent pipe;

[0050] 29. First air guide branch pipe; 30. Second air guide branch pipe; 31. Fifth switch valve; 32. Sixth switch valve;

[0051] 33. Seventh switch valve; 34. First liquid guide tube; 35. Second liquid guide tube; 36. Eighth switch valve;

[0052] 37. Ninth switch valve; 38. Rotary bracket; 39. O-ring seal; 40. Tee. Detailed Implementation

[0053] To provide a clearer understanding of the technical features, objectives, and effects of the present invention, specific embodiments are now described with reference to the accompanying drawings. The use of adjective or adverbial modifiers such as "upper" and "lower," "top" and "bottom," "inner" and "outer" is merely for the convenience of relative reference between multiple sets of terms and does not describe any specific directional limitation on the modified terms. Furthermore, the terms "first," "second," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Therefore, features defined with "first," "second," etc., may explicitly or implicitly include one or more of that feature. In the description of the present invention, unless otherwise stated, the term "connection" should be interpreted broadly. For example, it can refer to a fixed connection, a detachable connection, a direct connection, or an indirect connection through an intermediate medium. Those skilled in the art can understand the specific meaning of the above terms in this patent according to the specific circumstances.

[0054] Unless otherwise defined, all directions such as up and down referred to herein are those indicated by the present invention. Figure 4 The directions, such as up and down, are used as a reference, and will be explained here as well.

[0055] Implementation Method 1

[0056] The existing method for preparing shale physical models involves directly spraying cement 300 onto the surface of sand grains 100. However, this method has the following problems: Figure 1 As shown, even if the droplets are small, they are distributed on the surface of the sand particles 100 in the form of local adsorption. During the pressing process, the bonding between the sand particles 100 is uneven; the binder 300 is too concentrated between the pores (e.g., Figure 1 Position A in the middle occupies a large amount of pore space; the binder 300 is locally adsorbed (e.g., Figure 1 Position B in the middle does not act as a binder; the surface of small particles is easily completely coated by binder 300 (e.g., Figure 1 (C) in the middle position, it loses the characteristics of the rock surface.

[0057] like Figure 2 As shown, the present invention provides a shale physical model, the components of which include sand grains 100, a water-absorbing solid binder 200 (or solidified microparticles) and a binder 300. The particle size of the solid binder 200 is smaller than that of the sand grains 100. The shale physical model is formed by spraying a water-diluted binder 300 onto a uniformly mixed sand grains 100 and solid binder 200 and then pressing it, thus ensuring effective pore space.

[0058] The shale physical model of this invention utilizes a water-absorbing solid binder 200. When preparing the shale physical model, sand particles 100 are first uniformly mixed with the solid binder 200, and then a water-diluted binder 300 (hereinafter referred to as binder solution) is sprayed on. Even if there is uneven adsorption of binder droplets on the surface of the sandstone particles at this time, during the subsequent pressing process, the water-absorbing solid binder 200 will absorb water from the droplets in the form of molecularly bound water. The higher the pressure, the better the absorption effect. Figure 2 As shown, the solid binder 200, after absorbing a certain amount of moisture, also has a cementing effect; that is, the local surfaces of the solid binder 200 not covered by the binder 300 also have cementing ability, such as... Figure 2 As shown in position D, under ideal conditions, the cementitious agent 300 is gradually and uniformly adsorbed onto the particle surface of the solid cementitious material 200. Since some of the cementitious agent 300 is adsorbed onto the particle surface of the solid cementitious material 200, the contact area between the cementitious agent 300 and the sandstone particle surface is significantly reduced, thereby reducing the aforementioned problems in the preparation of shale physical models using existing technologies. Under the dual action of the cementitious agent 300 and the solid cementitious material 200, not only is the cementation quality guaranteed, but also the effective pore space is ensured, forming a pore structure with shale characteristics.

[0059] The shale physical model of this invention has shale reservoir characteristics and can be used for displacement experiments to study the seepage mechanism of shale oil. It does not require sampling from the reservoir rock, thus solving the problem of difficulty in obtaining shale core samples and laying the foundation for experimental research and technology development related to shale oil reservoirs.

[0060] For example, the shale physical model is a saturated oil shale physical model, and the components of the saturated oil shale physical model also include crude oil located in the pores.

[0061] Furthermore, by weight percentage, the solid phase binder 200 comprises the following components: aqueous calcium carbonate: 80%–90%; clay: 10%–15%; gypsum: 5%–10%; and other substances, such as carbonates, may be added at a percentage of 2%–5% depending on the specific geological conditions of the reservoir. The solid phase binder is composed of the above components mixed in specific proportions, the exact proportions of which can be determined based on the characteristics of the shale being prepared. Aqueous calcium carbonate has good water absorption properties and can quickly absorb water from the binder solution. Clay is an inorganic binder that acts as an adhesive. Gypsum primarily provides temporary water absorption, and some water can be released during the pressing process. Its main purpose is to ensure that the epoxy resin is evenly distributed on the surface of the solid phase binder particles.

[0062] Furthermore, sand particles 100 and solid binder 200 constitute the solid phase raw material of the shale physical model. The content of sand particles 100 accounts for 85% to 90% of the total weight of the solid phase raw material, for example, 90%; the content of solid binder 200 accounts for 10% to 15% of the total weight of the solid phase raw material, for example, 10%. The sand particles are selected according to the actual shale sand particle size and proportion, preferably sand particles with good roundness, as this shape of sand particle highly simulates the characteristics of actual shale sand particles. For example, the sand particles 100 selected in this invention have a particle size of less than 100 μm (i.e., 150 mesh or larger).

[0063] Furthermore, the particle size of the solid phase binder 200 is 15μm to 25μm, that is, the particle size of the aqueous calcium carbonate is 15μm to 25μm, the particle size of the clay is 15μm to 25μm, and the particle size of the gypsum is 15μm to 25μm.

[0064] Furthermore, the binder 300 is a water-based epoxy resin. Solid particles such as sand particles 100 and solid binder 200 achieve bonding and consolidation between particles under the action of the water-based epoxy resin. Before spraying, the binder 300 is diluted with water to form a low-concentration, low-viscosity fluid, for example, with a viscosity less than 2 cp. Using ultrasonic spraying, it is evenly sprayed onto the solid particles to form the raw material to be pressed. After standing in air for 30 minutes to 1 hour, the raw material to be pressed is added to a shale pressing device for pressing and molding.

[0065] Implementation Method 2

[0066] Please see Figure 2 The present invention also provides a method for preparing saturated oil shale core samples, the method comprising:

[0067] Sand particles 100 and water-absorbing solid binder 200 are mixed evenly to obtain solid raw material, wherein the particle size of solid binder 200 is smaller than that of sand particles 100.

[0068] Dilute the binder with water to obtain a binder solution;

[0069] A solid raw material is sprayed with a binder solution and mixed evenly to obtain the raw material to be pressed. For example, the spraying method is ultrasonic spraying.

[0070] The raw material to be pressed is immersed in oil and then pressed to obtain saturated oil shale core samples.

[0071] Existing research indicates that shale oil formation involves the direct transformation of organic matter within rock pores, significantly differing from the typical sandstone oil reservoir formation process of transformation followed by migration. Based on this understanding, this invention employs a pressing method within an oil-phase environment. After the rock solidifies, the oil phase is naturally sealed within the pores, completing the oil saturation step. Mechanistically, this method perfectly simulates the distribution of the oil phase within the pores of actual shale oil reservoirs, ensuring that pores at all levels are filled with the oil phase and achieving a maximum oil saturation rate of 100%. Compared to existing methods that inject fluid into shale core samples, this method avoids the problem of fluid difficulty entering micropores, resulting in better oil saturation. It solves the problem of difficulty in core oil saturation in existing technologies, realistically simulating the initial state of shale oil reservoirs and providing a reliable experimental basis for displacement experiments.

[0072] Furthermore, by weight percentage, the solid phase binder 200 comprises the following components: aqueous calcium carbonate: 80%–90%; clay: 10%–15%; gypsum: 5%–10%; and other substances, such as carbonates, may be added at a percentage of 2%–5% depending on the specific geological conditions of the reservoir. The solid phase binder is composed of the above components mixed in specific proportions, the exact proportions of which can be determined based on the characteristics of the shale being prepared. Aqueous calcium carbonate has good water absorption properties and can quickly absorb water from the binder solution. Clay is an inorganic binder that acts as an adhesive. Gypsum primarily provides temporary water absorption, and some water can be released during the pressing process. Its main purpose is to ensure that the epoxy resin is evenly distributed on the surface of the solid phase binder particles.

[0073] Furthermore, the content of sand particles 100 accounts for 85% to 90% of the total weight of the solid raw materials, for example, 90%; the content of solid binder 200 accounts for 10% to 15% of the total weight of the solid raw materials, for example, 10%. The sand particles are selected according to the actual shale sand particle size and proportion, with sand particles having good roundness being preferred, as this shape of sand particle highly simulates the characteristics of actual shale sand particles. For example, the sand particles 100 selected in this invention have a particle size of less than 100 μm (150 mesh or larger).

[0074] Furthermore, the particle size of the solid phase binder 200 is 15μm to 25μm, that is, the particle size of the aqueous calcium carbonate is 15μm to 25μm, the particle size of the clay is 15μm to 25μm, and the particle size of the gypsum is 15μm to 25μm.

[0075] Furthermore, the binder 300 is a water-based epoxy resin. Solid particles such as sand particles 100 and solid binder 200 achieve bonding and consolidation between particles under the action of the water-based epoxy resin. Before spraying, the binder 300 is diluted with water to form a low-concentration, low-viscosity fluid, for example, with a viscosity less than 2 cp. Using ultrasonic spraying, it is evenly sprayed onto the solid particles to form the raw material to be pressed. After standing in air for 30 minutes to 1 hour, the raw material to be pressed is added to a shale pressing device for pressing and molding.

[0076] Implementation Method 3

[0077] like Figure 3 As shown, the present invention also provides an apparatus for preparing saturated oil shale core samples, which is used in the method for preparing saturated oil shale core samples in Embodiment 2, for preparing saturated oil shale core samples. The apparatus includes a pressing cylinder, an upper pressurizing pipe 9, a lower pressurizing pipe 10, an upper connecting pipe 11, a lower connecting pipe 12, a pressurizing container 13 for containing pressurizing liquid, and a pressurizing pump 14.

[0078] The pressing cylinder includes a cylinder body 1, an upper end cap 2 and a lower end cap 3 respectively located at the upper and lower ends of the cylinder body 1, and an upper piston 4 and a lower piston 5 located inside the cylinder body 1. The upper end cap 2 is detachably and sealed to the cylinder body 1, and the lower end cap 3 is detachably and sealed to the cylinder body 1. The upper piston 4 and the lower piston 5 are respectively slidably and sealed to the cylinder body 1. A pressing chamber 6 (or filling space) is formed between the upper piston 4 and the lower piston 5 to accommodate sand particles 100, solid phase binder 200, binder solution and oil. An upper pressurizing chamber 7 is formed between the upper piston 4 and the upper end cap 2, and a lower pressurizing chamber 8 is formed between the lower piston 5 and the lower end cap 3.

[0079] The upper pressurizing pipe 9 passes through the upper end cover 2 and communicates with the upper pressurizing chamber 7. The lower pressurizing pipe 10 passes through the lower end cover 3 and communicates with the lower pressurizing chamber 8. The upper connecting pipe 11 passes through the upper end cover 2 and the upper piston 4 and communicates with the pressing chamber 6. The lower connecting pipe 12 passes through the lower end cover 3 and the lower piston 5 and communicates with the pressing chamber 6. The pressurizing container 13 is connected to the upper pressurizing pipe 9 and the lower pressurizing pipe 10. The pressurizing pump 14 is connected to the pressurizing container 13. For example, the pressurizing pump 14 is a high-pressure plunger pump. The pressurizing pump 14 can pump the pressurizing liquid in the pressurizing container 13 into the upper pressurizing chamber 7 and the lower pressurizing chamber 8. By injecting pressurizing liquid (e.g., water) into the upper pressurizing chamber 7 and the lower pressurizing chamber 8, the pressurizing liquid drives the upper piston 4 and the lower piston 5 to squeeze the raw material to be pressed in the pressing chamber 6 to press and form a saturated oil shale core sample. During the pressing process, as the pressing chamber 6 is compressed, the oil inside it is discharged from the upper connecting pipe 11 and the lower connecting pipe 12.

[0080] The preparation apparatus of this invention is simple and convenient for preparing saturated oil shale core samples.

[0081] Furthermore, such as Figure 4 As shown, the inner wall of the cylinder 1 includes an upper cylindrical section 101, an upper conical section 102, a lower conical section 103, and a lower cylindrical section 104 connected sequentially from top to bottom. The upper piston 4 is located on the upper cylindrical section 101, and the lower piston 5 is located on the lower cylindrical section 104 to facilitate sliding up and down. The inner diameter of the upper conical section 102 gradually decreases from top to bottom, and the inner diameter of the lower conical section 103 gradually decreases from bottom to top. The advantage of using a conical inner wall surface is that, when pressing the model, this conical surface helps to reduce the frictional resistance caused by the inner wall and facilitates the tight concentration of solid phase particles. For example, the cone angle of the upper conical section 102 and the lower conical section 103 is 10° to 20°, which is a relatively small angle cone surface. The pressed model is basically not much different from a cylinder. In the displacement experiment, since the seepage is usually concentrated around the center line of the core sample and the edge is the weakest, this cone angle has no effect on the seepage process.

[0082] Furthermore, the pressure resistance of the cylinder 1 is not less than 150 MPa, and the inner wall of the cylinder 1 is smooth with a roughness of less than 1.6 μm.

[0083] Furthermore, such as Figure 5 , Figure 6 , Figure 7 As shown, both the upper end cap 2 and the lower end cap 3 include a cap body 15 and a plug 16. The cap body 15 has a stepped hole, which includes a large hole 151 and a small hole 152. The diameter of the large hole 151 is larger than the diameter of the small hole 152. The plug 16 includes a large-diameter section 161 and a small-diameter section 162. The outer diameter of the large-diameter section 161 is larger than the outer diameter of the small-diameter section 162. The outer diameter of the large-diameter section 161 is smaller than the diameter of the large hole 151 but larger than the diameter of the small hole 152. The outer diameter of the small-diameter section 162 is smaller than the diameter of the small hole 152. The large-diameter section 161 is located inside the large hole 151, and the small-diameter section 162 passes through the small hole 152. An annular insertion hole 153 is formed between the outer wall of section 161 and the inner wall of the large hole 151, which can mate with the side wall of the cylinder 1. The inner wall of the large hole 151 is provided with internal threads, and the outer wall of the large diameter section 161 is provided with an O-ring seal 39. The outer walls of both ends of the cylinder 1 are provided with external threads. When the end cap is installed on the cylinder 1, the side wall of the cylinder 1 is screwed into the annular insertion hole 153. Therefore, the cylinder 1 is threadedly connected to the inner wall of the large hole 151, and the cylinder 1 is sealed to the outer wall of the large diameter section 161, thereby realizing the detachable connection and overall sealing between the cylinder 1 and the end cap. The sealing effect is good, the pressure bearing capacity is strong, and the disassembly and assembly are convenient.

[0084] Furthermore, such as Figure 4 , Figure 5As shown, both the upper connecting pipe 11 and the lower connecting pipe 12 are pressure-resistant steel pipes. The plug 16 has a sealing through hole 163 for the pressure-resistant steel pipe to pass through. The pressure-resistant steel pipe and the inner wall of the sealing through hole 163 are sealed by a sealing ring. The upper piston 4 has a piston through hole 401 for the pressure-resistant steel pipe to pass through, and the lower piston 5 has a piston through hole 501 for the pressure-resistant steel pipe to pass through. The pressure-resistant steel pipe and the inner wall of the piston through hole are also sealed by an O-ring 39. The pressure-resistant steel pipe and the piston through hole are both aligned with the central axis of the cylinder 1. Parallel to facilitate piston sliding up and down, the inner wall of the piston through hole is smooth, for example, its roughness is less than 1.6μm, for example, the length of the straight section of the pressure-resistant steel pipe is not less than 20cm, the outer diameter of the pressure-resistant steel pipe is 3mm, the inner diameter is 1mm, and the outer wall of the pressure-resistant steel pipe is smooth, for example, its roughness is less than 1.6μm; the plug 16 is also provided with an injection through hole 164, the pressurizing pipe is threaded to the injection through hole 164, and the pressurizing fluid is injected into the pressurizing space from the pressurizing pipe through the injection through hole 164.

[0085] Furthermore, both the upper piston 4 and the lower piston 5 are made of stainless steel with flat end faces. The inner end face facing the pressing chamber 6 is sandblasted, with a surface roughness in the range of 100μm to 200μm. The outer surfaces can be conventionally treated. The outer surfaces of the upper piston 4 and the lower piston 5 are sealed to the inner wall of the cylinder 1 by O-ring seals 39. To ensure reliable sealing, double-layer O-ring grooves can be provided on the outer wall of the piston. The O-ring seals 39 installed in the O-ring grooves play a role in sealing and guiding smooth movement. Similarly, to ensure reliable sealing between the pressure-resistant steel pipe and the piston through hole, double-layer O-ring grooves can also be provided on the inner wall of the piston through hole. The installed O-ring seals can play a role in sealing and keeping the piston moving in a straight line with the pressure-resistant steel pipe.

[0086] Furthermore, such as Figure 3 As shown, the upper pressure pipe 9 is equipped with a first switch valve 17, the lower pressure pipe 10 is equipped with a second switch valve 18, the upper connecting pipe 11 is equipped with a third switch valve 19, and the lower connecting pipe 12 is equipped with a fourth switch valve 20, so as to control the opening and closing of the pipeline and facilitate experimental operation.

[0087] Furthermore, there are two upper connecting pipes 11 spaced apart, and two lower connecting pipes 12 spaced apart, to provide sufficient outflow channels for the oil and sufficient injection channels for the subsequent injection of displacement fluid, so that the displacement fluid can be injected into the core sample from multiple locations to ensure the displacement effect.

[0088] In one embodiment of the present invention, such as Figure 3As shown, the preparation apparatus also includes a displacement container 21 for containing the displacement fluid. The displacement container 21 is connected to the upper connecting pipe 11 or the lower connecting pipe 12. The displacement container 21 is connected to a pressure pump 14. The pressure pump 14 can pump the displacement fluid in the displacement container 21 into the pressure chamber 6. For example, the displacement fluid is gas or water, to simulate a gas-driven oil displacement experiment or a water-driven oil displacement experiment.

[0089] The preparation apparatus in this embodiment has the functions of preparing saturated oil shale core samples and conducting displacement experiments. After the preparation of saturated oil shale core samples is completed, displacement experiments can be carried out continuously, realizing continuous operation of core preparation, saturated oil and displacement experiments.

[0090] Furthermore, such as Figure 3 As shown, the preparation device also includes a back pressure controller 22, which is connected to the upper connecting pipe 11 and the lower connecting pipe 12. By setting the back pressure controller 22, it is easy to control the pressure, so as to prepare saturated oil shale core samples and carry out displacement experiments under isobaric conditions.

[0091] Furthermore, such as Figure 3 As shown, the preparation apparatus also includes a fluid metering device 23, which is connected to the upper connecting pipe 11 and the lower connecting pipe 12 to measure the oil discharged from the upper connecting pipe 11 and the lower connecting pipe 12.

[0092] Furthermore, such as Figure 3 As shown, the preparation device also includes a first multi-way valve 24, a second multi-way valve 25, and a third multi-way valve 26. The upper pressurization pipe 9 and the lower pressurization pipe 10 are connected to the pressurization container 13 through the first multi-way valve 24. The upper connecting pipe 11 is connected to the fluid metering device 23, the displacement container 21, and the back pressure controller 22 through the second multi-way valve 25. The lower connecting pipe 12 is connected to the fluid metering device 23, the displacement container 21, and the back pressure controller 22 through the third multi-way valve 26. This reduces the number of pipes, simplifies the device structure, and facilitates experimental control.

[0093] Furthermore, such as Figure 3 As shown, the first multi-way valve 24 is connected to the pressurized container 13 and the displacement container 21 through the inlet pipeline 27, and the second multi-way valve 25 and the third multi-way valve 26 are connected to the displacement container 21 through the first multi-way valve 24 and the inlet pipeline 27, respectively, which further reduces the number of pipelines and simplifies the device structure.

[0094] Furthermore, such as Figure 3As shown, the first multi-way valve 24 is connected to a main air supply pipe 28. The main air supply pipe 28 is connected to the second multi-way valve 25 via a first branch air supply pipe 29. The main air supply pipe 28 is connected to the third multi-way valve 26 via a second branch air supply pipe 30. A fifth switching valve 31 is provided on the main air supply pipe 28, a sixth switching valve 32 is provided on the first branch air supply pipe 29, and a seventh switching valve 33 is provided on the second branch air supply pipe 30. Therefore, the fluid in the displacement container 21 can flow sequentially through the inlet pipe 27, the first multi-way valve 25, the second branch air supply pipe 26, and the third multi-way valve 26. The gas can be injected into the core sample in the pressurization space via the following flow paths: through the inlet pipe 24, the main gas pipe 28, the first gas branch pipe 29, the second multi-way valve 25, and the upper connecting pipe 11. Alternatively, the gas can be injected into the core sample in the pressurization space via the inlet pipe 27, the first multi-way valve 24, the main gas pipe 28, the second gas branch pipe 30, the third multi-way valve 26, and the lower connecting pipe 12. During the experiment, one flow path can be selected to inject the displacement fluid. That is, one end of the pressing cylinder is used as the injection end, and the other end is used as the output end.

[0095] Furthermore, such as Figure 3 As shown, the second multi-way valve 25 is connected to a first liquid guide pipe 34, and the third multi-way valve 26 is connected to a second liquid guide pipe 35. The first liquid guide pipe 34 is equipped with an eighth switching valve 36, and the second liquid guide pipe 35 is equipped with a ninth switching valve 37. The second multi-way valve 25 is connected to the fluid metering device 23 and the back pressure controller 22 through the first liquid guide pipe 34, and the third multi-way valve 26 is connected to the fluid metering device 23 and the back pressure controller 22 through the second liquid guide pipe 35. Therefore, during the pressing process, the upper oil in the pressing chamber 6 flows sequentially through the upper connecting pipe 11, the second multi-way valve 25, and the first liquid guide pipe 34 into the fluid metering device 23, and the upper oil flows sequentially through the lower connecting pipe 12, the third multi-way valve 26, and the second liquid guide pipe 35 into the fluid metering device 23.

[0096] Specifically, the first liquid guide pipe 34, the second liquid guide pipe 35, the fluid metering device 23, and the back pressure controller 22 are connected and linked through two tees 40.

[0097] In one embodiment of the present invention, such as Figure 3 As shown, the preparation device also includes a rotating support 38 that supports the pressing cylinder. The cylinder 1 is rotatably connected to the rotating support 38. When preparing saturated oil shale core samples, the pressing cylinder is rotated to a vertical position. During the displacement experiment, the pressing cylinder is rotated to a horizontal position to simulate a horizontal oil displacement experiment.

[0098] The preparation apparatus of the present invention is used to prepare saturated oil shale core samples, and the specific operation is as follows:

[0099] ①Preparation before suppression

[0100] Adjust the pressing cylinder to a vertical position, open the upper end cover 2, take out the upper piston 4, install the lower piston 5, tighten the bottom end cover 3, connect the lower connecting pipe 12 and the lower pressurizing pipe 10 and other injection lines, and then inject water into the lower pressurizing chamber 8 through the lower pressurizing pipe 10. During the water injection process, the lower piston rises slowly and stops injecting when it reaches the preset position.

[0101] Oil is added from the top of cylinder 1, and the volume of the oil is denoted as Voil. Then, the fully mixed raw material to be pressed is added, and its volume is denoted as Vso. Vso is the net volume of the raw material to be pressed. The volume of sand particles can be measured by the water displacement method and then dried. The volume of solid binder can be calculated by the water displacement method from equal masses of particles. The binder solution is a liquid, and its volume can be precisely measured by a graduated cylinder. Voil > 1.5Vso means that the oil completely soaks the raw material to be pressed.

[0102] ② Vacuuming

[0103] After the oil has completely soaked the raw material to be pressed, check the inner wall of cylinder 1, especially the inner wall of the upper cylindrical section of cylinder 1, for solid particles to adhere to it. After confirming that the wall surface is smooth, install the upper end cover 2.

[0104] Open the third switch valve 19 on the upper connecting pipe 11, and evacuate from the vent valve of the second multi-way valve 25. Under the condition of -0.1MPa, the evacuation time shall not be less than three hours, so that the oil phase and solid phase particles can be in complete contact through evacuation.

[0105] ③ Install piston 4 and upper end cap 2

[0106] After vacuuming, open the upper cover 2, and after confirming that the inner wall surface of the cylinder 1 is smooth, insert the upper piston 4;

[0107] Open the third switch valve 19 on the upper connecting pipe 11, and slowly push the piston 5 down by hand. Stop when oil phase flows out of the vent valve of the second multi-way valve 25, and install the upper end cover 2.

[0108] ④ Pressing and core sample molding

[0109] Open the first switch valve 17 on the upper pressure pipe 9, and the high-pressure plunger pump slowly injects the water in the displacement container into the upper pressure chamber 7. Stop the pump when the pressure tends to rise.

[0110] Open the first switch valve 17 on the upper pressure pipe 9 and the second switch valve 18 on the lower pressure pipe 10 so that water can be injected into the upper pressure chamber 7 and the lower pressure chamber 8 at the same time.

[0111] Open the third switch valve 19 on the upper connecting pipe 11 and the fourth switch valve 20 on the lower connecting pipe 12, open the corresponding second multi-way valve 25 and third multi-way valve 26, close the fifth switch valve 31, the sixth switch valve 32 and the seventh switch valve 33, adjust the back pressure controller, and preset the pressure to 1MPa;

[0112] When the high-pressure plunger pump is turned on, water is slowly injected into the upper pressurization chamber 7 and the lower pressurization chamber 8. The water pushes the upper piston 4 and the lower piston 5 to move towards the middle of the cylinder 1, squeezing the filled raw material to be pressed. During the squeezing process, some of the oil in the pressing chamber 6 flows out from the upper connecting pipe 11 and the lower connecting pipe 12. Its volume is accurately measured by the fluid metering device 23, and the measured volume is recorded as Voou.

[0113] When no oil flows out, preset the pressure of the back pressure controller 22 to more than twice the working pressure of the displacement experiment. For example, if the working pressure is 40MPa, the preset pressure should not be less than 80MPa. Continue to inject water and squeeze the upper piston 4 and the lower piston 5. When no oil flows out, let it stand and wait for the epoxy resin and solid phase binder to bond, solidify and harden for no less than 72 hours. Due to the slight expansion and subsequent shrinkage effect of the solid phase particles during the bonding process, the pressure will fluctuate slightly, which is normal.

[0114] After settling, the preparation of saturated oil shale core samples is complete.

[0115] When the first switch valve 17 on the upper pressure pipe 9 and the second switch valve 18 on the lower pressure pipe 10 are closed, the pressure in the upper pressure chamber 7 and the lower pressure chamber 8 is maintained at the preset pressure of 80MPa.

[0116] Then, the pressure of the back pressure controller 22 is adjusted to the working pressure of the displacement experiment (i.e., 40MPa). The final value of the outflowing oil volume Voou is determined, and the total volume Vsat of saturated oil in the core sample is Vooil-Voou.

[0117] Displacement experiments were conducted using the preparation apparatus of this invention. Taking a gas-driven oil displacement experiment as an example, a horizontal oil displacement experiment was simulated. Gas was injected through the upper connecting pipe 11 (referred to as the injection end), and oil was produced through the lower connecting pipe 12 (referred to as the production end). The preset working pressure of the production end was 40 MPa. The specific operation is as follows:

[0118] ① Experimental preparation

[0119] Adjust the pressing cylinder to a horizontal position, open the fifth switch valve 31 and the sixth switch valve 32, close the seventh switch valve 33, open the third switch valve 19 on the upper connecting pipe 11 and the fourth switch valve 20 on the lower connecting pipe 12, open the corresponding third multi-way valve 26, open the ninth switch valve 37, and close the eighth switch valve 36.

[0120] ② Gas injection for oil displacement

[0121] The gas pressure in the displacement container 21 is pre-adjusted to 40MPa. The high-pressure plunger pump is turned on and the gas is displaced at a rate of 0.05mL / min. The gas gradually enters the pores of the core sample and displaces it until a large amount of gas is produced at the producing end and no more oil is produced. Then the displacement process ends.

[0122] ③ Device arrangement

[0123] After the experiment, the pressure in the compression cylinder is released. Then, the upper end cover 2 and the lower end cover 3 are opened, and the upper piston 4 and the lower piston 5 are taken out. Then, the core sample inside the cylinder is broken and removed with a steel chisel. It can be used to analyze the pore structure characteristics, etc. After drying for a few days, there are particles adhering to the inner wall of the core sample. These can be removed by gently tapping. Then, the inner surface of the core sample is cleaned for the next use.

[0124] The shale physical model, the method for preparing saturated oil shale core samples, and the apparatus of the present invention have the following characteristics:

[0125] 1. This invention provides a method for cementing solid-phase binders in an oil-phase environment, forming a method for creating rock models under oil-phase conditions, and producing rock samples similar to those of shale reservoirs;

[0126] 2. This invention provides a method for directly saturating oil under oil phase conditions, so that the pores at all levels can be filled with the oil phase, and the saturation of oil can reach a maximum of 100%.

[0127] 3. This invention provides a simulation device that can perform core preparation and oil displacement experiments under isobaric conditions, realizing continuous operation of core preparation, saturated oil and displacement / development steps;

[0128] 4. This invention achieves a high degree of simulation of the micropore structure and original formation oil distribution in shale oil reservoirs, and the prepared rock samples lay the foundation for related experimental research and technology development in shale oil reservoirs.

[0129] The above description is merely an illustrative embodiment of the present invention and is not intended to limit the scope of the invention. Any equivalent changes and modifications made by those skilled in the art without departing from the concept and principles of the present invention should fall within the scope of protection of the present invention. Furthermore, it should be noted that the components of the present invention are not limited to the overall application described above. Each technical feature described in the specification can be used individually or in combination as needed. Therefore, the present invention naturally covers other combinations and specific applications related to the inventive points of this case.

Claims

1. A shale physical model, characterized in that, The shale physical model includes sand grains, a cementing agent, and a water-absorbing solid binder, wherein the particle size of the solid binder is smaller than that of the sand grains. The solid binder comprises the following components by weight percentage: Water-based calcium carbonate: 80%–90%; clay: 10%–15%; gypsum: 5%–10%.

2. The shale physical model as described in claim 1, characterized in that, The sand particles and the solid phase binder constitute the solid phase raw material of the shale physical model. The content of the sand particles accounts for 85% to 90% of the total weight of the solid phase raw material, and the content of the solid phase binder accounts for 10% to 15% of the total weight of the solid phase raw material.

3. The shale physical model as described in claim 1, characterized in that, The sand particles have a diameter of less than 100 μm, and the solid phase binder has a diameter of 15 μm to 25 μm.

4. The shale physical model as described in claim 1, characterized in that, The binder is an aqueous epoxy resin.

5. A method for preparing a saturated oil shale core sample, characterized in that, The preparation method includes: Sand particles and a water-absorbing solid binder are mixed evenly to obtain a solid raw material, wherein the particle size of the solid binder is smaller than that of the sand particles. Dilute the binder with water to obtain a binder solution; The solid raw material is sprayed with a binder solution and mixed evenly to obtain the raw material to be pressed; The raw material to be pressed was immersed in oil and pressed to obtain a saturated oil shale core sample. The solid binder comprises the following components by weight percentage: Water-based calcium carbonate: 80%–90%; clay: 10%–15%; gypsum: 5%–10%.

6. The method for preparing saturated oil shale core samples as described in claim 5, characterized in that, The sand particles account for 85% to 90% of the total weight of the solid raw materials, and the solid binder accounts for 10% to 15% of the total weight of the solid raw materials.

7. The method for preparing saturated oil shale core samples as described in claim 5, characterized in that, The sand particles have a diameter of less than 100 μm, and the solid phase binder has a diameter of 15 μm to 25 μm.

8. The method for preparing saturated oil shale core samples as described in claim 5, characterized in that, The binder is an aqueous epoxy resin.

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