Physical simulation experiment device and method for casing deformation in window section of shale hydraulic fracturing

Abstract

The present application relates to the technical field of oil and gas field development, and provides a shale hydraulic fracturing window section casing deformation physical simulation experiment device and method, the device comprises: a shale sample; a pipeline, one end of the pipeline is arranged in the interior of the shale sample, the other end of the pipeline extends out of the surface of the shale sample; the extension direction of the pipeline and the extension direction of the shale sample bedding plane form a preset angle; an induction part is arranged in the interior of the shale sample; wherein, the induction part is arranged at intervals with the one end of the pipeline in the interior of the shale sample, and the arrangement direction of the induction part is perpendicular to the extension direction of the pipeline.The induction part is arranged in the interior of the sample adjacent to the lower end of the pipeline, which is perpendicular to the extension direction of the pipeline, effectively realizing the physical simulation of the stress environment of the vertical section casing, accurately simulating the shear slip effect induced by the interaction of bedding and fractures, and significantly improving the dynamic perception ability of the window section casing deformation mechanism.

Description

Technical Field

[0001] This invention relates to the field of oil and gas field development technology, and in particular to a physical simulation experimental device and method for the deformation of casing in the window section of shale hydraulic fracturing. Background Technology

[0002] Shale oil and gas reservoirs in my country generally exhibit complex tectonic stress fields, well-developed bedding, and significant anisotropy. This is particularly pronounced in tectonically active areas such as the Sichuan Basin, where casing deformation during horizontal well hydraulic fracturing is a significant problem. Existing research categorizes casing deformation in shale reservoirs into three main types: shear-type, compression-type, and combined types. Shear-type deformation is primarily caused by interlayer shear slip induced by the interaction between hydraulic fractures and natural bedding planes during fracture propagation.

[0003] In recent years, the overall casing deformation rate has been significantly reduced through optimization of wellbore trajectory design and completion technology. However, near the horizontal well entry point (i.e., the junction between the end of the build-up section and the beginning of the horizontal section, usually corresponding to geological target point A), casing deformation problems still occur frequently and there is a lack of effective control measures.

[0004] Current indoor physical simulation research has significant limitations: on the one hand, experimental setups and methods mostly focus on the horizontal fracturing process, paying insufficient attention to the mechanical response of the vertical segment, especially the entry window region; on the other hand, existing monitoring methods largely rely on destructive cutting or discrete point measurements after fracturing, making it difficult to achieve in-situ, continuous, and real-time observation of bedding slip behavior and casing strain evolution. Therefore, the control mechanism of shale bedding structure on vertical casing deformation remains unclear. Summary of the Invention

[0005] This invention provides a physical simulation experimental device and method for casing deformation in the window section of shale hydraulic fracturing, which solves the technical problems in the prior art, such as insufficient monitoring and research on the vertical section of shale hydraulic fracturing, and the inability to obtain dynamic response data of bedding slip and casing strain in real time.

[0006] This invention provides a physical simulation experimental device for the deformation of the casing in the window section of shale hydraulic fracturing, comprising: Shale sample; A conduit, one end of which is disposed inside the shale sample, and the other end of which extends out of the surface of the shale sample; the extending direction of the conduit forms a predetermined angle with the extending direction of the bedding plane of the shale sample. The sensing element is located inside the shale sample; The sensing element and the pipeline are spaced apart at one end inside the shale sample, and the arrangement direction of the sensing element is perpendicular to the extension direction of the pipeline.

[0007] According to the present invention, a physical simulation experimental device for deformation of casing in shale hydraulic fracturing window section is provided, wherein the number of pipelines is multiple, and the multiple pipelines are arranged at intervals along the arrangement direction of the induction unit; The distance between the end of each of the pipes located inside the shale sample and the sensing element is different.

[0008] According to the present invention, a physical simulation experimental device for the deformation of the casing in the window section of shale hydraulic fracturing is provided, wherein the sensing unit includes: The induction tube is perpendicular to a set of opposing surfaces of the shale sample; The outer wall of the sensing tube is provided with a first optical fiber and / or a first strain gauge.

[0009] According to the present invention, a physical simulation experimental device for deformation of the casing in the window section of shale hydraulic fracturing is provided, wherein the number of the first optical fiber is one, and the first optical fiber is spirally arranged along the axial direction of the induction tube. Alternatively, there may be multiple first optical fibers, which are arranged in a straight line along the axial direction of the sensing tube, and the multiple first optical fibers are arranged at intervals along the circumference of the sensing tube.

[0010] According to the present invention, a physical simulation experimental device for the deformation of the casing in the window section of shale hydraulic fracturing is provided, wherein multiple sets of the first strain gauge are arranged at intervals along the axial direction of the induction tube; In this configuration, there are multiple first strain gauges in each group, and the multiple first strain gauges in the group are arranged at intervals along the circumference of the sensing tube.

[0011] According to the present invention, a physical simulation experimental device for the deformation of the casing in the window section of shale hydraulic fracturing is provided, wherein the sensing unit includes: The sensing plate is located on a plane that is perpendicular to the extension direction of the pipeline; The surface of the sensing plate is provided with a second optical fiber and / or a second strain gauge.

[0012] According to the present invention, a physical simulation experimental device for deformation of the casing in the window section of shale hydraulic fracturing is provided, wherein the second optical fiber is arranged along the length or width direction of the induction plate; The second optical fiber is multiple, and these multiple second optical fibers are spaced apart along the width or length direction of the sensing plate.

[0013] According to the present invention, a physical simulation experimental device for deformation of the casing in the window section of shale hydraulic fracturing is provided, wherein the number of the second strain gauges is multiple, and the multiple second strain gauges are arranged in a quincunx pattern on the surface of the induction plate.

[0014] This invention also provides a physical simulation experimental method for the deformation of the casing in the window section of shale hydraulic fracturing, using the above-mentioned physical simulation experimental device for the deformation of the casing in the window section of shale hydraulic fracturing, comprising the following steps: The induction unit is embedded according to the type of shale sample; Stress loading was applied to the shale sample; Inject fracturing fluid to fracturing shale samples and collect data simultaneously; Evaluate the effect of layer slip on the deformation of the sensing element.

[0015] According to the present invention, a physical simulation experimental method for the deformation of the casing section in shale hydraulic fracturing is provided, wherein the step of injecting fracturing fluid to fracturing the shale sample specifically includes: Fracturing fluid is injected into the pipeline to perform fracturing; Alternatively, fracturing fluid may be injected into multiple pipelines in a preset order for fracturing.

[0016] The above-mentioned technical solutions provided by this invention have at least the following beneficial technical effects: By arranging the pipeline at a preset angle in a shale sample with a layered structure, and setting a sensing element perpendicular to the pipeline extension direction near the lower end of the pipeline inside the sample, a high-fidelity physical simulation of the stress environment of the vertical casing section is effectively achieved. This not only realistically reproduces the spatial geometric relationship between the wellbore and the shale bedding plane during hydraulic fracturing, thus accurately simulating the shear slip effect induced by the interaction between bedding and fracture, but also, through the directional embedding of the sensing element, allows for in-situ, continuous, and non-destructive monitoring of the radial or circumferential strain response of the surrounding rock mass during fracturing, significantly improving the dynamic sensing capability of the casing deformation mechanism. Compared to existing experimental methods that focus on horizontal sections or rely on destructive observation, this device is particularly suitable for revealing the deformation mechanism of the vertical casing section under complex anisotropic formation conditions, providing a reliable experimental platform and data support for the design of casing integrity at the shale oil and gas well entry point and the optimization of fracturing operations. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in this invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0018] Figure 1 This is one of the schematic diagrams of the shale sample and pipeline provided in the embodiments of the present invention; Figure 2 This is a second schematic diagram of the shale sample and pipeline provided in an embodiment of the present invention; Figure 3 This is the third schematic diagram of the shale sample and pipeline provided in the embodiments of the present invention; Figure 4 This is one of the schematic diagrams of the physical simulation experimental device for the deformation of the casing in the shale hydraulic fracturing window section provided in the embodiment of the present invention; Figure 5 This is the second schematic diagram of the physical simulation experimental device for the deformation of the casing in the shale hydraulic fracturing window section provided in the embodiment of the present invention; Figure 6 This is the third schematic diagram of the physical simulation experimental device for the deformation of the casing in the shale hydraulic fracturing window section provided in the embodiment of the present invention; Figure 7 This is one of the schematic diagrams of the sensing tube provided in an embodiment of the present invention; Figure 8 This is a second schematic diagram of the sensing tube provided in an embodiment of the present invention; Figure 9 This is the fourth schematic diagram of the physical simulation experimental device for the deformation of the casing in the shale hydraulic fracturing window section provided in the embodiment of the present invention; Figure 10 This is the fifth schematic diagram of the physical simulation experimental device for the deformation of the casing in the shale hydraulic fracturing window section provided in the embodiments of the present invention; Figure 11 This is the sixth schematic diagram of the physical simulation experimental device for the deformation of the casing in the shale hydraulic fracturing window section provided in the embodiment of the present invention; Figure 12 This is one of the schematic diagrams of the sensing plate provided in an embodiment of the present invention; Figure 13 This is a second schematic diagram of the sensing plate provided in an embodiment of the present invention; Figure 14 This is the seventh schematic diagram of the physical simulation experimental device for the deformation of the casing in the shale hydraulic fracturing window section provided in the embodiment of the present invention.

[0019] Figure label: 1. Shale sample; 11. Bedding plane; 2. Pipeline; 31. Induction tube; 32. First optical fiber; 33. First strain gauge; 34. Induction plate; 35. Second optical fiber; 36. Second strain gauge; 4. Pressure loading section. Detailed Implementation

[0020] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0021] The following is combined with Figures 1-14 This invention describes a physical simulation experimental apparatus and method for the deformation of the casing in the shale hydraulic fracturing window section according to an embodiment of the present invention.

[0022] like Figures 4-6 , Figures 9-11 As shown, this embodiment of the invention provides a physical simulation experimental device for the deformation of the casing in the window section of shale hydraulic fracturing, comprising: a shale sample 1; a pipe 2, one end of which is disposed inside the shale sample 1, and the other end of which extends out of the surface of the shale sample 1; the extension direction of the pipe 2 forms a preset angle with the extension direction of the bedding plane 11 of the shale sample 1; and a sensing unit disposed inside the shale sample 1; wherein the sensing unit and the end of the pipe 2 located inside the shale sample 1 are spaced apart, and the arrangement direction of the sensing unit is perpendicular to the extension direction of the pipe 2.

[0023] It should be understood that, in this embodiment, by arranging the pipeline 2 at a preset angle within the shale sample 1 with a layered structure, and by placing a sensing element perpendicular to the extension direction of the pipeline 2 near the lower end of the pipeline 2 inside the sample, a high-fidelity physical simulation of the stress environment of the vertical casing section is effectively achieved. This not only realistically reproduces the spatial geometric relationship between the wellbore and the shale bedding plane 11 during hydraulic fracturing, thus accurately simulating the shear slip effect induced by the interaction between bedding and fracture, but also, through the directional embedding of the sensing element, allows for in-situ, continuous, and non-destructive monitoring of the radial or circumferential strain response of the surrounding rock mass during fracturing, significantly enhancing the dynamic sensing capability of the casing deformation mechanism. Compared to existing experimental methods that focus on horizontal sections or rely on destructive observation, this device is particularly suitable for revealing the deformation mechanism of the vertical casing section under complex anisotropic formation conditions, providing a reliable experimental platform and data support for the design of casing integrity at the shale oil and gas well entry point and the optimization of fracturing operations.

[0024] like Figures 1-3 As shown, in some possible implementations, when the shale sample 1 is a natural core, it is preferably a columnar core from the target reservoir. The bedding plane 11 is oriented along the axial or transverse direction of the sample to control the bedding dip angle. When artificial shale is used, it can be formed by layering and casting a cement-quartz sand-mica mixture according to a preset ratio, and directional pressure is applied during the curing process to simulate the layered anisotropic structure of natural shale. The extension direction of the bedding plane 11 of the shale sample 1 is pre-marked in the sample coordinate system as a reference for subsequent wellbore layout; for example, the bedding plane 11 can be set parallel, perpendicular or inclined to the pipeline 2.

[0025] like Figures 1-4As shown, according to an embodiment of the present invention, a physical simulation experimental device for deformation of the casing in the window section of shale hydraulic fracturing is provided. The number of pipes 2 is multiple, and the multiple pipes 2 are arranged at intervals along the arrangement direction of the induction unit. The distance between the end of each pipe 2 inside the shale sample 1 and the induction unit is different.

[0026] It should be understood that there are multiple pipes 2 (e.g., 3, 5, or 7), and each pipe 2 is spaced apart along the direction of the induction unit, i.e., perpendicular to the extension direction of the pipe 2, to cover different depths in the key area of ​​the entry window section. In particular, the distance between the end of each pipe 2 extending into the shale sample 1 (i.e., the distal end) and the induction unit is different. This differentiated arrangement allows each pipe 2 to act on or monitor the rock mass response at different radial distances in front of the induction unit, thereby constructing a multi-point pressure / fluid injection gradient along the propagation path of the fracturing fracture.

[0027] like Figures 4-6 As shown, a physical simulation experimental device for deformation of the casing in the window section of shale hydraulic fracturing according to an embodiment of the present invention includes a sensing unit comprising: a sensing tube 31, which is perpendicular to a set of opposing surfaces of the shale sample 1; wherein, the outer wall of the sensing tube 31 is provided with a first optical fiber 32 and / or a first strain gauge 33.

[0028] It should be understood that the axis of the sensing tube 31 is orthogonal to the axis of the pipeline 2, and is used to monitor the lateral strain response of the rock mass adjacent to the casing during fracturing. The sensing tube 31 is made of polycarbonate or stainless steel, which has good rigidity and mechanical compatibility, and is completely embedded in the shale sample 1 to avoid contact with external loading components and ensure that the measurement signal is not interfered with. A first optical fiber 32 and / or a first strain gauge 33 are set on the outer wall of the sensing tube 31 as sensing elements. The first optical fiber 32 can be attached linearly along the axial direction or wound in a spiral manner, and can achieve continuous strain monitoring with high spatial resolution in conjunction with a distributed optical fiber demodulation system; the first strain gauge 33 can be arranged at key measuring points and connected to a dynamic acquisition device through wires to obtain local strain data. The distributed optical fiber monitoring is suitable for full-length casing deformation monitoring, and can realize full-section deformation monitoring of the casing in the axial and circumferential directions, accurately capturing the casing deformation position corresponding to the bedding slip surface. Strain gauge array monitoring is suitable for fine measurement of local deformation of the sleeve. By attaching a resistance strain gauge array to the surface of the sleeve, high-precision strain monitoring at specific locations of the sleeve can be achieved. It is suitable for complementing distributed fiber optic monitoring to verify the local deformation characteristics of the sleeve.

[0029] like Figures 7-8As shown, according to an embodiment of the present invention, a physical simulation experimental device for deformation of the casing in the window section of shale hydraulic fracturing is provided. The number of first optical fibers 32 is one, and the first optical fibers 32 are spirally arranged along the axial direction of the induction tube 31; or, the number of first optical fibers 32 is multiple, and the first optical fibers 32 are arranged in a straight line along the axial direction of the induction tube 31, and the multiple first optical fibers 32 are spaced apart along the circumferential direction of the pipeline 2.

[0030] It should be understood that, in the first arrangement, the helical pitch of the first optical fiber 32 can be set according to the spatial resolution and circumferential coverage requirements. Through this helical arrangement, a single optical fiber can simultaneously sense axial tensile / compression and circumferential shear deformation within a finite length, making it suitable for capturing asymmetric strain responses induced by the interaction between hydraulic cracks and the bedding plane 11. This optical fiber is preferably a single-mode communication optical fiber, which can be fixed to the surface of the sensing tube 31 using UV-curable adhesive or flexible epoxy resin.

[0031] In the second arrangement, the number of first optical fibers 32 is multiple (e.g., 2, 4, or 6). Each fiber is attached to the outer wall of the sensing tube 31 in a straight line along its axial direction, and they are evenly spaced apart from each other along the circumference of the sensing tube 31. Since the axis of the sensing tube 31 is perpendicular to the axis of the pipe 2, and the pipe 2 represents the actual casing, the circumferential spacing of the multiple optical fibers essentially corresponds to different azimuth angles around the circumference of the pipe 2. This configuration enables independent strain monitoring of the rock mass surrounding the casing in multiple azimuths, effectively identifying non-uniform mechanical behaviors such as local compression, off-center loading, or directional slippage. Each optical fiber can share the same light source and demodulation equipment, or it can be connected to a multi-channel acquisition system to improve data synchronization and signal-to-noise ratio.

[0032] It should be noted that both of the above-mentioned fiber optic arrangement schemes can achieve in-situ, continuous, and high-dimensional sensing of strain evolution in key areas of the vertical section without damaging the integrity of shale sample 1. This is significantly superior to traditional point-based or discrete measurement methods, providing reliable experimental evidence for a deeper understanding of the mechanism of casing deformation induced by shale fracturing. Those skilled in the art can flexibly select or combine the above arrangement methods according to specific geological conditions, bedding attitude, and research focus, and all such combinations should be considered to fall within the protection scope of this invention.

[0033] like Figures 7-8 As shown, according to an embodiment of the present invention, a physical simulation experimental device for deformation of the casing in the window section of shale hydraulic fracturing is provided, wherein multiple groups of first strain gauges 33 are arranged at intervals along the axial direction of the induction tube 31; wherein, the number of first strain gauges 33 in each group is multiple, and the multiple first strain gauges 33 in the group are arranged at intervals along the circumferential direction of the induction tube 31.

[0034] It should be understood that, in order to achieve precise capture of the multidimensional strain field of shale sample 1 during fracturing, the first strain gauges 33 are arranged in multiple groups along the axial direction of the induction tube 31, with each group corresponding to a monitoring section along the axial direction of the induction tube 31. The axial spacing between adjacent groups can be set according to the experimental resolution requirements to cover the key deformation area in the vicinity of the pipeline 2. Each group contains multiple first strain gauges 33, typically 3, 4, or 6, with each strain gauge evenly distributed along the circumference of the induction tube 31, thereby acquiring strain data at different azimuth angles at the same axial position. Since the axis of the induction tube 31 is perpendicular to the axial direction of the pipeline 2, and the pipeline 2 is used to simulate the actual casing, this circumferential arrangement essentially corresponds to multi-point monitoring around the circumference of the casing, which can effectively identify circumferential non-uniform strain caused by bedding slip, asymmetric crack propagation, or local compression.

[0035] Furthermore, the first strain gauge 33 is preferably a miniature foil resistance strain gauge, which is firmly attached to the outer wall of the sensing tube 31 with a special strain adhesive, and connected to the dynamic strain acquisition system via a thin-diameter lead through the sealed terminal of the shale sample 1. In addition, the first strain gauges 33 can be densely arranged near the bedding plane 11 of the shale sample 1.

[0036] like Figures 9-11 As shown, a physical simulation experimental device for deformation of the casing in the window section of shale hydraulic fracturing according to an embodiment of the present invention includes a sensing unit comprising: a sensing plate 34, wherein the plane of the sensing plate 34 is perpendicular to the axis of the pipeline 2; wherein, a second optical fiber 35 and / or a second strain gauge 36 are disposed on the surface of the sensing plate 34.

[0037] It should be understood that, to avoid situations where the sensing tube 31 fails to detect fracturing fractures, a flat plate or other shape can be used to replace the tubular sensing element. The plane of the sensing plate 34 is orthogonal to the central axis of the pipeline 2. This arrangement allows the sensing plate 34 to effectively capture and respond to stress waves propagating radially along the pipeline 2 during fracturing, fracture propagation fronts, or local mechanical changes caused by formation deformation. Since the development of fractures during fracturing cannot be accurately predicted, this provides a spatially defined sensing reference surface for dynamic monitoring of fracturing.

[0038] Furthermore, a second optical fiber 35 and / or a second strain gauge 36 are integrated as sensing elements on the surface of the sensing plate 34. The second optical fiber 35 can be a Brillouin scattering, Raman scattering, or fiber grating (FBG) sensor, used for distributed or quasi-distributed measurement of strain, temperature, or vibration signals in various areas of the plate surface; the second strain gauge 36 is preferably a high-sensitivity metal foil or semiconductor strain gauge, attached or embedded in key stress locations of the sensing plate 34 to acquire high-precision strain data at local points. The sensing plate 34 itself is made of rigid materials, such as aluminum alloy, stainless steel, or high-strength engineering plastics. Its thickness and dimensions are designed according to the expected load range of the simulated strata, ensuring sufficient structural strength to accurately transmit external mechanical responses while avoiding interference with the natural crack propagation behavior due to excessive stiffness. In some embodiments, the sensing plate 34 may have microchannels or cavities inside for laying sensing leads or achieving temperature compensation, while its edges are chamfered to reduce disturbance to the simulated medium.

[0039] like Figures 12-13 As shown, according to an embodiment of the present invention, a physical simulation experimental device for deformation of the casing in the window section of shale hydraulic fracturing is provided, wherein the second optical fiber 35 is arranged along the length or width direction of the induction plate 34; wherein, there are multiple second optical fibers 35, and the multiple second optical fibers 35 are arranged at intervals along the width or length direction of the induction plate 34.

[0040] It should be understood that multiple second optical fibers 35 are arranged parallel to each other and at equal or unequal intervals along the width or length direction of the sensing plate 34, forming a one-dimensional linear array or quasi-two-dimensional sensing network. The spacing between adjacent second optical fibers 35 is set according to the spatial resolution requirements of the simulation experiment. In a preferred embodiment, multiple second optical fibers 35 are arranged parallel to each other along the width direction of the sensing plate 34, and each fiber extends through the entire sensing area along the length direction, thereby achieving continuous strain sensing in the length direction and multi-point discrete sampling in the width direction; in another embodiment, the second optical fibers 35 are arranged along the length direction, and multiple optical fibers are distributed along the width direction, which is suitable for situations where it is necessary to focus on monitoring the propagation of transverse cracks. Each second optical fiber 35 can be fixed to the surface of the sensing plate 34 by surface bonding, embedding in microgrooves, or encapsulating in a flexible substrate to ensure that it deforms synchronously with the plate body under stress.

[0041] like Figures 12-13 As shown, according to an embodiment of the present invention, a physical simulation experimental device for deformation of the casing in the window section of shale hydraulic fracturing is provided. The number of second strain gauges 36 is multiple, and the multiple second strain gauges 36 are arranged in a quincunx pattern on the surface of the induction plate 34.

[0042] It should be understood that the "plum blossom arrangement" refers to using the central area of ​​the induction plate 34 as a reference point, with several strain gauges evenly distributed circumferentially around it, and further, multiple rings of measuring points can be set at different radial distances. Typically, this arrangement includes a central second strain gauge 36, and four, six, or eight peripheral second strain gauges 36 arranged in a ring around it. Each peripheral strain gauge is equidistant from the central point or distributed according to a preset gradient, forming a geometric configuration similar to plum blossom petals. The advantages of this arrangement are: on the one hand, the central strain gauge can directly monitor the maximum principal strain response when the fracturing crack orthogonally crosses the induction section; on the other hand, the peripheral strain gauges can capture the local strain gradient changes caused by the crack's eccentric passage, oblique propagation, or induced asymmetric distribution of the stress field. By comparing the strain amplitude, phase, and time sequence relationship of each measuring point, key parameters such as the crack's direction, dip angle, aperture, and propagation rate can be effectively inverted.

[0043] Alternatively, strain gauges can be attached to the top / bottom of the sensing tube 31 or sensing plate 34 away from the lamina 11 as a blank control group to eliminate the overall deformation interference of the loading system.

[0044] like Figure 14 As shown, the physical simulation experimental device for deformation of the casing in the window section of shale hydraulic fracturing according to an embodiment of the present invention further includes: a pressure loading part 4, used to apply triaxial stress to the shale sample 1; wherein, the sensing part is completely embedded in the interior of the shale sample 1, and no part of the sensing part is exposed on the surface of the shale sample 1.

[0045] It should be understood that the pressure loading unit 4 typically includes three mutually orthogonal hydraulic or servo-controlled loading units, which apply controllable and independent pressure loads to the shale sample 1 along the horizontal direction of maximum principal stress, the horizontal direction of minimum principal stress, and the vertical stress direction, respectively. The stress values ​​in each direction can be set according to the geological parameters of the target reservoir. The sensing unit is completely embedded inside the shale sample 1, and none of its components—including the sensing plate 34, the second optical fiber 35, the second strain gauge 36, and its leads or encapsulation structure—are exposed on the outer surface of the shale sample 1. This fully embedded arrangement effectively avoids the problems of surface-mounted sensors being susceptible to boundary effects, loading plate friction, or external interference, making the measured data more accurately reflect the stress-strain state inside the sample. At the same time, since no components of the sensing unit are exposed, it will not interfere with the uniform pressure applied to the sample surface by the pressure loading unit 4, nor will it form leakage channels or stress concentration points in the high-pressure sealed cavity, ensuring the integrity of the triaxial stress loading and the safety of the experiment.

[0046] This invention also provides a physical simulation experimental method for the deformation of the casing in the shale hydraulic fracturing window section, using the aforementioned physical simulation experimental device for the deformation of the casing in the shale hydraulic fracturing window section, including the following steps: S1, according to the type of shale sample 1, an induction unit is installed, specifically including: Before preparing shale sample 1, the location, depth, and spatial orientation of the induction unit are determined based on the geological characteristics of the target shale (such as the degree of bedding development, anisotropy intensity, and distribution of natural fractures). For strongly bedding shale, the induction unit is preferably placed near the bedding plane 11 or across the bedding region to effectively capture local deformation caused by bedding slip.

[0047] S2, stress loading is applied to shale sample 1, specifically including: The formed shale sample 1 was installed in the pressure loading unit 4, and the triaxial stress loading system was activated to apply in-situ stress loads conforming to the target reservoir conditions along the vertical direction, the horizontal direction of maximum principal stress, and the horizontal direction of minimum principal stress, respectively. The loading process adopted a staged pressure holding method, gradually increasing to the set value and stabilizing for a period of time to eliminate the influence of initial porosity and microfractures inside the sample, establish a stable initial stress field, and truly restore the in-situ underground mechanical environment.

[0048] S3, inject fracturing fluid to fracturing shale sample 1, and simultaneously collect data, specifically including: A constant-speed pump injects fluorescently stained fracturing fluid, and a pressure sensor monitors the pressure within the fracture. Strain changes in the sensing tube 31 are acquired via a fiber optic sensor / strain gauge, and a high-speed camera records the migration path of the fluorescent fluid to monitor fracture propagation. An 8-channel sensor acoustic emission array captures the spatiotemporal characteristics of fracture development. During this process, a data acquisition system synchronously acquires strain, temperature, or acoustic signals output from the sensing unit in real time, recording the dynamic response characteristics of the fracture as it approaches, crosses, or bypasses the sensing area. The multi-point sensing layout allows for the capture of the fracture propagation path, velocity, and spatial evolution of the induced stress field.

[0049] S4, Evaluate the effect of layer slip on the deformation of the sensing element, specifically including: Data synchronization processing: The acquisition systems of distributed optical fibers and strain gauge arrays are synchronized in time (with a unified trigger signal) to ensure that the data from different monitoring methods are consistent in the time dimension, which facilitates subsequent data fusion and analysis.

[0050] Deformation location: The location of the strain abrupt change is found by using the strain distribution curve of the distributed optical fiber. This location is the corresponding position of the shale bedding slip surface.

[0051] Deformation pattern recognition: If the strain gauges in the circumferential direction show uneven tension and compression signals, it indicates that the induction tube 31 has undergone elliptic deformation (the shear forces on both sides of the lamination slip surface are asymmetrical); if the strain gauges in the axial direction show continuous tension and compression changes, it indicates that the induction tube 31 has undergone overall bending deformation (the shear forces of the lamination slip surface are transmitted along the axial direction of the induction tube 31).

[0052] Deformation Quantification: The rock sample was bisected along the axial direction of the induction tube 31 (or perpendicular to the bedding plane 11) using a diamond wire saw, ensuring a flat cut surface that passed through the center of the induction tube 31 and exposing its internal / external cross-section. High-contrast speckle patterns (such as matte black and white paint) were sprayed onto the surface of the induction tube 31 on the cut surface to eliminate interference from rock powder and surface reflection. A microscopic optical 3D scanner was used to scan the morphology of the induction tube 31 on the cut surface, obtaining 3D point cloud data of the induction tube 31 cross-section. The cross-sectional morphology of the induction tube 31 after the experiment was registered and compared with the scan data of the initial cross-section (scanning results at the same location before the experiment). The curvature of the induction tube 31 was calculated using fiber optic strain data. The degree of elliptic deformation and local concavity / protrusion of the induction tube 31 was quantified, and it could be correlated with the bedding slip position on the cut surface, establishing a quantitative relationship between "bedding slip amount - induction tube 31 deformation amount".

[0053] According to an embodiment of the present invention, a physical simulation experimental method for the deformation of the casing section in hydraulic fracturing of shale is provided. The step of embedding the induction unit according to the type of shale sample 1 specifically includes: S11, When shale sample 1 is natural shale, a blind hole is drilled inside the natural shale, and the induction unit is placed in the blind hole and sealed and fixed. Specifically, this includes: First, the natural rock core is cleaned and its structure characterized to identify the orientation of bedding plane 11 and the distribution of natural fractures. Then, blind holes are drilled at predetermined monitoring locations, perpendicular or parallel to the bedding direction. The diameter of the blind hole is slightly larger than the outer contour of the sensing element, and the depth is set according to monitoring requirements. Sufficient thickness is maintained between the bottom of the hole and the outer surface of the sample to preserve structural integrity. After drilling, the sensing element is carefully placed into the blind hole and filled with a low-modulus sealant (such as epoxy resin-quartz sand composite adhesive or flexible silicone) that matches the mechanical properties of the shale. This ensures a tight fit between the sensing element and the hole wall, enabling effective stress transfer while preventing fracturing fluid from seeping in and interfering with the sensing signal. After the sealant cures, the sensing element is completely embedded inside the rock mass, with no components exposed on the sample surface.

[0054] S12, when shale sample 1 is artificial shale, the artificial shale material is poured in layers in the mold, and the sensing element is pre-embedded in the predetermined monitoring position during the pouring process. Specifically, this includes: X-ray diffraction analysis was used to determine the mineral composition (quartz, clay, carbonates, etc.) of the target shale. Mechanical parameters (elastic modulus, Poisson's ratio, compressive strength, etc.) of the shale were obtained through triaxial testing and acoustic wave testing. A steel mold (300mm×300mm×300mm) was used, with a release agent applied to the inner wall, for layered casting. A mixture of cement, quartz sand, and water in a specific ratio was selected as the shale matrix, and the matrix material was poured to 1 / 3 of its height and compacted by vibration. Shale bedding was created by adding mica powder and inserting A3-sized ordinary wood pulp paper in layers, with a bedding angle of 0°. The layered casting operation was repeated, with induction tubes 31 or induction plates 34 placed perpendicular to the bedding direction, and optical fibers and / or strain gauges attached. The samples were cured in a constant temperature curing chamber (temperature 25±1℃, humidity 90%±5%) for 14 days. Standard-sized rock cores were drilled and tested for mechanical properties. The results were compared with natural rock core samples, with an error not exceeding 20%, thus completing the preparation of artificial shale samples.

[0055] According to the present invention, a physical simulation experiment method for deformation of the casing in the window section of shale hydraulic fracturing is provided. The steps of injecting fracturing fluid to fracturing shale sample 1 specifically include: injecting fracturing fluid into pipeline 2 for fracturing; or, injecting fracturing fluid into multiple pipelines 2 in a preset order for fracturing.

[0056] It should be understood that the following two optional modes are specifically included: In the first mode, fracturing fluid is injected into the shale sample 1 through only one selected pipeline 2 until hydraulic fractures are induced and the sample ruptures. This pipeline 2 is typically located in the vicinity of the induction zone to focus on the direct impact of local fracture initiation and propagation on casing deformation. The fracturing fluid can be water, slickwater, or proppant-carrying fluid. The injection process is controlled by a high-precision plunger pump, and the injection pressure, flow rate, and strain response data of the induction zone are recorded in real time.

[0057] In the second mode, fracturing fluid is injected sequentially into multiple pipelines 2 in a preset order for staged fracturing. The "preset order" can be set according to the geological model or experimental objectives, such as from far to near (injecting into pipelines 2 farther from the induction unit first, and then gradually advancing towards the near end), from near to far, or alternating injection to simulate asynchronous fracturing initiation behavior. Pressure stabilization periods or injection stop intervals can be set between each stage to observe the impact of fracture propagation in the previous stage on the subsequent injection pressure response and casing load. This mode can effectively reproduce the complex mechanical behaviors such as fracture interference, stress shadowing, and bedding activation during multi-stage / multi-cluster fracturing in the field, thereby more realistically revealing the deformation mechanism of the casing in the inlet section under non-uniform loads.

[0058] It should be noted that, regardless of the injection mode used, the entire fracturing process synchronously collects the mechanical response data of the sensing part through a distributed fiber optic sensing system, strain gauge array, or multi-point displacement sensor. Combined with acoustic emission monitoring and high-speed video recording, it enables multi-dimensional analysis of the coupling relationship between the crack initiation location, propagation path, and casing deformation.

[0059] The device embodiments described above are merely illustrative. The units described as separate components may or may not be physically separate, and the components shown as units may or may not be physical units; that is, they may be located in one place or distributed across multiple network units. Some or all of the modules can be selected to achieve the purpose of this embodiment according to actual needs. Those skilled in the art can understand and implement this without any creative effort.

[0060] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A physical simulation experimental method for the deformation of the casing section in the hydraulic fracturing window of shale, characterized in that, A physical simulation experimental device for the deformation of the casing section in shale hydraulic fracturing is used. The device includes: Shale sample (1); Pipeline (2), one end of which is disposed inside the shale sample (1), and the other end of which extends out of the surface of the shale sample (1); the extension direction of the pipeline (2) forms a preset angle with the extension direction of the bedding plane (11) of the shale sample (1); sensing part, disposed inside the shale sample (1), and no part of the sensing part is exposed on the surface of the shale sample (1); The sensing part and the pipeline (2) are spaced apart at one end inside the shale sample (1), and the arrangement direction of the sensing part is perpendicular to the extension direction of the pipeline (2). The sensing element includes: The sensing tube (31) is perpendicular to a set of opposing surfaces of the shale sample (1), and the axis of the sensing tube (31) is orthogonal to the axis of the pipeline (2). It is used to monitor the lateral strain response of the rock mass adjacent to the casing during the fracturing process; and realizes a high-fidelity physical simulation of the stress environment of the vertical section casing. The outer wall of the sensing tube (31) is provided with a first optical fiber (32) and / or a first strain gauge (33). The method includes: The induction unit is installed according to the type of shale sample (1); Stress loading was applied to the shale sample (1); Fracturing fluid was injected to fracturing the shale sample (1), and data was collected simultaneously. Evaluate the effect of layer slip on the deformation of the sensing element; The evaluation of the effect of layer slip on the deformation of the sensing element specifically includes: The shale sample (1) is split into two halves along the axial direction of the induction tube (31) to expose the cross-section of the induction tube (31); the shape of the induction tube (31) is scanned to obtain three-dimensional point cloud data of the cross-section of the induction tube (31). The cross-sectional shape of the induction tube (31) after the experiment was registered and compared with the scanning data of its initial cross-section; the curvature of the induction tube (31) was calculated, and the degree of elliptic deformation and local depression / protrusion of the induction tube (31) was quantified. At the same time, the bedding slip position of the cutting surface was corresponded to establish the quantitative relationship between the amount of bedding slip and the amount of deformation of the induction tube (31); the deformation mechanism of the vertical section casing under the anisotropic conditions of complex strata was revealed.

2. The physical simulation experimental method for the deformation of the casing section in the shale hydraulic fracturing window as described in claim 1, characterized in that, The number of the pipes (2) is multiple, and the multiple pipes (2) are arranged at intervals along the arrangement direction of the sensing part; The distance between the end of each of the pipes (2) located inside the shale sample (1) and the sensing part is different.

3. The physical simulation experimental method for deformation of the casing section in shale hydraulic fracturing according to claim 1, characterized in that, The number of the first optical fiber (32) is one, and the first optical fiber (32) is spirally arranged along the axis of the sensing tube (31); Alternatively, there may be multiple first optical fibers (32), which are arranged in a straight line along the axial direction of the sensing tube (31), and the multiple first optical fibers (32) are arranged at intervals along the circumferential direction of the sensing tube (31).

4. The physical simulation experimental method for the deformation of the casing section in the shale hydraulic fracturing window as described in claim 1, characterized in that, Multiple sets of the first strain gauge (33) are arranged at intervals along the axial direction of the sensing tube (31); In this group, there are multiple first strain gauges (33), and the multiple first strain gauges (33) in the group are arranged at circumferential intervals along the sensing tube (31).

5. The physical simulation experimental method for deformation of the casing section in shale hydraulic fracturing according to claim 1 or 2, characterized in that, The sensing element includes: The plane of the sensing plate (34) is perpendicular to the extension direction of the pipeline (2); The surface of the sensing plate (34) is provided with a second optical fiber (35) and / or a second strain gauge (36).

6. The physical simulation experimental method for the deformation of the casing section in the shale hydraulic fracturing window as described in claim 5, characterized in that, The second optical fiber (35) is arranged along the length or width of the sensing plate (34); The second optical fiber (35) is multiple, and the multiple second optical fibers (35) are spaced apart along the width or length direction of the sensing plate (34).

7. The physical simulation experimental method for the deformation of the casing section in the shale hydraulic fracturing window as described in claim 5, characterized in that, The number of the second strain gauges (36) is multiple, and the multiple second strain gauges (36) are arranged in a quincunx pattern on the surface of the sensing plate (34).

8. The physical simulation experimental method for deformation of the casing section in shale hydraulic fracturing according to claim 1, characterized in that, The step of injecting fracturing fluid to fracturing the shale sample (1) specifically includes: Fracturing fluid is injected into the pipeline (2) for fracturing; Alternatively, fracturing fluid may be injected into multiple pipelines (2) in a preset order for fracturing.

Images