True triaxial hydrofracture fault slip casing deformation monitoring method and system

Abstract

The invention relates to the technical field of hydrofracture simulation experiments, in particular to a true triaxial hydrofracture fault slippage casing deformation monitoring method and system, and the method comprises the steps: preparing a target reservoir simulation sample; arranging and installing a shaft and a sensor; carrying out a water pressure physical model experiment and recording experiment data; and analyzing and processing the experimental data, and performing quantitative evaluation by combining the final state of the target reservoir simulation sample. According to the method, the shear deformation influence of fault slippage on the shaft casing under the true triaxial hydraulic fracturing condition can be quantitatively evaluated; scientific basis is provided for optimization of fracturing optimization design parameters, and engineering practical significance is achieved for optimization of the horizontal well casing damage prevention and control theory and on-site construction design.

Description

Technical Field

[0001] The invention relates to the technical field of hydraulic fracturing simulation experiments, and in particular to a true triaxial hydraulic fracturing fault slip casing deformation monitoring method and system. Background Art

[0002] Unconventional oil and gas reservoirs, due to their common low porosity and low permeability, pose great challenges to exploration and development. In order to achieve economical gas flow acquisition and commercial exploitation goals, it is necessary to transform the reservoir with the help of volume fracturing technology to improve the formation conductivity. However, during the fracturing process of the reservoir, the invasion of high-pressure fluid into the fault plane will cause the pore pressure to rise, thereby reducing the normal stress acting on the fault. At the same time, the shear stress parallel to the fault plane may exceed the shear strength of the fault, inducing shear slip of the fault. The fault slip phenomenon has a significant impact on the stress state of the surrounding casing-cement sheath system, resulting in uneven stress distribution. When the slip displacement reaches a certain amplitude, it will cause casing deformation, and in severe cases, it will even significantly reduce the gas production of a single well and shorten the service life of the wellbore. In response to this complex problem, domestic and foreign scholars have widely carried out numerical simulation and theoretical research on the shear characteristics of the fault structure and casing deformation. Despite this, there is still a relative lack of experimental research in the laboratory on casing damage caused by fault slip. Summary of the invention

[0003] The purpose of the present invention is to provide a true triaxial hydraulic fracturing fault slip casing deformation monitoring method and system in order to solve at least one of the above technical problems.

[0004] The present invention achieves the above-mentioned purpose through the following technical solutions:

[0005] A true triaxial hydraulic fracturing fault slip casing deformation monitoring method comprises the following steps:

[0006] Prepare target reservoir simulation samples;

[0007] Arrange and install wellbore and sensors;

[0008] Carry out hydraulic pressure model experiments and record the experimental data;

[0009] The experimental data are analyzed and processed, and quantitative evaluation is performed in combination with the final state of the target reservoir simulation sample.

[0010] Furthermore, the target reservoir is a tight reservoir containing faults.

[0011] Further, preparing a target reservoir simulation sample includes:

[0012] Use real rocks as sample raw materials;

[0013] The fault is prepared by cutting first and then cementing.

[0014] Furthermore, the fault is prepared by cutting first and then cementing, specifically:

[0015] According to the test design requirements, the fault cutting line is drawn on the specimen, and a large rock table saw is used to cut the specimen along the cutting line. The cutting thickness is determined according to the bonding material.

[0016] Furthermore, the wellbore and sensors are arranged and installed, including:

[0017] According to the test design requirements, wellbores are drilled at the center points of the front and rear surfaces of the target reservoir simulation sample along the direction of the minimum horizontal principal stress; wherein the first wellbore used for arranging the fracturing wellbore does not pass through the fault, and the second wellbore used for arranging the monitoring wellbore passes through the fault, and the first wellbore is not connected to the second wellbore; wherein the space between the fracturing wellbore and the target reservoir simulation sample is filled with a material with high strength and good sealing performance; and the space between the monitoring wellbore and the target reservoir simulation sample is filled with a material with a relatively soft texture;

[0018] Optical fiber sensors are arranged on the surface of the monitoring wellbore.

[0019] Furthermore, an optical fiber sensor is arranged on the surface of the monitoring wellbore, including:

[0020] Winding the optical fiber sensor from the top to the bottom of the monitoring wellbore, and leading the optical fiber sensor out through the inside of the monitoring wellbore at the bottom, the inlet and outlet ends of the monitoring wellbore are both connected to the optical fiber;

[0021] The surface of the target reservoir simulation sample is provided with an optical fiber groove for leading out the optical fiber, and the optical fiber groove is filled after the optical fiber is arranged.

[0022] Furthermore, water pressure modeling experiments were carried out, including:

[0023] Connect the various components of the monitoring system to ensure tightness;

[0024] According to the test design requirements, a true triaxial model testing machine is used to apply triaxial stress, and the triaxial stress is stable for more than 15 minutes after loading;

[0025] Simultaneously start the servo pump pressure control system and the optical signal monitoring system to collect the experimental data according to preset conditions;

[0026] When the pump pressure curve shows an obvious rise to a rapid drop point and tends to be stable, the servo pump pressure control system is stopped, the true triaxial model testing machine is controlled to unload the triaxial stress, and the optical signal monitoring system is turned off.

[0027] Furthermore, the controllable experimental parameters in the water pressure physical model experiment include the fracture approach angle, three-dimensional stress, and fracturing fluid displacement.

[0028] Further, the experimental data is analyzed and processed, and quantitative evaluation is performed in combination with the final state of the target reservoir simulation sample, including:

[0029] By processing the optical signal of the optical fiber sensor, the strain of the optical fiber sensor at any time under true triaxial hydraulic fracturing conditions is obtained, and the slip amount of the fault and the deformation amount of the wellbore are obtained;

[0030] Actual measurement data is obtained by performing on-site actual measurement on the monitoring wellbore, and the actual measurement data is compared with the data collected by the optical fiber sensor monitoring to obtain a quantitative evaluation of the final state.

[0031] A true triaxial hydraulic fracturing fault slip casing deformation monitoring system, used to implement any of the true triaxial hydraulic fracturing fault slip casing deformation monitoring methods described above, the system comprising:

[0032] A sample preparation module is used to prepare target reservoir simulation samples;

[0033] Wellbore and sensor layout module, used for arranging and installing wellbore and sensors;

[0034] The water pressure model experiment development module is used to carry out the water pressure model experiment and record the experimental data;

[0035] The experimental data analysis and evaluation module is used to analyze and process the experimental data and to perform quantitative evaluation in combination with the final state of the target reservoir simulation sample.

[0036] The beneficial effects of the present invention are:

[0037] The present invention systematically explores the impact of fault slip on horizontal wells under different experimental conditions, achieving in-depth analysis and precise evaluation; it can accurately predict the shear deformation of casing under various geological and fracturing conditions, providing solid technical support for the optimization of fracturing construction parameters.

[0038] In response to the difficulty in monitoring and quantitative characterization of casing damage caused by fault-activated slip in unconventional reservoir transformation, the present invention comprehensively examines the influence of key parameters such as fault type, fracturing fluid displacement, and fracture approach angle on casing deformation, and provides accurate quantitative evaluation results. This not only provides a scientific basis for fracturing layer optimization and field parameter design, but also significantly promotes the development of horizontal well casing damage prevention and control theory and technology, and has important engineering guidance significance and practical application value for the optimization of field construction design. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 This is a flow chart of a method for monitoring deformation of a fault slip casing in true triaxial hydraulic fracturing according to an embodiment of the present invention;

[0040] Figure 2 This is a flow chart of a method for monitoring deformation of a fault slip casing in true triaxial hydraulic fracturing according to another embodiment of the present invention;

[0041] Figure 3 This is a flow chart of a method for monitoring deformation of a fault slip casing in true triaxial hydraulic fracturing according to another embodiment of the present invention;

[0042] Figure 4 A schematic diagram of a target reservoir simulation sample according to an embodiment of the present invention; wherein: Figure 4 (a) is a three-dimensional schematic diagram of the target reservoir simulation sample; Figure 4 (b) is a schematic diagram of the target reservoir simulation sample;

[0043] Figure 5 A schematic diagram of a wellbore arrangement according to an embodiment of the present invention; wherein: Figure 5 (a) is a three-dimensional schematic diagram of the wellbore layout; Figure 5 (b) is a schematic plan view of the wellbore layout;

[0044] Figure 6 Schematic diagram of the arrangement and extraction of optical fiber sensors according to one embodiment of the present invention; Figure 6 (a) Schematic diagram of the optical fiber sensor layout; Figure 6 (b) is a schematic diagram of the target reservoir simulation sample led out by optical fiber;

[0045] Figure 7 This is a structural diagram of a true triaxial hydraulic fracturing fault slip casing deformation monitoring system according to another embodiment of the present invention.

[0046] Among them, ①, fault, ②, hydraulic fracture, ③, fracturing wellbore, ④, monitoring wellbore. DETAILED DESCRIPTION

[0047] The content of the present invention will now be discussed with reference to exemplary embodiments. It should be understood that the embodiments discussed are only to enable those skilled in the art to better understand and thus implement the content of the present invention, rather than implying any limitation on the scope of the present invention.

[0048] As used herein, the term “including” and variations thereof are to be interpreted as open-ended terms meaning “including, but not limited to.” The term “based on” is to be interpreted as “based, at least in part, on.” The terms “one embodiment” and “an embodiment” are to be interpreted as “at least one embodiment.”

[0049] Embodiment 1

[0050] Figure 1 The flowchart of the method for monitoring the deformation of the sliding casing of the true triaxial hydraulic fracturing fault according to one embodiment of the present invention is shown in FIG. Figure 1 As shown, according to one embodiment of the present invention, a true triaxial hydraulic fracturing fault slip casing deformation monitoring method comprises the following steps:

[0051] Step S102, preparing a target reservoir simulation sample;

[0052] Step S104, arranging and installing the wellbore and sensors;

[0053] Step S106, conducting a water pressure physical model experiment and recording the experimental data;

[0054] Step S108, analyzing and processing the experimental data, and performing quantitative evaluation based on the final state of the target reservoir simulation sample.

[0055] In this embodiment, a true triaxial hydraulic fracturing fault slip casing deformation monitoring method is proposed. This method carefully prepares a tight reservoir simulation sample containing a fault (i.e., a target reservoir simulation sample), arranges a wellbore and sensors on it, and then conducts a hydraulic modeling experiment to simulate the actual fracturing process and record key data. Through in-depth analysis and processing of the experimental data, combined with the final state of the simulation sample, this method can quantitatively evaluate the impact of fault slip on the casing shear deformation of the wellbore. This method is not only suitable for evaluating the specific impact of faults in tight reservoir rock mass on the wellbore under different geostress characteristics and fracturing process parameters, but also provides a scientific basis for the optimization of fracturing optimization design parameters, and has important engineering practical significance for promoting the optimization of horizontal well casing damage prevention theory, technology and field construction design.

[0056] The present invention can quantitatively evaluate the shear deformation effect of fault slip on wellbore casing under true triaxial hydraulic fracturing conditions; it provides a scientific basis for the optimization of fracturing design parameters, and has engineering practical significance for the optimization of horizontal well casing damage prevention theory and field construction design.

[0057] Figure 4 A schematic diagram of a target reservoir simulation sample according to an embodiment of the present invention; wherein: Figure 4 (a) is a three-dimensional schematic diagram of the target reservoir simulation sample; Figure 4 (b) is a schematic diagram of the target reservoir simulation sample. Figure 4 As shown, according to one embodiment of the present invention, the target reservoir is a tight reservoir containing faults.

[0058] Preferably, step S102 includes:

[0059] Use real rocks as sample raw materials;

[0060] The fault is prepared by cutting first and then cementing.

[0061] Preferably, the fault is prepared by cutting first and then gluing, specifically:

[0062] According to the test design requirements, the fault cutting line is drawn on the specimen, and a large rock table saw is used to cut the specimen along the cutting line. The cutting thickness is determined according to the bonding material.

[0063] In this embodiment, real rocks or other similar materials are first selected as sample raw materials to ensure the accuracy and reliability of the experimental results. In the preparation process, in order to simulate the faults in actual geological conditions, the faults are finely prepared by cutting first and then bonding. The specific operation steps include: according to the specific requirements of the test design, the fault cutting line is accurately drawn on the sample, and then a large rock table saw is used to cut the whole along the cutting line. The cutting thickness is determined according to the selected bonding material. If high-strength glue such as 502 glue and epoxy resin glue is used as the bonding material, the fault cutting thickness must be strictly controlled within 3 mm; if gypsum mortar, cement mortar and other materials with strong bonding ability are used, the fault cutting thickness can be appropriately relaxed to between 5 mm and 10 mm. Through this fine preparation process, samples with a size of 300×300×300 mm or 500×500×500 mm can be prepared to meet the requirements of the true triaxial test system, thereby realizing an effective evaluation of the impact of faults on wellbore casing under different ground stress characteristics and fracturing process parameters.

[0064] The present invention adopts real rock as the sample raw material and uses the method of cutting first and then cementing to finely prepare the fault, so as to prepare the target reservoir simulation sample suitable for the true triaxial test system, realize the effective evaluation of the impact of the fault in the tight reservoir containing fault on the wellbore casing under different ground stress characteristics and fracturing process parameters, and ensure the accuracy and reliability of the experimental results.

[0065] Figure 5 A schematic diagram of a wellbore arrangement according to an embodiment of the present invention; wherein: Figure 5 (a) is a three-dimensional schematic diagram of the wellbore layout; Figure 5 (b) is a schematic plan view of the wellbore layout. Figure 6 Schematic diagram of the arrangement and extraction of optical fiber sensors according to one embodiment of the present invention; Figure 6 (a) Schematic diagram of the optical fiber sensor layout; Figure 6 (b) is a schematic diagram of the target reservoir simulation sample led out by optical fiber. Figure 5-6 As shown, according to one embodiment of the present invention, step S104 includes:

[0066] According to the test design requirements, wellbores are drilled at the center points of the front and rear surfaces of the target reservoir simulation sample along the direction of the minimum horizontal principal stress; the first wellbore used for arranging the fracturing wellbore does not pass through the fault, the second wellbore used for arranging the monitoring wellbore passes through the fault, and the first wellbore is not connected to the second wellbore; the space between the fracturing wellbore and the target reservoir simulation sample is filled with a material with high strength and good sealing performance; the space between the monitoring wellbore and the target reservoir simulation sample is filled with a material with a softer texture;

[0067] Optical fiber sensors are arranged on the surface of the monitoring wellbore.

[0068] Preferably, an optical fiber sensor is arranged on the surface of the monitoring wellbore, including:

[0069] Wind the optical fiber sensor from the top to the bottom of the monitoring wellbore, and lead the optical fiber sensor out through the inside of the monitoring wellbore at the bottom, and both the inlet and outlet ends of the monitoring wellbore are connected to the optical fiber;

[0070] The surface of the target reservoir simulation sample is provided with an optical fiber groove for leading out the optical fiber, and the optical fiber groove is filled after the optical fiber is arranged.

[0071] In this embodiment, in the prepared fault-containing tight reservoir simulation sample (target reservoir simulation sample), according to the test design requirements, two wellbores are accurately drilled at the center points of the front and rear surfaces of the sample along the direction of the minimum horizontal principal stress: one is used to arrange the fracturing wellbore (not passing through the fault), and the other is used to arrange the monitoring wellbore (passing through the fault), and the two wellbores are not connected. The fracturing wellbore and the sample are filled with high-strength and good sealing materials (such as epoxy resin), and the distance between the hydraulic fracture and the fault can be controlled by adjusting the length of the fracturing wellbore; and the monitoring wellbore and the sample are filled with softer materials (such as 10°~30° silica gel).

[0072] On the surface of the monitoring wellbore, the fiber optic sensor is carefully arranged, winding from the top to the bottom of the wellbore, and leading out through the inside of the wellbore at the bottom. The inlet and outlet are connected to the optical fiber, and moisture-proof and other protective measures are taken. In order to facilitate the lead-out of the optical fiber and protect it from the influence of force conduction during the test, the surface of the sample is also provided with an optical fiber groove, which is filled with hydraulic mortar and other materials after the optical fiber is arranged. Not only does it ensure the accuracy and reliability of the experiment, but it also realizes the effective monitoring of the shear deformation of the casing caused by fault slip through the fiber optic sensing technology.

[0073] The present invention realizes accurate simulation and effective monitoring of casing shear deformation caused by fault slip under hydraulic fracturing conditions in tight reservoirs containing faults by accurately drilling wells, reasonably filling materials and arranging optical fiber sensors.

[0074] According to an embodiment of the present invention, in step S106, a water pressure modeling experiment is carried out, including:

[0075] Connect the various components of the monitoring system to ensure tightness;

[0076] According to the test design requirements, a true triaxial model testing machine was used to apply triaxial stress, and the triaxial stress was stabilized for more than 15 minutes after loading;

[0077] At the same time, the servo pump pressure control system and the optical signal monitoring system are started to collect experimental data according to the preset conditions;

[0078] When the pump pressure curve shows an obvious rise to a rapid drop point and tends to be stable, the servo pump pressure control system is stopped, the true triaxial model testing machine is controlled to unload the triaxial stress, and the optical signal monitoring system is turned off.

[0079] In this embodiment, when conducting a hydraulic model experiment, first ensure that the components of the monitoring system (including light source, optical fiber, optical fiber sensor, modulator, optoelectronic device, etc.) are well connected and airtight without light leakage, and then connect the prefabricated threaded end of the simulated casing to the hydraulic fracturing pump outlet high-pressure hose to ensure sealing. Next, use a true triaxial model test machine to apply triaxial stress according to the experimental design requirements, and stabilize for more than 15 minutes after stress loading. After that, set the displacement parameters and the optical fiber sensor data acquisition frequency, and start the servo pump pressure control system and the optical signal monitoring system at the same time to start collecting experimental data. With the increase of pumped fracturing fluid, the pump pressure increases rapidly. When the pump pressure curve shows a rapid drop after a significant rise and tends to stabilize, stop the servo pump pressure control system, control the triaxial model test machine to unload the triaxial stress, and turn off the optical signal monitoring system, thereby completing the entire experimental process, and realizing accurate monitoring of the shear deformation of the casing caused by fault slip under the hydraulic fracturing conditions of the tight reservoir containing faults.

[0080] The present invention achieves accurate and real-time monitoring of casing shear deformation caused by fault slip during hydraulic fracturing of tight reservoirs containing faults by precisely connecting monitoring system components, applying stable three-dimensional stress, synchronously collecting pump pressure and optical signal data, and promptly stopping the experiment and unloading stress at the characteristic points of the pump pressure curve, thereby improving the accuracy and reliability of the experiment.

[0081] According to one embodiment of the present invention, controllable experimental parameters in the hydraulic pressure physical model experiment include fracture approach angle, triaxial stress, and fracturing fluid displacement.

[0082] In this embodiment, the hydraulic physical simulation experiment can comprehensively monitor and record the dynamic process of fault slip and wellbore deformation during the experiment by flexibly controlling key experimental parameters such as the fracture approach angle, three-dimensional stress loading, and fracturing fluid displacement, and then conduct a comprehensive evaluation of the final state of the experiment.

[0083] The present invention not only deepens the understanding of the interaction mechanism between faults and wellbores during hydraulic fracturing, but also provides valuable scientific basis and technical support for optimizing wellbore layout, selecting the best fracturing layer, and adjusting fracturing construction parameters.

[0084] According to one embodiment of the present invention, step S108 includes:

[0085] By processing the optical signal of the optical fiber sensor, the strain of the optical fiber sensor at any time under true triaxial hydraulic fracturing conditions is obtained, and the slip amount of the fault and the deformation amount of the wellbore are obtained;

[0086] Actual measurement data are obtained by conducting on-site actual measurements of the monitoring wellbore, and the actual measurement data are compared with the data collected by the optical fiber sensor monitoring to obtain a quantitative evaluation of the final state.

[0087] In this embodiment, step S108 describes in detail how to process the optical signal of the fiber optic sensor and how to use this data to quantitatively evaluate the fault slip and wellbore deformation. Specifically, by modulating, decoding, and converting the optical signal of the fiber optic sensor, we can accurately obtain the strain of the fiber optic sensor at any time under true triaxial hydraulic fracturing conditions, and then indirectly calculate the slip of the fault and the deformation of the wellbore. Afterwards, after the experiment, the loading plate of the triaxial testing machine is disassembled, the sample is taken out and cut, the monitoring wellbore is taken out for actual on-site measurement, and the actual measurement data is compared with the data collected by the fiber optic sensor monitoring to perform a quantitative evaluation of the final state.

[0088] The present invention realizes accurate quantitative evaluation of fault slip and wellbore deformation under true triaxial hydraulic fracturing conditions by processing optical fiber sensor optical signals and comparing actual measurement data.

[0089] Based on the research results of predecessors, the present invention cleverly utilizes the existing sensor technology and proposes an innovative sample preparation method, which aims to simulate the casing damage and deformation test caused by fault slip under indoor true triaxial hydraulic fracturing conditions. It can not only realize the dynamic monitoring of the wellbore status during the test, but also accurately evaluate the wellbore deformation.

[0090] The optical fiber sensor technology used in the present invention is based on the following working principle: the light emitted by the light source is sent into the modulator through the optical fiber, so that the parameter to be measured (such as wellbore deformation) interacts with the light entering the modulation area, thereby changing the optical properties of the light (such as intensity, wavelength, frequency, phase, polarization state, etc.) to form a modulated signal light. Subsequently, the influence of the monitored object (such as the wellbore) on the transmission characteristics of the light is used to complete the measurement process.

[0091] During the fracturing process, the expansion of hydraulic fractures may activate faults and cause instability and slip, which in turn causes shear stress on the wellbore passing through the fault, resulting in shear deformation. This deformation will cause changes in the optical signal in the optical fiber sensor. By monitoring these changes, the local deformation characteristics of the wellbore can be indirectly obtained. The present invention provides valuable theoretical guidance and practical basis for the optimization design of unconventional oil and gas reservoir transformation parameters.

[0092] Embodiment 2

[0093] Figure 2 FIG. 1 is a flow chart of a method for monitoring deformation of a fault slip casing in true triaxial hydraulic fracturing according to another embodiment of the present invention. Figure 2 As shown, according to one embodiment of the present invention, a method for monitoring casing shear deformation caused by fault slip during true triaxial hydraulic fracturing comprises the following steps:

[0094] Step S202, preparing a simulated sample of a tight reservoir containing faults;

[0095] The raw material of the sample can be real rock or other similar materials. In order to adapt to the true triaxial test system, the overall size of the sample can be 300×300×300mm or 500×500×500mm;

[0096] The fault is prepared by cutting first and then bonding. The specific operation process is as follows: according to the test design requirements, the fault cutting line is drawn on the specimen, and a large rock table saw is used to cut the entire specimen along the cutting line. The cutting thickness may vary depending on the bonding material. If glue with different bonding strengths (such as 502 glue, epoxy resin glue, etc.) is used, the fault cutting thickness must be controlled within 3 mm. If materials with bonding ability such as gypsum mortar and cement mortar are used, the fault cutting thickness must be between 5 mm and 10 mm.

[0097] Step S204, arranging and installing the wellbore and sensors;

[0098] According to the test design requirements, boreholes are drilled at the center points of the front and rear surfaces of the specimen along the direction of the minimum horizontal principal stress. The borehole used to arrange the fracturing wellbore does not pass through the fault, while the borehole used to arrange the monitoring wellbore must pass through the fault, and the two boreholes are not connected. The space between the fracturing wellbore and the specimen is filled with high-strength epoxy resin or other materials with high strength and good sealing performance. The distance between the hydraulic fracture and the fault can be controlled by adjusting the length of the fracturing wellbore; 10°~30° silica gel or other softer materials are used to fill the space between the monitoring wellbore and the specimen.

[0099] The optical fiber sensor is arranged on the surface of the monitoring wellbore. The arrangement method is: winding from the top of the wellbore to the bottom, and the optical fiber sensor is led out through the wellbore at the bottom. The inlet and outlet ends are connected to the optical fiber, and moisture-proof and other protective measures are taken. The optical fiber groove needs to be cut on the surface of the sample for leading out the optical fiber. In order to protect the optical fiber and avoid uneven force transmission during the test, the optical fiber groove needs to be filled with hydraulic mortar or other similar materials.

[0100] Step S206, conducting a water pressure physical model experiment and recording the test data;

[0101] After the sample is installed by a crane, the light source, optical fiber, fiber optic sensor, modulator, optoelectronic devices, etc. are connected to ensure no light leakage, and finally the layout of the monitoring system is completed.

[0102] Connect the prefabricated threaded end casing of the simulated casing to the high-pressure hose of the hydraulic fracturing pump and ensure the sealing; according to the test design requirements, a true triaxial model test machine is used to apply triaxial stress, and the stress needs to be stabilized for more than 15 minutes after loading. Set the displacement parameters and the data acquisition frequency of the optical fiber sensor, and start the servo pump pressure control system and the optical signal monitoring system at the same time to collect experimental data. As the fracturing fluid is pumped in, the pump pressure increases rapidly. When the pump pressure curve shows an obvious rise to a rapid drop point and tends to stabilize, stop the servo pump pressure control system, control the triaxial model test machine to unload the triaxial stress, and turn off the optical signal monitoring system.

[0103] Step S208, analyzing and processing the data, and performing quantitative evaluation based on the final state of the sample;

[0104] By modulating, decoding, converting and other steps of the optical signal of the optical fiber sensor, the strain of the optical fiber sensor at any time in the experiment can be obtained under true triaxial hydraulic fracturing conditions, thereby indirectly obtaining the slip amount of the fault and the deformation amount of the wellbore;

[0105] The loading plate of the triaxial testing machine was disassembled, and then the sample was taken out, the fracturing sample was sectioned, and the monitoring wellbore was removed to conduct actual on-site measurements, and compared with the data collected by the optical fiber sensor to conduct a quantitative evaluation of the final state;

[0106] For the above experimental operations, by controlling different experimental parameters (fracture approach angle, triaxial stress, fracturing fluid displacement, etc.), it is also possible to monitor fault slip and wellbore deformation during the experiment and evaluate the final state. This will provide technical support for reasonable wellbore layout, optimization of fracturing layers, and optimization design of fracturing construction site parameters.

[0107] The present invention proposes a method for comprehensive monitoring and evaluation of shear deformation of wellbore casing induced by fault slip in a true triaxial hydraulic fracturing environment. The method can not only accurately simulate the actual response of tight reservoirs under different geostress conditions and fracturing operation parameters, but also quantitatively evaluate the specific impact of fault activity on wellbore integrity. Through the implementation of the present invention, researchers and engineers can gain in-depth insights into the interaction mechanism between faults and wellbores during the fracturing process, providing a scientific basis for the optimal design of fracturing schemes. The present invention can assist in determining the optimal wellbore layout, fracturing layer selection, and fracturing construction parameters, thereby effectively avoiding or reducing the risk of casing damage caused by fault activation and slip. The present invention is of great value in promoting the theoretical development and practical application of horizontal well casing damage prevention and control technology. It can not only improve the long-term stability and production efficiency of oil and gas wells, but also provide strong technical support for the optimization of on-site construction design in related fields, showing a wide range of engineering application prospects.

[0108] Embodiment 3

[0109] Figure 3 This is a flow chart of a method for monitoring deformation of a true triaxial hydraulic fracturing fault slip casing according to another embodiment of the present invention. Figure 3 As shown, according to one embodiment of the present invention, a true triaxial hydraulic fracturing fault slip casing deformation monitoring method comprises the following steps:

[0110] Step 1: The unconventional reservoir simulation sample used is a real shale outcrop, which is processed into a cube of 300×300×300 mm by hydraulic cutting;

[0111] Step 2: According to the design requirements of the test fault, the fault cutting line is drawn on the surface of the specimen with a marker pen, and a large rock table saw is used to perform overall cutting along the cutting line;

[0112] Step 3: Place one half of the sample in a detachable 300 mm cubic mold, evenly apply the cementing material on the fault surface, and then place the other half in the mold and reassemble it into a 300×300×300 mm cubic sample;

[0113] Step 4: Drill wells on both non-fault cutting surfaces. The shorter well does not pass through the fault surface and will be used for fracturing wellbore. The longer well needs to pass through the fault surface and will be used for monitoring wellbore. The distance between the tail ends of the two wells is at least 25 mm.

[0114] Step 5: The fracturing wellbore and the monitoring wellbore are made of the same steel pipe material. The fracturing wellbore and the sample are filled and sealed with high-strength epoxy resin glue; the monitoring wellbore and the sample are coupled with softer silicone to ensure that the monitoring wellbore can smoothly monitor the movement trend of the fault;

[0115] Step 6: The optical fiber sensor is wound from the top to the bottom of the monitoring wellbore and passes through the bottom of the wellbore; both ends of the optical fiber sensor are connected to the optical fiber, and corresponding protective measures are taken;

[0116] Step 7: Use a cutting machine to cut the fiber optic slot on the sample surface where the monitoring well is arranged. Place the optical fiber in the fiber optic slot, take moisture-proof and other protective measures, and then use high-strength silicate cement or other similar materials to smooth the fiber optic slot;

[0117] Step 8: After all the materials used above have been cured, operate the crane to install the sample, connect the optical fiber led out of the sample to the optical signal monitoring and conversion system; connect the prefabricated threaded end of the fracturing wellbore to the high-pressure hose of the hydraulic fracturing pump to inject fracturing fluid, and ensure the sealing performance;

[0118] Step nine, using a true triaxial model testing machine to apply triaxial stress conditions and keep the triaxial stress constant; setting the monitoring system to collect data frequency, setting the pumping displacement, and simultaneously starting the optical signal monitoring system and the fracturing fluid pumping system, and synchronously collecting data;

[0119] Step 10: As the fracturing fluid is pumped, the pump pressure gradually increases to reach the fracture pressure. After the pump pressure drops suddenly and is in a stable state, the fracturing fluid pumping system is stopped, the three-dimensional stress is unloaded, the optical signal monitoring system is turned off, and the corresponding experimental data is saved;

[0120] Step 11: Analyze the optical fiber strain data collected during the experiment, which can indirectly determine the slip amount of the fault during the experiment and infer the deformation amount of the wellbore under the corresponding conditions. The sample can also be cut, the monitoring wellbore can be removed, and quantitative evaluation can be performed in combination with the test data;

[0121] Step 12. Repeating steps 2 and 3 can quantitatively study the effect of the approach angle of the hydraulic fracture on the fault slip; repeating step 4 can quantitatively study the intersection length of the hydraulic fracture and the fault; repeating steps 9 and 10 can set different test parameters for research.

[0122] The present invention uses real shale outcrops as unconventional reservoir simulation samples, combined with sophisticated fault preparation and wellbore layout methods, to achieve effective monitoring of casing shear deformation caused by fault slip under true triaxial hydraulic fracturing conditions. Through the application of optical fiber sensors and accurate data collection and analysis, the present invention can not only indirectly obtain the fault slip amount and wellbore deformation amount, but also quantitatively study the influence of hydraulic fracture approach angle, intersection length and different test parameters on fault slip, providing strong technical support for the optimization design of fracturing construction parameters and the prevention and control of casing damage.

[0123] Embodiment 4

[0124] Figure 7 This is a structural diagram of a true triaxial hydraulic fracturing fault slip casing deformation monitoring system according to another embodiment of the present invention. Figure 7 As shown, according to an embodiment of the present invention, a true triaxial hydraulic fracturing fault slip casing deformation monitoring system is used to implement any true triaxial hydraulic fracturing fault slip casing deformation monitoring method of the present invention, and the system includes:

[0125] The sample preparation module 10 is used to prepare a target reservoir simulation sample;

[0126] Wellbore and sensor arrangement module 20, used to arrange and install wellbore and sensors;

[0127] A water pressure modeling experiment carrying out module 30 is used to carry out a water pressure modeling experiment and record the experimental data;

[0128] The experimental data analysis and evaluation module 40 is used to analyze and process the experimental data and to perform quantitative evaluation in combination with the final state of the target reservoir simulation sample.

[0129] Those skilled in the art can clearly understand that, for the convenience and brevity of description, the specific working process of the system described above can refer to the corresponding process in the aforementioned method embodiment, and will not be repeated here.

[0130] The above description is only a preferred embodiment of the present application and an explanation of the technical principles used. Those skilled in the art should understand that the scope of the invention involved in the present application is not limited to the technical solution formed by a specific combination of the above technical features, but should also cover other technical solutions formed by any combination of the above technical features or their equivalent features without departing from the inventive concept. For example, the above features are replaced with (but not limited to) technical features with similar functions disclosed in the present application.

[0131] It should be understood that the size of the serial numbers of each step in the content of the invention and the embodiments of the present invention does not absolutely mean the order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of the present invention.

Claims

1. A true triaxial hydraulic fracturing fault slip casing deformation monitoring method, characterized in that: The following steps are involved: Prepare target reservoir simulation samples; Arrange and install wellbore and sensors; Carry out hydraulic pressure model experiments and record the experimental data; The experimental data are analyzed and processed, and quantitative evaluation is performed in combination with the final state of the target reservoir simulation sample.

2. The method for monitoring deformation of fault slip casing in true triaxial hydraulic fracturing according to claim 1, characterized in that: The target reservoir is a tight reservoir containing faults.

3. The method for monitoring deformation of fault slip casing in true triaxial hydraulic fracturing according to claim 2, characterized in that: Prepare target reservoir simulation samples, including: Use real rocks as sample raw materials; The fault is prepared by cutting first and then cementing.

4. The method for monitoring deformation of fault slip casing in true triaxial hydraulic fracturing according to claim 3, characterized in that: The fault is prepared by cutting first and then cementing, specifically: According to the test design requirements, the fault cutting line is drawn on the specimen, and a large rock table saw is used to cut the specimen along the cutting line. The cutting thickness is determined according to the bonding material.

5. The method for monitoring deformation of fault slip casing in true triaxial hydraulic fracturing according to claim 1, characterized in that: Arrange and install the wellbore and sensors, including: According to the test design requirements, wellbores are drilled at the center points of the front and rear surfaces of the target reservoir simulation sample along the direction of the minimum horizontal principal stress; wherein the first wellbore used for arranging the fracturing wellbore does not pass through the fault, and the second wellbore used for arranging the monitoring wellbore passes through the fault, and the first wellbore is not connected to the second wellbore; wherein the space between the fracturing wellbore and the target reservoir simulation sample is filled with a material with high strength and good sealing performance; and the space between the monitoring wellbore and the target reservoir simulation sample is filled with a material with a relatively soft texture; Optical fiber sensors are arranged on the surface of the monitoring wellbore.

6. The method for monitoring deformation of fault slip casing in true triaxial hydraulic fracturing according to claim 5, characterized in that: Arranging an optical fiber sensor on the surface of the monitoring wellbore includes: Winding the optical fiber sensor from the top to the bottom of the monitoring wellbore, and leading the optical fiber sensor out through the inside of the monitoring wellbore at the bottom, the inlet and outlet ends of the monitoring wellbore are both connected to the optical fiber; The surface of the target reservoir simulation sample is provided with an optical fiber groove for leading out the optical fiber, and the optical fiber groove is filled after the optical fiber is arranged.

7. The method for monitoring deformation of fault slip casing in true triaxial hydraulic fracturing according to claim 1, characterized in that: Carry out water pressure modeling experiments, including: Connect the various components of the monitoring system to ensure tightness; According to the test design requirements, a true triaxial model testing machine is used to apply triaxial stress, and the triaxial stress is stable for more than 15 minutes after loading; Simultaneously start the servo pump pressure control system and the optical signal monitoring system to collect the experimental data according to preset conditions; When the pump pressure curve shows an obvious rise to a rapid drop point and tends to be stable, the servo pump pressure control system is stopped, the true triaxial model testing machine is controlled to unload the triaxial stress, and the optical signal monitoring system is turned off.

8. The method for monitoring casing deformation of true triaxial hydraulic fracturing fault slip according to claim 1, characterized in that: The controllable experimental parameters in the water pressure physical model experiment include the fracture approach angle, three-dimensional stress, and fracturing fluid displacement.

9. The method for monitoring deformation of fault slip casing in true triaxial hydraulic fracturing according to claim 1, characterized in that: Analyze and process the experimental data, and conduct quantitative evaluation based on the final state of the target reservoir simulation sample, including: By processing the optical signal of the optical fiber sensor, the strain of the optical fiber sensor at any time under true triaxial hydraulic fracturing conditions is obtained, and the slip amount of the fault and the deformation amount of the wellbore are obtained; Actual measurement data is obtained by performing on-site actual measurement on the monitoring wellbore, and the actual measurement data is compared with the data collected by the optical fiber sensor monitoring to obtain a quantitative evaluation of the final state.

10. A true triaxial hydraulic fracturing fault slip casing deformation monitoring system, characterized in that: Used to implement the true triaxial hydraulic fracturing fault slip casing deformation monitoring method as described in any one of claims 1 to 9, the system comprises: A sample preparation module is used to prepare target reservoir simulation samples; Wellbore and sensor layout module, used for arranging and installing wellbore and sensors; The water pressure model experiment development module is used to carry out the water pressure model experiment and record the experimental data; The experimental data analysis and evaluation module is used to analyze and process the experimental data and to perform quantitative evaluation in combination with the final state of the target reservoir simulation sample.

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