Three-dimensional fracture-cavity type oil reservoir acid fracturing flow simulation method and system based on 3D printing

Abstract

The invention provides a three-dimensional fracture-cavity type oil reservoir acid fracturing flow simulation method and system based on 3D printing, and the method comprises the steps: building a three-dimensional rock sample digital model through scanning and reconstruction of a solid rock sample, setting printing process parameters according to the characteristics of the rock sample, and carrying out the layer-by-layer printing and fusion through printing equipment to form a three-dimensional fracture-cavity body test piece; the method comprises the following steps: performing mechanical property test to determine test pieces with mass matching meeting conditions, performing batch printing to obtain a sample set, performing acid fracturing process simulation based on the samples, analyzing and determining fracture-cavity body communication conditions after fracturing, and extracting stress distribution and deformation distribution information to evaluate fracture-cavity type oil reservoir acid fracturing effects under different conditions. According to the method, the fracture-cavity rock mass sample is printed on the basis of set parameters, the problems that in the prior art, sample preparation is high in uncertainty and it is difficult to consider geometric mechanics consistency are solved, acid fracturing simulation is achieved on the basis of the sample, the defect that after-fracturing stress distribution and fracture form characterization are difficult can be overcome, and the method has good application prospects. And accurate and efficient fracture-cavity reservoir acid fracturing simulation is realized.

Description

Technical Field

[0001] The present invention relates to the field of oilfield development and testing technology, and in particular to a 3D printing-based three-dimensional fracture-cavity oil reservoir acid fracturing flow simulation method and system. Background Art

[0002] The methods for studying the macroscopic mechanical properties, failure characteristics and fracture mechanical behavior of complex rock masses containing cracks and caves mainly include three types of methods: on-site in-situ monitoring methods, numerical simulation methods and indoor physical experimental simulation methods. Among them, the indoor physical experimental method is convenient for observing the three-dimensional spatial distribution of artificial cracks, and can intuitively reflect how the expansion of artificial cracks in the rock mass is affected by pre-existing cracks or caves. It can realistically simulate the flow process of oil, gas and water three-phase fluid in the fracture-cavity body and the spatial distribution of residual oil. At the same time, it can also obtain the typical bottom hole pressure history curve during fracturing or production. Therefore, it is one of the important means to study the acid fracturing and development plan optimization of complex fracture-cavity oil and gas reservoirs.

[0003] One of the most critical technologies for laboratory physics experiments is the fabrication and processing of repeatable, indistinguishable, and mass-producible test samples. For a long time, samples for laboratory rock tests have primarily been taken from target reservoir rock. Due to the heterogeneity of natural rock, multiple similar tests are required, with statistical methods employed to mitigate the uncertainty associated with natural samples from the target reservoir. However, existing methods have been unable to adequately address the accuracy challenges of laboratory tests on rock mechanics containing complex structural surfaces.

[0004] 3D printing technology has the advantages of automation, intelligence, and high preparation precision. It can quickly and efficiently produce test samples similar to the target reservoir rock mass. However, existing 3D printing technology has the following two main problems in preparing fracture-cavity media containing caves and cracks:

[0005] (1) The prepared rock samples are difficult to meet the consistency with real fracture-cavity carbonate rocks in both mechanical and chemical aspects.

[0006] Existing 3D printing technologies either only consider the mechanical similarity of prepared rock samples or only consider the geometric similarity of the caves and cracks in the printed specimens. How to preserve the geometric morphology of cracks and caves while ensuring the similarity of the mechanical and chemical characteristics of carbonate rocks, so as to obtain 3D printed specimens suitable for exploring the acidizing and fracturing transformation of fracture-cavity carbonate reservoirs, is one of the difficult problems worthy of attention and solution.

[0007] (2) It is difficult to characterize the stress distribution and crack morphology of the prepared rock samples after dynamic acid fracturing test.

[0008] The greatest advantage of 3D printing technology is its ability to reproducibly prepare specimens using the same printing materials and processes, yielding nearly identical specimens in terms of geometry and mechanics. This avoids the uncertainties inherent in conducting tests using natural rock samples, making it suitable for conducting extensive repeated or comparative tests. However, current 3D printing technology presents significant challenges in facilitating the real-time extraction of stress states in rock masses containing fractures and cavities. Fracture characterization typically relies on directly opening rock samples after fracturing to observe, sketch, and reconstruct hydraulic fractures, natural fractures, and cavities. Therefore, there is a need to develop 3D printing technologies that can easily extract stress distribution and the morphology of fractures and cavities induced by conventional or acid fracturing.

[0009] The information disclosed in the background technology section of the present invention is only intended to deepen the understanding of the general background technology of the present invention, and should not be regarded as an admission or any form of suggestion that the information constitutes the prior art known to those skilled in the art. Summary of the Invention

[0010] To address the above-mentioned issues, the present invention provides a 3D printing-based acid fracturing flow simulation method for fracture-vuggy reservoirs. This solution can effectively overcome the problems of high uncertainty in sample preparation and difficulty in balancing geometric mechanical consistency in the prior art. Furthermore, acid fracturing simulation based on the sample of the present invention can address the difficulties in characterizing post-fracturing stress distribution and fracture morphology, thereby achieving accurate and efficient acid fracturing simulation of fracture-vuggy reservoirs. Preferably, in one embodiment, the method comprises:

[0011] The steps for preparing outcrop rock samples are as follows: collecting fracture-cavity carbonate rock outcrop samples, and cutting and preparing outcrop rock samples with sizes that meet the set standards based on the collected rock samples as typical fracture-cavity rock samples;

[0012] The steps of constructing the digital model of the fracture-cavity body are as follows: by performing 3D scanning and 3D reconstruction on the typical fracture-cavity body rock sample, the corresponding 3D rock sample digital model is established;

[0013] Printing path determination step: layering the three-dimensional rock sample digital model to form multiple printing slices according to the requirements of the printing device, and determining a layer-by-layer printing path that can be recognized by a computer based on the printing slice information;

[0014] Printing parameter configuration steps: According to the characteristics of the current typical fracture-cavity rock sample, set the printing process parameters for different printing slice layers, including printing resolution, density, specimen size, structural material, filling rate and layer thickness parameters;

[0015] Specimen printing steps: using a printing device to print layer by layer based on the printing slice information and printing process parameters, and then fusing each layer to form a three-dimensional fracture-cavity specimen;

[0016] Specimen processing and testing steps: After removing the specimen's support material, polishing and coloring are performed, and the specimen is cured. The specimen is then tested for mechanical properties, and the quality matching of the specimen is determined based on the test results. If the quality matching of the current specimen meets the set conditions, the subsequent sample printing steps are executed; otherwise, the printing parameter configuration steps, specimen printing steps, and specimen processing and testing steps are repeated.

[0017] Sample batch printing step: Based on the current three-dimensional rock sample digital model, printing path and printing process parameters, batch printing is performed to obtain a sample set for fracturing simulation test;

[0018] Acid fracturing simulation steps: Based on the printed sample, the acid fracturing process is simulated under true triaxial load according to the set acid fracturing simulation conditions;

[0019] Simulation information collection and analysis steps: Collect the evolution images of the fracture-vuggy specimens during the acid fracturing process, build a three-dimensional fracture-vuggy geometric distribution model based on them, analyze and determine the connectivity of the fracture-vuggy bodies after fracturing, and extract stress and deformation distribution information based on photoelastic stripes and stress analysis algorithms. Based on the obtained deformation distribution information and fracture-vuggy body connectivity information, evaluate the acid fracturing effect of fracture-vuggy reservoirs under different conditions.

[0020] In one embodiment, in the printing parameter configuration step, setting the structural material includes selecting and setting the printing material ratio of the matrix, cracks and caves, using crack-cavity type carbonate rock grinding powder material and liquid photosensitive resin as the matrix material, using white opaque material Vero White Plus as the filler-containing crack and cave material, using paraffin as the temporary support molding material for unfilled caves, and using grid support material as the support material for preparing unfilled cracks.

[0021] Optionally, in one embodiment, fracture-cavity carbonate rock ground powder material and liquid photosensitive resin are mixed in a volume ratio of 1:5 to prepare the matrix; and grid support material Fullcure 705 is used to prepare unfilled fractures.

[0022] Furthermore, in one embodiment, the specimen processing and testing steps include the following operations:

[0023] Laser irradiation is used to uniformly solidify the printed specimens and form a seamless fusion with the carbonate rock powder material;

[0024] Through heating and temperature-raising treatment, the paraffin wax, the supporting molding material of the cave body, is gradually melted and removed, and finally a three-dimensional rock-like specimen is formed, which includes matrix, filled cracks and caves, and unfilled cracks and caves.

[0025] Specifically, in an optional embodiment, during the specimen processing and testing steps, conventional mechanics and fracture mechanics performance tests are performed on the processed specimens respectively, and the macroscopic mechanical parameters, strain field evolution laws and three-dimensional failure characteristics of the specimens are analyzed to determine whether the requirements are met.

[0026] Preferably, in one embodiment, in the acid fracturing simulation step, multiple single variable factors are set according to the test requirements to realize the acid fracturing simulation test, and the single variable factors include acid injection rate, injection position and fracture-cavity distribution conditions.

[0027] Furthermore, in one embodiment, in the simulation information collection and analysis step, a fast camera is used to capture the evolution image of the fracture-cavity sample during the acid fracturing process, and a corresponding three-dimensional fracture-cavity geometric distribution model is constructed based on machine learning. The corresponding fracture-cavity connectivity information is analyzed and obtained, and the optical properties of the Vera Clear transparent photoelastic matrix material and the stress freezing properties under temperature load are utilized to extract the full-field stress distribution and deformation distribution information through photoelastic stripes and stress analysis algorithms.

[0028] Specifically, in an optional embodiment, the process of evaluating the acid fracturing effect of fracture-cavity reservoirs under different conditions based on the acquired deformation distribution information and fracture-cavity connectivity information includes:

[0029] Based on the deformation distribution information, the aperture distribution information of each fracture is calculated to determine the fracture size information. Then, based on the obtained fracture width, fracture length, and fracture-cavity connectivity information, the acid fracturing effect of fracture-cavity reservoirs under different conditions is evaluated.

[0030] Based on other aspects of the method described in any one or more of the above embodiments, the present invention further provides a storage medium storing program codes that can implement the method described in any one or more of the above embodiments.

[0031] Based on the application aspects of the method described in any one or more of the above embodiments, the present invention also provides a three-dimensional fracture-cavity oil reservoir acid fracturing flow simulation system based on 3D printing, which executes the method described in any one or more of the above embodiments.

[0032] Compared with the closest prior art, the present invention also has the following beneficial effects:

[0033] The present invention provides a three-dimensional fracture-cavity oil reservoir acid fracturing flow simulation method and system based on 3D printing. The method establishes a three-dimensional rock sample digital model by performing three-dimensional solid CT scanning and three-dimensional reconstruction on a fracture-cavity rock sample entity; then the three-dimensional rock sample digital model is layered to form multiple printing slices, a computer printing path is determined, and the three-dimensional rock sample digital model is imported into a printing device. The printing device prints and fuses the three-dimensional fracture-cavity specimen layer by layer based on the printing slice information and printing process parameters; in this way, a specimen with similar geometric and mechanical properties to the fracture-cavity rock sample entity can be accurately obtained; the characteristics of complex fracture-cavity combined rock masses can be reliably characterized to realize required simulation tests, and batch preparation is facilitated, and there is no uncertainty difference between different prepared specimens; the stability and accuracy of the test matrix object are fundamentally guaranteed, and the authenticity of the test data is improved.

[0034] Furthermore, the prepared events are post-printed and processed. After removing the support materials of the specimens, they are polished and painted, and then cured. Based on the mechanical property test results, it is determined whether the consistency between the current specimens and the real rock samples meets the requirements. If not, optimization and adjustment are performed before batch preparation. This avoids waste of preparation materials and redundant operations, and improves the timeliness of specimen preparation while ensuring the quality of the specimens.

[0035] Then, based on the printed sample, the acid fracturing process was simulated under true triaxial load based on the set acid fracturing simulation conditions; the evolution image of the fracture-vuggy sample during the acid fracturing process was collected, and a three-dimensional fracture-vuggy geometric distribution model was constructed based on it. The connectivity of the fracture-vuggy body after fracturing was analyzed and determined, and the stress distribution and deformation distribution information were extracted. The acid fracturing effect of the fracture-vuggy reservoir under different conditions was evaluated based on the obtained deformation distribution information and fracture-vuggy body connectivity information. The 3D-printed fracture-vuggy sample is convenient for truly reflecting the acid fracturing evolution data, and can effectively extract the fracture-vuggy body connectivity, stress distribution information and deformation distribution information of the sample after the acid fracturing test. Based on this, the acid fracturing effect of the sample corresponding to the typical fracture-vuggy rock mass is accurately analyzed, which not only provides effective support for the multiphase seepage law, remaining oil distribution law and acid fracturing transformation effect of fracture-vuggy carbonate reservoirs, but also provides a theoretical basis for better guiding the targeted acid fracturing reservoir transformation of fracture-vuggy carbonate rock salt and efficient oil and gas development, and provides technical and theoretical support for improving the quality and efficiency of oil and gas reservoir development and stabilizing and increasing production.

[0036] Other features and advantages of the present invention will be described in the following description, and in part will become apparent from the description, or will be understood by practicing the present invention. The purposes and other advantages of the present invention can be realized and obtained by the structures particularly pointed out in the description, claims and drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] The accompanying drawings are used to provide a further understanding of the present invention and constitute a part of the specification. Together with the embodiments of the present invention, they are used to explain the present invention and do not constitute a limitation of the present invention. In the accompanying drawings:

[0038] Figure 1 3D printing-based three-dimensional fracture-cavity reservoir acid fracturing flow simulation method provided by one embodiment of the present invention;

[0039] Figure 2 This is a schematic diagram of the printing process of a fracture-cavity sample of a three-dimensional fracture-cavity reservoir acid fracturing flow simulation method based on 3D printing provided by an embodiment of the present invention;

[0040] Figure 3 This is an example diagram of a printing device for a 3D printing-based three-dimensional fracture-cavity reservoir acid fracturing flow simulation method provided in an embodiment of the present invention;

[0041] Figure 4 This is a schematic diagram of the printing effect of an unfilled cave in a three-dimensional fracture-cavity reservoir acid fracturing flow simulation method based on 3D printing provided by one embodiment of the present invention;

[0042] Figure 5 This is a schematic diagram of the printing effect of a fracture-cavity medium sample of the three-dimensional fracture-cavity oil reservoir acid fracturing flow simulation method based on 3D printing provided by an embodiment of the present invention;

[0043] Figure 6 This is an example diagram of oil and gas saturation distribution in an injection-production experiment of a three-dimensional fracture-cavity reservoir acid fracturing flow simulation method based on 3D printing provided by one embodiment of the present invention;

[0044] Figure 7 This is an example of a statistical diagram of the gas injection displacement efficiency of the 3D fracture-cavity reservoir acid fracturing flow simulation method based on 3D printing provided in an embodiment of the present invention;

[0045] Figure 8 It is a structural schematic diagram of a three-dimensional fracture-cavity oil reservoir acid fracturing flow simulation system based on 3D printing provided in another embodiment of the present invention. DETAILED DESCRIPTION

[0046] The following will describe in detail the implementation methods of the present invention in conjunction with the accompanying drawings and embodiments, so that practitioners of the present invention can fully understand how the present invention applies technical means to solve technical problems and achieve the implementation process of technical effects, and can implement the present invention in accordance with the above implementation process. It should be noted that as long as no conflict exists, the various embodiments and various features of each embodiment in the present invention can be combined with each other, and the resulting technical solutions are all within the scope of protection of the present invention.

[0047] Although the flowcharts depict the operations as sequential processes, many of the operations can be performed in parallel, concurrently, or simultaneously. The order of the operations can be rearranged. A process can be terminated when its operations are completed, but can also have additional steps not included in the figures. A process can correspond to a method, function, procedure, subroutine, subprogram, etc.

[0048] Computer devices include user devices and network devices. User devices or clients include, but are not limited to, computers, smartphones, and PDAs (Personal Digital Assistants). Network devices include, but are not limited to, a single network server, a server group consisting of multiple network servers, or a cloud computing-based cloud consisting of a large number of computers or network servers. Computer devices can operate independently to implement the present invention, or they can connect to a network and interact with other computer devices in the network to implement the present invention. The network in which the computer device resides includes, but is not limited to, the Internet, wide area networks, metropolitan area networks, local area networks, and VPN networks.

[0049] The terms used herein are intended only to describe specific embodiments and are not intended to limit exemplary embodiments. Unless the context clearly indicates otherwise, the singular forms "a", "an", "an item" used herein are also intended to include the plural. It should also be understood that the terms "comprise" and / or "include" used herein specify the presence of stated features, integers, steps, operations, units and / or components, and do not preclude the presence or addition of one or more other features, integers, steps, operations, units, components and / or combinations thereof.

[0050] In the field of oilfield development, it is of great significance to study the macroscopic mechanical properties, failure characteristics and fracture mechanics behavior of complex rock masses containing cracks and caves. In existing research, the implementation methods mainly include three types of methods: on-site in-situ monitoring methods, numerical simulation methods and indoor physical experimental simulation methods. Among them, the indoor physical experimental method is convenient for observing the three-dimensional spatial distribution of artificial fractures, and can intuitively reflect how the expansion of artificial fractures in the rock mass is affected by pre-existing cracks or caves. It can realistically simulate the flow process of oil, gas and water three-phase fluid in the fracture-cavity body and the spatial distribution of residual oil. At the same time, it can also obtain the typical bottom hole pressure history curve during fracturing or production. Therefore, it is one of the important means to study the acid fracturing and development plan optimization of complex fracture-cavity oil and gas reservoirs.

[0051] One of the most critical technologies for laboratory physics experiments is the fabrication and processing of repeatable, indistinguishable, and mass-producible test samples. For a long time, samples for laboratory rock tests have primarily been taken from target reservoir rock. Due to the heterogeneity of natural rock, multiple similar tests are required, with statistical methods employed to mitigate the uncertainty associated with natural samples from the target reservoir. However, existing methods have been unable to adequately address the accuracy challenges of laboratory tests on rock mechanics containing complex structural surfaces.

[0052] Subsequently, concrete casting sample processing technology was applied to study the influence of specific structural surfaces on the mechanical behavior of rock mass. This method solved the problem of customized processing of rock mass structural surfaces to a certain extent. However, in terms of how to select suitable casting materials to construct cast samples with highly similar characteristics to the original rock in terms of porosity, permeability, mechanical parameters, fracture parameters, etc., a series of challenges were encountered (including the matching of aggregate and cement, the particle size distribution and roundness of aggregate, the mineral composition and physicochemical properties of particles, etc.), which greatly restricted the research on concrete casting sample processing in rock mechanical tests of different types of oil and gas reservoirs.

[0053] 3D printing technology (or additive manufacturing technology), which has developed rapidly in recent years, boasts advantages such as automation, intelligence, and high production precision. Based primarily on three-dimensional digital models and employing mechanical equipment to form mechanical deposits, it can quickly and efficiently produce test specimens similar to the target reservoir rock mass. Currently, major 3D printing technologies include photolithography, deposition modeling, and selective sintering. Key printing materials include magnet powder, quartz sand, gypsum, photosensitive and thermosetting resins, ceramics, polymethyl methacrylate (PMMA), SR20 acrylic copolymer, carbon fiber, and tough plastics. Materials commonly used for rock-like printing include PMMA, magnet powder, quartz sand, rock powder, gypsum, resin, concrete, and a mixture of various materials.

[0054] For example, Ishutov et al. used plastic materials to print relevant specimens, and through X-ray computer tomography technology, proved that the specimens had good consistency with the internal pore characteristics of sandstone; Jiang Quan and Song Leibo used powdered gypsum as printing material to prefabricate rock specimens containing porous and fractured structures, and preliminarily proved that 3D printed specimens had good consistency in simulating the mechanical properties and failure modes of real rock samples; Jiang et al. used a mixture of polymer PLA and gypsum powder as 3D printing material, and through a series of conventional mechanics and fracture mechanics tests, found that the used mixture material had similar mechanical properties and failure modes to those of real rock samples; Ju Yang et al. used transparent photopolymer material Vero Clear and grid support material Fullcure were used as 3D printing materials to prepare samples, and the geometric and distribution characteristics of the fracture structure of natural coal rock were obtained. The specimens were subjected to tension and compression tests. The test results showed that the overall mechanical properties of the mixed material were close to those of natural fractured coal rock. Li Zhengwei et al. used a mixture of magnet powder, quartz powder, cement and gypsum as 3D printing raw materials to prepare thin-layered rock-like specimens. Through uniaxial compression tests and non-contact strain observations, the test results showed that this method can construct artificial specimens with mechanical properties and failure modes similar to those of real thin-layer rocks. Song et al. used gypsum powder, silica powder and stone 3D printing was performed using fine sand as raw material. The printed specimens have properties similar to those of natural specimens and can be used to simulate sandstone with high porosity and high permeability. Wang et al. used natural carbonate rock powder and epoxy resin to prepare the matrix, used thin silicone rubber to simulate secondary pores, and used polypropylene particles of different diameters to simulate spherical pores, thereby artificially constructing carbonate rock specimens containing matrix, micropores and macropores. Zhou et al. used a concrete pouring method to prefabricate a cubic fracturing specimen with a side length of 300 mm containing cracks and caves, and used true triaxial fracturing equipment to carry out the interaction between hydraulic fractures in the fractures and caves and pre-existing natural fractures and caves.

[0055] Although 3D printing technology has been introduced into rock mechanics experimental research and widely used to prepare homogeneous or layered rock samples and rock samples containing different cracks and pores (filled or unfilled), and has made rapid progress in terms of control accuracy, molding speed, and preparation quality, existing 3D printing technology has the following two main problems in preparing fracture-cavity media containing caves and cracks:

[0056] (1) The prepared rock samples are difficult to meet the consistency with real fracture-cavity carbonate rocks in both mechanical and chemical aspects.

[0057] Existing 3D printing technologies either only consider the mechanical similarity of prepared rock samples or only consider the geometric similarity of the caves and cracks in the printed specimens. How to preserve the geometric morphology of cracks and caves while ensuring the similarity of the mechanical and chemical characteristics of carbonate rocks, so as to obtain 3D printed specimens suitable for exploring the acidizing and fracturing transformation of fracture-cavity carbonate reservoirs, is one of the difficult problems worthy of attention and solution.

[0058] (2) It is difficult to characterize the stress distribution and crack morphology of the prepared rock samples after dynamic acid fracturing test.

[0059] The greatest advantage of 3D printing technology is its ability to reproducibly prepare specimens using the same printing materials and processes, yielding nearly identical specimens in terms of geometry and mechanics. This avoids the uncertainties inherent in conducting tests using natural rock samples, making it suitable for conducting extensive repeated or comparative tests. However, current 3D printing technology presents significant challenges in facilitating the real-time extraction of stress states in rock masses containing fractures and cavities. Fracture characterization typically relies on directly opening rock samples after fracturing to observe, sketch, and reconstruct hydraulic fractures, natural fractures, and cavities. Therefore, there is a need to develop 3D printing technologies that can easily extract stress distribution and the morphology of fractures and cavities induced by conventional or acid fracturing.

[0060] In response to the problem that current 3D printing technology is difficult to obtain synchronous consistency with the mechanical properties and chemical properties of complex media with real fractures and caves, and the technical problem that stress distribution and fracture geometry information after fracturing simulation tests are difficult to extract and analyze, the present invention establishes a three-dimensional fracture-cavity oil reservoir acid fracturing flow simulation method and system based on 3D printing. This method can realize 3D printing of carbonate fracture-cavity medium systems, better restore the spatial geometry information of fractures and caves, and ensure the similarity of mechanical and chemical properties of specimens with real fracture-cavity complex media. At the same time, it is easy to extract information such as stress distribution and fracture morphology after the test, and has high practical value. The embodiment of the present invention realizes reservoir acid fracturing flow simulation research based on printed three-dimensional fracture-cavity carbonate complex media, providing technical support for studying the seepage law of fracture-cavity media, residual oil potential, acidizing fracturing transformation mechanism, and acidizing fracturing scheme design.

[0061] Next, the detailed process of the method according to the embodiment of the present invention is described in detail based on the accompanying drawings. The steps shown in the flowcharts of the accompanying drawings can be executed in a computer system including, for example, a set of computer-executable instructions. Although the logical order of the steps is shown in the flowcharts, in some cases, the steps shown or described can be executed in a different order than here.

[0062] Example 1:

[0063] Figure 1 The flow chart of the 3D printing-based three-dimensional fracture-cavity reservoir acid fracturing flow simulation method provided in the first embodiment of the present invention is shown. Figure 1 It can be seen that the method includes the following steps.

[0064] The steps for preparing outcrop rock samples are as follows: collecting fracture-cavity carbonate rock outcrop samples, and cutting and preparing outcrop rock samples with sizes that meet the set standards based on the collected rock samples as typical fracture-cavity rock samples;

[0065] The steps of constructing the digital model of the fracture-cavity body are as follows: by performing 3D solid CT scanning and 3D reconstruction on the typical fracture-cavity body rock sample, the corresponding 3D rock sample digital model is established;

[0066] Printing path determination step: layering the three-dimensional rock sample digital model to form multiple printing slices according to the requirements of the printing device, and determining the layer-by-layer printing path recognized by the computer based on the printing slice information;

[0067] Printing parameter configuration steps: Set appropriate printing process parameters according to the characteristics of the current typical fracture-cavity rock sample, including printing resolution, density, specimen size, structural material, filling rate and layer thickness parameters of different layers;

[0068] Specimen printing step: importing the three-dimensional rock sample digital model into a printing device, and having the printing device print layer by layer based on the printing slice information and printing process parameters, and then fusing the layers to form a three-dimensional fracture-cavity specimen;

[0069] Specimen processing and testing steps: After removing the specimen's support material, polishing and coloring are performed, and the specimen is cured. The specimen is then tested for mechanical properties, and the quality matching of the specimen is determined based on the test results. If the quality matching of the current specimen meets the set conditions, the subsequent sample printing steps are executed; otherwise, the printing parameter configuration steps, specimen printing steps, and specimen processing and testing steps are repeated.

[0070] Sample batch printing step: Based on the current three-dimensional rock sample digital model, printing path and printing process parameters, batch printing is performed to obtain a sample set for fracturing simulation test;

[0071] Acid fracturing simulation steps: Based on the printed sample, the acid fracturing process is simulated under true triaxial load according to the set acid fracturing simulation conditions;

[0072] Simulation information collection and analysis steps: Collect the evolution images of the fracture-vuggy specimens during the acid fracturing process, build a three-dimensional fracture-vuggy geometric distribution model based on them, analyze and determine the connectivity of the fracture-vuggy bodies after fracturing, and extract stress and deformation distribution information based on photoelastic stripes and stress analysis algorithms. Based on the obtained deformation distribution information and fracture-vuggy body connectivity information, evaluate the acid fracturing effect of fracture-vuggy reservoirs under different conditions.

[0073] The solution of the embodiment of the present invention provides effective guidance for 3D printing of carbonate fracture-cavity media systems and operational guidance for simulating the acid fracturing process based on the 3D printed model. This allows for the preparation of samples with mechanical and chemical properties similar to those of real fracture-cavity carbonate rock media. Furthermore, acid fracturing simulation tests based on these samples facilitate the extraction of post-test stress distribution and fracture-cavity geometry information.

[0074] Figure 2 FIG. 1 shows a flow chart of a 3D printing method for a typical fracture-cavity rock sample in the method according to an embodiment of the present invention. Figure 2 As shown in the figure, this method uses different matrix materials, simulated fracture materials and cave support materials to print fracture-cavity rock samples, which can provide effective technical means for studying the multiphase seepage law, residual oil distribution law and acid fracturing transformation effect of carbonate rock fracture-cavity system, and at the same time better guide the targeted acid fracturing reservoir transformation of fracture-cavity carbonate rock salt and the efficient development of oil and gas.

[0075] In summary, the embodiment of the present invention prepares fracture-cavity rock samples representing the complex porous medium system of fracture-cavity carbonate rocks through a 3D printing method. The 3D printing process of the fracture-cavity rock samples mainly includes the preparation of outcrop original rock samples and the construction of three-dimensional fracture-cavity digital models, setting relevant printing paths according to sample preparation requirements, determining the matrix-crack-cavity printing material ratio, setting detailed printing parameters and printed specimen maintenance operations. Based on this, the consistency of the printed specimens with the field outcrop specimens is confirmed by testing the mechanical and flow properties. If necessary, the material ratio and printing parameters are adjusted until they meet the requirements before batch printing. This can effectively ensure the quality stability of batch printed specimens and avoid waste of time costs and material resources.

[0076] In actual application, in the step of constructing the digital model of the fracture-cavity body, a three-dimensional digital model of the printed sample is established (such as constructing a three-dimensional data model STL file) by performing three-dimensional solid CT scanning and three-dimensional reconstruction on the typical fracture-cavity body rock sample prepared by cutting.

[0077] The three-dimensional digital model is then "sliced" in a layered manner according to the set method to complete the computer's planning of the layer-by-layer printing path; that is, the printing path determination step is executed, and the three-dimensional rock sample digital model is layered according to the requirements of the printing equipment to form multiple printing slices, and the layer-by-layer printing path recognized by the computer is determined based on the printing slice information.

[0078] Furthermore, the printing parameter configuration step is performed to set appropriate printing process parameters according to the characteristics of the current typical fracture-cavity rock sample, including the printing resolution, density, specimen size, structural material, filling rate and layer thickness parameters of different layers.

[0079] In actual application, appropriate printing process parameters (such as printing resolution, density, specimen size, filling rate, layer thickness, etc.) are selected according to the characteristics of the fracture-cavity rock sample, and the three-dimensional digital model is imported into a 3D printing device (such as the Object Connex 500 printing device developed by Stratasys in the United States). The printer reads the "slice" information and prints layer by layer using liquid, powder, or sheet materials, and fuses the corresponding interfaces of each layer in a set manner to construct a three-dimensional solid specimen. Preferably, the corresponding interfaces of each layer can be fused by laser irradiation and curing to construct a three-dimensional solid specimen.

[0080] Preferably, in one embodiment, in the printing parameter configuration step, setting the structural material includes selecting and setting the printing material ratio of the matrix, cracks and caves, using crack-cavity type carbonate rock grinding powder material and liquid photosensitive resin as the matrix material, using white opaque material Vero White Plus as the filler-containing crack and cave material, using paraffin as the temporary support molding material for unfilled caves, and using grid support material as the support material for preparing unfilled cracks.

[0081] Specifically, in an optional embodiment, the matrix is ​​prepared by mixing fracture-cavity type carbonate rock grinding powder material and liquid photosensitive resin in a volume ratio of 1:5; and the grid support material Fullcure 705 is used to prepare the unfilled fractures.

[0082] In the embodiment of the present invention, the fracture-cavity carbonate rock grinding powder material and the liquid photosensitive resin (VeraClear) are used as the matrix materials (mixed in a volume ratio of carbonate rock powder: resin = 1:5), the white opaque material Vero White Plus is used as the filler-containing fracture and cave material, paraffin is used as the temporary support molding material for the unfilled cave body, and the grid support material Fullcure 705 is used to prepare the unfilled fracture; this design can ensure the geometric, mechanical and chemical consistency of the printed specimen with the real fracture-cavity carbonate rock body, while also facilitating the extraction of stress evolution and fracture-cavity body geometric information.

[0083] Next, the specimen printing step is performed. The three-dimensional rock sample digital model is imported into the printing device. The printing device prints layer by layer based on the printing slice information and printing process parameters, and then fuses each layer to form a three-dimensional fracture-cavity specimen. The example diagram of the printing device can be seen in the attached Figure 3 ;

[0084] Further execute the specimen processing and testing steps, remove the supporting material of the specimen, perform polishing and coloring, and cure the specimen, then perform mechanical property testing on the specimen, and determine the quality matching of the specimen based on the test results; if the quality matching of the current specimen meets the set conditions, execute the subsequent sample printing steps; otherwise, re-execute the printing parameter configuration steps, specimen printing steps and specimen processing and testing steps; wherein, the method of curing the specimen can be set according to the actual specimen requirements, for example, the formed three-dimensional fracture and cavity specimen is left to stand for a set time at room temperature to complete the curing treatment; optionally, the set time is usually set to not less than 2 hours.

[0085] The specimen handling and testing steps include the following operations:

[0086] Laser irradiation is used to uniformly solidify the printed specimens and form a seamless fusion with the carbonate rock powder material;

[0087] By heating and raising the temperature, the paraffin wax, the supporting molding material of the cave body, is gradually melted and removed. After the paraffin wax melts, it automatically flows out by gravity, and finally forms a three-dimensional rock specimen containing matrix, filled cracks and caves, and unfilled cracks and caves. An example of a 3D printed specimen without filled caves is shown in the figure. Figure 4 As shown in the figure, the example of 3D printed specimen of the whole complex fracture and cavity body is as follows Figure 5 shown.

[0088] During the specimen processing and testing steps, a three-dimensional rock-like specimen consisting of a matrix, filled fractures and caves, and unfilled fractures and caves is ultimately formed. Conventional mechanics and fracture mechanics tests are then performed on the processed specimens, analyzing their macroscopic mechanical parameters, strain field evolution, and three-dimensional failure characteristics. Mechanical and flow property tests confirm the consistency of the printed specimens with typical fracture-cavity rock samples prepared from field outcrop rock samples. If the consistency between the current specimen and the typical fracture-cavity rock sample does not meet the set requirements, the printing parameter configuration steps, specimen printing steps, and specimen processing and testing steps are re-executed, adjusting the material ratio and printing parameters until they meet the requirements before batch printing. This effectively ensures the quality stability of batch-printed specimens and avoids redundant operations and waste of resources.

[0089] After determining that the consistency between the current specimen and the typical fracture-cavity rock sample does not meet the set requirements, the sample batch printing step is executed. Based on the current three-dimensional rock sample digital model, printing path and printing process parameters, batch printing is performed to obtain a sample set for fracturing simulation test.

[0090] Based on this, the acid fracturing simulation step is executed, and the acid fracturing process simulation is carried out under true triaxial load based on the printed sample and the set acid fracturing simulation conditions.

[0091] Preferably, in one embodiment, in the acid fracturing simulation step, multiple single variable factors are set according to the test requirements to realize the acid fracturing simulation test, and the single variable factors include acid injection rate, injection position and fracture-cavity distribution conditions.

[0092] In practical applications, the acid fracturing effect of fracture-cavity reservoirs is primarily determined by the depth of the etched fractures, the self-supporting aperture of the etched fractures, and the degree of connectivity of the etched fractures with discrete cave bodies. Therefore, the present invention provides an acid fracturing simulation test process for extracting fracture spatial morphology, dynamic fracture width distribution, and rock mass stress using cave body specimens based on 3D printing technology. After obtaining a 3D-printed specimen with a certain fracture-cavity distribution that is geometrically, dynamically, and mechanically similar to a typical fracture-cavity rock sample, the acid fracturing process is simulated based on the specimen under true triaxial loading at different acid injection rates, injection locations, and fracture-cavity distribution conditions.

[0093] The fracture-cavity distribution condition information includes the size and connectivity of caves and cracks, which is set before the printing operation. In actual operation, the fracture-cavity body is printed according to the pre-set fracture-cavity distribution information before the acid fracturing test is carried out.

[0094] Next, the simulation information collection and analysis steps are performed to collect evolution images of the fracture-vuggy specimens during the acid fracturing process. Based on these images, a three-dimensional fracture-vuggy geometric distribution model is constructed. The connectivity of the fracture-vuggy bodies after fracturing is analyzed and determined. The stress distribution and deformation distribution information are extracted based on the photoelastic stripes and stress analysis algorithm. Based on the obtained deformation distribution information and fracture-vuggy body connectivity information, the acid fracturing effect of fracture-vuggy reservoirs under different conditions is evaluated.

[0095] In a preferred embodiment, in the simulation information collection and analysis step, a fast camera is used to collect images of the fracture-cavity sample evolution during the acid fracturing process, and a corresponding three-dimensional fracture-cavity geometric distribution model is constructed based on machine learning. The corresponding fracture-cavity connectivity information is analyzed and obtained, and the optical properties of the Vera Clear transparent photoelastic matrix material and the stress freezing properties under temperature load are utilized to extract the full-field stress distribution and deformation distribution information through photoelastic stripes and stress analysis algorithms.

[0096] Furthermore, in one embodiment, the process of evaluating the acid fracturing effect of fracture-cavity reservoirs under different conditions based on the acquired deformation distribution information and fracture-cavity connectivity information includes:

[0097] Based on the deformation distribution information, the aperture distribution information of each fracture is calculated to determine the fracture size information. Then, based on the obtained fracture width, fracture size, and fracture-cavity connectivity information, the acid fracturing effect of fracture-cavity reservoirs under different conditions is evaluated.

[0098] The embodiment of the present invention designs a 3D printing method for complex fracture-cavity medium samples based on the mineral composition, three-dimensional fracture-cavity structure and mechanical properties of carbonate rock fracture-cavity media, which solves the problems of strong randomness in the distribution of fractures and cavities in fracture-cavity rock media and difficulty in specimen preparation. The test results are convenient for reflecting the real fluid flow and acid corrosion crack expansion law, forming a systematic stress distribution and real-time extraction technology for the geometric morphology of expanded fractures and cavities, which can be used to guide the acid fracturing transformation of fracture-cavity carbonate rock salt reservoirs and the potential development of remaining oil in fracture-cavity reservoirs. On the other hand, by simply adjusting the material ratio according to the properties of the carbonate rock to reflect the corresponding rock properties, it can be applied to the printing and acid fracturing parameter analysis of different types of carbonate rock fracture-cavity medium samples in different regions. It is highly practical and easy to be widely applied and promoted.

[0099] The present invention is further described below with reference to examples of implementation. The scope of the present invention is not limited by the examples, but is set forth in the claims.

[0100] Using this method, a typical well-connected section of a fracture-vuggy reservoir (i.e., the S67 fracture-vuggy unit TK625-TK666-TK602-TK644CH in the southern Tahe Block 6 of the Tahe Oilfield) was selected for fracture-vuggy structural characterization. A 3D-printed digital model was constructed based on similarity criteria. A physical model of the well group was then prepared using an Object Connex 500 3D printer. Using a "high-injection, low-production" strategy, gas injection flooding experiments were conducted based on the printed well group physical model and the results of acid fracturing flow simulation analysis.

[0101] When the gas injection rate LCN is -6, -5, and -3.56, the oil and gas saturation distribution diagrams at gas injection breakthrough and injection-production balance are as follows: Figure 6 As shown in the figure (where the transparent portion represents the oil phase and the green portion represents the gas phase), the swept volume efficiency increases by nearly 20% with increasing injection rate. Increasing the injection rate improves oil and gas recovery efficiency in two ways. First, rapid injection avoids the formation of localized dominant channels to a certain extent, facilitating the formation of a more dispersed diversion system, thereby increasing the injected gas swept volume. Second, rapid injection generates local turbulence, which helps maximize the potential of remaining oil in localized dead zones, thereby improving ultimate recovery.

[0102] Figure 7Comparisons of oil displacement sweep efficiency at gas injection breakthrough and when injection-production equilibrium is reached are presented. The results demonstrate that the method of the present invention can be used to print a scaled-down physical model that closely resembles the actual fracture-cavity system. By setting different injection and production rates and wellbore sizes based on similarity criteria, it can be used to simulate the volume of oil displacement swept by gas injection, the distribution of residual oil, and the corresponding recovery rate when using different injection and production schemes under different injection rates. Therefore, the present invention can provide an efficient and reliable research method for designing and optimizing injection and production schemes, exploring the distribution of residual oil, and improving oil and gas recovery rates. By optimizing injection and production schemes, oil and gas recovery rates can be increased by approximately 20%, resulting in significant economic benefits.

[0103] For simplicity of description, the aforementioned method embodiments are described as a series of actions. However, those skilled in the art should be aware that the present invention is not limited by the order of the actions described, as certain steps can be performed in other orders or simultaneously according to the present invention. Furthermore, those skilled in the art should also be aware that the embodiments described in this specification are preferred embodiments, and the actions and modules involved are not necessarily required for the present invention.

[0104] It should be pointed out that in other embodiments of the present invention, the method can also obtain a new three-dimensional fracture-cavity oil reservoir acid fracturing flow simulation method based on 3D printing by combining one or several of the above embodiments, so as to realize efficient and accurate fracturing simulation research on fracture-cavity oil reservoirs.

[0105] It should be noted that, based on the method in any one or more of the above-mentioned embodiments of the present invention, the present invention also provides a storage medium, which stores program code that can implement the method described in any one or more of the above-mentioned embodiments. When the code is executed by the operating system, it can implement the three-dimensional fracture-cavity oil reservoir acid fracturing flow simulation method based on 3D printing as described above.

[0106] Example 2:

[0107] The methods disclosed in the above embodiments of the present invention are described in detail. The methods of the present invention can be implemented using various devices or systems. Therefore, based on other aspects of the methods described in any one or more of the above embodiments, the present invention further provides a 3D-printed three-dimensional fracture-cavity reservoir acid fracturing flow simulation system. This system is used to implement the 3D-printed three-dimensional fracture-cavity reservoir acid fracturing flow simulation method described in any one or more of the above embodiments. Specific embodiments are provided below for detailed description.

[0108] Specifically, Figure 8 FIG. 3 shows a schematic structural diagram of a three-dimensional fracture-cavity oil reservoir acid fracturing flow simulation system based on 3D printing provided in an embodiment of the present invention. Figure 8 As shown, the system includes:

[0109] An outcrop rock sample preparation module is configured to collect fracture-cavity carbonate rock outcrop samples, and cut and prepare outcrop rock samples with sizes that meet set standards based on the collected rock samples as typical fracture-cavity rock samples;

[0110] A fracture-cavity body digital model building module is configured to build a corresponding three-dimensional rock sample digital model by performing three-dimensional scanning and three-dimensional reconstruction on a typical fracture-cavity body rock sample;

[0111] a printing path determination module configured to layer the three-dimensional rock sample digital model to form a plurality of printing slices according to the requirements of the printing device, and determine a computer-recognizable layer-by-layer printing path based on the printing slice information;

[0112] The printing parameter configuration module is configured to set the printing process parameters for different printed slice layers according to the characteristics of the current typical fracture-cavity rock sample, including printing resolution, density, specimen size, structural material, filling rate and layer thickness parameters;

[0113] A specimen printing module is configured to use a printing device to print layer by layer based on printing slice information and printing process parameters, and then fuse the layers to form a three-dimensional fracture-cavity specimen;

[0114] The specimen processing and testing module is configured to remove the supporting material of the specimen, perform polishing and coloring, and cure the specimen, and then perform mechanical property testing on the specimen, and determine the quality matching of the specimen based on the test results; if the quality matching of the current specimen meets the set conditions, the subsequent sample printing module is started to operate; otherwise, the printing parameter configuration module, the specimen printing module, and the specimen processing and testing module are restarted to operate;

[0115] A sample batch printing module is configured to perform batch printing based on the current three-dimensional rock sample digital model, printing path, and printing process parameters to obtain a sample set for conducting a fracturing simulation test;

[0116] Acid fracturing simulation module, which is configured to simulate the acid fracturing process under true triaxial loading based on the printed specimen and the set acid fracturing simulation conditions;

[0117] The simulation information acquisition and analysis module is configured to collect images of the evolution of fracture-vuggy specimens during the acid fracturing process, build a three-dimensional fracture-vuggy geometric distribution model based on the images, analyze and determine the connectivity of the fracture-vuggy bodies after fracturing, and extract stress and deformation distribution information based on photoelastic stripes and stress analysis algorithms. Based on the acquired deformation distribution information and fracture-vuggy body connectivity information, the acid fracturing effect of fracture-vuggy reservoirs under different conditions is evaluated.

[0118] In one embodiment, the printing parameter configuration module is used to set the structural materials, including selecting and setting the printing material ratio of the matrix, cracks and caves, using crack-cavity type carbonate rock grinding powder material and liquid photosensitive resin as the matrix material, using white opaque material Vero White Plus as the filler-containing crack and cave material, using paraffin as the temporary support molding material for unfilled caves, and using grid support material as the support material for preparing unfilled cracks.

[0119] Optionally, in one embodiment, the printing parameter configuration module mixes fracture-cavity carbonate rock grinding powder material and liquid photosensitive resin in a volume ratio of 1:5 to prepare a matrix; and uses grid support material Fullcure 705 to prepare unfilled fractures.

[0120] Furthermore, in one embodiment, the specimen processing and testing module is configured to perform the following operations:

[0121] Laser irradiation is used to uniformly solidify the printed specimens and form a seamless fusion with the carbonate rock powder material;

[0122] Through heating and temperature-raising treatment, the paraffin wax, the supporting molding material of the cave body, is gradually melted and removed, and finally a three-dimensional rock-like specimen is formed, which includes matrix, filled cracks and caves, and unfilled cracks and caves.

[0123] Specifically, in an optional embodiment, the specimen processing and testing module performs conventional mechanics and fracture mechanics performance tests on the treated specimens, analyzes the macroscopic mechanical parameters, strain field evolution laws and three-dimensional failure characteristics of the specimens, and determines whether the requirements are met.

[0124] Preferably, in one embodiment, the acid fracturing simulation module is configured to set multiple single variable factors according to test requirements to implement the acid fracturing simulation test, and the single variable factors include acid injection rate, injection position and fracture-cavity distribution conditions.

[0125] Furthermore, in one embodiment, the simulation information acquisition and analysis module uses a fast camera to capture the evolution images of the fracture-cavity specimen during the acid fracturing process, and constructs a corresponding three-dimensional fracture-cavity geometric distribution model based on machine learning. The corresponding fracture-cavity connectivity information is analyzed and obtained. The optical properties of the Vera Clear transparent photoelastic matrix material and the stress freezing properties under temperature load are utilized to extract the full-field stress distribution and deformation distribution information through photoelastic stripes and stress analysis algorithms.

[0126] Specifically, in an optional embodiment, the process of the simulation information acquisition and analysis module evaluating the acid fracturing effect of fracture-cavity reservoirs under different conditions based on the acquired deformation distribution information and fracture-cavity connectivity information includes:

[0127] Based on the deformation distribution information, the aperture distribution information of each fracture is calculated to determine the fracture size information. Then, based on the obtained fracture width, fracture length, and fracture-cavity connectivity information, the acid fracturing effect of fracture-cavity reservoirs under different conditions is evaluated.

[0128] In the three-dimensional fracture-cavity oil reservoir acid fracturing flow simulation system based on 3D printing provided by the embodiment of the present invention, each module or unit structure can operate independently or in combination according to the actual printing configuration requirements and simulation test data processing requirements to achieve corresponding technical effects.

[0129] It should be understood that the embodiments disclosed herein are not limited to the specific structures, processing steps, or materials disclosed herein, but should extend to equivalent substitutions of these features understood by those skilled in the relevant art. It should also be understood that the terminology used herein is for the purpose of describing specific embodiments only and is not intended to be limiting.

[0130] The phrase "one embodiment" mentioned in the specification means that a particular feature, structure, or characteristic described in conjunction with the embodiment is included in at least one embodiment of the present invention. Therefore, the phrase "one embodiment" appearing in various places throughout the specification does not necessarily refer to the same embodiment.

[0131] Although the embodiments disclosed herein are as described above, the contents described herein are merely embodiments for facilitating understanding of the present invention and are not intended to limit the present invention. Any person skilled in the art may make any modifications and variations in the form and details of the embodiments without departing from the spirit and scope of the present invention. However, the scope of patent protection of the present invention shall remain subject to the scope defined by the appended claims.

Claims

1. A 3D printing-based acid fracturing flow simulation method for a three-dimensional fracture-cavity reservoir, characterized in that: The method comprises: The steps for preparing outcrop rock samples are as follows: collecting fracture-cavity carbonate rock outcrop samples, and cutting and preparing outcrop rock samples with sizes that meet the set standards based on the collected rock samples as typical fracture-cavity rock samples; The steps of constructing the digital model of the fracture-cavity body are as follows: by performing 3D scanning and 3D reconstruction on the typical fracture-cavity body rock sample, the corresponding 3D rock sample digital model is established; Printing path determination step: layering the three-dimensional rock sample digital model to form multiple printing slices according to the requirements of the printing device, and determining a layer-by-layer printing path that can be recognized by a computer based on the printing slice information; Printing parameter configuration steps: According to the characteristics of the current typical fracture-cavity rock sample, set the printing process parameters for different printing slice layers, including printing resolution, density, specimen size, structural material, filling rate and layer thickness parameters; Specimen printing steps: using a printing device to print layer by layer based on the printing slice information and printing process parameters, and then fusing each layer to form a three-dimensional fracture-cavity specimen; Specimen processing and testing steps: After removing the specimen's support material, polishing and coloring are performed, and the specimen is cured. The specimen is then tested for mechanical properties, and the quality matching of the specimen is determined based on the test results. If the quality matching of the current specimen meets the set conditions, the subsequent sample printing steps are executed; otherwise, the printing parameter configuration steps, specimen printing steps, and specimen processing and testing steps are repeated. Sample batch printing step: Based on the current three-dimensional rock sample digital model, printing path and printing process parameters, batch printing is performed to obtain a sample set for fracturing simulation test; Acid fracturing simulation steps: Based on the printed sample, the acid fracturing process is simulated under true triaxial load according to the set acid fracturing simulation conditions; Simulation information collection and analysis steps: Collect the evolution images of the fracture-vuggy specimens during the acid fracturing process, build a three-dimensional fracture-vuggy geometric distribution model based on them, analyze and determine the connectivity of the fracture-vuggy bodies after fracturing, and extract stress and deformation distribution information based on photoelastic stripes and stress analysis algorithms. Based on the obtained deformation distribution information and fracture-vuggy body connectivity information, evaluate the acid fracturing effect of fracture-vuggy reservoirs under different conditions.

2. The method according to claim 1, characterized in that In the printing parameter configuration step, setting the structural material includes selecting and setting the printing material ratio of the matrix, cracks and caves. The fracture-cavity type carbonate rock grinding powder material and liquid photosensitive resin are used as the matrix material, the white opaque material Vero White Plus is used as the material for cracks and caves containing fillers, paraffin is used as the temporary support molding material for unfilled caves, and mesh support material is used as the support material for preparing unfilled cracks.

3. The method according to claim 1, characterized in that The matrix was prepared by mixing fracture-cavity carbonate rock powder material and liquid photosensitive resin in a volume ratio of 1:5; the grid support material Fullcure 705 was used to prepare unfilled fractures.

4. The method according to claim 1, wherein The specimen handling and testing steps include the following operations: Laser irradiation is used to uniformly solidify the printed specimens and form a seamless fusion with the carbonate rock powder material; Through heating and temperature-raising treatment, the paraffin wax, the supporting molding material of the cave body, is gradually melted and removed, and finally a three-dimensional rock-like specimen is formed, which includes matrix, filled cracks and caves, and unfilled cracks and caves.

5. The method according to claim 1, wherein During the specimen processing and testing steps, conventional mechanics and fracture mechanics performance tests are performed on the treated specimens respectively, and the macroscopic mechanical parameters, strain field evolution law and three-dimensional failure characteristics of the specimens are analyzed to determine whether they meet the requirements.

6. The method according to claim 1, characterized in that In the acid fracturing simulation step, multiple single variable factors are set according to the test requirements to realize the acid fracturing simulation test. The single variable factors include acid injection rate, injection position and fracture-cavity distribution conditions.

7. The method according to claim 1, characterized in that During the simulation information collection and analysis steps, a fast camera was used to capture images of the fracture-cavity specimen evolution during the acid fracturing process. A corresponding three-dimensional fracture-cavity geometric distribution model was constructed based on machine learning. The corresponding fracture-cavity connectivity information was analyzed and obtained. Utilizing the optical properties of the Vera Clear transparent photoelastic matrix material and the stress freezing properties under temperature load, the full-field stress and deformation distribution information was extracted using photoelastic stripes and stress analysis algorithms.

8. The method according to claim 1, characterized in that The process of evaluating the acid fracturing effect of fracture-cavity reservoirs under different conditions based on the acquired deformation distribution information and fracture-cavity connectivity information includes: Based on the deformation distribution information, the aperture distribution information of each fracture is calculated to determine the fracture size information. Then, based on the obtained fracture width, fracture length, and fracture-cavity connectivity information, the acid fracturing effect of fracture-cavity reservoirs under different conditions is evaluated.

9. A storage medium, characterized in that: The storage medium stores program code that can implement the method according to any one of claims 1 to 8.

10. A 3D printing-based three-dimensional fracture-cavity reservoir acid fracturing flow simulation system, characterized in that: The system executes the method according to any one of claims 1 to 8.

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