3D printing carbonate reservoir physical model, preparation method thereof and acidification test system

Abstract

The invention discloses a 3D printing carbonate reservoir physical model, a preparation method thereof and an acidification test system. The model is formed by taking CaO powder as a main body and doping 5-10wt% of a mixture of quartz powder and clay powder, 8wt% of fly ash and 3wt% of a material of resin in a 3D printing manner, the model is cut layer by layer by a mechanical arm according to preset parameters in the forming process to form cracks with target width and orientation, and a karst cave is formed in a hollow printing manner, so that a crack-karst cave configuration is integrally formed in a sample body. The acidification test system comprises a simulation shaft, an acid injection pressure sensor arranged on the simulation shaft, loading devices in the horizontal direction and the vertical direction, an acid injection pipeline, a pump liquid bin, an acid storage tank, a water storage tank and a pump liquid control panel. According to the invention, fine control and monitoring of the acidification test process of the fractured rock mass can be guaranteed, and important test and theoretical guidance can be provided for on-site reservoir acidification construction.

Description

Technical Field

[0001] This invention belongs to the field of reservoir rock mechanics, specifically relating to a 3D-printed physical model of a carbonate reservoir and its preparation method, as well as a corresponding acidification test system. Background Technology

[0002] Reservoir acidizing is a common technique used to modify carbonate reservoirs and enhance their oil, gas, and geothermal resource production. The principle behind this process is based on the reaction of acid with the rock, creating non-uniform etching on the fracture walls to obtain high-conductivity channels. Furthermore, under high-pressure fluid action, hydraulic fractures are created and connect with discontinuous media (fractures, caves, etc.) near the wellbore, forming a fracture network that improves reservoir resource extraction efficiency. Different acidizing parameters not only determine the etching characteristics and conductivity of the fracture surface but also significantly control the communication patterns between hydraulic fractures and natural fractures and caves, influencing the formation mode of the fracture network. Therefore, in-depth analysis of the acidizing mechanism within carbonate fractures and the interaction behavior between fractures is helpful in improving the extraction efficiency of carbonate reservoir resources.

[0003] However, due to the difficulty in obtaining deep samples and the complexity of discontinuous structures, existing experimental studies suffer from insufficient reproducibility and limited quantitative evaluation. The lack of sample preparation techniques that can embed cracks / cavities within the sample and precisely control their size and spatial location makes it difficult to conduct in-situ and accurate monitoring of the temporal evolution of seepage and pore pressure within the rock mass under acidification, thus hindering the quantitative characterization of conductivity evolution and the connectivity of discontinuous media. Summary of the Invention

[0004] (a) Technical problems to be solved One of the technical problems this invention aims to solve is that existing physical simulation tests of acidizing in carbonate reservoirs struggle to simultaneously replicate the multi-mineral assemblages, heterogeneous weak interlayer structures, and natural fracture / cavity geometries of in-situ reservoirs. This results in insufficient representativeness and poor repeatability of the experimental models, significantly limiting the quantitative evaluation of acidizing connectivity behavior and stimulation effects. Another problem this invention addresses is that existing carbonate reservoir tests cannot embed fractures / cavities within the sample and precisely control their size and spatial location. Furthermore, they struggle to accurately monitor the temporal evolution of seepage and pore pressure within the rock mass under acidizing conditions in situ. (II) Technical Solution To solve the above-mentioned technical problems, the first aspect of the present invention is to provide a 3D printed physical model of a carbonate reservoir, which is formed by 3D printing of the following materials: a mixture of CaO powder, quartz powder and clay powder, fly ash and resin, wherein the mixture of quartz powder and clay powder accounts for 5 wt% to 10 wt%, fly ash accounts for 8 wt%, and resin accounts for 3 wt%.

[0005] According to a preferred embodiment of the present invention, the physical model includes cracks and / or caves inside.

[0006] According to a preferred embodiment of the present invention, when the carbonate reservoir includes a cave structure, each cave or cave group is provided with at least one desiccation channel communicating with the outer surface of the physical model.

[0007] According to a preferred embodiment of the present invention, the diameter of the powder removal channel is 0.5 mm to 2 mm.

[0008] According to a preferred embodiment of the present invention, the physical model further includes a sealing element for sealing the powder removal channel.

[0009] According to a preferred embodiment of the present invention, the physical model is divided into at least two layers along the thickness direction, and the porosity and compressive strength of each layer are different from each other.

[0010] The second aspect of this invention proposes a method for preparing a 3D-printed physical model of a carbonate reservoir, comprising the following steps: using CaO powder as the main component, incorporating a mixture of quartz powder and clay powder, fly ash, and resin to form a 3D printing material, wherein the mixture of quartz powder and clay powder accounts for 5 wt% to 10 wt%, fly ash accounts for 8 wt%, and resin accounts for 3 wt%; using a powder-based 3D printing device to print the physical model of the carbonate reservoir, during the forming process, a robotic arm cuts layer by layer according to preset parameters to form cracks of target width and orientation; within the cavity envelope, a powder self-supporting cavity cavity printing strategy is used to form cavities, so that the crack-cavity configuration is integrally formed inside the sample.

[0011] According to a preferred embodiment of the present invention, the powder is NaCl powder, and the self-supporting cavity printing strategy using powder includes: selectively spraying a binder in the corresponding area of ​​the cavity wall according to the curved surface trajectory of the cavity boundary to form a closed shell, so that the uncured NaCl powder serves as a temporary support material during the printing process.

[0012] According to a preferred embodiment of the present invention, the method further includes: embedding a pressure sensor and a miniature acoustic emission sensor at a specified location inside the physical model.

[0013] According to a preferred embodiment of the present invention, when the carbonate rock reservoir includes a cave structure, a powder removal channel connected to the inner cavity of the cave is simultaneously formed during the printing process, so that the powder filling the cave can establish a communication channel with the external environment, so that the NaCl powder inside the cave can dissolve after water is passed through it.

[0014] A third aspect of the present invention also proposes an acidizing test system for a 3D-printed physical model of a carbonate reservoir, comprising: a simulated wellbore disposed on the physical model; an acid injection pressure sensor disposed on the simulated wellbore; a horizontal loading device disposed on the side of the physical model and a vertical loading device disposed above the physical model; an acid injection pipeline, a pump fluid chamber, an acid storage tank, a water storage tank, and a pump fluid control panel.

[0015] According to a preferred embodiment of the present invention, the acid storage tank and the water storage tank are disposed inside the pump liquid chamber, and the pump liquid control panel is disposed outside the pump liquid chamber; the pump liquid control panel is used to control the switch and power of the heating device inside the pump liquid chamber, as well as the switch and power of the pump inside the acid storage tank and the water storage tank, so as to control the mixing ratio of acid and water input to the acidification test system and their temperature. (III) Beneficial Effects Compared with the prior art, the beneficial effects of the present invention are: (1) The 3D printed carbonate reservoir physical model and its preparation method proposed in this invention can achieve a printed model with similar chemical composition to real carbonate rocks. At the same time, it can accurately prefabricate fractures and caves inside the printed model. The size, orientation and shape of these discontinuous structures can be precisely adjusted, which lays an important foundation for repeatable tests of the acidization process of fractured rock masses.

[0016] (2) The 3D printed carbonate reservoir physical model true triaxial acidizing test system proposed in this invention can integrate monitoring elements such as permeability and acoustic emission at predetermined positions of the model and link them with pipeline-side flow meters to monitor the changes in pressure and flow rate during the acidizing process in real time, as well as monitor the interaction behavior between fractures and caverns.

[0017] (3) This invention can ensure the precise control and monitoring of the acidizing test process of fractured rock mass, and can provide important experimental and theoretical guidance for on-site reservoir acidizing construction. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the structure of the 3D-printed physical model of a carbonate reservoir with a discontinuous structure according to the present invention.

[0019] Figure 2 This is a schematic diagram of the maintenance chamber for the 3D-printed physical model of a carbonate reservoir with a discontinuous structure according to the present invention.

[0020] Figure 3 This is a schematic diagram of the high-pressure acid injection true triaxial acidification test system of the present invention.

[0021] Figure 4 This is a flowchart illustrating the 3D printing preparation and acidification test process of the physical model of the carbonate reservoir according to the present invention.

[0022] Figure 5 This is a schematic diagram of a pre-fabricated hydraulic fracture 3D-printed carbonate reservoir physical model according to the first embodiment of the present invention.

[0023] Figure 6 This is a schematic diagram of a 3D-printed physical model of a carbonate reservoir containing non-connected fractures and caverns, according to the second embodiment of the present invention. Detailed Implementation

[0024] To address the aforementioned technical problems, the first aspect of this invention proposes a 3D-printed physical model of a carbonate reservoir and its preparation method. The physical model of this invention is formed by 3D printing from the following materials: a mixture of CaO powder as the main component, incorporating 8 wt% fly ash and 3 wt% resin, and quartz powder and clay powder, comprising 5 wt% to 10 wt%. The physical model includes fractures and / or caves formed by 3D printing. The 3D-printed physical model of the carbonate reservoir can achieve a chemical composition similar to that of real carbonate rocks.

[0025] The present invention discloses a method for preparing a 3D-printed physical model of a carbonate reservoir. The model uses CaO powder as the main component, mixed with a mixture of 8 wt% fly ash, 3 wt% resin, quartz powder, and clay powder (5 wt%–10 wt%) to form a 3D printing material. A powder-based 3D printing device is used to print the physical model of the carbonate reservoir. During the forming process, a robotic arm cuts layer by layer according to preset parameters to form cracks of target width and orientation. Hollow-printing is used to form cavities, integrating the crack-cavity configuration within the sample. Therefore, this invention can accurately prefabricate cracks and cavities within the printed model. The size, orientation, and shape of these discontinuous structures are precisely adjustable, laying an important foundation for repeatable testing of the acidizing process in fractured rock masses.

[0026] Preferably, a pressure sensor and a miniature acoustic emission sensor are embedded at a designated location within the physical model.

[0027] Another aspect of this invention proposes an acidizing test system for a 3D-printed physical model of a carbonate reservoir. The system includes a simulated wellbore mounted on the physical model, an acid injection pressure sensor mounted on the simulated wellbore, a horizontal loading device mounted on the side of the physical model, and a vertical loading device mounted above the physical model. It also includes an acid injection pipeline, a pump fluid chamber, an acid storage tank, a water storage tank, and a pump fluid control panel. The acid storage tank and water storage tank are located inside the pump fluid chamber, and the pump fluid control panel is located outside the pump fluid chamber. The pump fluid control panel controls the on / off switch and power of the heating device inside the pump fluid chamber, as well as the on / off switch and power of the pumps inside the acid storage tank and water storage tank, thereby controlling the mixing ratio and temperature of the acid and water input to the acidizing test system. This acidizing test system is a true triaxial acidizing test system for a 3D-printed physical model of a carbonate reservoir. It can integrate monitoring elements such as permeability and acoustic emission at predetermined locations on the physical model and link them with a flow meter on the pipeline side to monitor pressure and flow rate changes during the acidizing process in real time, as well as the interaction behavior between fractures and caverns.

[0028] To make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be further described in detail below with reference to specific embodiments and accompanying drawings.

[0029] Figure 1 This is a schematic diagram of the physical model of a 3D-printed carbonate reservoir with a discontinuous structure, as per the present invention. Figure 1 As shown, the physical model 1 of the present invention includes 3D-printed cracks 2 and 3D-printed caverns 3 inside. Furthermore, a pressure sensor 4 and a miniature acoustic emission sensor 5 are also arranged inside the model.

[0030] Figure 2 This is a schematic diagram of the model curing chamber for 3D printing a physical model of a carbonate reservoir with discontinuous structures, provided as an embodiment of the present invention. Figure 2 As shown, the curing chamber 6 is a carbon dioxide curing chamber, and its internal space is connected to an external carbon dioxide cylinder 8 via pipelines. Furthermore, a control panel 7 is located on the outer surface of the curing chamber 6, used to adjust parameters such as temperature and carbon dioxide concentration within the chamber.

[0031] Figure 3 This is a schematic diagram of a high-pressure acid injection true triaxial acidification test system provided in an embodiment of the present invention. Figure 3As shown, this experimental system is used to conduct acidizing simulation tests on a 3D-printed physical model 1 of a carbonate reservoir. The system includes a simulated wellbore 10 inserted into the physical model 1 and an acid injection pressure sensor 11 mounted on the simulated wellbore 10. It also includes a horizontal loading device 12 positioned on the side of the physical model 1 and a vertical loading device 13 positioned above the physical model 1. The horizontal loading device 12 applies load to the physical model 1 along two orthogonal directions on the horizontal plane, while the vertical loading device 13 applies stress to the model in the vertical direction.

[0032] In addition, the test system 1 also includes an acid injection pipeline 14, a pump fluid chamber 15, an acid storage tank 16, a water storage tank 17, and a pump fluid control panel 18. The acid storage tank 16 and the water storage tank 17 are located inside the pump fluid chamber 15, and the pump fluid control panel 18 is located on the outside of the pump fluid chamber 15. The simulated wellbore 10 is connected to the acid storage tank 16 and the water storage tank 17 via the acid injection pipeline 14. The pump fluid control panel 18 is used to control the on / off switch and power of the heating device inside the pump fluid chamber 15, as well as the on / off switch and power of the pumps inside the acid storage tank 16 and the water storage tank 17, to control the mixing ratio of the acid and water input to the test system 1, and their temperatures.

[0033] Figure 4 This invention provides a 3D printing process for preparing a physical model of a carbonate reservoir and an acidification test procedure. For example... Figure 4 As shown, the method includes the following steps: S1. Preparation of printing materials and parametric modeling.

[0034] In this embodiment, CaO powder is used as the main component, and a mixture of 5 wt% to 10 wt% quartz powder and clay powder is added according to the mineral composition of the target carbonate reservoir to simulate the second mineral phases such as argillaceous and siliceous materials. 8 wt% fly ash and 3 wt% resin are added to form a reinforced cementing system. Using imaging logging or core interpretation results of the target carbonate reservoir, the statistical distribution of the orientation, dip angle, length, and spacing of natural fractures is obtained to establish a parametric geometric description of the 3D printing model. The external dimensions are determined to be 300 mm × 300 mm × 300 mm. The Monte Carlo method is used to generate the geometric morphology and spatial coordinates (fracture width, orientation, and dip angle, and cavity size and location) of internal fractures / cavities within the model volume that meet the statistical characteristics, forming a parametric fracture-cavity network model. The output is a control path that can be recognized by the 3D printing equipment.

[0035] Furthermore, for the karst cave structure, in addition to defining the boundary surface of the karst cave in the parametric geometric model, at least one powder removal channel connected to the outer surface of the model is pre-arranged for each karst cave or karst cave group; the diameter of the powder removal channel is preferably 0.5 mm to 2 mm, and the channel is arranged along the local steepest gravity direction or the shortest path direction to reduce the impact on the overall mechanical characteristics of the model and facilitate the complete discharge of internal powder and the sealing of the channel.

[0036] S2, Printing of physical models of fracture-cavity reservoirs.

[0037] A physical model of a carbonate reservoir (Model 1) was fabricated using powder-based 3D printing equipment. The printing material was homogenized and mixed before being layered by a powder supply system. A robotic arm constructed the model structure layer by layer according to the control path of the parametric geometric model. Based on the set fracture orientation, width, and spatial coordinates, fracture channels were formed by selectively cutting paths, achieving directional embedding and precise spatial positioning of fractures within the model.

[0038] Based on the preset geometric parameters of the karst cave, a powder-supported karst cavity printing strategy is adopted within the karst cave envelope: A binder is selectively sprayed along the karst cave boundary surface trajectory in the corresponding area of ​​the karst cavity wall to form a closed shell. NaCl powder is then laid within the shell's internal volume, allowing the uncured NaCl powder to serve as a temporary support material during printing. After curing, it remains water-soluble (the NaCl powder does not change its properties after carbonization curing; it does not clump or transform into other substances and can dissolve upon subsequent water flow). Simultaneously, according to the arrangement in S1, a powder removal channel connected to the karst cave cavity is formed during printing, establishing a communication pathway between the NaCl powder inside the karst cave and the external environment.

[0039] Furthermore, while printing the cave-powder removal channel structure, several cylindrical sealing components are simultaneously printed on the outer edge of the model or in the empty area, so that they can be inserted into the powder removal channel for sealing later; the cross-sectional shape of the sealing component is the same as that of the powder removal channel, the diameter is slightly smaller than that of the powder removal channel, preferably 0.90 to 0.98 times the diameter of the powder removal channel, and the length is equal to the length of the powder removal channel; the sealing component and the model substrate are formed and cured simultaneously using the same printing material and curing process for later use.

[0040] Under this process, cracks and cavities are constructed simultaneously during printing and maintain geometric continuity and fluid connectivity. The integrated forming of this crack-cavity system avoids structural disturbances caused by subsequent mechanical processing, providing a repeatable and observable physical model basis for studying the acidification behavior and connectivity mechanism of carbonate rock fracture networks.

[0041] Furthermore, the physical model 1 is divided into at least two layers along the thickness direction, and the porosity and compressive strength of each layer are different to simulate the layered heterogeneous structure of reservoir-intercalator-reservoir; wherein the thickness, planar distribution morphology and spatial location of the weak intercalator are determined based on the logging response characteristics of the target carbonate reservoir and the sequence correlation / core interpretation results, so that the geometric morphology and mechanical properties of the intercalator have consistent or similar distribution characteristics with the weak intercalator in the field, thereby more realistically characterizing the vertical heterogeneity of the target carbonate reservoir.

[0042] S3, Sensor Embedded Layout Calibration.

[0043] A pore pressure sensor and a miniature acoustic emission sensor are embedded at designated locations within the model to acquire pore pressure response and connectivity criteria. The data acquisition system records the temporal changes in acid injection pressure, acid injection rate, and acoustic emission information, enabling real-time monitoring and response analysis of the acidification process.

[0044] S4, CO2 carbonization maintenance model.

[0045] The printed physical model 1 was placed in a carbon dioxide curing chamber 6 for high-temperature curing. The curing temperature was controlled at 50-65℃, the CO2 volume fraction was ≥85%, and the curing time was 8-16 h. Curing was terminated when the mass increment rate of the 3D printed physical model was <0.1% / h. This process induces the formation of a rock-like structure mainly composed of CaCO3 within the model, improving the overall strength and stability from both material composition and interfacial bonding aspects, while also achieving acid-etchable characteristics for the physical model.

[0046] After curing, physical model 1 is placed in a dry and ventilated environment. Clean water or low-mineralized water is injected through the preset powder removal channel to gradually dissolve the NaCl powder inside the cave cavity. The NaCl powder is then discharged out of the model by gravity and / or by the external hose. If necessary, pulsed water injection, reverse injection, or slight vibration are used to improve the dissolution and discharge efficiency of powder inside deep caves and complex cave groups, thereby forming a real cave cavity structure consistent with the parametric geometric model before the acid etching test.

[0047] After the NaCl powder inside the karst cave is completely dissolved, emptied, and allowed to dry naturally, cylindrical plugs corresponding to each powder removal channel are selected and inserted into the openings on the outer surface of the powder removal channel, ensuring that the axis of the plug is substantially aligned with the axis of the powder removal channel, and that the end face of the plug is flush with or slightly lower than the outer surface of the model. Before insertion, a layer of printing material paste with the same proportion as the model substrate is uniformly coated onto the outer circumference of the plug. The thickness of the coating layer is preferably equivalent to the annular gap between the powder removal channel wall and the outer diameter of the plug, so that after the plug is inserted, the coating layer basically fills the annular gap near the channel opening.

[0048] After the sealing component is inserted and the coating layer is filled in place, the physical model 1 is placed in the CO2 curing chamber for secondary carbonization curing. This reliably connects the sealing component and the channel wall near the channel opening into an integrated rock-like structure, thus completing the reliable sealing of the desilting channel and the integrated treatment of the matrix without changing the morphology of the karst cave and the overall structural characteristics of the reservoir.

[0049] S5, 3D printed physical model true triaxial acidification test system construction.

[0050] Holes were drilled into the outer surface of the cured 3D-printed physical model, and a simulated wellbore 10, made of corrosion-resistant Hastelloy, was poured into the holes. This simulated wellbore 10 serves as an acid injection wellbore. The wellbore can be extended to the acidizing section of the model, with perforations in the wellbore wall to serve as acid flow channels; alternatively, a shorter wellbore can be used to ensure the acid injection section is exposed, serving as an acid etching channel. A true triaxial acidizing test system was constructed, with all components in contact with the acid, such as pipelines, valves, and pump heads, made of Hastelloy. An acid injection pressure sensor 11 was installed at the wellhead to monitor the injection pressure. The wellhead was connected to the acid injection pipeline, and the other end was connected to the pump reservoir. The pump reservoir contained an acid storage tank and a water storage tank, both connected to the acid injection pipeline, with the acid storage tank also made of Hastelloy. The acid injection pipeline was wrapped with thermal insulation material. The temperature (controlling acid injection temperature), pumping rate, and acid concentration (high-concentration acid mixed with water) within the pump tank can be controlled via the control panel. Pressure sensors and miniature acoustic emission sensors within the physical model are connected to a computer for real-time monitoring of the acidizing process. A triaxial principal stress boundary (0-50 MPa) is applied using a loading system, and a heating device with an adjustable temperature between 50-100℃ is installed to analyze the acid etching process of carbonate rock fractures under the influence of temperature and stress.

[0051] S6, 3D printed physical model true triaxial acidification test and monitoring.

[0052] The 3D-printed physical model described in S1 is placed in the true triaxial acidification test system described in S2, and acidification is carried out under the set triaxial principal stress and temperature conditions of 50-100 ℃. The 3D-printed physical model corresponds to two scenarios: First, a 3D-printed physical model containing a connected fracture network is placed in the test system for acidification testing, allowing analysis of the acid etching characteristics of the fracture surface and the changing law of the fracture network's conductivity. Second, a 3D-printed physical model containing non-connected fractures and cavities is placed in the test system for acidification testing, allowing analysis of the mechanical behavior of the interaction between fractures and cavities under acid injection conditions, and also analyzing the changing characteristics of the conductivity within the system after acid etching. During the test, different acidification control parameters are set (including acid injection pressure, acid injection flow rate, acid injection type, acid injection concentration, acid injection temperature, triaxial confining pressure, system temperature, etc.). The data acquisition system synchronously records the pressure difference-time, flow rate-time, and pore pressure time series, and combines this with the acoustic emission event time series to identify connectivity behavior, thereby forming parameter-response relationships and result records for different connectivity states.

[0053] The following two examples further illustrate this point. Example

[0054] Figure 5 This is a schematic diagram of a pre-fabricated hydraulic fracture 3D-printed carbonate reservoir physical model according to the first embodiment of the present invention. Figure 5 As shown, in this embodiment, a physical model containing fractures and caverns is fabricated using a 3D printing method for carbonate reservoir physical models. Multiple parallel, continuous hydraulic fractures are pre-placed horizontally. Furthermore, randomly distributed natural fractures and caverns are generated inside the model during the printing process. The model is then placed in a high-temperature carbon dioxide curing chamber for curing. Holes are drilled into the outer surface of the cured 3D-printed physical model, and artificial wellbores are poured into these holes. In the figure, 19 represents the 3D-printed physical model, 20 represents the simulated wellbore, 21 represents the hydraulic fracture, 22 represents the natural fracture, and 23 represents the cavern. Acidizing tests are conducted using a high-pressure acid injection true triaxial acidizing test system and method. The treated physical model sample is placed in the true triaxial acidizing test system, and the wellbore position and the connections of the pipelines within the pumping chamber are checked. The sample surface is preheated at a set temperature. Once the overall sample temperature reaches the set value, triaxial stress is applied, and the pumping chamber control panel parameters, including acid injection temperature, acid injection rate, and acid injection concentration, are set to conduct acid injection tests. This sample is mainly used to analyze the acid corrosion characteristics of hydraulic fractures and their connected natural fractures and caves. The acid injection pressure does not need to be too high, and the focus can be on monitoring the seepage change characteristics of discontinuous media. Example

[0055] Figure 6 This is a schematic diagram of a 3D-printed physical model of a carbonate reservoir containing non-connected fractures and caverns, according to the second embodiment of the present invention.

[0056] like Figure 6 As shown, in this embodiment, a physical model containing fractures and caverns is fabricated using a 3D printing method for carbonate reservoir physical models. During the printing process, randomly distributed natural fractures and caverns are generated inside the model, resulting in poor overall connectivity. The model is then cured in a high-temperature carbon dioxide curing chamber. Holes are drilled into the outer surface of the cured 3D-printed physical model, and artificial wellbores are poured into these holes. In the figure, 24 represents the 3D-printed physical model, 25 represents the simulated wellbore, 26 represents the natural fracture, and 27 represents the cavern. Acidification tests are conducted using a high-pressure acid injection true triaxial acidification test system and method. The physical model sample treated as described above is placed in the true triaxial acidification test system, and the wellbore position and the connection status of the pipelines in the pumping chamber are checked. The sample surface is preheated at a set temperature. Once the overall temperature of the sample reaches the set value, triaxial stress is applied, and the parameters of the pumping chamber control panel, including acid injection temperature, acid injection rate, and acid injection concentration, are set to conduct acid injection test research. This sample is primarily used to analyze the mechanical behavior of the interaction between cracks and cavities under acid injection conditions, and also to analyze the changes in the conductivity of the system after acid etching. Therefore, a high acid injection pressure is required, generally greater than the crack initiation pressure of the physical model, to generate hydraulic cracks. The interaction characteristics and seepage changes of discontinuous structures can be monitored using pressure sensors and miniature acoustic emission sensors.

[0057] In summary, this application provides a method for 3D printing and acidizing testing of physical models of carbonate reservoirs. The aim is to achieve efficient preparation of physical models of carbonate reservoirs with complex discontinuous structures, and to conduct repeatable tests on the acidizing process of carbonate reservoirs, exploring the influence mechanism of discontinuous structures (fractures, karst, etc.) on the acidizing process. This method enables quantitative analysis of the acidizing process of carbonate reservoirs, providing theoretical and experimental guidance for optimizing in-situ carbonate reservoir acidizing techniques.

[0058] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above descriptions are merely specific embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A 3D-printed physical model of a carbonate reservoir, characterized in that, The mixture of CaO powder, quartz powder and clay powder, fly ash and resin is formed by 3D printing. The mixture of quartz powder and clay powder accounts for 5 wt% to 10 wt%, fly ash accounts for 8 wt%, and resin accounts for 3 wt%.

2. The 3D-printed physical model of carbonate reservoir according to claim 1, characterized in that, The physical model includes cracks and / or caves.

3. The 3D-printed physical model of carbonate reservoir according to claim 2, characterized in that, When the carbonate reservoir includes cave structures, each cave or cave group is provided with at least one desiccation channel communicating with the outer surface of the physical model.

4. The 3D-printed physical model of carbonate reservoir according to claim 3, characterized in that, It also includes a sealing component for sealing the powder removal channel.

5. The 3D-printed physical model of a carbonate reservoir according to claim 1, characterized in that, The physical model is divided into at least two layers along the thickness direction, and the porosity and compressive strength of each layer are different from each other.

6. A method for preparing a 3D-printed physical model of a carbonate reservoir, characterized in that, Includes the following steps: A 3D printing material is formed by incorporating CaO powder as the main component, a mixture of quartz powder and clay powder, fly ash, and resin. The mixture of quartz powder and clay powder accounts for 5 wt% to 10 wt%, fly ash accounts for 8 wt%, and resin accounts for 3 wt%. A physical model of a carbonate reservoir was printed using powder 3D printing equipment. During the forming process, a robotic arm cut the model layer by layer according to preset parameters to form cracks of the target width and orientation. A powder-supported cavity printing strategy is used to form cavities within the cavity envelope, so that the crack-cavity configuration is formed as a whole inside the sample.

7. The method for preparing a 3D-printed physical model of a carbonate reservoir according to claim 6, characterized in that, The powder is NaCl powder, and the powder self-supporting cavern printing strategy includes: selectively spraying a binder in the corresponding area of ​​the cavern wall according to the cavern boundary surface trajectory to form a closed shell, so that the uncured NaCl powder serves as a temporary support material during the printing process.

8. The method for preparing a 3D-printed physical model of a carbonate reservoir according to claim 7, characterized in that, When the carbonate rock reservoir includes a cave structure, a powder removal channel connected to the cave cavity is formed simultaneously during the printing process, so that the powder filling the cave cavity establishes a communication channel with the external environment, so that the NaCl powder inside the cave cavity can dissolve after water is passed through it.

9. An acidizing test system for a 3D-printed physical model of a carbonate reservoir, characterized in that, include: The simulated wellbore is set in a physical model, wherein the physical model is a 3D printed carbonate reservoir physical model as described in any one of claims 1 to 5; An acid injection pressure sensor is installed on the simulated wellbore; A horizontal loading device is installed on the side of the physical model and a vertical loading device is installed above the physical model. Acid injection pipeline, pump liquid tank, acid storage tank, water storage tank, and pump liquid control panel.

10. The acidizing test system for the 3D-printed physical model of carbonate reservoirs according to claim 9, characterized in that, The acid storage tank and water storage tank are located inside the pump liquid chamber, and the pump liquid control panel is located on the outside of the pump liquid chamber; The pump control panel is used to control the switch and power of the heating device inside the pump compartment, as well as the switch and power of the pumps inside the acid storage tank and water storage tank, so as to control the mixing ratio of acid and water input to the acidification test system and their temperature.

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