Artificial rock core preparation and detection process and artificial rock core

Abstract

The invention relates to the technical field of oil-gas field development, in particular to an artificial rock core preparation and detection process and an artificial rock core. A preparation and detection process for an artificial core comprises the following steps: firstly, obtaining a stratum core structure slice according to a stratum core structure, and preparing a flexible mold; secondly, heating the water-soluble hot-melt material to a molten state, and pouring the water-soluble hot-melt material into the flexible mold to prepare the water-soluble fracture-cavity filler; meanwhile, quartz sand and a consolidation agent are mixed according to a set proportion to form a rock core mixture; thirdly, pressurizing and curing the mixture of the water-soluble fracture-cavity filler and the rock core to form a rock core reconstruction body; then, the rock core reconstruction body is placed in water, the water-soluble fracture-cavity filler is dissolved, and an artificial rock core consistent with a stratum rock core fracture-cavity structure is formed; and finally, detecting the reliability of the artificial core fracture-cavity structure. According to the artificial rock core preparation and detection process provided by the invention, the fracture-cavity space structure in the stratum rock core can be re-engraved with high precision under the condition that the rock core matrix is not damaged.

Description

Technical Field

[0001] This application relates to the field of oil and gas field development technology, and in particular to a process for preparing and testing artificial rock cores and an artificial rock core. Background Technology

[0002] As a core pillar of global energy supply, the efficient development and rational utilization of oil and gas resources are directly related to national energy security and sustainable economic development. Formation cores are key research objects for revealing reservoir characteristics and optimizing development plans in oil and gas field exploration and development. Their physical properties and pore-permeability structure are the core basis for analyzing reservoir oil and gas occurrence patterns and assessing exploitation potential. However, during drilling, coring, transportation, and sample pretreatment, external disturbances such as drill string vibration and impact, annular drilling fluid erosion, and clamping and squeezing of coring tools can easily lead to irreversible changes in the original pore and fracture structure of the core, severely affecting the authenticity and reliability of experimental test data such as reservoir permeability characteristics and mechanical parameters. Furthermore, the physical properties of different parts of the same core vary, making it impossible to meet the requirements of a single experimental variable. Therefore, there is an urgent need to develop an artificial core preparation method that can replicate the multi-dimensional fracture and pore structure characteristics of formation cores.

[0003] Existing technologies include methods for preparing artificial rock core fractures and cavities such as cutting and bonding, external force fracturing, and 3D printing. The cutting and bonding method involves using a CNC milling machine or high-pressure water jet to carve fracture / hole / cavity structures at multiple cross-sections of the rock core, and then using a binder to join the rock cores together. The external force fracturing method uses mechanical loading, pressure needles, or injection of fracturing fluid to force fractures into the artificial rock core. 3D printing allows for customized printing based on digital images.

[0004] However, existing technologies struggle to accurately reproduce the internal fracture structure of rock cores and ensure that the embedded materials do not deform under the temperature conditions of the curing process. Summary of the Invention

[0005] This application aims to address at least one of the technical problems existing in the prior art. To this end, this application proposes a process for preparing and testing artificial rock cores, which can accurately replicate the fracture and cavity spatial structure inside the stratum rock core without damaging the core matrix.

[0006] This application also proposes an artificial rock core having the above-mentioned preparation and testing process.

[0007] A process for preparing and testing artificial rock cores according to a first aspect of this application includes the following steps: Based on the stratigraphic core structure, slices of stratigraphic core structure are obtained, and flexible molds are prepared; the flexible molds are used to replicate the fracture and cavity structure in stratigraphic cores. A water-soluble hot-melt material is heated to a molten state and poured into the flexible mold to prepare a water-soluble fracture filler; the water-soluble fracture filler is compatible with the fracture structure of the formation core. Quartz sand and consolidating agent are mixed in a set ratio to form a core mixture; The water-soluble fracture filler and the core mixture are subjected to pressure solidification treatment to form a core reconstruction body; The reconstructed core is placed in water to dissolve the water-soluble cavity filler, forming an artificial core with the same cavity structure as the stratum core. To test the reliability of the artificial rock core fracture structure.

[0008] According to an embodiment of this application, a process for preparing and testing artificial rock cores has at least the following beneficial effects: Based on the obtained stratigraphic core structure slices, a flexible mold adapted to the stratigraphic core structure is prepared for cooling a water-soluble hot-melt material heated to a molten state. The molten water-soluble hot-melt material is then cooled and solidified into a water-soluble cavity filler. The water-soluble cavity filler is then demolded from the flexible mold. The flexible mold facilitates demolding of the water-soluble cavity filler. Under heating conditions, the water-soluble hot-melt material can transform from a solid state to a molten state that is easy to shape. The structure of a geological core is replicated with high precision through the gaps in a flexible mold. Under cooling conditions, the water-soluble hot-melt material can be transformed from a molten state to a solid state. Furthermore, by placing the reconstructed core in water, the water-soluble cavity filler inside the core reconstructed core is dissolved. The water dissolution process is safe, pollution-free, and does not involve chemical reactions or bubble generation, ensuring that the water-soluble cavity filler can be fully dissolved, thereby forming cavities inside the artificial core that are highly similar to those in the geological core. Testing the cavity structure of the artificial core can verify the reliability of the cavity structure in the prepared artificial core. Optionally, obtaining stratigraphic core structure slices based on the stratigraphic core structure and preparing flexible molds includes: Core fracture and cavity slices are obtained from the strata using non-destructive testing methods; these core fracture and cavity slices are used to reflect the spatial location of the core fractures and cavities. Based on the fractured core slices of the strata, fractured grooves are opened in a flexible mold that are consistent with the fractured core slices of the strata.

[0009] Optionally, heating the water-soluble hot-melt material to a molten state and pouring it into the flexible mold to prepare the water-soluble crevice filler includes: Weigh out a set mass of water-soluble hot-melt material based on the volume of the fractures in the stratum core. The water-soluble hot melt material is placed in a crucible and heated to 120~150°C to transform the water-soluble hot melt material into a composite filling medium in a molten flow state. The composite filling medium in the crucible is transferred to the flexible mold using a feeder. After the composite filling medium cools and solidifies into a water-soluble crevice filler, the water-soluble crevice filler is peeled off from the flexible mold.

[0010] Optionally, mixing quartz sand and a consolidating agent in a set ratio to form a core mixture includes: determining the particle size distribution of quartz sand based on the average permeability and porosity of the formation core, and mixing and stirring it with the consolidating agent to ensure that the consolidating agent uniformly coats the quartz sand.

[0011] Optionally, the process of pressurizing and solidifying the mixture of the water-soluble fracture filler and the core to form a core reconstruction includes: The core mixture is filled into a steel mold, and the water-soluble fracture filler is inserted into the core mixture according to the location of the fractures in the fracture slices of the stratum core. The steel mold is placed in a pressurizing device and the pressurizing pressure is set to 3~10MPa for pressurization treatment to solidify the mixture of water-soluble cavity filler and core material, thus preparing a core reconstruction.

[0012] Optionally, placing the reconstructed core in water to dissolve the water-soluble fracture filler includes: The reconstructed core was placed in a water-filled container and subjected to vacuuming and ultrasonic vibration to dissolve the water-soluble cavity filler, thus forming an artificial core.

[0013] Optionally, the reconstructed core is placed in a water-filled container and subjected to vacuuming and ultrasonic vibration to dissolve the water-soluble cavity filler, forming an artificial core, including: The core reconstruction was placed in a water-filled container and subjected to vacuum treatment and ultrasonic vibration treatment for 30 to 150 minutes.

[0014] Optionally, the reliability of the artificial rock core fracture structure can be tested, including: Prepare seamless cavern-structured artificial rock cores based on the geological rock core structure; The artificial rock core and the seamless hole structure artificial rock core were placed in a permeability and porosity tester to measure the actual permeability and actual porosity of the artificial rock core and the seamless hole structure artificial rock core. The theoretical pore volume of the artificial rock core is calculated based on the volume, porosity, and volume of the water-soluble cavity filling material of the seamless cavity structure. The theoretical porosity of the artificial rock core is calculated using the theoretical pore volume of the artificial rock core. The ratio of the actual porosity to the theoretical porosity of the artificial rock core is calculated to assess the reliability of the fracture-cavity structure of the artificial rock core.

[0015] Optionally, the reliability of the artificial rock core fracture structure can be detected by: detecting the reliability of the artificial rock core fracture structure by means of a light transmission detection method; wherein the light transmission detection method involves placing the artificial rock core in a single light source environment, with a single light source on one side of the artificial rock core and an imaging device on the other side; the artificial rock core is illuminated by a single light source and an image is formed on the imaging device to detect the reliability of the artificial rock core fracture structure.

[0016] According to the second aspect of this application, the artificial rock core has a cavity inside that is consistent with the cavity structure of the stratum rock core. The cavity is made by heating and cooling a water-soluble hot-melt material and finally dissolving it in water.

[0017] The artificial rock core according to the embodiments of this application has at least the following beneficial effects: The fracture cavity is made by heating and cooling a water-soluble hot-melt material and finally dissolving it in water. It can not only accurately replicate the fracture cavity structure of the stratum core, but also reduce the risk of structural damage to the core matrix of the artificial core during the formation of the fracture cavity. Additional aspects and advantages of this application will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of this application. Attached Figure Description

[0018] The present application will be further illustrated below with reference to the accompanying drawings and embodiments. It should be noted that the embodiments illustrated in the following drawings are exemplary and are only used to explain the present application, and should not be construed as limiting the present application.

[0019] Figure 1 This is a flowchart of the artificial rock core preparation and testing process described in Embodiment 1 of this application; Figure 2 This is a flowchart of the preparation of the flexible mold as described in Embodiment 1 of this application; Figure 3 This is a flowchart of the preparation of water-soluble crevice filler as described in Example 1 of this application; Figure 4 This is a flowchart of the preparation of the core reconstruction body as described in Example 1 of this application; Figure 5 This is a cross-sectional view of the flexible mold with a single slot as described in Embodiment 1 of this application; Figure 6 This is an exploded structural diagram of the steel mold described in Embodiment 1 of this application; Figure 7 This is a cross-sectional structural diagram of the artificial rock core containing a straight-line slot as described in Embodiment 1 of this application; Figure 8 This is a cross-sectional view of the T-shaped slotted flexible mold described in Embodiment 2 of this application; Figure 9This is a cross-sectional structural diagram of the artificial rock core containing T-shaped fissures as described in Embodiment 2 of this application; Figure 10 This is a cross-sectional view of the flexible mold with cross-shaped slots described in Embodiment 2 of this application; Figure 11 This is a cross-sectional structural diagram of the artificial rock core containing the cross-shaped slotted structure described in Embodiment 2 of this application; Figure 12 This is a cross-sectional view of the spherical hole flexible mold described in Embodiment 3 of this application; Figure 13 This is a cross-sectional structural diagram of the artificial rock core containing a spherical cavity structure as described in Embodiment 3 of this application; Figure 14 This is a flowchart of the permeability and porosity difference detection method described in Embodiment 3 of this application; Figure 15 This is a cross-sectional structural diagram of the artificial rock core described in Embodiment 4 of this application; Figure 16 This is a cross-sectional structural diagram of the artificial rock core described in Embodiment 5 of this application.

[0020] Reference numerals: 100, artificial rock core; 101, rock core reconstruction; 200, flexible mold; 201, slot; 300, steel mold; 301, receiving column; 302, bottom column; 3021, receiving groove; 303, compaction column; 304, receiving cavity; 3041, positioning shoulder. Detailed Implementation

[0021] The embodiments of this application are described in detail below with reference to the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain this application, and should not be construed as limiting this application.

[0022] In the description of this application, it should be understood that the terms "center", "middle", "longitudinal", "transverse", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "axial", "radial", "circumferential", etc., indicating the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this application.

[0023] In the description of this application, "several" means one or more, "multiple" means two or more, "greater than," "less than," and "exceeding" are understood to exclude the stated number, while "above," "below," and "within" are understood to include the stated number. The use of "first" and "second" in the description is merely for distinguishing technical features and should not be construed as indicating or implying relative importance, or implicitly indicating the number of indicated technical features, or implicitly indicating the order of the indicated technical features.

[0024] In the description of this application, unless otherwise expressly specified and limited, the terms "set up," "install," "connect," and "link" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this application based on the specific circumstances.

[0025] In the description of this application, the use of terms such as "one embodiment," "some embodiments," "an example," "some instances," "some embodiments," "illustrative embodiment," "example," "specific example," and "some examples" indicates that the specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0026] Example 1: Reference Figure 1 This application provides a process for preparing and testing artificial rock cores, including the following steps: Step S110: Obtain stratigraphic core structure slices based on stratigraphic core structure, and prepare flexible mold 200; flexible mold 200 is used to replicate the fracture-cavity structure of stratigraphic core. In step S120, the water-soluble hot-melt material is heated to a molten state and poured into a flexible mold 200 to prepare a water-soluble cavity filler; the water-soluble cavity filler is compatible with the cavity structure of the formation core. Step S130: Mix quartz sand and consolidating agent in a set ratio to form a core mixture; Step S140: The mixture of water-soluble fracture filler and core is subjected to pressure solidification treatment to form core reconstruction body 101; Step S150: Place the core reconstruction body 101 in water to dissolve the water-soluble cavity filler and form an artificial core 100 that is consistent with the cavity structure of the stratum core. Step S160: Detect the reliability of the 100-slot structure in the artificial rock core.

[0027] Specifically, core slices are obtained based on the stratigraphic core structure, and a flexible mold 200 is prepared. To accurately reproduce the fracture-cavity network inside the core and ensure that the material used to prepare the fracture-cavity network is fully dissolved during the preparation process, a water-soluble hot-melt material is used to prepare a water-soluble fracture-cavity filler. The specific process is as follows: a predetermined mass of water-soluble hot-melt material is weighed according to the core slices, and heated to 120℃~150℃, causing the solid water-soluble hot-melt material to transform into a molten and flowing state. The molten and flowing water-soluble hot-melt material is then poured into the flexible mold 200, filling it completely. After cooling to room temperature, the water-soluble fracture-cavity filler is separated from the flexible mold 200 for demolding. At this point, the molten and flowing water-soluble hot-melt material has transformed into a solid water-soluble fracture-cavity filler adapted to the fracture-cavity structure of the core. The quartz content is determined based on the average permeability and porosity of the core. The sand is particle size-graded and mixed with a consolidating agent to fully coat the quartz sand, forming a core mixture. Subsequently, the water-soluble fracture filler and the core mixture are subjected to pressure solidification to form a core reconstruction 101, wherein the position of the water-soluble fracture filler corresponds to the fracture location in the formation core. To prepare an artificial core 100 with the same fracture structure as the formation core, the water-soluble fracture filler in the core reconstruction 101 needs to be dissolved. In this embodiment, the core reconstruction 101 is placed in water. On the one hand, water does not react with the core mixture and will not damage the structure of the core reconstruction 101 except for the water-soluble fracture filler; on the other hand, no bubbles are generated during the reaction between water and the water-soluble fracture filler, ensuring sufficient contact between water and the water-soluble fracture filler, dissolving the water-soluble fracture filler, and forming an artificial core 100 containing a fracture structure. Finally, the reliability of the fracture structure of the artificial core 100 can be verified by testing the artificial core 100.

[0028] It should be noted that water-soluble hot melt materials can transform from a solid state to a easily shaped molten flow state under heating conditions, and then transform back to a solid state upon cooling. Solid water-soluble fillers do not chemically react with water during dissolution and do not deform under the curing heating temperature. Water-soluble hot melt materials can be selected from one or more of the following: isomaltitol, polyethylene glycol, hydroxypropyl cellulose, and recrystallized sucrose, which are solid at room temperature.

[0029] Reference Figure 2 Based on the stratigraphic core structure, obtain stratigraphic core structure slices and prepare a flexible mold 200, including: Step S210: Obtain core fracture and cavity slices of the strata using non-destructive testing methods; the core fracture and cavity slices of the strata are used to reflect the spatial location of the core fractures and cavities in the strata. Step S220: Based on the fractured core slice of the stratum, a fractured groove 201 is opened in the flexible mold 200 that is consistent with the fractured core slice of the stratum.

[0030] Reference Figure 2 The specific location of fractures and cavities in the formation core, overlying pressure, permeability, porosity, and particle size distribution of quartz sand are obtained through non-destructive testing (NDT) methods. Based on the NDT results, the structure and location of fractures and cavities in the formation core are determined, and a flexible mold 200 consistent with the fracture and cavity structure of the formation core is then prepared. Core CT can be used as the NDT method. Using NDT to obtain fracture and cavity sections from the formation core avoids the risk of damaging the formation core structure while obtaining the spatial structure of the fractures and cavities, thus supporting the preparation of the flexible mold 200.

[0031] Reference Figure 2 and Figure 5 The flexible mold 200 has a cavity groove 201 that corresponds to the cavity section of the formation core. The cavity groove 201 can be located at the bottom of the flexible mold 200. In this embodiment, the cavity groove 201 has a straight-line structure, and its size can be accurate to the micrometer level compared with the cavity of the formation core. The flexible mold 200 can be a low-cost, easy-to-demold silicone mold; the silicone mold has high flexibility, which facilitates the demolding operation of the water-soluble cavity filler in the cavity groove 201.

[0032] Reference Figure 3 The process of heating a water-soluble hot-melt material to a molten state and pouring it into a flexible mold 200 to prepare a water-soluble crevice filler includes: Step S310: Weigh a set mass of water-soluble hot-melt material according to the volume of the fracture cavity in the stratum core; Step S320: Place the water-soluble hot melt material in a crucible and heat it to 120~150℃ to transform the water-soluble hot melt material into a composite filling medium in a molten flow state; In step S330, the composite filling medium in the crucible is transferred to the flexible mold 200 using a feeder. After the composite filling medium cools and solidifies into a water-soluble crevice filler, the water-soluble crevice filler is peeled off from the flexible mold 200.

[0033] Reference Figure 3The required amount of water-soluble hot-melt material for preparing water-soluble cavity fillers varies depending on the cavity structure. A predetermined mass of water-soluble hot-melt material is weighed and placed in a crucible, then heated to 120-150°C. The solid water-soluble hot-melt material transforms into a molten, flowing composite filling medium. A transfer device is then used to transfer the composite filling medium from the crucible to the flexible mold 200 until the cavity grooves 201 in the flexible mold 200 are filled. The transfer device can be preheated to reduce the risk of the composite filling medium solidifying due to a sudden temperature drop during transfer, ensuring smooth transfer to the flexible mold 200 and filling the edges and corners of the cavity grooves 201, thus improving the accuracy of preparing the water-soluble cavity filler. A quartz syringe can be used as the transfer device. After the cavity grooves 201 are filled, the composite filling medium is cooled to form a solid water-soluble cavity filler. The operator can then press the flexible mold 200 by hand to separate the water-soluble cavity filler from the flexible mold 200.

[0034] Reference Figure 1 and Figure 4 A core mixture is formed by mixing quartz sand and a consolidating agent according to a set ratio. This includes determining the particle size distribution of the quartz sand based on the average permeability and porosity of the formation core, and mixing and stirring it with the consolidating agent to ensure uniform coating of the quartz sand. The quartz sand is granular. For a formation core with an average permeability of 203.8 mD and a porosity of 18.13%, 78.95% 50-100 mesh quartz sand and 21.05% 30-50 mesh quartz sand can be uniformly mixed with the consolidating agent. The consolidating agent can be composed of 69.2% epoxy prepolymer, 23.1% ethylenediamine, and 7.7% acetone. In this embodiment, a total of 38g of quartz sand and 6.5g of quartz sand can be weighed. g of consolidating agent; wherein, 30g of 50-100 mesh quartz sand and 8g of 30-50 mesh quartz sand; 4.5g of epoxy prepolymer, 1.5g of ethylenediamine, and 0.5g of acetone are mixed evenly and placed in a vacuum chamber. After degassing at 25°C for 40 minutes, the mixture is removed to obtain the consolidating agent. Then, the prepared quartz sand is poured into the consolidating agent and stirred evenly to form a core mixture.

[0035] Reference Figures 4-7 The process of pressurizing and solidifying a mixture of water-soluble fracture filler and core material to form a core reconstruction 101 includes: Step S410: Fill the core mixture into the steel mold 300, and insert the water-soluble fracture filler into the core mixture according to the location of the fracture in the core fracture slice. In step S420, the steel mold 300 is placed in a pressurizing device and the pressurizing pressure is set to 3~10MPa for pressurization treatment to solidify the water-soluble cavity filler and the core mixture, thus preparing the core reconstruction body 101.

[0036] Reference Figures 4-7 The steel mold 300 includes a receiving column 301, a bottom column 302, and a compaction column 303. A receiving cavity 304 is provided through the receiving column 301 along the axis. The receiving cavity 304 is adapted to the compaction column 303, and a positioning shoulder 3041 is provided on the side wall of the receiving cavity 304 near one end. The positioning shoulder 3041 is adapted to the bottom column 302, and a receiving groove 3021 is provided on the bottom column 302 for receiving the core reconstruction body 101 after pressure solidification treatment. To facilitate the removal of the core reconstruction 101 after processing, Vaseline can be applied to the sidewall of the receiving cavity 304. Before adding the core mixture, the end of the bottom column 302 away from the opening of the receiving groove 3021 is used to hold the positioning shoulder 3041. Then, the core mixture is added to the receiving cavity 304, and the water-soluble fracture filler is inserted into the designated position in the core mixture, ensuring that the position of the water-soluble fracture filler is consistent with the position of the fracture structure in the formation core. After the water-soluble fracture filler is placed, the compaction column 303 is inserted into the receiving cavity 304, and the steel mold 300 is placed in the pressurization device to prepare the core reconstruction 101. In addition, to facilitate the compaction of the core mixture... The steel mold 300 can be pressurized using a press at a set temperature. Here, the set temperature can be set to 60℃, the press pressure is 9.0MPa, and after the press reading stabilizes, continue pressing for 2 hours before removing the core reconstruction body 101. At this time, the bottom column 302 can be removed first, and the end of the bottom column 302 with the receiving groove 3021 is placed against the positioning shoulder 3041. The steel mold 300 is then placed into the pressurizing device again. By applying pressure to the compaction column 303, the core reconstruction body 101 in the receiving cavity 304 falls into the receiving groove 3021. At this time, pressurization is stopped, the steel mold 300 is removed, and the core reconstruction body 101 in the bottom column 302 is removed. It should be noted that: First, the set temperature did not reach the temperature at which the water-soluble cavity filler dissolves; Second, in order to facilitate verification of the reliability of the cavity structure in the prepared artificial core 100, the prepared artificial core 100 is a cylindrical structure, and the height of the artificial core 100 is twice the diameter of the bottom surface.

[0037] Reference Figures 4-7 The core reconstruction 101 was placed in water to dissolve the water-soluble cavity filler, including: The reconstructed core 101 was placed in a water-filled container and subjected to vacuuming and ultrasonic vibration to dissolve the water-soluble fracture filler, forming an artificial core 100. After placing the reconstructed core 101 in the water-filled container, the container was placed in a vacuum chamber for vacuuming to ensure the core 101 was completely filled with water. It was then removed and subjected to ultrasonic vibration to form an artificial core 100 with a fracture structure. The specific vacuuming conditions were 25°C for 35 minutes; ultrasonic vibration was then performed to accelerate the dissolution of the water-soluble fracture filler. Ultrasonic vibration could be performed at 65°C for 60 minutes.

[0038] Reference Figure 1 and Figure 7 After the artificial rock core 100 is prepared, the reliability of its fracture-cavity structure can be tested using the light transmission detection method. This method involves placing the artificial rock core 100 in a single-light source environment, with a single light source on one side and an imaging device on the other. The artificial rock core 100 is illuminated by the single light source, and an image is formed on the imaging device to detect the reliability of its fracture-cavity structure. Specifically, the prepared artificial rock core 100 can be placed in a darkroom environment, ensuring no other interfering light sources besides the single light source. The single light source on one side can be a semiconductor laser capable of emitting a high-intensity collimated light source, and the imaging device on the other side can be a device capable of high-sensitivity imaging. During testing, the light source is turned on, and the light passing through the linear fracture-cavities is preferentially transmitted to the imaging device, forming a brighter strip-shaped, linear, or spot-shaped light transmission pattern, thereby achieving rapid visual identification of the fracture-cavity network's orientation, distribution range, and connectivity. Alternatively, the reliability of the fracture-cavities in the artificial rock core 100 can also be tested using a laser cutting detection method. The laser cutting detection method involves placing the prepared artificial rock core 100 on a laser cutter and using a high-energy laser beam to cut the rock core along the cross section of the I-shaped crack structure, and then comparing it with the corresponding real crack structure.

[0039] The implementation principle of this embodiment is as follows: First, a core structure slice of the formation is obtained through non-destructive testing technology, and a flexible mold 200 consistent with the fracture and cavity structure in the formation is prepared. Second, a set mass of water-soluble hot-melt material is weighed and placed in a crucible and heated to a molten and flowing state to form a composite filling medium. Third, the composite filling medium in the crucible is transferred to the fracture and cavity groove 201 of the flexible mold 200 through a conveyor, so that the composite filling medium fills the fracture and cavity groove 201. After the composite filling medium cools into a water-soluble fracture and cavity filler, the operator can press the flexible mold 200 to demold the water-soluble fracture and cavity filler, allowing the water-soluble filler to be released. The fracture filler is separated from the flexible mold 200. Simultaneously, the particle size distribution of quartz sand is determined based on the average permeability and porosity of the formation core, and it is mixed with a consolidating agent to form a core mixture. The core mixture is then placed in a steel mold 300, and water-soluble fracture filler is inserted into the core mixture according to the location of fractures in the fractured core slices. Pressure curing is then applied to obtain a reconstructed core 101. Finally, the reconstructed core 101 is placed in water, and vacuuming and ultrasonic vibration are used to ensure the water-soluble fracture filler fully contacts and dissolves in the water, forming an artificial core 100 with a fracture structure. The reliability of the fracture structure in the artificial core 100 can be tested using light transmission and laser cutting methods.

[0040] Example 2: Reference Figures 8-11 The difference between this embodiment and Embodiment 1 is that the fissure groove 201 in this embodiment has a vertically intersecting structure. Therefore, the water-soluble fissure filler prepared after cooling the fissure groove 201 also has a vertically intersecting structure. Specifically, the vertically intersecting structure can be a T-shaped structure or a cross-shaped structure. When the vertically intersecting structure is a T-shaped structure, the fissure groove 201 in the flexible mold 200 has a T-shaped structure, and correspondingly, the prepared water-soluble fissure filler also has a T-shaped structure. At this time, the average permeability of the formation core can be 1225.90 mD, and the porosity is 35.34%. Thus, the particle size distribution of the quartz sand is determined to be 26.32% 50-100 mesh quartz sand and 73.68% 30-50 mesh quartz sand. At the same time, since the fissure structure in the artificial core 100 is different, the time and temperature required for ultrasonic vibration are also different. In this embodiment, in order to fully dissolve the T-shaped water-soluble fissure filler, ultrasonic vibration treatment can be performed at 70°C for 70 minutes.

[0041] When the vertical intersecting structure is a cross-shaped structure, the slot 201 in the flexible mold 200 is also a cross-shaped structure. Correspondingly, the prepared water-soluble slot filler is also a cross-shaped structure. At this time, the average permeability of the formation core can be 1821.20 mD and the porosity is 39.84%. Therefore, the particle size distribution of the quartz sand is determined to be 47.37% 30-50 mesh quartz sand and 52.63% 20-30 mesh quartz sand. The parameters of the ultrasonic vibration treatment can be set to 75℃ for 80 min.

[0042] The implementation principle of this embodiment is as follows: For the preparation of artificial rock cores 100 containing different fracture structures, the structure of the fracture groove 201 in the flexible mold 200 is consistent with the corresponding fracture structure. The parameters for ultrasonic vibration treatment need to be adjusted accordingly, and the particle size distribution of the quartz sand used to prepare the rock core mixture also needs to be adjusted according to the average permeability and porosity of the formation rock core to ensure that the water-soluble fracture fillers with different structures can fully contact and dissolve with water.

[0043] Example 3: Reference Figures 12-14 The difference between this embodiment and Embodiments 1 and 2 is that: in this embodiment, the fracture structure in the prepared artificial core 100 is a porous structure, specifically a spherical porous structure. In this case, the water-soluble fracture filler prepared in the flexible mold 200 is also a spherical structure. When the average permeability and porosity of the formation core are low, the quartz sand can be entirely composed of 50-100 mesh quartz sand particles. Furthermore, when the core reconstruction 101 is placed in water, the parameters for vacuum treatment and ultrasonic vibration treatment must be adjusted accordingly. Specifically, the vacuum treatment parameters can be set to 25°C for 65 minutes; the ultrasonic vibration treatment parameters can be set to 80°C for 90 minutes. It should be noted that when verifying the reliability of the porous structure in the artificial core 100, not only can the light transmission detection method and laser cutting detection method be used, but also the permeability and porosity difference detection method. The permeability and porosity difference detection method requires placing both the prepared artificial core 100 and the artificial core 100 with a seamless internal cavity structure into a permeability and porosity tester for testing; the specific steps of the permeability and porosity difference detection method are as follows: Step S510: Prepare a seamless cavern artificial core 100 based on the geological core structure; Step S520: Place the artificial rock core 100 and the seamless hole structure artificial rock core 100 in a permeability and porosity tester to measure the actual permeability and actual porosity of the artificial rock core 100 and the seamless hole structure artificial rock core 100. Step S530: Calculate the theoretical pore volume of the artificial core 100 based on its volume, porosity, and the volume of the water-soluble cavity filler. Step S540: The theoretical porosity of artificial core 100 is calculated by using the theoretical pore volume of artificial core 100. Step S550: Calculate the ratio of the actual porosity to the theoretical porosity of the artificial core 100 to assess the reliability of the fracture structure of the artificial core 100.

[0044] The formulas involved in the permeability and porosity difference detection method are as follows: ; ; ; in, The theoretical porosity of the artificial rock core is 100. The volume of the artificial rock core is 100. The porosity of a seamless, hollow artificial rock core 100; The volume of the water-soluble crevice filler; The actual porosity of artificial rock core 100; It is the ratio of actual porosity to theoretical porosity. The closer the value is to 1, the more completely the filler is dissolved and removed. This represents the penetration rate growth multiple. The permeability of the artificial rock core is 100. The permeability is the permeability of the seamless, perforated artificial core 100. It should be noted that, unless otherwise specified, the artificial core 100 in this application refers to an artificial core 100 with an internal perforated structure prepared using artificial core preparation and testing processes.

[0045] The implementation principle of this embodiment is as follows: For artificial cores 100 containing different fracture-cavity structures, the parameters of vacuuming and ultrasonic vibration treatment involved in dissolving water-soluble fracture-cavity fillers need to be adjusted accordingly. At the same time, the particle size distribution of quartz sand also needs to be adjusted accordingly based on the average permeability and porosity of the formation core. In addition, for artificial cores 100 with porous internal fracture-cavity structures, the reliability of the fracture-cavity structure in the artificial core 100 can be further verified by the permeability and porosity difference detection method.

[0046] Example 4: Reference Figure 15The difference between this embodiment and the previous embodiment is that, in this embodiment, the fracture structure in the prepared artificial core 100 is a combination of any two or more fracture structures in the previous embodiments; specifically, it can be a combination of I-shaped structure, T-shaped structure, cross-shaped structure and spherical cavity; at this time, when preparing the water-soluble fracture filling material, a flexible mold 200 containing I-shaped structure, T-shaped structure, cross-shaped structure and spherical fracture groove 201 should be used respectively. In addition, the parameters of vacuum treatment and ultrasonic vibration treatment involved in the process of dissolving water-soluble fracture filling material need to be adjusted accordingly, and the particle size distribution of quartz sand should be adjusted according to the average permeability and porosity of the formation core. Similarly, when preparing an artificial core 100 containing different types of fracture-cavity structures, a corresponding flexible mold 200 needs to be prepared, and the parameters of vacuuming and ultrasonic vibration treatment involved in dissolving the water-soluble fracture-cavity filler need to be adjusted accordingly. The particle size distribution of the quartz sand also needs to be adjusted according to the average permeability and porosity of the formation core. It should be noted that during the preparation of the core reconstruction 101, after the core mixture is filled into the steel mold 300, different types of water-soluble fracture-cavity fillers need to be inserted into the designated positions of the core mixture according to the location of the fractures in the fracture-cavity slices of the formation core. In addition, in this embodiment, the reliability of the fracture-cavity structure in the artificial core 100 can be detected by light transmission detection, laser cutting detection, and permeability and porosity difference detection.

[0047] The implementation principle of this embodiment is as follows: When preparing artificial core 100 containing different types of fracture-cavity combination structures, the artificial core 100 preparation and testing process proposed in this application requires the preparation of corresponding types of flexible molds; in addition, the parameters of vacuum treatment and ultrasonic vibration treatment involved in the process of dissolving water-soluble fracture-cavity filler need to be adjusted accordingly, and the particle size distribution of quartz sand also needs to be adjusted accordingly based on the average permeability and porosity of the formation core.

[0048] Example 5: Reference Figure 16This application provides an artificial rock core 100, which has internal fractures consistent with the fracture structure of a geological core. These fractures are made by heating and cooling a water-soluble hot-melt material, ultimately dissolving it in water. Specifically, the artificial rock core 100 can be a cylindrical structure. To facilitate permeability and porosity difference testing, the height of the cylindrical structure can be set to twice the diameter of the base circle, specifically a base circle diameter of 25 mm and a cylinder height of 50 mm. For artificial rock cores 100 containing different fracture structures, the particle size distribution of quartz sand can be determined based on the average permeability and porosity of the geological core to prepare the core mixture. The water-soluble hot-melt material can be recrystallized sucrose, specifically rock sugar. The water-soluble fractures prepared from the water-soluble hot-melt material... During the pressure curing process, the water-soluble cavity filler does not melt because the temperature does not reach the melting point of the water-soluble hot-melt material, thus affecting the preparation accuracy of the cavity in the artificial core 100. In addition, when the water-soluble cavity filler dissolves in water, it does not produce substances that affect the contact between the water-soluble cavity filler and water. Moreover, the water is mild, reducing the risk of damaging the overall structure of the artificial core 100 during the dissolution process. This allows the water-soluble cavity filler to fully dissolve in water, further improving the accuracy of the cavity in the prepared artificial core 100.

[0049] The implementation principle of this embodiment is as follows: the water-soluble hot-melt material will not deform due to the high temperature during the pressure curing process of the artificial rock core 100, while ensuring that it can be fully dissolved in water, thereby improving the reliability of the artificial rock core 100.

[0050] The embodiments of this application have been described in detail above with reference to the accompanying drawings. However, this application is not limited to the above embodiments. Within the scope of knowledge possessed by those skilled in the art, various changes can be made without departing from the spirit of this application. Furthermore, unless otherwise specified, the embodiments and features described in the embodiments of this application can be combined with each other.

Claims

1. A process for artificial core preparation and testing, characterized by, The method comprises the following steps: According to the structure of the formation core, the structure of the formation core is sliced to prepare a flexible mold; the flexible mold is used to reproduce the fracture-cave structure in the formation core; Heat the water-soluble hot melt material to a molten state, and pour it into the flexible mold to prepare a water-soluble fracture-cave filler; the water-soluble fracture-cave filler is adapted to the fracture-cave structure of the formation core; Mix quartz sand and a consolidating agent at a set ratio to form a core mixture; The water-soluble fracture-cave filler and the core mixture are subjected to pressure curing treatment to form a core reconstruction body; The core reconstruction body is placed in water to dissolve the water-soluble fracture-cave filler, thereby forming an artificial core consistent with the fracture-cave structure of the formation core; The reliability of the fracture-cave structure of the artificial core is detected.

2. The artificial core preparation and detection process according to claim 1, wherein, The method of obtaining the structure slice of the formation core according to the structure of the formation core and preparing the flexible mold comprises: The fracture-cave slice of the formation core is obtained by a non-destructive testing method; the fracture-cave slice of the formation core is used to reflect the spatial position of the fracture-cave in the formation core; According to the fracture-cave slice of the formation core, a fracture-cave groove consistent with the fracture-cave slice of the formation core is formed in the flexible mold.

3. The process of claim 1, wherein, The method of heating the water-soluble hot melt material to a molten state and pouring it into the flexible mold to prepare a water-soluble fracture-cave filler comprises: A water-soluble hot melt material with a set mass is weighed according to the volume of the fracture-cave of the formation core; The water-soluble hot melt material is placed in a crucible and heated to 120-150°C, so that the water-soluble hot melt material is converted into a composite filling medium in a molten and flowing state; The composite filling medium in the crucible is transferred to the flexible mold by using a flow feeder; after the composite filling medium cools and solidifies into a water-soluble fracture-cave filler, the water-soluble fracture-cave filler is peeled off from the flexible mold.

4. The process of claim 1, wherein, The method of mixing quartz sand and a consolidating agent at a set ratio to form a core mixture comprises: determining the particle size distribution of the quartz sand according to the average permeability and porosity of the formation core, and mixing and stirring the quartz sand and the consolidating agent to uniformly coat the quartz sand with the consolidating agent.

5. The artificial core preparation and detection process of claim 1, wherein, The method of subjecting the water-soluble fracture-cave filler and the core mixture to pressure curing treatment to form a core reconstruction body comprises: The core mixture is filled into a steel mold, and the water-soluble fracture-cave filler is inserted into the core mixture according to the position of the fracture-cave in the fracture-cave slice of the formation core; The steel mold is placed in a pressure device and subjected to pressure treatment at a pressure of 3-10 MPa to cure the water-soluble fracture-cave filler and the core mixture, thereby preparing a core reconstruction body.

6. The artificial core preparation and detection process of claim 1, wherein, The method of placing the core reconstruction body in water to dissolve the water-soluble fracture-cave filler comprises: The core reconstruction body is placed in a container filled with water, subjected to vacuumizing treatment and ultrasonic oscillation treatment, and the water-soluble fracture-cave filler is dissolved to form an artificial core.

7. The artificial core preparation and detection process of claim 6, wherein, The method of placing the core reconstruction body in a container filled with water, subjecting to vacuumizing treatment and ultrasonic oscillation treatment, and dissolving the water-soluble fracture-cave filler to form an artificial core comprises: The ultrasonic oscillation treatment time of the core reconstruction body placed in the container filled with water and subjected to vacuumizing treatment and ultrasonic oscillation treatment is 30-150 minutes.

8. The artificial core preparation and detection process of claim 1, wherein, The method of detecting the reliability of the fracture-cave structure of the artificial core comprises: An artificial core without fracture-cave structure is prepared according to the structure of the formation core; The artificial rock core and the seamless hole structure artificial rock core were placed in a permeability and porosity tester to measure the actual permeability and actual porosity of the artificial rock core and the seamless hole structure artificial rock core. The theoretical pore volume of the artificial rock core is calculated based on the volume, porosity, and volume of the water-soluble cavity filling material of the seamless cavity structure. The theoretical porosity of the artificial rock core is calculated using the theoretical pore volume of the artificial rock core. The ratio of the actual porosity to the theoretical porosity of the artificial rock core is calculated to assess the reliability of the fracture-cavity structure of the artificial rock core.

9. The artificial core preparation and detection process of claim 1, wherein, The reliability of the artificial rock core fracture structure is detected by: detecting the reliability of the artificial rock core fracture structure by means of a light transmission detection method; the light transmission detection method is to place the artificial rock core in a single light source environment, with a single light source on one side of the artificial rock core and an imaging device on the other side; the artificial rock core is illuminated by a single light source and an image is formed on the imaging device to detect the reliability of the artificial rock core fracture structure.

10. The artificial core prepared by the process for preparing and testing an artificial core according to any one of claims 1 to 9, characterized in that, The artificial rock core has a cavity structure that is consistent with that of the geological rock core. The cavity is made by heating and cooling a water-soluble hot-melt material and finally dissolving it in water.

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