Shale oil horizontal well zipper type fracturing casing deformation simulation device and simulation method

Abstract

The invention discloses a shale oil horizontal well zipper type fracturing casing deformation simulation device and a simulation method, the shale oil horizontal well zipper type fracturing casing deformation simulation device comprises two identical stratum shaft simulation units, the two stratum shaft simulation units are respectively provided with simulation stratum casing combination devices, and the simulation stratum casing combination devices respectively comprise a fault hanging wall, a fault, a fault footwall and a perforation casing. The fault is located between the fault hanging wall and the fault footwall, a borehole is drilled along the axes of the fault hanging wall, the fault and the fault footwall, the perforation sleeve is located in the borehole, and a cement sheath is formed on the periphery of the perforation sleeve through well cementation; the faults of the two stratum wellbore simulation units are connected through a fault connecting pipe, the fault connecting pipe controls the flow of fracturing fluid through a valve, and the pressure in the faults is monitored through a pressure gauge. The stratum shaft simulation unit is further provided with a ground stress loading system, a data monitoring system and a liquid injection and drainage system. According to the invention, the problem of damage or shear deformation of the adjacent well casing to a certain degree in the fracturing process is conveniently researched and solved.

Description

Technical Field

[0001] This invention relates to the deformation simulation of fracturing casing, and more particularly to a zipper-type fracturing casing deformation simulation device for shale oil horizontal wells. This invention also relates to a method for simulating the deformation of zipper-type fracturing casing for shale oil horizontal wells, belonging to the field of fracturing development technology in oil and gas exploration and development. Background Technology

[0002] Horizontal well staged fracturing technology, as an important stimulation measure for unconventional reservoirs, has been widely applied in shale reservoir development. To reduce construction costs, maximize reservoir stimulation volume, and further develop a well factory operation model, technologies such as simultaneous fracturing and zipper fracturing have been proposed. Zipper fracturing, in particular, is widely used due to its absolute advantage in reducing inter-well stress interference. Deep shale oil and gas wells are prone to casing deformation during development. Compared to simultaneous fracturing, the hydraulic fractures formed by the initial fracturing operation in zipper fracturing are more likely to extend to the wellbore of adjacent wells due to the absence of stress induced by hydraulic fractures in adjacent wells. This significantly increases the risk of casing deformation in adjacent wells, easily leading to fracturing stage loss or even the abandonment of the shale oil and gas well. Given the high risk of casing deformation during fracturing, it is necessary to study the casing deformation mechanism in deep shale oil and gas development using zipper fracturing, and to formulate appropriate construction parameters to ensure both maximum stimulation volume and wellbore integrity.

[0003] Casing deformation during deep shale fracturing is a multi-factor coupled problem, involving not only rock physical properties but also in-situ stress, fault fracture development, and construction factors. Domestic and international experts have conducted systematic and comprehensive research on casing deformation during fracturing, mainly focusing on: casing deformation mechanism research, casing deformation prediction research, comprehensive prevention and control research of casing deformation, and the influence of faults on casing deformation. Based on existing research, scholars primarily use analytical models of formation slip, finite element calculations coupling formation and casing, and physical simulation methods.

[0004] In the 2021 issue of *Petroleum Exploration and Development*, in the article "Mechanism of Casing Shear Deformation Caused by Hydraulic Fracturing and Calculation Model of Casing Variables," a stress model of the fracture surface was established based on stress analysis, and a calculation model of casing variables was established using complex variable functions. The influencing factors of wellbore shear stress and casing variables were analyzed. The study shows that the fracture approach angle and the wellbore approach angle have a significant impact on wellbore shear stress. When the fracture is not fully opened, the wellbore shear stress is positively correlated with the fluid pressure inside the fracture and negatively correlated with the friction coefficient.

[0005] The article "Mechanism and Physical Simulation Analysis of Fracturing Casing in Shale Gas Wells," published in the 11th issue of *Natural Gas Industry* in 2023, utilized a self-developed physical simulation experimental system for fracturing casing deformation. This system established a physical simulation method for fracturing casing deformation in outcrop rock samples with fractured surfaces. Physical simulations were conducted on outcrop rock samples with fractured surfaces under different geostress states and natural fracture dip angles. Pressure changes and acoustic emission characteristics were analyzed, clarifying the interaction between hydraulic fractures and natural fractures during fracturing and verifying the mechanism of casing deformation due to slippage at natural fracture surfaces. While the above research investigated the mechanism of casing deformation caused by fault slippage from both theoretical and experimental perspectives, there is limited research on the impact of fracturing on the casing stress state of adjacent wells during the twin-wellbore zipper fracturing process in deep shale oil and gas horizontal wells.

[0006] Chinese invention patent CN 113944452B, entitled "An Experimental Device for Casing Shear Deformation," discloses a method for studying casing fracture in hydraulic fracturing. This method can be used to investigate the influence of fault slip on casing deformation during hydraulic fracturing, and can elucidate the casing damage mechanism during shale gas well fracturing. The specific implementation steps include: preparing a downhole shale reservoir model; deploying a hydraulic fracturing control system; installing the casing through the downhole shale reservoir model; connecting the casing to the hydraulic fracturing control system; deploying a data acquisition system around the casing; performing hydraulic fracturing on the casing using the hydraulic fracturing control system; collecting fracture research data using the data acquisition system; and using the fracture research data to study the casing damage mechanism.

[0007] Chinese invention patent application CN116067801A, entitled "An Experimental Device for Casing Shear Deformation," aims to study the deformation mechanism of casing and provide an experimental device for casing shear deformation. This device can simulate casing shear deformation caused by formation slippage, accurately obtain the deformation during casing shearing, and thus reveal the casing deformation mechanism and provide experimental basis for casing deformation protection. The casing shear deformation experimental device mainly includes a loading platform, a base, a fixing fixture, a connecting plate, a strain sensor, a shear fixture, and a baffle. The baffle is connected to the fixing fixture via the connecting plate to limit the axial displacement of the shear fixture. The casing is located at the center of a circular through-hole inside the fixing fixture and the shear fixture, and is coaxial with it. The strain sensor is located on the inner wall of the casing at the shearing section between the fixing fixture and the shear fixture. When the loading platform applies a load to the shear fixture, the shear fixture shears the casing, and the strain sensor is used to detect the deformation during the shearing process.

[0008] The two inventions mentioned above simulate the shear deformation of the casing during fault slip or fracture deformation. However, this device can only apply a certain degree of shear force to the casing at a specific angle and direction. It cannot actually reflect how the fault slips after fracturing fluid is introduced during the fracturing process, nor can it consider under what fracturing conditions the fault slip will occur. Applying shear force to the casing does not truly represent the deformation effect of fault slip on the casing. Fault slip causing casing deformation is a very complex process involving fault displacement, fault size, the strength of the fault structure, fracturing parameters, etc.

[0009] Chinese invention patent CN 115573705B, entitled "Physical Simulation Method for Horizontal Section Casing Deformation in Deep Shale Gas Wells," discloses a physical simulation method for the deformation of horizontal section casing in deep shale gas wells. This method solves the problem of the correlation between casing deformation and perforation parameters during fracturing operations and can be used to analyze the relationship between fracture morphology and casing deformation under different perforation parameters. Specific steps include: conducting simulation experiments using artificial rock samples and drilling a circular hole in the center of the specimen; mixing cement into a cement slurry state, wrapping the perforation with absorbent paper, placing the casing into a pre-fabricated wellbore, slowly pouring in the cement slurry until the casing perforation is completely covered, then sealing and waiting for the cement slurry to completely solidify; placing the specimen in a true triaxial loading chamber, sealing the injection line to the casing, applying triaxial stress to the specimen, and injecting slickwater fracturing fluid containing a dye using a constant-speed, constant-pressure pump until the specimen fractures; unloading the confining pressure pump and removing the specimen to observe the fracture propagation morphology and casing deformation at the fracture site. In studying casing deformation, this invention does not employ real-time monitoring methods for the casing, making it impossible to determine under which working conditions and pressures the casing deformation is greatest. Furthermore, by modeling based on the crack description of the specimen and the deformation morphology of the casing, it can only infer the crack development law generated during the fracturing process and the magnitude of casing deformation caused by fracturing based on the results, without being able to study and explain it from the perspective of principles and mechanisms.

[0010] Chinese invention patent application CN 116575909A, entitled "A Method and Device for Early Warning of Shale Oil and Gas Casing Deformation," describes a method comprising: determining the risk level of microseismic event points in the real-time fractured section of the target fractured well based on microseismic event point data and a pre-determined risk level standard for microseismic event points; determining the construction pressure risk level of the real-time fractured section based on construction pressure data, construction displacement data, and a pre-determined construction pressure drop early warning standard; determining the probability of natural fracture / fault slippage based on the risk level of microseismic event points in the real-time fractured section of the target fractured well, the spatial distribution characteristics of microseismic event points, and the risk level of construction pressure; and issuing an early warning of casing deformation based on the probability of natural fracture / fault slippage and the positional relationship between the microseismic event points in the real-time fractured section and the wellbore.

[0011] Chinese invention patent application CN 117027678A, entitled "A Method for Preventing Deformation of Oil and Gas Well Casing," includes the following steps: S1, determining the risk points of casing deformation throughout the well section and establishing a stress analysis model at the risk points; S2, preparing a hollow ring based on the stress analysis model; S4, fitting the prepared hollow ring onto the outside of the casing, ensuring that the hollow ring is coaxial with the casing; S5, lowering the casing with the hollow ring into the well; S6, cementing the wellbore with the casing installed.

[0012] The two inventions mentioned above are devices and methods for preventing casing deformation in oil and gas wells. Both aim to prevent the risk of casing deformation caused by fracturing during the fracturing process. The risk level is determined based on existing microseismic data, and then corresponding preventive measures are proposed based on the risk level. The above methods can reduce the risk of casing deformation to a certain extent, but they do not consider the impact of the fracturing well on the casing of adjacent wells during the zipper-type fracturing process of horizontal wells. Summary of the Invention

[0013] The purpose of this section is to outline some aspects of embodiments of the present invention and to briefly describe some preferred embodiments. Simplifications or omissions may be made in this section, as well as in the abstract and title of this application, to avoid obscuring the purpose of these documents; however, such simplifications or omissions should not be construed as limiting the scope of the invention.

[0014] In view of the problems existing in the above and / or prior art, the present invention is proposed.

[0015] The primary objective of this invention is to investigate the casing deformation problem during the zipper-type fracturing process in shale oil horizontal wells and to provide a casing deformation simulation device for zipper-type fracturing in shale oil horizontal wells, so as to study and solve the problem of damage or shear deformation of the casing of adjacent wells during the fracturing process.

[0016] To address the above technical problems, the present invention provides a zipper-type fracturing casing deformation simulation device for shale oil horizontal wells, comprising two identical formation wellbore simulation units. Each of the two formation wellbore simulation units is equipped with a simulated formation casing assembly, which includes a fault upper plate, a fault, a fault lower plate, and a perforated casing. The fault is located between the fault upper plate and the fault lower plate, and a wellbore is drilled along the axis of the fault upper plate, the fault, and the fault lower plate. The perforated casing is located within the wellbore, and a cement sheath is formed around its outer periphery through cementing. The faults in the two formation wellbore simulation units are connected by a fault connecting pipe. The fault connecting pipe uses valves to control the flow rate of fracturing fluid and pressure gauges to monitor the pressure within the fault.

[0017] Furthermore, the formation wellbore simulation unit is also equipped with a geostress loading system, which includes a triaxial test frame, a hydraulic arm, and a pressure plate. The simulated formation casing assembly is placed in the triaxial test frame, and the pressure plates abut against the outer walls of the fault hanging wall and the fault footwall respectively. The center of the outer wall of each pressure plate is driven by the corresponding hydraulic arm to apply triaxial geostress to the fault hanging wall and the fault footwall respectively.

[0018] Furthermore, the ground stress loading system also includes a hydraulic pump, a high-pressure hydraulic pipeline, an integrated control box, and a hydraulic control pipeline. The high-pressure oil output by the hydraulic pump is provided to the integrated control box through the high-pressure hydraulic pipeline. The integrated control box distributes the high-pressure oil to each of the hydraulic arms and controls the movement and pressure of each hydraulic arm through the hydraulic control pipeline.

[0019] Furthermore, the ground stress loading system also includes a hydraulic control cabinet, which is equipped with a computer, multiple sets of ground stress pressure gauges and multiple sets of ground stress control knobs, and controls the integrated control box through an integrated box control line and the hydraulic pump through a hydraulic pump control line.

[0020] Furthermore, the formation wellbore simulation unit is also equipped with a data monitoring system, which includes an oscilloscope, a stress sensor, a data transmission line, and a transmission line protection tube. The stress sensor is installed on the inner wall near the perforation hole of the perforated casing and is connected to the oscilloscope through the data transmission line. The data processing terminal on the computer monitors the stress of the casing by processing the data in the oscilloscope.

[0021] Furthermore, the formation wellbore simulation unit is also equipped with an injection system and a drainage system. The injection system includes a fracturing fluid tank, an injection pump, and an injection pipeline. The inlet pipe of the injection pump is connected to the outlet of the fracturing fluid tank, and the outlet of the injection pump is connected to the inlet end of the perforated casing through the injection pipeline. The injection pipeline is equipped with an injection valve and an injection pressure gauge in sequence along the fracturing fluid flow direction. The drainage system includes a drainage pipeline and a fracturing fluid collection tank. The drainage end of the perforated casing is connected to the fracturing fluid collection tank through the drainage pipeline. The drainage pipeline is equipped with a drainage pressure gauge and a drainage valve in sequence along the flow direction of the fracturing fluid.

[0022] Furthermore, the fault was constructed using shale fragments and foamed concrete.

[0023] Another objective of this invention is to overcome the problems existing in the prior art and provide a method for simulating the deformation of zipper-type fracturing casing in shale oil horizontal wells, so as to study and solve the problem of damage or shear deformation of the casing of adjacent wells caused by fracturing.

[0024] To solve the above technical problems, the present invention provides a shale oil horizontal well zipper-type fracturing casing deformation simulation method, which employs the aforementioned shale oil horizontal well zipper-type fracturing casing deformation simulation device. The dual-wellbore zipper-type fracturing sequentially includes the following steps: S1. Collect shale outcrops or rock samples in the field or at the construction site, prepare the hanging wall and footwall of the fault, and mark them. S2. Place the hanging wall and footwall of the fault in the rock sample mold, leaving a fault gap in the middle of the rock sample mold. Pour shale debris and foamed concrete into the reserved fault gap in the middle and let it solidify to form a simulated formation connecting the hanging wall and footwall of the fault. According to the corresponding casing size, drill holes in the hanging wall, simulated formation and footwall of the fault to form a simulated wellbore, leaving space for casing to be lowered. S3. Based on the perforation parameters at the site, use a drilling machine to pre-drill perforations on the casing; place the perforated casing in the center of the simulated well, cement it with cementing cement, and after it solidifies to form a cement sheath, connect all the perforations to make a simulated formation casing assembly. S4. Install the simulated formation casing assembly into the triaxial test frame of Well 1 and Well 2 respectively, and attach the pressure plate to the outer walls of the hanging wall and footwall of the fault respectively; then turn on the in-situ stress loading system of Well 1 and Well 2 to apply triaxial in-situ stress to the fractured well and the adjacent well. S5. Open the injection system and fault connection pipe valve of Well 1, and inject fracturing fluid into the perforated casing of Well 1 through the injection pipeline. Observe the injection pressure gauge and record the pressure data. Set the fracturing pressure according to the on-site fracturing data. Stop pressurizing when the fracturing fluid pressure reaches the set pressure and keep the pressure stable. After the fracturing fluid enters the perforated casing of Well 1, as the pressure increases, it enters the simulated formation along the perforation, causing the strength of the fault structure to weaken and cracks to form in the hanging wall and footwall. By observing the horizontal planes of the hanging wall and footwall, it is determined whether the footwall or hanging wall will slip or displace under the action of the stress difference.

[0025] Furthermore, dual-wellbore zipper fracturing also includes the following steps: S6. The fracturing fluid enters the fault connection pipe along the fractures in the simulated formation and then enters the simulated formation in Well 2, causing a change in the stress on the casing of the adjacent well. The pressure in the simulated formation in Well 2 is monitored and recorded by observing the pressure gauge on the fault connection pipe. S7. Observe the oscilloscope and computer data processing terminal of Well 1 and Well 2. After the pressure fluctuation occurs, the stress sensor transmits the stress data to the oscilloscope through the data transmission line. The data processing terminal generates stress data by processing the signal of the oscilloscope. By observing the stress change of the casing, the stress change of the casing of Well 1 and Well 2 during the fracturing process of Well 1 can be monitored in real time, and the casing damage can be monitored in real time.

[0026] Furthermore, dual-wellbore zipper fracturing also includes the following steps: S8. When the casing stress in well 1 and well 2 tends to stabilize, close the injection valve and hydraulic pump of well 1, open the drain valves of well 1 and well 2, and drain the fracturing fluid in well 1 and well 2 to simulate the flowback stage in the fracturing process. During the backflow process, the pressure gauge of the drain fluid is monitored and the data is recorded. The backflow situation is analyzed through the pressure data of the drain fluid pipeline. At the same time, the stress of the sleeve in the data processing terminal is monitored to observe whether the backflow process will cause damage to the sleeve.

[0027] Furthermore, dual-wellbore zipper fracturing also includes the following steps: S9. Close the drain valves of Well 1 and Well 2, open the injection system of Well 2, and inject fracturing fluid into the perforated casing of Well 2 through the injection pipeline. Observe the injection pressure gauge and record the pressure data. Set the fracturing pressure according to the on-site fracturing data. When the fracturing fluid pressure reaches the set pressure, stop pressurizing and keep the pressure stable. After the fracturing fluid enters the perforated casing of Well 2, as the pressure increases, it enters the simulated formation along the perforation, causing the strength of the fault structure to weaken and cracks to form in the hanging wall and footwall. By observing the horizontal planes of the hanging wall and footwall, it is determined whether the footwall or hanging wall will slip or displace under the action of the stress difference.

[0028] Furthermore, dual-wellbore zipper fracturing also includes the following steps: S10. The fracturing fluid enters the fault connection pipe along the fracture of the simulated formation and then enters the simulated formation of Well 1, causing a change in the stress on the casing of the adjacent well. The pressure in the simulated formation of Well 1 is monitored and recorded by observing the pressure gauge on the fault connection pipe. S11. Observe the oscilloscope and computer data processing terminal of Well 1 and Well 2. After the stress sensor generates pressure fluctuation, it transmits stress data to the oscilloscope through the data transmission line. The data processing terminal generates stress data by processing the oscilloscope signal. By observing the stress change of the casing, the stress change of the casing of Well 1 and Well 2 during the fracturing process of Well 2 is monitored in real time, and the casing damage is monitored in real time.

[0029] Furthermore, dual-wellbore zipper fracturing also includes the following steps: S12. When the casing stress in Well 2 and Well 1 tends to stabilize, close the injection valve and hydraulic pump of Well 2, open the drainage valves of Well 2 and Well 1, and drain the liquid in Well 2 and Well 1 to simulate the flowback stage in the fracturing process. During the backflow process, the pressure gauge of the drain fluid is monitored and the data is recorded. The backflow situation is analyzed through the pressure data of the drain fluid pipeline. At the same time, the stress of the sleeve in the data processing terminal is monitored to observe whether the backflow process will cause damage to the sleeve.

[0030] Furthermore, dual-wellbore zipper fracturing also includes the following steps: S13. Close all switches and valves, remove the simulated formation casing assembly from the triaxial test frame, separate the perforated casing from the simulated formation, observe the morphological changes on the casing surface and the fracture propagation of the simulated formation for analysis and research, and take photos for recording.

[0031] Furthermore, in step S1, the outcrop or rock sample is cut into 500mm*500mm*400mm shale blocks using a large cutting device, which serve as the hanging wall and footwall of the fault, respectively. The lithology and size of the hanging wall and footwall are consistent.

[0032] Furthermore, in step S2, the dimensions of the rock sample mold are 1000mm*500mm*500mm, and the thickness of the reserved fault is determined based on the fault data obtained from well logging data or seismic data.

[0033] Furthermore, in step S4, while activating the geostress loading system, the data monitoring systems for well one and well two are also activated to monitor the stress on the casing of each well.

[0034] Furthermore, in step S4, the hydraulic pump is started, and high-pressure oil enters the integrated control box through the high-pressure hydraulic pipeline, and is then distributed to each hydraulic arm. Each hydraulic arm drives the corresponding pressure plate to push out, and the hydraulic control pipeline controls the movement and pressure of the hydraulic arm so that the pressure plate applies triaxial stress of different magnitudes to the hanging wall and footwall of the fault.

[0035] Compared with the prior art, the present invention has achieved the following beneficial effects: 1. When carrying out the zipper fracturing process near the fault, the pressure wave will preferentially be transmitted to the adjacent well along the fault, causing stress changes in the fault and the vicinity of the adjacent well, increasing the external extrusion force on the casing of the adjacent well; the present invention can simulate the real shale oil horizontal well dual-wellbore zipper fracturing process, and monitor the casing stress changes of the adjacent well through the data monitoring system during fracturing of the fracturing well, and judge the casing damage of the adjacent well by the magnitude of the stress; 2. By simulating the real zipper-like fracturing process, the fracture network development law of zipper-like fracturing can be obtained by studying the fracture development law in the rock sample after the experiment is completed; 3. The influence of various fault parameters on casing deformation can be studied by changing the fault distance, fault length, and fault structural strength. 4. It can provide different magnitudes of geostress for the hanging wall and footwall of a fault, simulating the real geostress state; 5. By monitoring stress changes in the casing, the strength and deformation state of the casing can be calculated. The risk of casing deformation can be assessed using fracturing parameters, allowing for optimization of these parameters and reducing the likelihood of casing deformation. 6. It can monitor the stress on the casing of adjacent wells during the dual-well fracturing process and determine whether the fracturing well will affect the safety performance of the casing of adjacent wells. 7. It can simulate not only dual-wellbore zipper fracturing but also single-wellbore fracturing, and can monitor whether casing damage or deformation will occur during the flowback stage. 8. It can be used in shale oil development to simulate the dual-wellbore zipper fracturing process of drilling into faults in an all-round way, evaluate the stress changes of casing in different wellbores during fracturing and the casing deformation risk during dual-wellbore fracturing, so as to achieve the purpose of controlling fracturing construction parameters. 9. This simulation device recreates the real zipper-like fracturing process, monitoring the stress levels in the fracturing well casing and adjacent well casing in real time. It explores various influencing factors on casing deformation by changing construction parameters, perforation parameters, fracturing parameters, formation lithology, fault angle, fault length, and fault size. The device and method of this invention can reveal the casing deformation mechanism during zipper-like fracturing, providing a reference for casing risk assessment and fracturing construction parameter design.

[0036] 10. This device can reveal the deformation and damage mechanism of casing during fracturing, and provide a reference for optimizing construction parameters and assessing the risk of casing deformation. Taking preventative measures before construction can improve production efficiency and reduce production risks. Attached Figure Description

[0037] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort. The drawings are provided for reference and illustration only and are not intended to limit the present invention. Wherein: Figure 1 This is a front view of the zipper-type fracturing casing deformation simulation device for shale oil horizontal wells according to the present invention; Figure 2 for Figure 1 A three-dimensional image; Figure 3 This is a schematic diagram of the geostress loading system in this invention; Figure 4 This is a perspective view of the perforated casing passing through a fault in this invention; Figure 5 This is a flowchart of the fracturing fluid injection and discharge system in this invention; In the diagram: 1. Triaxial experimental setup; 2. Hydraulic control cabinet; 2a. Computer; 2b. Ground stress pressure gauge; 2c. Ground stress control knob; 2d. Hydraulic pump control line; 2e. Integrated box control line; 3. Hydraulic pump; 4. High-pressure hydraulic pipeline; 5. Integrated control box; 6. Hydraulic arm; 7. Hydraulic control pipeline; 8. Pressure plate; 9. Fracturing fluid storage tank; 10. Injection pump; 11. Injection pipeline; 12. Injection valve; 13. Injection pressure gauge; 14. Upper plate of fault; 15. Fracturing plate of fault; 16. Perforation casing; 17. Casing cap; 18. Fracturing connection pipe; 19. Fracturing connection pipe valve; 20. Fracturing connection pipe pressure gauge; 21. Drainage pipeline; 22. Drainage pressure gauge; 23. Drainage valve; 24. Fracturing fluid collection tank; 25. Stress sensor; 26. Data transmission line; 27. Oscilloscope; 28. Detailed Implementation

[0038] In the following description of the present invention, the terms "upper", "lower", "front", "rear", "left", "right", "inner", "outer", etc., indicating the orientation or positional relationship are based on the orientation or positional relationship shown in the accompanying drawings. "Upper" is defined as the end closer to the wellhead or fracturing fluid inlet, and "lower" is defined as the end farther from the wellhead or fracturing fluid inlet. This is only for the convenience of describing the present invention and simplifying the description, and does not mean that the device must have a specific orientation.

[0039] To make the technical means, creative features, objectives, and effects of this invention easier to understand, the invention is further described below with reference to specific illustrations. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them.

[0040] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention.

[0041] like Figures 1 to 5 As shown, the shale oil horizontal well zipper-type fracturing casing deformation simulation device of the present invention includes two formation wellbore simulation units. The two formation wellbore simulation units have the same composition and structure, and are referred to as Well 1 and Well 2 respectively. The two formation wellbore simulation units respectively include a geostress loading system, a data monitoring system, a fluid injection and drainage system, and a simulated formation casing assembly device.

[0042] The simulated formation casing assembly includes a fault hanging wall 14, a fault footwall 16, a fault 15, a perforated casing 17, and a casing cap 18. The fault 15 is located between the fault hanging wall 14 and the fault footwall 16. A wellbore is drilled along the axis of the fault hanging wall 14, the fault 15, and the fault footwall 16. The perforated casing 17 is located in the wellbore and its outer periphery is cemented to form a cement sheath.

[0043] The perforated casing 17 is placed in the formation, and casing caps 18 are installed at both ends of the perforated casing 17. The fault in Well 1 and the fault in Well 2 are connected by a fault connection pipe 19. The fault connection pipe 19 is equipped with a fault connection pipe valve 20 and a fault connection pipe pressure gauge 21. The length of the fault connection pipe 19 can be controlled to control the fault displacement, the opening of the fault connection pipe valve 20 can be adjusted to control the flow rate in the fault, and the fault connection pipe pressure gauge 21 is used to monitor the pressure in the fault.

[0044] The in-situ stress loading system includes a triaxial test frame 1, a hydraulic control cabinet 2, a hydraulic pump 3, high-pressure hydraulic lines 4, a hydraulic arm 6, a pressure plate 8, and an integrated control box 5. The triaxial test frame 1 is a hollow box made of steel plate, with built-in hydraulic control lines 7. The simulated formation casing assembly is placed in the triaxial test frame 1. The triaxial test frame 1 provides different levels of in-situ stress to the hanging wall 14 and the footwall 16 of the fault through the hydraulic arm 6 and the pressure plate 8.

[0045] The high-pressure oil output by the hydraulic pump 3 is supplied to the integrated control box 5 through the high-pressure hydraulic pipeline 4. The integrated control box 5 distributes the high-pressure oil to each hydraulic arm 6 and controls the movement and pressure of each hydraulic arm 6 through the hydraulic control pipeline 7. The pressure plates 8 abut against the outer walls of the fault upper plate 14 and the fault lower plate 16, respectively. The center of the outer wall of each pressure plate 8 is driven by the corresponding hydraulic arm 6 to apply triaxial stress to the fault upper plate 14 and the fault lower plate 16.

[0046] The hydraulic control cabinet 2 contains a computer 2a, ten ground stress pressure gauges 2b, and ten ground stress control knobs 2c. The hydraulic control cabinet 2 controls the integrated control box 5 via integrated box control line 2e, and controls the hydraulic pump 3 to deliver pressure to the triaxial experimental frame 1 via hydraulic pump control line 2d. Different magnitudes of ground stress are applied to the hanging wall 14 and hanging wall 16 of the fault to simulate the real ground stress state.

[0047] The data monitoring system includes an oscilloscope 28, a stress sensor 26, a data processing terminal, a data transmission line 27, and a transmission line protection tube. The stress sensor 26 is installed near the hole of the perforated sleeve 17 and attached to the inner wall of the perforated sleeve 17. It senses stress by detecting the deformation of the inner wall of the sleeve. It is connected to the oscilloscope 28 through the data transmission line 27. The oscilloscope 28 is connected to the computer 2a. The data processing terminal on the computer 2a processes the data displayed on the oscilloscope 28 to monitor the stress changes and thus monitor the stress magnitude of the sleeve.

[0048] The injection system includes a fracturing fluid tank 9, an injection pump 10, and an injection line 11. The inlet pipe of the injection pump 10 is connected to the outlet of the fracturing fluid tank 9, and the outlet of the injection pump 10 is connected to the inlet of the perforated casing 17 via the injection line 11. The injection line 11 is equipped with an injection valve 12 and an injection pressure gauge 13 along the fracturing fluid flow direction. The injection valve 12 is opened and the injection pump 10 is started to inject fracturing fluid into the perforated casing 17. The pressure is observed using the injection pressure gauge 13.

[0049] The fracturing fluid drainage system includes a drainage pipeline 22 and a fracturing fluid collection tank 25. The drainage end of the perforated casing 17 is connected to the fracturing fluid collection tank 25 via the drainage pipeline 22. The drainage pipeline 22 is equipped with a drainage pressure gauge 23 and a drainage valve 24 sequentially along the fracturing fluid flow direction. Opening the drainage valve 24 allows the fracturing fluid to be drained, and the drainage pressure can be observed through the drainage pressure gauge 23.

[0050] This invention can simulate two processes: dual-wellbore zipper fracturing and single-wellbore conventional fracturing. It can also monitor the stress on the casing during the run-back process to simulate the casing deformation problem in the zipper fracturing process. Example

[0051] The dual-wellbore zipper-type fracturing process includes the following steps: S1. Collect shale outcrops or rock samples in the field or at the construction site. Use a large cutting device to cut the outcrops or rock samples into shale blocks of a specific size, usually 500mm*500mm*400mm, to make the hanging wall 14 and the footwall 16 of the fault and mark them. The lithology and size of the hanging wall 14 and the footwall 16 of the fault are consistent.

[0052] S2. Place the hanging wall 14 and footwall 16 of the fault in a rock sample mold. The size of the rock sample mold is 1000mm*500mm*500mm. Based on the fault data obtained from well logging or seismic data, reserve a fault space in the middle of the rock sample mold. Pour shale fragments and foamed concrete into the reserved fault space in the middle, allowing it to solidify and form a simulated formation, i.e., fault 15, connecting the hanging wall 14 and footwall 16. According to the corresponding casing size, use a drill bit of the appropriate size to drill holes in the hanging wall 14, the simulated formation, and the footwall 16 to form a simulated wellbore, reserving space for casing lowering.

[0053] S3. Based on the perforation parameters at the site, use a drilling machine to pre-drill perforations on the casing; place the perforated casing 17 in the center of the simulated well, cement it with cementing cement, and after it solidifies to form a cement sheath, connect all the perforations to make a simulated formation casing assembly.

[0054] S4. The simulated formation casing assembly is sent to the triaxial test frame 1 of well 1 and well 2 respectively via the rock sample transport frame, and the pressure plate 8 is attached to the outer walls of the fault upper plate 14 and the fault lower plate 16 respectively. Then, the hydraulic pump 3 is started, and the high-pressure oil enters the integrated control box 5 through the high-pressure hydraulic pipeline 4, and is then distributed to each hydraulic arm 6. Each hydraulic arm 6 drives the corresponding pressure plate 8 to push out. The hydraulic control pipeline 7 controls the movement and pressure of the hydraulic arm 6 so that the pressure plate 8 applies triaxial stress of different magnitudes to the upper wall 14 and the lower wall 16 of the fault. Simultaneously with activating the ground stress loading system, the data monitoring systems for well 1 and well 2 are also activated to monitor the stress levels on the casings of each well.

[0055] S5. Open the injection system and fault connection pipe valve 20 of well 1, and inject fracturing fluid into the perforated casing 17 of well 1 through the injection pipeline 11. Observe the injection pressure gauge 13 and record the pressure data. Set the fracturing pressure according to the on-site fracturing data. When the pressure of the fracturing fluid reaches the set pressure, stop pressurizing and keep the pressure stable. After the fracturing fluid enters the perforated casing 17 of Well 1, as the pressure increases, it enters the simulated formation along the perforation, causing the strength of the fault structure to weaken. Cracks are generated in the hanging wall 14 and the footwall 16 of the fault. By observing the horizontal planes of the hanging wall 14 and the footwall 16 of the fault, it is determined whether the footwall 16 or the hanging wall 14 of the fault will slip or displace under the action of the geostress difference.

[0056] S6. The fracturing fluid enters the fault connection pipe 19 along the fracture of the simulated formation and enters the simulated formation of Well 2 along the fault connection pipe 19, causing a change in the stress on the casing of the adjacent well. The pressure in the simulated formation of Well 2 is monitored and recorded by observing the fault connection pipe pressure gauge 21 on the fault connection pipe 19.

[0057] S7. Observe the data processing terminal of the oscilloscope 28 and computer 2a of well 1 and well 2. After the stress sensor 26 generates stress data through the data transmission line 27, the stress sensor 26 transmits the stress data to the oscilloscope 28 after the pressure fluctuation occurs. The data processing terminal generates stress data by processing the signal of the oscilloscope 28. By observing the stress change of the casing, the stress change of the casing of well 1 and well 2 is monitored in real time, and the casing damage is monitored in real time.

[0058] S8. When the casing stress in well 1 and well 2 tends to stabilize, close the injection valve 12 and hydraulic pump 3 in well 1, and open the drain valves 24 in well 1 and well 2 to drain the fracturing fluid in well 1 and well 2, simulating the flowback stage in the fracturing process; monitor the drain pressure gauge 23 and record the data during the flowback process, and analyze the flowback situation through the pressure data of the drain pipeline 22; at the same time, monitor the casing stress in the data processing terminal and observe whether the flowback process will cause casing damage.

[0059] S9. Close the drainage valves 24 of well 1 and well 2, open the injection system of well 2, inject fracturing fluid into the perforated casing 17 of well 2 through the injection pipeline 11, observe the injection pressure gauge 13 and record the pressure data; set the fracturing pressure according to the on-site fracturing data, stop pressurizing when the fracturing fluid pressure reaches the set pressure, and keep the pressure stable. After the fracturing fluid enters the perforated casing 17 of Well 2, as the pressure increases, it enters the simulated formation along the perforation, causing the strength of the fault structure to weaken. Cracks are generated in the hanging wall 14 and the footwall 16 of the fault. By observing the horizontal planes of the hanging wall 14 and the footwall 16 of the fault, it is determined whether the footwall 16 or the hanging wall 14 of the fault will slip or displace under the action of the geostress difference.

[0060] S10. The fracturing fluid enters the fault connection pipe 19 along the fracture of the simulated formation and enters the simulated formation of Well 1 along the fault connection pipe 19, causing a change in the stress on the casing of the adjacent well. The pressure in the simulated formation of Well 1 is monitored and recorded by observing the pressure gauge on the fault connection pipe 19.

[0061] S11. Observe the data processing terminal of the oscilloscope 28 and computer 2a of well 1 and well 2. After the stress sensor 26 generates stress data through the data transmission line 27, the stress sensor 26 transmits the stress data to the oscilloscope 28 after the pressure fluctuation occurs. The data processing terminal generates stress data by processing the signal of the oscilloscope 28. By observing the stress change of the casing, the stress change of the casing of well 1 and well 2 is monitored in real time during the fracturing process of well 2, and the casing damage is monitored in real time.

[0062] S12. When the casing stress in well 2 and well 1 tends to stabilize, close the injection valve 12 and hydraulic pump 3 of well 2, open the drain valve 24 of well 2 and well 1 to drain the liquid in well 2 and well 1, simulating the flowback stage in the fracturing process. During the backflow process, the pressure gauge 23 is monitored and the data is recorded. The backflow situation is analyzed through the pressure data of the backflow pipeline 22. At the same time, the stress of the sleeve in the data processing terminal is monitored to observe whether the backflow process will cause damage to the sleeve.

[0063] S13. Close all switches and valves, remove the simulated formation casing assembly from the triaxial test frame 1, separate the perforated casing 17 from the simulated formation, observe the morphological changes on the casing surface and the fracture propagation of the simulated formation for analysis and research, and take photos for recording. Example

[0064] Single-well zipper fracturing includes the following steps: D1. Collect shale outcrops or rock samples in the field or at the construction site. Use a large cutting device to cut the outcrops or rock samples into shale blocks of a specific size, usually 500mm*500mm*400mm, to make the hanging wall 14 and the footwall 16 of the fault and mark them. The lithology and size of the hanging wall 14 and the footwall 16 of the fault are consistent.

[0065] D2. Place the hanging wall 14 and footwall 16 of the fault in a rock sample mold. The size of the rock sample mold is 1000mm*500mm*500mm. Based on the fault data obtained from well logging or seismic data, reserve a fault space in the middle of the rock sample mold. Pour shale fragments and foamed concrete into the reserved fault space in the middle, allowing it to solidify and form a simulated formation, i.e., fault 15, connecting the hanging wall 14 and footwall 16. According to the corresponding casing size, use a drill bit of the appropriate size to drill holes in the hanging wall 14, the simulated formation, and the footwall 16 to form a simulated wellbore, reserving space for casing lowering.

[0066] D3. Based on the perforation parameters at the site, use a drilling machine to pre-drill perforations on the casing; place the perforated casing 17 in the center of the simulated well, cement it with cementing cement, and after solidification to form a cement sheath, connect all the perforations to make a simulated formation casing assembly.

[0067] D4. The simulated formation casing assembly is sent to a triaxial test frame 1 via a rock sample transport frame, and the pressure plate 8 is respectively attached to the outer walls of the fault hanging wall 14 and the fault footwall 16. Then, the hydraulic pump 3 is started, and the high-pressure oil enters the integrated control box 5 through the high-pressure hydraulic pipeline 4, and is then distributed to each hydraulic arm 6. Each hydraulic arm 6 drives the corresponding pressure plate 8 to push out. The hydraulic control pipeline 7 controls the movement and pressure of the hydraulic arm 6 so that the pressure plate 8 applies triaxial stress of different magnitudes to the upper wall 14 and the lower wall 16 of the fault. Simultaneously with activating the ground stress loading system, the data monitoring system is also activated to monitor the stress magnitude experienced by the casing.

[0068] D5. Open the injection system and inject fracturing fluid into the perforated casing 17 through the injection line 11. Observe the injection pressure gauge 13 and record the pressure data. Set the fracturing pressure according to the field fracturing data. Stop pressurizing when the fracturing fluid pressure reaches the set pressure and keep the pressure stable. After the fracturing fluid enters the perforated casing 17, as the pressure increases, it enters the simulated formation along the perforation, causing the strength of the fault structure surface to weaken. Cracks are generated in the hanging wall 14 and the footwall 16 of the fault. By observing the horizontal planes of the hanging wall 14 and the footwall 16 of the fault, it is determined whether the footwall 16 or the hanging wall 14 of the fault will slip or displace under the action of the stress difference.

[0069] D6. Observe the data processing terminal of oscilloscope 28 and computer 2a. After the stress sensor 26 generates stress data, it transmits the stress data to oscilloscope 28 through data transmission line 27. The data processing terminal generates stress data by processing the signal of oscilloscope 28. By observing the stress change of the casing, the stress change of the casing during fracturing is monitored in real time, and the casing damage is monitored in real time.

[0070] D7. When the casing stress tends to stabilize, close the injection valve 12 and hydraulic pump 3, open the drain valve 24 to drain the fracturing fluid, simulating the flowback stage in the fracturing process; during the flowback process, monitor the drain pressure gauge 23 and record the data, and analyze the flowback situation through the pressure data of the drain pipeline 22; at the same time, monitor the casing stress in the data processing terminal and observe whether the flowback process will cause casing damage.

[0071] D8. Close all switches and valves, remove the simulated formation casing assembly from the triaxial test frame 1, separate the perforated casing 17 from the simulated formation, observe the morphological changes on the casing surface and the fracture propagation of the simulated formation for analysis and research, and take photos for recording.

[0072] This invention utilizes foamed concrete and shale cuttings to simulate weak fault structures. By injecting fracturing fluid into the perforated casing 17, it simulates the situation where, during fracturing, the drilling encounters a fault, and the fracturing fluid enters the formation, causing deformation of the casing in both the main well and adjacent wells. The foamed concrete parameters of the fault can be adjusted to simulate weak fault surfaces of varying strengths, and the influence of pump pressure during fracturing on casing deformation can be determined.

[0073] The above description is merely a preferred embodiment of the present invention, showing and describing the basic principles, main features, and advantages of the present invention. It is not intended to limit the scope of patent protection of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. In addition to the above embodiments, the present invention may have other implementations without departing from the spirit and scope of the invention. Various changes and modifications to the present invention are possible, and all technical solutions formed by equivalent substitutions or equivalent transformations fall within the scope of protection claimed by the present invention. The scope of protection of the present invention is defined by the appended claims and their equivalents. Technical features not described in the present invention can be implemented by or using existing technology, and will not be elaborated here.

Claims

1. A zipper-type fracturing casing deformation simulation device for shale oil horizontal wells, characterized in that, The system comprises two identical formation wellbore simulation units, each equipped with a simulated formation casing assembly. Each simulated formation casing assembly includes a fault hanging wall, a fault, a fault footwall, and a perforated casing. The fault is located between the fault hanging wall and the fault footwall. A wellbore is drilled along the axis of the fault hanging wall, the fault, and the fault footwall. The perforated casing is located within the wellbore, and a cement sheath is formed around its outer periphery through cementing. The faults in the two formation wellbore simulation units are connected by a fault connecting pipe. The fault connecting pipe uses valves to control the flow rate of fracturing fluid and pressure gauges to monitor the pressure within the fault.

2. The shale oil horizontal well zipper-type fracturing casing deformation simulation device according to claim 1, characterized in that: The formation wellbore simulation unit is also equipped with a geostress loading system, which includes a triaxial test frame, a hydraulic arm, and a pressure plate. The simulated formation casing assembly is placed in the triaxial test frame. The pressure plates abut against the outer walls of the hanging wall and footwall of the fault, respectively. The center of the outer wall of each pressure plate is driven by the corresponding hydraulic arm to apply triaxial geostress to the hanging wall and footwall of the fault.

3. The shale oil horizontal well zipper-type fracturing casing deformation simulation device according to claim 1, characterized in that: The ground stress loading system also includes a hydraulic pump, a high-pressure hydraulic pipeline, an integrated control box, and a hydraulic control pipeline. The high-pressure oil output by the hydraulic pump is supplied to the integrated control box through the high-pressure hydraulic pipeline. The integrated control box distributes the high-pressure oil to each of the hydraulic arms and controls the movement and pressure of each hydraulic arm through the hydraulic control pipeline.

4. The shale oil horizontal well zipper-type fracturing casing deformation simulation device according to claim 3, characterized in that: The ground stress loading system also includes a hydraulic control cabinet, which is equipped with a computer, multiple sets of ground stress pressure gauges and multiple sets of ground stress control knobs. The integrated control box is controlled via an integrated box control line, and the hydraulic pump is controlled via a hydraulic pump control line.

5. The shale oil horizontal well zipper-type fracturing casing deformation simulation device according to claim 3, characterized in that: The formation wellbore simulation unit is also equipped with a data monitoring system, which includes an oscilloscope, a stress sensor, a data transmission line, and a transmission line protection tube. The stress sensor is installed on the inner wall near the perforation hole of the perforated casing and is connected to the oscilloscope through the data transmission line. The data processing terminal on the computer monitors the stress of the casing by processing the data in the oscilloscope.

6. The shale oil horizontal well zipper-type fracturing casing deformation simulation device according to claim 1, characterized in that: The formation wellbore simulation unit is also equipped with an injection system and a drainage system. The injection system includes a fracturing fluid tank, an injection pump, and an injection pipeline. The inlet pipe of the injection pump is connected to the outlet of the fracturing fluid tank, and the outlet of the injection pump is connected to the inlet end of the perforated casing through the injection pipeline. The injection pipeline is equipped with an injection valve and an injection pressure gauge in sequence along the fracturing fluid flow direction. The drainage system includes a drainage pipeline and a fracturing fluid collection tank. The drainage end of the perforated casing is connected to the fracturing fluid collection tank through the drainage pipeline. The drainage pipeline is equipped with a drainage pressure gauge and a drainage valve in sequence along the flow direction of the fracturing fluid.

7. The shale oil horizontal well zipper-type fracturing casing deformation simulation device according to claim 1, characterized in that: The fault was constructed using shale fragments and foamed concrete.

8. A method for simulating the deformation of a zipper-type fracturing casing in a shale oil horizontal well, employing the zipper-type fracturing casing deformation simulation device as described in claim 4, characterized in that... The dual-wellbore zipper-type fracturing process includes the following steps: S1. Collect shale outcrops or rock samples in the field or at the construction site, prepare the hanging wall and footwall of the fault, and mark them. S2. Place the hanging wall and footwall of the fault in the rock sample mold, leaving a fault gap in the middle of the rock sample mold. Pour shale debris and foamed concrete into the reserved fault gap in the middle and let it solidify to form a simulated formation connecting the hanging wall and footwall of the fault. According to the corresponding casing size, drill holes in the hanging wall, simulated formation and footwall of the fault to form a simulated wellbore, leaving space for casing to be lowered. S3. Based on the perforation parameters at the site, use a drilling machine to pre-drill perforations on the casing; place the perforated casing in the center of the simulated well, cement it with cementing cement, and after it solidifies to form a cement sheath, connect all the perforations to make a simulated formation casing assembly. S4. Install the simulated formation casing assembly into the triaxial test frame of Well 1 and Well 2 respectively, and attach the pressure plate to the outer walls of the hanging wall and footwall of the fault respectively; then turn on the in-situ stress loading system of Well 1 and Well 2 to apply triaxial in-situ stress to the fractured well and the adjacent well. S5. Open the injection system and fault connection pipe valve of Well 1, and inject fracturing fluid into the perforated casing of Well 1 through the injection pipeline. Observe the injection pressure gauge and record the pressure data. Set the fracturing pressure according to the on-site fracturing data. Stop pressurizing when the fracturing fluid pressure reaches the set pressure and keep the pressure stable. After the fracturing fluid enters the perforated casing of Well 1, as the pressure increases, it enters the simulated formation along the perforation, causing the strength of the fault structure to weaken and cracks to form in the hanging wall and footwall. By observing the horizontal planes of the hanging wall and footwall, it is determined whether the footwall or hanging wall will slip or displace under the action of the stress difference.

9. The method for simulating the deformation of zipper-type fracturing casing in shale oil horizontal wells according to claim 8, characterized in that, Dual-bore zipper fracturing also includes the following steps: S6. The fracturing fluid enters the fault connection pipe along the fractures in the simulated formation and then enters the simulated formation in Well 2, causing a change in the stress on the casing of the adjacent well. The pressure in the simulated formation in Well 2 is monitored and recorded by observing the pressure gauge on the fault connection pipe. S7. Observe the oscilloscope and computer data processing terminal of Well 1 and Well 2. After the pressure fluctuation occurs, the stress sensor transmits the stress data to the oscilloscope through the data transmission line. The data processing terminal generates stress data by processing the signal of the oscilloscope. By observing the stress change of the casing, the stress change of the casing of Well 1 and Well 2 during the fracturing process of Well 1 can be monitored in real time, and the casing damage can be monitored in real time.

10. The method for simulating the deformation of zipper-type fracturing casing in shale oil horizontal wells according to claim 9, characterized in that, Dual-bore zipper fracturing also includes the following steps: S8. When the casing stress in well 1 and well 2 tends to stabilize, close the injection valve and hydraulic pump of well 1, open the drain valves of well 1 and well 2, and drain the fracturing fluid in well 1 and well 2 to simulate the flowback stage in the fracturing process. During the backflow process, the pressure gauge of the drain fluid is monitored and the data is recorded. The backflow situation is analyzed through the pressure data of the drain fluid pipeline. At the same time, the stress of the sleeve in the data processing terminal is monitored to observe whether the backflow process will cause damage to the sleeve.

11. The method for simulating the deformation of zipper-type fracturing casing in shale oil horizontal wells according to claim 10, characterized in that, Dual-bore zipper fracturing also includes the following steps: S9. Close the drain valves of Well 1 and Well 2, open the injection system of Well 2, and inject fracturing fluid into the perforated casing of Well 2 through the injection pipeline. Observe the injection pressure gauge and record the pressure data. Set the fracturing pressure according to the on-site fracturing data. When the fracturing fluid pressure reaches the set pressure, stop pressurizing and keep the pressure stable. After the fracturing fluid enters the perforated casing of Well 2, as the pressure increases, it enters the simulated formation along the perforation, causing the strength of the fault structure to weaken and cracks to form in the hanging wall and footwall. By observing the horizontal planes of the hanging wall and footwall, it is determined whether the footwall or hanging wall will slip or displace under the action of the stress difference.

12. The method for simulating the deformation of zipper-type fracturing casing in shale oil horizontal wells according to claim 11, characterized in that, Dual-bore zipper fracturing also includes the following steps: S10. The fracturing fluid enters the fault connection pipe along the fracture of the simulated formation and then enters the simulated formation of Well 1, causing a change in the stress on the casing of the adjacent well. The pressure in the simulated formation of Well 1 is monitored and recorded by observing the pressure gauge on the fault connection pipe. S11. Observe the oscilloscope and computer data processing terminal of Well 1 and Well 2. After the stress sensor generates pressure fluctuation, it transmits stress data to the oscilloscope through the data transmission line. The data processing terminal generates stress data by processing the oscilloscope signal. By observing the stress change of the casing, the stress change of the casing of Well 1 and Well 2 during the fracturing process of Well 2 is monitored in real time, and the casing damage is monitored in real time.

13. The method for simulating the deformation of zipper-type fracturing casing in shale oil horizontal wells according to claim 12, characterized in that, Dual-bore zipper fracturing also includes the following steps: S12. When the casing stress in Well 2 and Well 1 tends to stabilize, close the injection valve and hydraulic pump of Well 2, open the drainage valves of Well 2 and Well 1, and drain the liquid in Well 2 and Well 1 to simulate the flowback stage in the fracturing process. During the backflow process, the pressure gauge of the drain fluid is monitored and the data is recorded. The backflow situation is analyzed through the pressure data of the drain fluid pipeline. At the same time, the stress of the sleeve in the data processing terminal is monitored to observe whether the backflow process will cause damage to the sleeve.

14. The method for simulating the deformation of zipper-type fracturing casing in shale oil horizontal wells according to claim 13, characterized in that, Dual-bore zipper fracturing also includes the following steps: S13. Close all switches and valves, remove the simulated formation casing assembly from the triaxial test frame, separate the perforated casing from the simulated formation, observe the morphological changes on the casing surface and the fracture propagation of the simulated formation for analysis and research, and take photos for recording.

15. The method for simulating the deformation of zipper-type fracturing casing in shale oil horizontal wells according to claim 8, characterized in that: In step S1, the outcrop or rock sample is cut into 500mm*500mm*400mm shale blocks using a large cutting device, which are respectively used as the hanging wall and footwall of the fault. The lithology and size of the hanging wall and footwall are the same.

16. The method for simulating the deformation of zipper-type fracturing casing in shale oil horizontal wells according to claim 8, characterized in that: In step S2, the dimensions of the rock sample mold are 1000mm*500mm*500mm, and the thickness of the reserved fault is determined based on the fault data obtained from well logging data or seismic data.

17. The method for simulating the deformation of zipper-type fracturing casing in shale oil horizontal wells according to claim 8, characterized in that: In step S4, while activating the ground stress loading system, the data monitoring systems for well 1 and well 2 are also activated to monitor the stress magnitude on the casing of each well.

18. The method for simulating the deformation of zipper-type fracturing casing in shale oil horizontal wells according to claim 8, characterized in that: In step S4, the hydraulic pump is started, and high-pressure oil enters the integrated control box through the high-pressure hydraulic pipeline, and is then distributed to each hydraulic arm. Each hydraulic arm drives the corresponding pressure plate to push out. The hydraulic control pipeline controls the movement and pressure of the hydraulic arm so that the pressure plate applies triaxial stress of different magnitudes to the hanging wall and footwall of the fault.

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