Method for measuring stress interference intensity between clusters of segmented multi-cluster fracturing of continental shale horizontal well

Abstract

The present application provides a kind of land phase shale horizontal well segmented multi-cluster fracturing cluster stress interference intensity measurement method, comprising: step 1, the geomechanical model of the rock matrix of horizontal well section is established;Step 2, the rock mass geomechanics coupling model containing fracture parameters is established;Step 3, the numerical simulation of the crack initiation and propagation process of single section multi-cluster perforation fracturing fracture is carried out;Step 4, the envelope volume of traditional SRV reconstruction body is extracted;Step 5, the inversion data of each layer of superimposed calculation area are obtained;Step 6, the volume size of step 4 and step 5 is compared, and the smaller one is the true reconstruction volume;Step 7, the fracturing parameters of different clusters and different cluster intervals under the same conditions are compared, and the optimized reconstruction volume is compared.The land phase shale horizontal well segmented multi-cluster fracturing cluster stress interference intensity can be used to optimize the cluster interval, construction displacement, construction scale and other process parameters of horizontal well fracturing process, and provide technical support for improving oilfield effective development.

Description

Technical Field

[0001] This invention relates to the field of oil and gas fracturing and production enhancement technology, and in particular to a method for measuring the stress interference intensity between fracturing clusters in multi-cluster fracturing of continental shale horizontal wells. Background Technology

[0002] Currently, the stimulation strategies for shale oil and gas reservoirs both domestically and internationally primarily employ large-volume fracturing techniques, utilizing multi-cluster perforations, low-viscosity fracturing fluid, high flow rates (12m³ / min-15m³ / min), and large-scale operations (1000m³-1500m³ of fracturing fluid). Fracture morphology has also evolved into "multiple fractures and fracture networks." This fracturing process significantly increases post-fracturing productivity by substantially increasing the volume of fracturing. Its core principle is to further shorten the distance the fluid travels from the matrix to the fractures, drastically reduce the driving pressure differential, increase the contact area between the matrix and fractures, and fully leverage the advantageous pathways of natural fractures. Unlike traditional theoretical deduction techniques, data-driven production is gradually becoming the mainstream in fracturing. For example, regional geological conditions, fracture network distribution patterns, and the combination of core analysis and imaging logging techniques are used to determine fracture strata. Production parameters are imported into numerical models for systematic study of production blocks. Horizontal well segmented multi-cluster close-cutting fracturing techniques are beneficial for increasing inter-cluster stress interference, enhancing fracture complexity and the utilization of natural fractures, and improving the efficiency of inter-cluster resource utilization to obtain the maximum reservoir stimulation volume. Disturbances in the stress field, particularly the stress deflection and reversal of horizontal principal stresses induced by the fracturing field, can significantly increase fracture complexity. Combining this with changes in sub-fracture parameters during production allows for the development of economical fracturing methods to reduce oil and gas losses in untreated zones.

[0003] Fracture description and modeling in fractured reservoirs is a global challenge. Discrete fracture network (DFN) models enable the integration of data from geophysics, geology, reservoir engineering, and other fields to form a systematic description of fractures. The emergence of the DFN model is a major milestone in fracture modeling, providing a relatively suitable solution to this problem. In hydraulic fracturing, fracture density, strike, dip angle, and azimuth must be considered. The stress interference problem in hydraulic fracturing is discussed under the consideration of the coupled field of fractures.

[0004] Extensive data indicate that the cluster spacing is the most significant factor affecting inter-crack interference. As the cluster spacing increases, inter-crack stress interference gradually decreases, and the propagation of each crack becomes more uniform. However, there is currently no effective and accurate method to quantify the interference intensity.

[0005] Chinese patent application CN202011070563.X discloses an optimization design method for horizontal well sections in shale gas, comprising the following steps: Step 1: Optimize the perforation spacing model for segmented fracturing in a horizontal well. During segmented fracturing in a horizontal well, the resulting fracture morphology is a transverse fracture perpendicular to the wellbore direction. The study of the induced stress field generated after fracture formation is based on a homogeneous and isotropic two-dimensional plane strain model, establishing a geometric model of fracture induced stress. Step 2: The fracture morphology is a vertical fracture with an elliptical longitudinal section and a half-fracture height of H / 2. The fracture height direction is taken as the y-axis, and the direction perpendicular to the fracture direction, i.e., the wellbore direction, is taken as the x-axis. The geometric model of the hydraulic fracture induced stress field from Step 1 is established, where tensile stress is defined as positive and compressive stress as negative.

[0006] Chinese patent application CN201710930701.9 discloses a method for predicting the volume of shale gas reservoir fracturing stimulation. The method includes the following steps: establishing a fracturing fracture model of the study area using drilling data, logging data, seismic data, and microseismic monitoring data; simulating fracturing by inputting fracturing construction data into the fracturing fracture model to reproduce the hydraulic fracturing simulation process in real time; analyzing the fracture activation status in the fracturing fracture model after hydraulic fracturing simulation and delineating the three-dimensional spatial envelope of the activated fractures; and calculating the volume of the three-dimensional spatial envelope of the activated fractures to obtain the volume of shale gas reservoir fracturing stimulation.

[0007] Chinese patent application CN201811108073.7 discloses a method for evaluating the effective stimulation volume of shale gas reservoirs. This method includes: Step S1: Introducing fractal permeability and fractal porosity into the stimulation volume region of a fractured vertical well, which exhibit a power-law relationship with both the fractal dimension d and the fractal exponent θ; Step S2: Introducing shale gas adsorption and diffusion characteristics, and based on the aforementioned power-law relationship, using a dual-pore single-permeability model, deriving an analytical evaluation model for the effective stimulation volume, and obtaining typical curves of the dimensionless pseudo-pressure at the bottom of the fractured vertical well in the shale gas reservoir and its derivative; Step S3: Calculating the stimulation volume size for homogeneous stimulation volume fractured vertical wells based on the curves; Step S4: Calculating the stimulation volume size for heterogeneous stimulation volume fractured vertical wells based on the typical curves of the dimensionless pseudo-pressure derivative at the bottom of the fractured vertical well; Step S5: Calculating the effective stimulation volume size based on field data and evaluating the relationship between the effective stimulation volume and the total stimulation volume.

[0008] The above-mentioned existing technologies are all significantly different from the present invention and have failed to solve the technical problem we want to solve. Therefore, we have invented a new method for measuring the stress interference intensity between multiple clusters of fracturing in horizontal wells of continental shale. Summary of the Invention

[0009] The purpose of this invention is to provide a method for measuring the stress interference intensity between multiple clusters of fracturing in a horizontal well in continental shale to determine the volume change of the fractured network modification zone caused by stress reversal.

[0010] The objective of this invention can be achieved through the following technical measures: a method for measuring the inter-cluster stress interference intensity of multi-cluster fracturing in horizontal wells of continental shale, comprising:

[0011] Step 1: Establish a geomechanical model of the rock matrix in the horizontal well section;

[0012] Step 2: Establish a coupled geomechanical model of the rock mass including fracture parameters;

[0013] Step 3: Perform numerical simulation of the initiation and propagation process of hydraulic fracturing fractures in a single-stage multi-cluster perforation.

[0014] Step 4: Extract the envelope volume of the traditional SRV modifier;

[0015] Step 5: Superimpose the inversion data of each layer in the calculation area to obtain the volume of the stress inversion zone;

[0016] Step 6: Compare the volumes in Step 4 and Step 5; the smaller one is the true modified volume.

[0017] Step 7: Compare the fracturing parameters of different clusters and different cluster spacings under the same conditions, and compare them to determine the optimized modification volume.

[0018] The objective of this invention can also be achieved through the following technical measures:

[0019] The method for measuring the inter-cluster stress interference intensity of multi-cluster fracturing in horizontal wells of continental shale also includes, before step 1, statistically analyzing the fractures in the field sample cores based on the logging data of the development wells, including structural fractures and bedding fractures, high-angle fractures and low-angle fractures, the formation distribution of the target wells and pilot wells in the block, analyzing the linear density of the fractures, and obtaining parameters such as fracture direction, dip angle, and density; and estimating the fracture distribution of the caprock, marl-sand-textured oil-bearing layer, and source layer in the fracturing area respectively.

[0020] In step 1, based on the geological data of the development block, a geomechanical model of the rock matrix of the horizontal well section containing rock mineral content, geostress, permeability, porosity, and brittleness index is established.

[0021] In step 1, when determining the geometric dimensions, the geometric dimensions of the selected model in the direction of maximum horizontal principal stress and the direction of minimum horizontal principal stress are 500m, and the dimension in the direction of vertical stress is 500m above and below the horizontal well track as the center.

[0022] The method for measuring the stress interference intensity between multiple clusters of fracturing in a horizontal well in continental shale also includes assigning values ​​to the shear strength and compressive strength of the fractures before step 2.

[0023] In step 2, geological parameters of the fractured continental shale horizontal well are coupled, including the permeability, equivalent radius, compressibility coefficient, and brittleness index of the rock matrix and fractures after coarsening and discretization. When determining the model boundary conditions, the maximum horizontal principal stress is obtained based on the original geostress data of the actual block. Minimum horizontal principal stress Maximum vertical principal stress ,Will , and Apply the treatment to each of the six faces of the model.

[0024] The method for measuring the stress interference intensity between multiple clusters of fracturing in a horizontal well in continental shale also includes, before step 3, extracting the maximum horizontal principal stress h1, the minimum horizontal principal stress h1, and the vertical principal stress H along the bedding direction of the grid.

[0025] In step 3, the design and construction parameters for fracture initiation include the amount of pre-placed liquid CO2, the injection volume, the amount of proppant carried, pump injection and pump shutdown, and other fracturing parameters; including the distribution ratio of fracturing fluid in the hydraulic main fracture and the fracture itself, and the attenuation of the permeability coefficient with formation conditions.

[0026] In step 5, the mesh of each layer is extracted, and the blocks in the stress redistribution region where the values ​​of the maximum and minimum horizontal principal stresses are reversed are counted. The reversed data of each layer in the calculation region are superimposed to obtain the volume of the stress reversal zone.

[0027] In step 5, after simulating the propagation process of the hydraulic fracturing crack and the evolution diagram of the stress field, the magnitude and direction of the three principal stresses after the coupled field fracturing are obtained; if the angle between the resultant forces of the two horizontal principal stresses deflects by 90 degrees, it is considered that the direction of the horizontal principal stress has reversed, and the area of ​​the stress reversal zone is obtained by superimposing the corresponding mesh elements.

[0028] In step 7, the stress reversal zone and SRV under different segment spacing, cluster number and fracturing construction parameters are compared and the smaller one is taken as the index for evaluating stress interference, and the cluster spacing and other parameters are optimized.

[0029] The method for measuring the inter-cluster stress interference intensity in multi-segment fracturing of continental shale horizontal wells in this invention determines the change in the volume of the fractured zone caused by stress reversal by measuring the range of stress vector angles between the maximum and minimum horizontal principal stresses in multiple segments of a continental shale horizontal well. This is then compared with the traditional fractured volume (SRV) to determine the actual fractured volume. Comparing the fractured volume under different segmentation and cluster spacing conditions reflects the intensity of stress interference. Attached Figure Description

[0030] Figure 1 This is a flowchart illustrating a specific embodiment of the present invention: a method for measuring the inter-cluster stress interference intensity in multi-cluster fracturing of a horizontal well in continental shale.

[0031] Figure 2 This is a schematic diagram showing the statistics and distribution of fracture parameters in a specific embodiment of the present invention;

[0032] Figure 3 This is a schematic diagram of the geomechanical coupling field considering the caprock, reservoir, and source layer in a specific embodiment of the present invention;

[0033] Figure 4 This is a stress vector diagram in a specific embodiment of the present invention;

[0034] Figure 5 This is a schematic diagram of a conventional modified volume SRV in a specific embodiment of the present invention;

[0035] Figure 6 This is a schematic diagram of the stress reversal zone volume of two clusters of fracturing cracks in a specific embodiment of the present invention. Detailed Implementation

[0036] It should be noted that the following detailed descriptions are exemplary and intended to provide further illustration of the invention. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0037] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the exemplary embodiments of the present invention. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, and / or combinations thereof.

[0038] To enable those skilled in the art to better understand the technical solution of the present invention, the technical solution of the present invention will be described in detail below with reference to specific embodiments.

[0039] Unless otherwise specified, the instruments, reagents, and materials used in the following embodiments are all conventional instruments, reagents, and materials already available in the prior art and can be obtained through legitimate commercial channels. Unless otherwise specified, the experimental methods and detection methods used in the following embodiments are all conventional experimental methods and detection methods already available in the prior art.

[0040] This invention is based on the idea that the fracture field and stress field of the three-dimensional geomechanical model should be fully considered during construction. By describing natural fractures, calculating the turning angle of hydraulic fractures, calculating the fracture development radius, and calculating the modification volume, the stress interference intensity is obtained.

[0041] like Figure 1 The diagram shows a flowchart of the method for measuring the inter-cluster stress interference intensity in multi-cluster fracturing in a horizontal well in continental shale, according to the present invention. This method includes the following steps:

[0042] Step 101: Establish a regional fracture model for the horizontal well section. Based on development well logging data, statistical analysis of fractures in field core samples (including structural fractures and bedding fractures, high-angle fractures and low-angle fractures), formation distribution of target wells and pilot wells in the block, and analysis of fracture linear density, such as... Figure 2 As shown, parameters such as fracture direction, dip angle, and density are obtained. The fracture distribution of the caprock, marl-sand layer, oil-bearing layer, and source oil layer in the fracturing zone is estimated respectively.

[0043] Step 102: Based on the geological data of the development block, establish a geomechanical model of the rock matrix of the horizontal well section containing rock mineral content, geostress, permeability, porosity, and brittleness index.

[0044] When determining the geometric dimensions, the selected model has geometric dimensions of 500m in the direction of maximum horizontal principal stress and minimum horizontal principal stress, respectively, and the dimension in the direction of vertical stress is 500m above and below the horizontal well track as the center.

[0045] Step 103: Assign values ​​to the shear strength and compressive strength of the crack.

[0046] Step 104: Establish a coupled geomechanical model of the rock mass including fracture parameters. For example... Figure 3 The figure shows the coupled geological parameters of a horizontal well in fractured continental shale, including the permeability, equivalent radius, compressibility coefficient, and brittleness index of the rock matrix and fractures after coarsening and discretization. When determining the model boundary conditions, the maximum horizontal principal stress is obtained based on the original geostress data of the actual block. Minimum horizontal principal stress Maximum vertical principal stress ,Will , and Apply the treatment to each of the six faces of the model.

[0047] Step 105: Extract the maximum horizontal principal stress h1, minimum horizontal principal stress h1, and vertical principal stress H along the bedding direction of the mesh, as follows: Figure 4 As shown.

[0048] Step 106: Perform numerical simulation of the initiation and propagation process of fracturing fractures in a single-stage multi-cluster perforation system. The design and construction parameters for fracture initiation include the amount of pre-positioned liquid CO2, injection volume, proppant carrying capacity, pumping and pump shutdown, and other fracturing parameters. These include the distribution ratio of fracturing fluid in the hydraulic main fracture and the fracture itself, and the attenuation of the permeability coefficient with formation conditions.

[0049] Step 107: Extract the envelope volume of the traditional SRV modifier, such as... Figure 5 As shown.

[0050] Step 108: Extract the mesh of each layer and statistically analyze the blocks in the stress redistribution region where the values ​​of the maximum and minimum horizontal principal stresses are reversed. Overlay the reversed data from each layer of the computational region to obtain the volume of the stress reversal zone, as shown below. Figure 6 As shown.

[0051] After simulating the propagation process of the hydraulic fracturing crack and the evolution of the stress field, the magnitudes and directions of the three principal stresses after coupled-field fracturing are obtained. If the angle between the resultant forces of the two horizontal principal stresses deflects by 90 degrees, it is assumed that the direction of the horizontal principal stress has reversed, and the area of ​​the stress reversal zone is obtained by superimposing the corresponding mesh elements.

[0052] Step 109: Compare the volumes in Step 107 and Step 108; the smaller one is the true modified volume.

[0053] Step 110: Compare the fracturing parameters of different clusters and different cluster spacings under the same conditions to determine the optimized stimulation volume. Larger volumes result in lower stress interference. The stress interference intensity between clusters in this multi-cluster fracturing process of a continental shale oil horizontal well can be used to optimize process parameters such as cluster spacing, fracturing displacement, and fracturing scale, providing technical support for improving the effective development of the oilfield.

[0054] Specifically, this includes comparing the stress reversal zone under different segment spacing, cluster number, and fracturing operation parameters, and taking the smaller value of SRV as an indicator for evaluating stress interference, and then optimizing the process.

[0055] The following are several specific embodiments of the application of the present invention.

[0056] Example 1:

[0057] In a specific embodiment 1 of the present invention, the method for measuring the inter-cluster stress interference intensity of multi-cluster fracturing in a horizontal well in continental shale includes:

[0058] Step 1: Based on the logging data from the development wells, statistically analyze the fractures in the field sample cores (including structural fractures and bedding fractures, high-angle fractures and low-angle fractures), the formation distribution of the target wells and pilot wells in the block, analyze the linear density of fractures, and obtain parameters such as fracture direction, dip angle, and density. Also, estimate the fracture distribution of the caprock, marl-sand-crack layer, oil-bearing layer, and source layer in the fracturing area.

[0059] Step 2: Based on the geological data of the development block, establish a geomechanical model of the rock matrix of the horizontal well section, including rock mineral content, geostress, permeability, porosity, and brittleness index. Model geometry: The selected model dimensions are 500m in the direction of maximum horizontal principal stress, minimum horizontal principal stress, and vertical direction. Geomechanical parameters: Based on geological data, continuous logging data, and core rock mechanics test data from actual core samples, the specific geomechanical parameters are as follows: Reservoir elastic modulus 40 GPa, Poisson's ratio 0.25, cohesion 5 MPa, internal friction angle 30°, tensile strength 3 MPa, permeability 0.4 mD. Caprock and source layer elastic modulus 60 GPa, Poisson's ratio 0.20, cohesion 25 MPa, internal friction angle 35°, tensile strength 4 MPa, permeability 0.1 mD.

[0060] Step 3: Assign a shear strength of 25 MPa / mm and a compressive strength of 50 MPa / mm to the crack.

[0061] Step 4: Establish a coupled geomechanical model of the rock mass including fracture parameters. Specifically, this includes coupling geological parameters of a horizontal well in fractured continental shale, including, after coarsening and discretization, coupling parameters such as permeability, equivalent radius, compressibility coefficient, and brittleness index of the rock matrix and fractures. Model external boundary condition: maximum horizontal principal stress. =72MPa, minimum horizontal principal stress =64MPa, vertical principal stress =80MPa, , and Apply boundary conditions to all six faces of the model (Z, X, and Y directions); select two clusters of perforations along a section of the horizontal well track in the model and apply a constant flow boundary condition with a flow rate of 8 m³ / s. 3 / min, injection time 4h, cluster spacing 16m.

[0062] Step 5: Extract the maximum horizontal principal stress h1, the minimum horizontal principal stress h1, and the vertical principal stress H along the bedding direction of the mesh.

[0063] Step 6: Perform numerical simulation of the initiation and propagation process of fracturing fractures in a single-stage multi-cluster perforation system. The design and construction parameters for fracture initiation include a pre-positioned liquid CO2 volume of 200t, injection volume, pump injection and shutdown parameters, etc. These parameters include the distribution ratio of fracturing fluid in the hydraulic main fracture and the fracture itself (1:4), and the variation of permeability coefficient with formation conditions (attenuation radius 200m).

[0064] Step 7: Extract the envelope volume of the traditional SRV modifier, which is 400,000 m³.

[0065] Step 8: Extract the mesh of each layer and statistically analyze the blocks in the stress redistribution region where the values ​​of the maximum and minimum horizontal principal stresses are reversed. Superimpose the reversed data of each layer in the calculation region to obtain the volume of the stress reversal zone as 260,000 m³.

[0066] Step 9: Compare the volumes obtained in Steps 7 and 8; the smaller one represents the actual modified volume, which is 260,000 m³. Actual microseismic monitoring data shows that the fracture height is 61.5 m, the fracture height is 27 m, and the modified volume is 286,200 m³.

[0067] Step 10: Compare the fracturing parameters of different clusters and different cluster spacings under the same conditions to determine the optimized stimulation volume. Larger volumes result in lower stress interference. The stress interference intensity between clusters in the multi-cluster fracturing of this continental shale oil horizontal well can be used to optimize process parameters such as cluster spacing, fracturing flow rate, and fracturing scale, providing technical support for improving the effective development of the oilfield. Comparing a 40m section with 3 clusters perforated with a cluster spacing of 16m and 4 clusters perforated with a cluster spacing of 12m, the former has a larger stimulation volume in the reversal zone, weaker stress interference, and is easier to proppant. Therefore, the optimized fracturing process uses 3 clusters with a spacing of 16m, which is reasonable.

[0068] Example 2:

[0069] In a specific embodiment 2 of the present invention, the method for measuring the inter-cluster stress interference intensity of multi-cluster fracturing in a horizontal well in continental shale includes:

[0070] Step 1: Based on the logging data from the development wells, statistically analyze the fractures in the field sample cores (including structural fractures and bedding fractures, high-angle fractures and low-angle fractures), the formation distribution of the target wells and pilot wells in the block, analyze the linear density of fractures, and obtain parameters such as fracture direction, dip angle, and density. Also, estimate the fracture distribution of the caprock, marl-sand-crack layer, oil-bearing layer, and source layer in the fracturing area.

[0071] Step 2: Based on the geological data of the development block, establish a geomechanical model of the rock matrix of the horizontal well section, including rock mineral content, geostress, permeability, porosity, and brittleness index. Model geometry: The selected model dimensions are 500m in the direction of maximum horizontal principal stress, minimum horizontal principal stress, and vertical direction. Geomechanical parameters: Based on geological data, continuous logging data, and core rock mechanics test data from actual core samples, the specific geomechanical parameters are as follows: Reservoir elastic modulus 50 GPa, Poisson's ratio 0.10, cohesion 10 MPa, internal friction angle 30°, tensile strength 3 MPa, permeability 0.4 mD. Caprock and source layer elastic modulus 80 GPa, Poisson's ratio 0.20, cohesion 20 MPa, internal friction angle 35°, tensile strength 4 MPa, permeability 0.1 mD.

[0072] Step 3: Assign a shear strength of 10 MPa / mm and a compressive strength of 30 MPa / mm to the crack.

[0073] Step 4: Establish a coupled geomechanical model of the rock mass including fracture parameters. Specifically, this includes coupling geological parameters of a horizontal well in fractured continental shale, including, after coarsening and discretization, coupling parameters such as permeability, equivalent radius, compressibility coefficient, and brittleness index of the rock matrix and fractures. Model external boundary condition: maximum horizontal principal stress. =70MPa, minimum horizontal principal stress =60MPa, vertical principal stress =75MPa, , and Apply boundary conditions to all six faces of the model (Z, X, and Y directions); select two clusters of perforations along a section of the horizontal well track in the model and apply a constant flow boundary condition with a flow rate of 8 m³ / s. 3 / min, injection time 4h, cluster spacing 16m.

[0074] Step 5: Extract the maximum horizontal principal stress h1, the minimum horizontal principal stress h1, and the vertical principal stress H along the bedding direction of the mesh.

[0075] Step 6: Perform numerical simulation of the initiation and propagation process of fracturing fractures in a single-stage multi-cluster perforation system. The design and construction parameters for fracture initiation include a pre-positioned liquid CO2 volume of 100t, injection volume, pump injection and shutdown parameters, etc. These parameters include the distribution ratio of fracturing fluid in the hydraulic main fracture and the fracture itself (1:4), and the variation of permeability coefficient with formation conditions (attenuation radius 200m).

[0076] Step 7: Extract the envelope volume of the traditional SRV modifier, which is 320,000 m³.

[0077] Step 8: Extract the mesh of each layer and statistically analyze the blocks in the stress redistribution region where the values ​​of the maximum and minimum horizontal principal stresses are reversed. Superimpose the reversed data of each layer in the calculation region to obtain the volume of the stress reversal zone as 280,000 m³.

[0078] Step 9: Compare the volumes obtained in Steps 7 and 8; the smaller one represents the actual modified volume, which is 280,000 m³. Actual microseismic monitoring data shows that the joint height is 63 m, the joint height is 28 m, and the modified volume is 286,200 m³.

[0079] Step 10: Compare the fracturing parameters of different clusters and different cluster spacings under the same conditions to determine the optimized stimulation volume. Larger volumes result in lower stress interference. The stress interference intensity between clusters in the multi-cluster fracturing of this continental shale oil horizontal well can be used to optimize process parameters such as cluster spacing, fracturing flow rate, and fracturing scale, providing technical support for improving the effective development of the oilfield. Comparing a 40m section with 3 clusters perforated with a cluster spacing of 16m and 4 clusters perforated with a cluster spacing of 12m, the former has a larger stimulation volume in the reversal zone, weaker stress interference, and is easier to proppant. Therefore, the optimized fracturing process uses 4 clusters with a spacing of 12m, which is reasonable.

[0080] Example 3:

[0081] In a specific embodiment 3 of the present invention, the method for measuring the inter-cluster stress interference intensity of multi-cluster fracturing in a horizontal well in continental shale includes:

[0082] Step 1: Based on the logging data from the development wells, statistically analyze the fractures in the field sample cores (including structural fractures and bedding fractures, high-angle fractures and low-angle fractures), the formation distribution of the target wells and pilot wells in the block, analyze the linear density of fractures, and obtain parameters such as fracture direction, dip angle, and density. Also, estimate the fracture distribution of the caprock, marl-sand-crack layer, oil-bearing layer, and source layer in the fracturing area.

[0083] Step 2: Based on the geological data of the development block, establish a geomechanical model of the rock matrix of the horizontal well section, including rock mineral content, geostress, permeability, porosity, and brittleness index. Model geometry: The selected model dimensions are 500m in the direction of maximum horizontal principal stress, minimum horizontal principal stress, and vertical direction. Geomechanical parameters: Based on geological data, continuous logging data, and core rock mechanics test data from actual core samples, the specific geomechanical parameters are as follows: Reservoir elastic modulus 55 GPa, Poisson's ratio 0.10, cohesion 10 MPa, internal friction angle 30°, tensile strength 3 MPa, permeability 0.4 mD. Caprock and source layer elastic modulus 80 GPa, Poisson's ratio 0.20, cohesion 20 MPa, internal friction angle 35°, tensile strength 4 MPa, permeability 0.1 mD.

[0084] Step 3: Assign a shear strength of 15 MPa / mm and a compressive strength of 30 MPa / mm to the crack.

[0085] Step 4: Establish a coupled geomechanical model of the rock mass including fracture parameters. Specifically, this includes coupling geological parameters of a horizontal well in fractured continental shale, including, after coarsening and discretization, coupling parameters such as permeability, equivalent radius, compressibility coefficient, and brittleness index of the rock matrix and fractures. Model external boundary condition: maximum horizontal principal stress. =75MPa, minimum horizontal principal stress =60MPa, vertical principal stress =90MPa, , and Apply boundary conditions to all six faces of the model (Z, X, and Y directions); select two clusters of perforations along a section of the horizontal well track in the model and apply a constant flow boundary condition with a flow rate of 8 m³ / s. 3 / min, injection time 4h, cluster spacing 16m.

[0086] Step 5: Extract the maximum horizontal principal stress h1, the minimum horizontal principal stress h1, and the vertical principal stress H along the bedding direction of the mesh.

[0087] Step 6: Perform numerical simulation of the initiation and propagation process of fracturing fractures in a single-stage multi-cluster perforation system. The design and construction parameters for fracture initiation include a pre-positioned liquid CO2 volume of 150t, injection volume, pump injection and shutdown parameters, etc. These parameters include the distribution ratio of fracturing fluid in the hydraulic main fracture and the fracture itself (1:4), and the variation of permeability coefficient with formation conditions (attenuation radius 200m).

[0088] Step 7: Extract the envelope volume of the traditional SRV modifier, which is 300,000 m³.

[0089] Step 8: Extract the mesh of each layer and statistically analyze the blocks in the stress redistribution region where the values ​​of the maximum and minimum horizontal principal stresses are reversed. Superimpose the reversed data of each layer in the calculation region to obtain the volume of the stress reversal zone as 280,000 m³.

[0090] Step 9: Compare the volumes obtained in Steps 7 and 8; the smaller one represents the actual modified volume, which is 250,000 m³. Actual microseismic monitoring data shows that the fracture height is 47 m, the fracture height is 28 m, and the modified volume is 243,200 m³.

[0091] Step 10: Compare the fracturing parameters of different clusters and different cluster spacings under the same conditions to determine the optimized stimulation volume. Larger volumes result in lower stress interference. The stress interference intensity between clusters in the multi-cluster fracturing of this continental shale oil horizontal well can be used to optimize process parameters such as cluster spacing, fracturing flow rate, and fracturing scale, providing technical support for improving the effective development of the oilfield. Comparing a 40m section with 3 clusters perforated with a cluster spacing of 16m and 4 clusters perforated with a cluster spacing of 12m, the former has a larger stimulation volume in the reversal zone, weaker stress interference, and is easier to proppant. Therefore, the optimized fracturing process uses 4 clusters with a spacing of 12m, which is reasonable.

[0092] Finally, it should be noted that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

[0093] Except for the technical features described in the specification, all other technologies are known to those skilled in the art.

Claims

1. A method for measuring the stress interference intensity between fracturing clusters in multi-cluster segmented horizontal wells of continental shale, characterized in that, The method for measuring the inter-cluster stress interference intensity in multi-cluster fracturing of horizontal wells in continental shale includes: Step 1: Establish a geomechanical model of the rock matrix in the horizontal well section; Step 2: Establish a coupled geomechanical model of the rock mass including fracture parameters; Step 3: Perform numerical simulation of the initiation and propagation process of hydraulic fracturing fractures in a single-stage multi-cluster perforation. Step 4: Extract the envelope volume of the traditional SRV modifier; Step 5: Superimpose the inversion data of each layer in the calculation area to obtain the volume of the stress inversion zone; Step 6: Compare the volumes in Step 4 and Step 5; the smaller one is the true modified volume. Step 7: Compare the true modified volume under different cluster spacings and different numbers of clusters under the same conditions. Use this as an indicator to evaluate stress interference. Select the cluster spacing and number of clusters corresponding to the larger true modified volume, and optimize the cluster spacing and number of clusters parameters.

2. The method for measuring the inter-cluster stress interference intensity of multi-cluster fracturing in horizontal wells of continental shale as described in claim 1, further comprising, before step 1, based on the logging data of the development well, statistically analyzing the fractures in the field sampled cores, including structural fractures and bedding fractures, high-angle fractures and low-angle fractures, the formation distribution of the target wells and pilot wells in the block, analyzing the linear density of the fractures, and obtaining parameters such as fracture direction, dip angle, and density; and respectively estimating the fracture distribution of the caprock, marl-sand-textured oil-bearing layer, and source layer in the fracturing area.

3. The method for measuring the stress interference intensity between multiple clusters of fracturing in a horizontal well segment of continental shale as described in claim 1, wherein in step 1, a geomechanical model of the rock matrix of the horizontal well segment containing rock mineral content, geostress, permeability, porosity, and brittleness index is established based on the geological data of the development block.

4. According to the method for measuring the inter-cluster stress interference intensity of multi-cluster fracturing in a horizontal well in continental shale as described in claim 3, in step 1, when determining the geometric dimensions, the geometric dimensions of the selected model in the direction of maximum horizontal principal stress and the direction of minimum horizontal principal stress are 500m respectively, and the dimension in the direction of vertical stress is 500m above and below the horizontal well track as the center.

5. The method for measuring the inter-cluster stress interference intensity of multi-cluster fracturing in a horizontal well in continental shale as described in claim 1, further comprising, before step 2, assigning values ​​to the shear strength and compressive strength of the fractures.

6. The method for measuring the inter-cluster stress interference intensity of multi-cluster fracturing in a horizontal well in continental shale according to claim 1, in step 2, the geological parameters of the fractured horizontal well in continental shale are coupled, including the permeability, equivalent radius, compressibility coefficient, and brittleness index of the rock matrix and fractures after coarsening and discretization; when determining the model boundary conditions, the maximum horizontal principal stress is obtained based on the original geostress data of the actual block. Minimum horizontal principal stress Maximum vertical principal stress ,Will , and Apply the treatment to each of the six faces of the model.

7. The method for measuring the inter-cluster stress interference intensity of segmented multi-cluster fracturing in a horizontal well of continental shale according to claim 1, further comprising, before step 3, extracting the maximum horizontal principal stress h1, the minimum horizontal principal stress h1, and the vertical principal stress H along the bedding direction of the grid.

8. The method for measuring the inter-cluster stress interference intensity of multi-cluster fracturing in a horizontal well in continental shale as described in claim 1, wherein in step 3, the design and construction parameters for fracture initiation include fracturing parameters such as the amount of pre-filled liquid CO2, the injection volume, the proppant carrying volume, pump injection, and pump shutdown; and the distribution ratio of fracturing fluid in the hydraulic main fracture and the fracture itself, and the attenuation of the permeability coefficient with formation conditions.

9. The method for measuring the stress interference intensity between multiple clusters of fracturing in a horizontal well in continental shale as described in claim 1, in step 5, the mesh of each layer is extracted, and the blocks in the stress redistribution area where the values ​​of the maximum and minimum horizontal principal stresses are reversed are statistically analyzed; the reversed data of each layer in the calculation area are superimposed to obtain the volume of the stress reversal zone.

10. The method for measuring the stress interference intensity between multiple clusters of fracturing in a horizontal well of continental shale as described in claim 9, in step 5, after simulating the propagation process of the fracturing fracture and the evolution diagram of the stress field, the magnitude and direction of the three principal stresses after fracturing in the coupled field are obtained; if the angle between the resultant forces of the two horizontal principal stresses deflects by 90 degrees, it is considered that the direction of the horizontal principal stress has reversed, and the corresponding grid cells are superimposed to obtain the area of ​​the stress reversal zone.

Images