High-pressure water injection simulation device for fracture-cavity reservoirs

Abstract

The present invention relates to a high-pressure water injection simulation device for fracture-cavity oil reservoirs, comprising a water storage tank, a first valve, a second valve, an oil storage tank, an injection pump, a pressure gauge, a fracture-cavity simulation box, a data display, a flow meter, a liquid storage tank, a production well bore, a cave simulation unit, a connected fracture, a pressure gauge, a liquid inlet a, a stress-sensitive fracture, a pressure-sensitive switch, a check valve, a liquid inlet b, a box body support, a box body bottom plug, a reinforcement hole, an external thread, a cave simulation unit pipeline, an electric submersible pump, an electric control switch, and an internal thread, and belongs to the field of oil and gas reservoir development and recovery enhancement. The present invention has the following beneficial effects: (1) It can accurately simulate the connected and closed states between caves with stress-sensitive fractures; (2) It can perform high-pressure testing to meet the testing requirements of more ultra-deep oil reservoirs; (3) It has three layers (check valve, sand filling, steel box) of safety protection measures to achieve the purpose of safe experiments.

Description

Technical Field

[0001] The invention relates to a high-pressure water injection simulation device in the process of exploitation of fracture-cavity oil reservoirs, belonging to a water injection simulation device for improving crude oil recovery. Background Art

[0002] The purpose of water injection in fracture-cave reservoirs is to utilize the difference in oil-water density, and in the fracture connection system of single caves and multiple caves, use the gravity differentiation of oil and water to form water to "lift" oil, that is, gradually lift the oil-water interface at a low position, so as to continuously produce the upper crude oil and improve the crude oil recovery rate. The laboratory small-scale simulation is carried out, and the relevant parameters obtained during the simulation process can be used to verify and assess whether the water injection scheme meets the requirements of the current development plan of the reservoir. Secondly, the laboratory simulation water injection device can study the window of reservoir water injection pressure (the upper and lower limits of the appropriate water injection pressure), as well as the influence of parameters such as injection volume and injection medium on the degree of crude oil recovery. In summary, the laboratory reservoir water injection simulation device can simulate and optimize the process and important parameters of water injection to improve the degree of recovery in fracture-cave reservoirs in advance.

[0003] High-pressure water injection into fracture-cavity reservoirs has been applied in the practice of Tahe Oilfield as a new measure to further improve the recovery of crude oil from fracture-cavity reservoirs (the pressure unit mentioned in this patent application is MPa, which is the unit of pressure in physics; due to industry practice, this patent application continues to use the term pressure). Due to the complex geological origin of fracture-cavity reservoirs and the known and unknown connectivity between reservoir bodies (underground caves), it is extremely difficult to evaluate the reserves of fracture-cavity reservoirs and improve the recovery of crude oil from the reservoirs. During the development of Tahe Oilfield, it was found that increasing the injection water pressure (increasing the injection volume and injection speed, i.e., high-pressure water injection) can improve the recovery of known reservoirs (the first unit). After analysis, it was found that high-pressure water injection increased the pressure in the cave, and the pressure in the cave was held to open the stress-sensitive fractures around the cave (stress-sensitive fractures: when the pressure in the fracture reaches a certain value, the fracture will be opened, forming a connected fracture, and the fluid begins to flow freely; after a period of high-pressure water injection, the water injection is stopped and the well is shut down, the pressure tends to balance and the fluid flow tends to stop. In this process, due to the density difference, the oil flows to a higher place; when the well is shut down for a period of time and then the well is started for production, the pressure at the bottom of the production well decreases, gradually affecting the entire cave, and the stress-sensitive fractures slowly close after the pressure decreases to a certain extent), and the known cave is connected with the unknown cave (the second unit) in the distance. Due to the difference in oil and water density, the water entering the unknown cave (the second unit) replaces part of the oil back to the known cave (the first unit). In this way, the surrounding connected reservoirs are exploited using the existing wells and the recovery of fracture-cave oil reservoirs in this area is further improved.

[0004] At present, there is no laboratory simulation device for high-pressure water injection in fracture-cavity reservoirs. The main limiting factors are the stress-sensitive fracture connections between reservoir bodies (cavities), the ultimate pressure-bearing containers and the safety protection measures of the device.

[0005] The purpose of the present invention is to provide a high-pressure water injection simulation device for fracture-cavity reservoirs that can simulate stress-sensitive fracture communication between fractures and caves in fracture-cavity reservoirs, withstand high pressure and ensure accurate and safe experiments. Summary of the invention

[0006] The purpose of the present invention is to provide a high-pressure water injection simulation device for fracture-cavity reservoirs which can simulate stress-sensitive fracture communication between fractures and caves in fracture-cavity reservoirs, withstand high pressure and ensure accurate and safe experiments.

[0007] To achieve the above-mentioned purpose, the present invention adopts the following technical scheme: a high-pressure water injection simulation device for a fracture-cave oil reservoir, including a water storage tank, a first valve, a second valve, an oil storage tank, an injection pump, a pressure gauge, a fracture-cave simulation box, a data display, a flow meter, a liquid storage tank, a production well bore, a cave simulation unit, a connected fracture, a pressure gauge, a liquid inlet a, a stress-sensitive fracture, a pressure-sensitive switch, a check valve, a liquid inlet b, a bracket inside the box, a bottom plug of the box, a reinforcement hole, an external thread, a cave simulation unit pipeline, an electric submersible pump, an electric control switch, and an internal thread. The characteristics are as follows: the water storage tank is used as the water source for high-pressure water injection and is connected to the first valve through a pipeline; the first valve and the second valve control the flow of fluid in their respective pipelines, and when water injection is required, the first valve of the corresponding pipeline can be opened, and the first valve and the second valve are respectively connected to the water storage tank, the oil storage tank and the injection pump at both ends; the oil storage tank is used as the source of the oil phase in the simulation device, and the oil is first injected into the cave simulation unit before high-pressure water injection to simulate the oil content in the underground cave, and the pipeline is directly connected to the second valve; the injection pump is the power equipment in the simulation device, which is driven by electricity. Before the experiment starts, the oil and water in the tank are injected into the cave simulation unit, and later As an injection device for high-pressure water injection, the water in the water storage tank is injected into the cave simulation unit through the production wellbore. The two ends of the injection pump are respectively connected to the first valve, the second valve and the pressure gauge; the pressure gauge is used as a pressure monitoring device for the injection pump pipeline. The left side is connected to the injection pump through the pipeline, and the right side is connected to the cave simulation unit in the fracture-cavity simulation box. The device in the fracture-cavity simulation box is the core of this simulation device, which contains the cave simulation unit, connected fractures and stress-sensitive fractures, etc. The left side of the fracture-cavity simulation box is connected to the pressure gauge through the cave simulation unit pipeline, and the right end is connected to the electric submersible pump through the cave simulation unit pipeline; the data display is a simulation The electronic display device in the device is connected to all the pressure gauges in the fracture-cavity simulation box, receives the pressure data in the cave simulation unit in real time and displays it on the display screen; the flow meter is connected between the liquid storage tank and the electric submersible pump to measure the volume of liquid flowing out of the fracture-cavity simulation box; the electric submersible pump is used to extract the liquid in the cave where the production well is located, and is connected to the flow meter; the liquid storage tank is used as a container to collect the liquid output from the electric submersible pump, and is directly connected to the flow meter, which is the last link of the simulation device; the production well bore is a section of pipeline directly connecting the cave simulation unit to the injection / output pipeline; the cave simulation unit can be directly connected to the injection / output pipeline through the production well bore The pipeline and the output pipeline are connected, a plurality of the cave simulation units 11 constitute a first unit, and a plurality of the cave simulation units 11 constitute a second unit. The connected fractures and the stress-sensitive fractures are used to connect a plurality of cave simulation units; the connected fractures are only connected to the cave simulation unit inside the first unit or the second unit, and play the role of directly connecting the two cave simulation units (the fluids in the two cave simulation units can flow freely); the pressure gauge is directly connected to the cave simulation unit and the data display, and is a device for accurately collecting pressure data; the liquid inlet a is connected to the injection pipeline, and directly injects the liquid into the cave simulation unit of the first unit;The stress-sensitive crack connects the first unit and the second unit, and will only open when the pressure reaches the crack opening condition, and is usually in a closed state; the pressure-sensitive switch is a pressure control device in the pipeline connecting the first unit and the second unit. The function of this switch is to determine whether the pressure reaches the crack opening condition, and its pressure value can be set; the check valve is a flow-limiting device on the stress-sensitive crack between the first unit and the second unit. Its function is to only allow the fluid in the second unit to flow into the first unit, and not to flow in the opposite direction; the liquid inlet b is a section of the pipeline connecting the injection pipeline and the second unit, and the liquid is injected into the second unit; the bracket in the box is a movable metal rod, which is fixed in the crack simulation box through a corner groove, in order to place multiple cave simulation units in the crack simulation box in an orderly and safe manner. The box body is in the simulated box to prevent the pipeline from being excessively bent and ruptured when under pressure; the box body bottom plug is a rubber plug placed inside the box body. After the cave simulation units are placed in the box body, the box body is filled with sand until the quartz sand covers the cave simulation unit and is flush with the box body cover. After the experiment, the box body bottom plug is pulled out to allow the quartz sand in the box body to leak out from the bottom, thus ensuring that if the high-pressure pipeline is ruptured, it will not cause a serious accident; the reinforcement hole is located on the cave simulation unit, the purpose is to further reinforce the cave simulation unit for pressure bearing; the internal and external threads are located at the contact port of the cave simulation unit, which plays a sealing and reinforcement role; the cave simulation unit pipeline is the way to connect the cave simulation unit and the injection / output pipeline, the cave simulation unit and other cave simulation units; the electric control switch is installed on the production wellbore. ;

[0008] As a further optimization of this solution, the injection pump of the present invention plays the role of early liquid injection and high-pressure water injection, plays different injection roles at different times and has different injection ports. In the early stage, oil and water are injected into the model through the injection pump (4) respectively connected to the liquid inlet a and the liquid inlet b to achieve liquid injection into the cave simulation unit; after the test begins, the injection pump (4) is connected to the production wellbore to achieve the effect of high-pressure water injection.

[0009] As a further optimization of this solution, the fracture cave simulation box described in the present invention is a steel hollow box, which realizes liquid in / out and data transmission by reserving injection / output pipeline holes and pressure gauge data line outlets. Two layers of removable box brackets are provided in the box in the longitudinal direction, dividing the box space into three layers: upper, middle and lower, for orderly placing multiple cave simulation units. The connected cave simulation units are also buried in the box by filling sand to avoid high-pressure fluid impact caused by pipeline rupture and cave simulation unit leakage.

[0010] As a further optimization of the present solution, the data display described in the present invention can monitor the pressure data of each cave simulation unit in real time by collecting the pressure data of different cave simulation units in the first unit and the second unit, and check whether the stress-sensitive cracks between the first unit and the second unit are normally opened.

[0011] As a further optimization of this scheme, the production wellbore described in the present invention is connected to the high-pressure injection pipeline and also to the output pipeline. The electric control switch on the production wellbore is remotely controlled by the experimenter to play the role of opening and closing the production wellbore (open for high-pressure water injection or production, close for shutting down the well and waiting for the system pressure to balance). This is to simulate the need to shut down (stifle the well) for a period of time for high-pressure water injection in fracture-cavity reservoirs, and then open the well for production after the pressure between the fractures and caves is balanced (at this time, the crude oil migration is completed). At this time, the oil in the oil-bearing caves that communicate with the stress-sensitive fractures will flow into the high-level caves, achieving the purpose of "changing" oil by water injection.

[0012] As a further optimization of this solution, the cave simulation unit described in the present invention is a split hemispherical steel structure. The sphere has two layers of sealing and reinforcement measures. First, the sphere is combined by rotating and tightening the internal and external threads, and a rubber ring is built in for sealing; after the sphere threads are tightened, screws and nuts are used to tighten the reinforcement holes, and the two hemispheres are tightened again. Such two tightening measures can ensure that the sphere will not leak liquid or burst due to failure of thread matching and tightening. In addition, the small holes on the surface of the sphere are connected to the cave simulation unit pipeline through threads, which plays the role of connecting multiple cave simulation units.

[0013] As a further optimization of this solution, the connectivity fractures described in the present invention are pressure-resistant steel pipelines, which are used to directly connect the two cave simulation units. The main body of the stress-sensitive fracture is also a pressure-resistant steel pipeline. Due to the presence of the pressure-sensitive switch and the check valve, the pipeline can only be opened when the opening condition is met, and is closed at other times, preventing fluid from flowing.

[0014] As a further optimization of this solution, the liquid inlet a and the liquid inlet b described in the present invention are only opened during the process of injecting liquid into the first unit and the second unit before the start of the simulation experiment, and are completely closed at other times to prevent fluid from flowing.

[0015] The present invention has the following beneficial effects: (1) it can accurately simulate the connected and closed states between stress-sensitive fracture caves; (2) it can perform high-pressure testing to meet the testing requirements of more ultra-deep oil reservoirs; and (3) it has three layers (check valve, sand filling, steel box) of safety protection measures to achieve the purpose of safe experiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 It is a flow chart of the present invention.

[0017] Figure 2 This is a diagram of the multi-unit fracture-hole connectivity and initial oil-water distribution of the present invention.

[0018] Figure 3 This is the oil-water distribution diagram of the initial stage of ordinary water injection in multi-unit fractures and caves of the present invention.

[0019] Figure 4 This is the oil-water distribution diagram of the later stage of ordinary water injection in multi-unit fractures and caves of the present invention.

[0020] Figure 5 This is the oil-water distribution diagram of the multi-unit fracture-hole high-pressure water injection of the present invention.

[0021] Figure 6 This is a cross-sectional view of the seam hole simulation box of the present invention.

[0022] Figure 7 This is the front view of the cave simulation unit of the present invention.

[0023] Figure 8 It is the right view of the cave simulation unit of the present invention.

[0024] Fig. 9 It is a right side cross-sectional view of the cave simulation unit of the present invention.

[0025] In the figure: water storage tank 1, first valve 2a, second valve 2b, oil storage tank 3, injection pump 4, pressure gauge 5, fracture simulation box 6, data display 7, flow meter 8, liquid storage tank 9, production wellbore 10, cave simulation unit 11, connected fracture 12, pressure gauge 13, liquid inlet a14, stress sensitive fracture 15, pressure sensitive switch 16, check valve 17, liquid inlet b18, box body bracket 19, box bottom plug 20, reinforcement hole 21, external thread 22, cave simulation unit pipeline 23, electric submersible pump 24, electric control switch 25, internal thread 26. DETAILED DESCRIPTION

[0026] The present invention is described in detail below in conjunction with the accompanying drawings.

[0027] like Figure 1 , Figure 2 , Figure 3 , Figure 4 , Figure 5 , Figure 6 , Figure 7 , Figure 8 , Fig. 9As shown, the high-pressure water injection simulation device for fracture-cavity reservoirs includes a water storage tank 1, a first valve 2a, a second valve 2b, an oil storage tank 3, an injection pump 4, a pressure gauge 5, a fracture-cavity simulation box 6, a data display 7, a flow meter 8, a liquid storage tank 9, a production well bore 10, a cave simulation unit 11, a connected fracture 12, a pressure gauge 13, a liquid inlet a14, a stress-sensitive fracture 15, a pressure-sensitive switch 16, a check valve 17, a liquid inlet b18, a box body bracket 19, a box body bottom plug 20, a reinforcement hole 21, an external thread 22, a cave simulation unit pipeline 23, an electric submersible pump 24, an electric control switch 25, and an internal thread 26.The invention is characterized in that: the water storage tank 1 is connected to the first valve 2a through a steel pipeline, and the oil storage tank 3 is connected to the second valve 2b through a steel pipeline; the pipeline where the injection pump 4 is located is connected to the pipeline where the water storage tank 1 and the oil storage tank 3 are located, and the on-off of the pipeline is controlled by the first valve 2a and the second valve 2b. Before starting the simulation, the pipeline where the injection pump 4 is located is respectively connected to the liquid inlet a14 and the liquid inlet b18 to inject liquid into the first unit and the second unit, and then the liquid inlet a14 and the liquid inlet b18 are closed, and the pipeline where the injection pump 4 is located is connected to the production wellbore 10 to achieve the purpose of high-pressure water injection; the pressure gauge 5 is installed on the pipeline where the injection pump 4 is located to monitor the injection pipeline pressure; the crack hole The simulation box 6 is installed between the pressure gauge 5 and the electric submersible pump 24, and is connected to an external data display 7; the flow meter 8 is installed between the fracture-cavity simulation box 6 and the liquid storage tank 9, and is used to measure the volume of the fluid in the output pipeline; the liquid storage tank 9 is installed at the end of the output pipeline of the device, and is used to receive the liquid produced in the fracture-cavity simulation box 6; the production well bore 10 is installed on the cave simulation unit 11, connecting the injection pipeline and the output pipeline, and is used to perform high-pressure water injection and well production on the first unit; the cave simulation unit 11 is placed in the fracture-cavity simulation box 6, and is connected to other solution units through the connected fractures 12, the stress-sensitive fractures 15, the production well bore 10, the liquid inlet a14, the liquid inlet b18 and the pressure gauge 13. The cave simulation unit 11, the injection pipeline, the output pipeline and the data display 7 are connected, a plurality of the cave simulation units 11 constitute a first unit, and a plurality of the cave simulation units 11 constitute a second unit; the connectivity fracture 12 is installed between the two cave simulation units 11, and plays a role in communicating the pressure between the cave simulation units 11, and only plays a connecting role inside the first unit and the second unit; the stress sensitive fracture 15 only exists between the first unit and the second unit, and the cave simulation units 11 of the first unit and the second unit are opened after the fracture opening requirement is met; the pressure sensitive switch 16 is installed on the stress sensitive fracture 15, and is used to control the opening of the stress sensitive fracture 15; the check valve 17 is installed on the stress sensitive fracture The stress-sensitive crack 15 is used to control the flow direction of the fluid in the stress-sensitive crack 15; the box body bracket 19 is installed in the crack simulation box 6 to separate the box space longitudinally; the box bottom plug 20 is installed in the crack simulation box 6; the reinforcement hole 21 and the external thread 22, the internal thread 26 and are distributed on the cave simulation unit 11 to reinforce the cave simulation unit 11; the cave simulation unit pipeline 23 is installed on the cave simulation unit 11 to connect other cave simulation units 11 and the production wellbore; the electric submersible pump 24 is installed on the output pipeline to extract the liquid in the production wellbore 10; the electric control switch 25 is installed on the production wellbore 10 to control the switch of the production wellbore 10.

[0028] The injection pump 4 plays the role of early liquid injection and high-pressure water injection, and plays different injection roles at different times and has different injection ports. In the early stage, oil / water is injected into the simulation device, and the injection pump (4) is respectively connected to the liquid inlet a14 and the liquid inlet b18 to inject liquid into the cave simulation unit 11; after the test starts, the injection pump (4) is connected to the production wellbore 10 to achieve the effect of high-pressure water injection.

[0029] The fracture-cavity simulation box 6 is a steel hollow box, which realizes the inlet / outlet of liquid and data transmission by reserving injection / output pipeline holes and pressure gauge data line holes. Multiple layers of removable box internal brackets 19 are arranged longitudinally inside the box, dividing the box space into multiple layers for orderly placing the cave simulation units 11. The connected cave simulation units 11 are buried in the box by filling sand to avoid high-pressure fluid impact caused by pipeline rupture and leakage of the cave simulation unit 11.

[0030] The data display 7 can monitor the pressure data of each cave simulation unit 11 in real time by collecting the pressure data of different cave simulation units 11 in the first unit and the second unit, and check whether the stress-sensitive cracks 15 of the first unit and the second unit are normally opened.

[0031] The production wellbore 10 is connected to the high-pressure injection pipeline and the output pipeline. The electric switch 25 on the production wellbore 10 is remotely controlled by the experimenter to play the role of opening and closing the production wellbore 10 (open for high-pressure water injection or production, and close for system pressure balance). This is to simulate the need to shut down (stifle) the well for a period of time for high-pressure water injection in fracture-cavity reservoirs, and then open the well for production after the pressure of the cave system is balanced. At this time, the oil in the oil-bearing cave of the communicating stress-sensitive fracture 15 will flow into the high-position cave, achieving the purpose of "changing" oil by water injection.

[0032] The cave simulation unit 11 is a split hemispherical steel structure. The sphere has two layers of sealing and reinforcement measures. First, the sphere is combined by rotating and tightening the internal thread 26 and the external thread 22, and a rubber ring is built in for sealing; after the internal thread 26 and the external thread 22 are tightened, the reinforcement hole 21 is tightened with screws and nuts, and the two hemispheres are tightened again. Such two tightening measures can ensure that the sphere will not leak liquid or burst due to thread failure. In addition, the small holes on the surface of the sphere are connected to the cave simulation unit pipeline 23 through threads, which plays the role of connecting multiple cave simulation units 11.

[0033] The connecting fracture 12 is a pressure-resistant steel pipeline, which directly connects the two cave simulation units 11. The main body of the stress-sensitive fracture 15 is also a pressure-resistant steel pipeline. Due to the presence of the pressure-sensitive switch 16 and the check valve 17, the pipeline can only be opened when the opening condition is met; the rest of the time it is in a closed state, and the fluid cannot flow.

[0034] Of course, the above description is not a limitation of the present invention, and the present invention is not limited to the above examples. Changes, modifications, additions or substitutions made by ordinary technicians in this technical field within the essential scope of the present invention also fall within the protection scope of the present invention.

Claims

1. A high-pressure water injection simulation device for a fracture-cave oil reservoir, comprising a water storage tank (1), a first valve (2a), a second valve (2b), an oil storage tank (3), an injection pump (4), a pressure gauge (5), a fracture-cave simulation box (6), a data display (7), a flow meter (8), a liquid storage tank (9), a production wellbore (10), a karst cave simulation unit (11), a connected fracture (12), a pressure gauge (13), a liquid inlet a (14), a stress-sensitive fracture (15), a pressure-sensitive switch (16), a check valve (17), a liquid inlet b (18), a box body support (19), a box body bottom plug (20), a reinforcement hole (21), an external thread (22), a karst cave simulation unit pipeline (23), an electric submersible pump (24), an electric control switch (25), and an internal thread (26); characterized in that: The water storage tank (1) and the first valve (2a) are installed on one pipeline, the oil storage tank (3) and the second valve (2b) are installed on another pipeline, the injection pump (4) is installed between the first valve (2a), the second valve (2b) and the pressure gauge (5), the pressure gauge (5) is installed between the injection pump (4) and the fracture-hole simulation box (6), the data display (7) is externally connected to the fracture-hole simulation box (6), the box bottom plug (20) and the box internal bracket (19) are installed in the fracture-hole simulation box (6), and the cave simulation unit (11) is externally connected to the stress-sensitive crack ( 15), a pressure-sensitive switch (16), a connected fracture (12), a pressure gauge (13), a liquid inlet a (14), a liquid inlet b (18), a production wellbore (10) and a karst cave simulation unit pipeline (23) are placed on a bracket (19) in a box body, a plurality of the karst cave simulation units (11) constitute a first unit, a plurality of the karst cave simulation units (11) constitute a second unit, a stress-sensitive fracture (15) exists only between the first unit and the second unit, and the karst cave simulation units (11) of the first unit and the second unit are opened after the fracture opening requirement is met; The pressure-sensitive switch (16) is installed on the stress-sensitive crack (15) to control the opening of the stress-sensitive crack (15). The reinforcement hole (21), the external thread (22) and the internal thread (26) are located on the cave simulation unit (11). The electric submersible pump (24), the flow meter (8) and the liquid storage tank (9) are installed in sequence behind the crack cave simulation box (6). The injection pump (4) plays different injection roles at different times and the injection ports are also different. When injecting oil / water into the cave simulation unit (11) in the early stage, the injection pump (4) is connected to the liquid inlet a (14) and the liquid inlet b. (18) injecting liquid into the cave simulation unit (11); after the test starts, the injection pump (4) is connected to the production wellbore (10) to perform high-pressure water injection. The fracture cave simulation box (6) is a steel hollow box. Liquid inlet / outlet and data transmission are carried out through reserved injection / output pipeline holes and pressure gauge data line holes. Two layers of removable box brackets (19) are provided in the box in the longitudinal direction, dividing the box space into upper, middle and lower layers for orderly placing the cave simulation units (11). The connected cave simulation units (11) are also buried in the box by filling sand.

2. The high pressure water injection simulation device for fracture-cavity reservoirs according to claim 1 is characterized in that: The production wellbore (10) is connected to the pipelines of the injection pump (4) and the submersible pump (24). The electric control switch (25) on the production wellbore (10) is controlled by the experimenter remotely to open and close the production wellbore (10). When the well is opened, high-pressure water injection or production is carried out; after the well is closed, the pressure of the fracture-cavity system gradually tends to balance.

3. The high pressure water injection simulation device for fracture-cavity reservoirs according to claim 1 is characterized in that: The karst cave simulation unit (11) is a split hemispherical steel structure, and the sphere has two layers of sealing and reinforcement measures. First, the sphere is combined by rotating and tightening the internal thread (26) and the external thread (22), and a rubber ring is built in for sealing; after the internal thread (26) and the external thread (22) are tightened, the reinforcement hole (21) is fixed by screws and nuts, and the two hemispheres are tightened again; the sphere and the karst cave simulation unit pipeline (23) are connected by threaded matching, and multiple karst cave simulation units (11) can be connected. The size of the karst cave volume can be achieved by connecting multiple karst cave simulation units (11) in parallel or in series.

4. The high pressure water injection simulation device for fracture-cavity reservoirs according to claim 1 is characterized in that: The connecting fracture (12) is a pressure-resistant steel pipeline, and its function is to directly connect the two cave simulation units (11); the stress-sensitive fracture (15) is also based on the pressure-resistant steel pipeline, and is characterized in that a pressure-sensitive switch (16) and a check valve (17) are installed on the stress-sensitive fracture (15), so that the stress-sensitive fracture (15) automatically opens when the opening condition is met, and is in a closed state at other times, preventing the flow of fluid.

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