Method and device for determining critical injection pressure of shale reservoir

Abstract

The invention discloses a method and device for determining the critical injection pressure of a shale reservoir, and relates to the technical field of unconventional oil-gas exploration and development, and the method comprises the steps: constructing a discontinuous mechanical grid according to rock core experiment data, regional faults and spatial distribution characteristics of natural fractures; according to the physical property and geomechanical parameters, a continuous body mechanical grid is constructed; according to the discontinuous body mechanical grid and the continuous body mechanical grid, an infinite stratum mechanical grid model is constructed; setting pore pressure and strain boundaries, and inverting stress field distribution of the infinite stratigraphic mechanics grid model by adopting a finite element calculation method; the crustal stress state is determined according to the crustal stress; calculating the maximum effective stress and the minimum effective stress according to different crustal stress states; and according to the maximum effective stress and the minimum effective stress, determining the minimum pore pressure increment required by shear failure of the shale reservoir in different crustal stress states. According to the method, regional rock mass instability risk quantitative evaluation under a complex crustal stress field condition can be realized.

Description

Technical Field

[0001] The present invention relates to the technical field of unconventional oil and gas exploration and development, and in particular to a method and device for determining the critical injection pressure of a shale reservoir. Background Art

[0002] This section is intended to provide a background or context to the embodiments of the invention recited in the claims. No admission is made that the description herein is prior art by inclusion in this section.

[0003] Hydraulic fracturing technology is an important measure to increase production of unconventional oil and gas resources such as shale gas and tight oil and gas. Hydraulic fracturing technology uses a high-pressure pump group on the ground to pump fluid carrying proppant into the formation; the formation is destroyed and cracks are generated under the action of high-pressure fluid, and under the action of proppant, a channel for oil and gas to migrate is provided. Hydraulic fracturing improves the recovery rate of unconventional oil and gas resources by improving the flow channel of oil and gas downhole. With the increasing scale of hydraulic fracturing transformation, the problems encountered in the process of reservoir transformation are becoming more and more prominent. In particular, the high-pressure fluid is pressed into the ground, which is bound to cause the increase of deep fluid pressure, rock temperature change and formation deformation, and may cause the activation of existing faults and induce seismic activity. After the fluid is injected into the deep reservoir, the risk of geological body damage and instability caused by the change of the original stress field has become a potential problem. At the same time, during the horizontal well volume fracturing process, some wells experienced casing shear deformation due to reservoir displacement, resulting in the inability to smoothly insert the bridge plug during the fracturing process and the inability of the continuous tubing to smoothly drill the bridge plug, which affected the timely implementation of subsequent operations.

[0004] In the process of shale gas horizontal well fracturing, in order to prevent and control the risk of shale reservoir damage and instability caused by fracturing fluid injection in the region, a geomechanical-based instability risk assessment technology was proposed. According to the results of the fine geostress field of the reservoir, the Mohr circle was determined using the effective principal stress, and then the stress state that the intact rock mass can withstand was analyzed. When the fluid injection causes the pore pressure to increase, the equilibrium stress state of the intact rock mass is broken, the effective stress decreases, and the Mohr circle moves toward the failure line that characterizes the rock strength. When the Mohr circle contacts the failure envelope, the rock mass will be damaged.

[0005] At present, the instability risk assessment technology based on geomechanics has been widely used in geotechnical engineering. The relevant research mainly focuses on the risk of fracture shear slip, the risk of fault instability induced by water injection, or the risk of complete slope instability. There is still a lack of risk assessment technology for the complete rock mass in deep reservoir areas that is damaged and unstable after fluid injection. Therefore, it is urgent to establish a prediction method for the critical injection pressure of shale reservoirs, fully consider the impact of injected fluids on the ground stress field, predict the instability risk of the complete rock mass in real time, and then optimize and adjust the scale of fracturing fluid to achieve the goal of safe and efficient transformation of shale reservoirs. Summary of the invention

[0006] The embodiment of the present invention provides a method for determining the critical injection pressure of a shale reservoir, which is used to achieve quantitative assessment of the risk of regional rock mass instability under complex geostress field conditions, solves the problem of judging the risk of regional rock mass instability caused by hydraulic fracturing injection fluid, and can be used to support optimization and adjustment of the strength of fluid used for hydraulic fracturing reservoir reconstruction. The method includes:

[0007] Obtaining reservoir characterization data of a designated area of ​​a shale reservoir; the reservoir characterization data includes physical property parameters, geomechanical parameters, and spatial distribution characteristic parameters of faults and natural fractures in the designated area;

[0008] Construct a discontinuum mechanics grid based on pre-acquired core experimental data and spatial distribution characteristic parameters of faults and natural fractures in a specified area;

[0009] Construct a continuum mechanics grid based on the physical parameters and geomechanical parameters of the specified area;

[0010] An infinite formation mechanical grid model of a shale reservoir is constructed according to the discontinuum mechanical grid and the continuum mechanical grid; the infinite formation mechanical grid model includes a plurality of mechanical grid units;

[0011] According to the preset pore pressure conditions and strain boundary conditions, the finite element calculation method is used to invert the stress field distribution of the infinite formation mechanical grid model to determine the maximum horizontal principal stress, minimum horizontal principal stress, vertical stress and pore pressure of each mechanical grid unit;

[0012] Determine the ground stress state information of each mechanical grid unit according to the maximum horizontal principal stress, the minimum horizontal principal stress and the vertical stress of each mechanical grid unit;

[0013] According to the ground stress state information and pore pressure of each mechanical grid unit, the maximum effective stress and the minimum effective stress of each mechanical grid unit are calculated;

[0014] The critical injection pressure of the shale reservoir is determined according to the maximum effective stress and the minimum effective stress of each mechanical grid unit. The critical injection pressure is the minimum pore pressure increment required for shear failure of the shale reservoir under different ground stress states.

[0015] The embodiment of the present invention also provides a device for determining the critical injection pressure of a shale reservoir, which is used to achieve quantitative assessment of the risk of regional rock mass instability under complex geostress field conditions, solves the problem of determining the risk of regional rock mass instability caused by hydraulic fracturing injection fluid, and can be used to support optimization and adjustment of the strength of fluid used for hydraulic fracturing reservoir reconstruction. The device includes:

[0016] A data acquisition module is used to acquire reservoir characterization data of a specified area of ​​a shale reservoir; the reservoir characterization data includes physical property parameters, geomechanical parameters, and spatial distribution characteristic parameters of faults and natural fractures in the specified area;

[0017] The first grid construction module is used to construct a discontinuum mechanics grid based on pre-acquired core experimental data and spatial distribution characteristic parameters of faults and natural fractures in a specified area;

[0018] The second grid construction module is used to construct a continuum mechanics grid according to the physical property parameters and geomechanical parameters of the specified area;

[0019] A third grid construction module is used to construct an infinite formation mechanical grid model of the shale reservoir according to the discontinuum mechanical grid and the continuum mechanical grid; the infinite formation mechanical grid model includes a plurality of mechanical grid units;

[0020] The ground stress determination module is used to invert the stress field distribution of the infinite formation mechanical grid model using the finite element calculation method according to the pre-set pore pressure conditions and strain boundary conditions, and determine the maximum horizontal principal stress, minimum horizontal principal stress, vertical stress and pore pressure of each mechanical grid unit;

[0021] A stress state determination module is used to determine the ground stress state information of each mechanical grid unit according to the maximum horizontal principal stress, the minimum horizontal principal stress and the vertical stress of each mechanical grid unit;

[0022] An effective stress calculation module is used to calculate the maximum effective stress and the minimum effective stress of each mechanical grid unit according to the ground stress state information and pore pressure of each mechanical grid unit;

[0023] The critical injection pressure determination module is used to determine the critical injection pressure of the shale reservoir according to the maximum effective stress and the minimum effective stress of each mechanical grid unit. The critical injection pressure is the minimum pore pressure increment required for shear failure of the shale reservoir under different ground stress states.

[0024] An embodiment of the present invention further provides a computer-readable storage medium, wherein the computer-readable storage medium stores a computer program, and when the computer program is executed by a processor, the method for determining the critical injection pressure of a shale reservoir is implemented.

[0025] An embodiment of the present invention further provides a computer program product, which includes a computer program. When the computer program is executed by a processor, the method for determining the critical injection pressure of a shale reservoir is implemented.

[0026] In the embodiment of the present invention, reservoir characterization data of a designated area of ​​a shale reservoir is obtained; the reservoir characterization data includes physical property parameters, geomechanical parameters, and spatial distribution characteristic parameters of faults and natural fractures in the designated area; a discontinuum mechanical grid is constructed based on pre-acquired core experimental data and spatial distribution characteristic parameters of faults and natural fractures in the designated area; a continuum mechanical grid is constructed based on the physical property parameters and geomechanical parameters of the designated area; an infinite formation mechanical grid model of the shale reservoir is constructed based on the discontinuum mechanical grid and the continuum mechanical grid; the infinite formation mechanical grid model includes a plurality of mechanical grid units; a finite element calculation is adopted based on the pre-set pore pressure conditions and strain boundary conditions. Methods Invert the stress field distribution of the infinite formation mechanical grid model to determine the maximum horizontal principal stress, minimum horizontal principal stress, vertical stress and pore pressure of each mechanical grid unit; determine the geostress state information of each mechanical grid unit according to the maximum horizontal principal stress, minimum horizontal principal stress and vertical stress of each mechanical grid unit; calculate the maximum effective stress and minimum effective stress of each mechanical grid unit according to the geostress state information and pore pressure of each mechanical grid unit; determine the critical injection pressure of the shale reservoir according to the maximum effective stress and minimum effective stress of each mechanical grid unit, which is the minimum pore pressure increment required for shear failure of the shale reservoir under different geostress states. In this way, according to the minimum pore pressure increment required for shear failure of the shale reservoir under different geostress states, the quantitative assessment of the risk of regional rock mass instability under complex geostress field conditions can be realized, which solves the judgment of the risk of regional rock mass instability caused by hydraulic fracturing injection fluid, and can be used to support the optimization and adjustment of the strength of hydraulic fracturing reservoir reconstruction fluid. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the prior art descriptions. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work. In the drawings:

[0028] Figure 1 A flow chart of a method for determining a critical injection pressure of a shale reservoir provided in an embodiment of the present invention;

[0029] Figure 2 A schematic diagram of a discontinuum mechanical grid including faults and natural fractures provided in an embodiment of the present invention;

[0030] Figure 3 A top view and a side view of a formation mechanics grid model of a shale reservoir provided in an embodiment of the present invention;

[0031] Figure 4 A schematic diagram of an infinite formation mechanics grid model of a shale reservoir provided in an embodiment of the present invention;

[0032] Figure 5 A schematic diagram of different ground stress states provided in an embodiment of the present invention;

[0033] Figure 6 A schematic diagram of the distribution of critical injection pressure of a regional shale reservoir provided in an embodiment of the present invention;

[0034] Figure 7 A schematic diagram of a device for determining a critical injection pressure of a shale reservoir provided in an embodiment of the present invention;

[0035] Figure 8 A schematic diagram of a computer device provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0036] To make the purpose, technical solution and advantages of the embodiments of the present invention more clear, the embodiments of the present invention are further described in detail below in conjunction with the accompanying drawings. Here, the exemplary embodiments of the present invention and their descriptions are used to explain the present invention, but are not intended to limit the present invention.

[0037] In the description of this specification, the terms "include", "including", "have", "contain", etc. are all open terms, which mean including but not limited to. The descriptions with reference to the terms "one embodiment", "a specific embodiment", "some embodiments", "for example", etc. mean that the specific features, structures or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present application. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures or characteristics described may be combined in a suitable manner in any one or more embodiments or examples. The order of steps involved in each embodiment is used to schematically illustrate the implementation of the present application, and the order of steps is not limited and can be appropriately adjusted as needed.

[0038] In order to overcome the problem that the prior art only considers the instability risk caused by shear slippage of faults and cracks, and that there is still a lack of risk assessment technology for the destruction and instability of intact rock mass in deep reservoir areas after fluid injection, an embodiment of the present invention proposes a method and device for determining the critical injection pressure of shale reservoirs, which are used to fully consider the impact of the injected fluid on the ground stress field, predict the instability risk of the intact rock mass in real time, and then optimize and adjust the scale of fracturing fluid volume to achieve the goal of safe and efficient transformation of shale reservoirs.

[0039] Figure 1A flow chart of a method for determining a critical injection pressure of a shale reservoir provided in an embodiment of the present invention, the method comprising the following steps:

[0040] Step 101, obtaining reservoir characterization data of a designated area of ​​a shale reservoir; the reservoir characterization data includes physical property parameters, geomechanical parameters, and spatial distribution characteristic parameters of faults and natural fractures in the designated area;

[0041] Step 102, constructing a discontinuum mechanics grid based on pre-acquired core experimental data and spatial distribution characteristic parameters of faults and natural fractures in a designated area;

[0042] Step 103, constructing a continuum mechanics grid according to the physical parameters and geomechanical parameters of the designated area;

[0043] Step 104, constructing an infinite formation mechanical grid model of the shale reservoir according to the discontinuum mechanical grid and the continuum mechanical grid; the infinite formation mechanical grid model includes a plurality of mechanical grid units;

[0044] Step 105, according to the preset pore pressure conditions and strain boundary conditions, the finite element calculation method is used to invert the stress field distribution of the infinite formation mechanical grid model, and the maximum horizontal principal stress, the minimum horizontal principal stress, the vertical stress and the pore pressure of each mechanical grid unit are determined;

[0045] Step 106, determining the ground stress state information of each mechanical grid unit according to the maximum horizontal principal stress, the minimum horizontal principal stress and the vertical stress of each mechanical grid unit;

[0046] Step 107, calculating the maximum effective stress and the minimum effective stress of each mechanical grid unit according to the ground stress state information and the pore pressure of each mechanical grid unit;

[0047] Step 108, determining the critical injection pressure of the shale reservoir according to the maximum effective stress and the minimum effective stress of each mechanical grid unit, wherein the critical injection pressure is the minimum pore pressure increment required for shear failure of the shale reservoir under different ground stress states.

[0048] In the embodiment of the present invention, reservoir characterization data of a designated area of ​​a shale reservoir is obtained; the reservoir characterization data includes physical property parameters, geomechanical parameters, and spatial distribution characteristic parameters of faults and natural fractures in the designated area; a discontinuum mechanical grid is constructed based on pre-acquired core experimental data and spatial distribution characteristic parameters of faults and natural fractures in the designated area; a continuum mechanical grid is constructed based on the physical property parameters and geomechanical parameters of the designated area; an infinite formation mechanical grid model of the shale reservoir is constructed based on the discontinuum mechanical grid and the continuum mechanical grid; the infinite formation mechanical grid model includes a plurality of mechanical grid units; a finite element calculation is adopted based on the pre-set pore pressure conditions and strain boundary conditions. Methods Invert the stress field distribution of the infinite formation mechanical grid model to determine the maximum horizontal principal stress, minimum horizontal principal stress, vertical stress and pore pressure of each mechanical grid unit; determine the geostress state information of each mechanical grid unit according to the maximum horizontal principal stress, minimum horizontal principal stress and vertical stress of each mechanical grid unit; calculate the maximum effective stress and minimum effective stress of each mechanical grid unit according to the geostress state information and pore pressure of each mechanical grid unit; determine the critical injection pressure of the shale reservoir according to the maximum effective stress and minimum effective stress of each mechanical grid unit, which is the minimum pore pressure increment required for shear failure of the shale reservoir under different geostress states. In this way, according to the minimum pore pressure increment required for shear failure of the shale reservoir under different geostress states, the quantitative assessment of the risk of regional rock mass instability under complex geostress field conditions can be realized, which solves the judgment of the risk of regional rock mass instability caused by hydraulic fracturing injection fluid, and can be used to support the optimization and adjustment of the strength of hydraulic fracturing reservoir reconstruction fluid.

[0049] Below Figure 1 The method for determining the critical injection pressure of the shale reservoir shown is described in detail.

[0050] In the above step 101, it is necessary to collect reservoir characterization data of a designated area of ​​the shale reservoir.

[0051] Among them, reservoir characterization data may include physical property parameters, geomechanical parameters, and spatial distribution characteristic parameters of faults and natural fractures in a specified area.

[0052] In one embodiment, the above-mentioned physical property parameters may include density, porosity and permeability of the three-dimensional shale reservoir;

[0053] The above-mentioned geomechanical parameters may include Young's modulus and Poisson's ratio;

[0054] The spatial distribution characteristic parameters of the above-mentioned faults and natural fractures may include the length, fault distance, dip and strike of the faults and natural fractures.

[0055] In the above step 102, a discontinuum mechanical grid may be constructed based on the spatial distribution characteristic parameters of faults and natural fractures in the designated area in the above reservoir characterization data and pre-acquired core experimental data.

[0056] In one embodiment, the core test data may include: normal stiffness, shear stiffness, cohesion, friction angle, dilatancy angle and tensile strength.

[0057] In specific implementation, a discontinuum mechanics grid describing the spatial distribution characteristics of faults and natural fractures in the reservoir can be constructed according to the spatial distribution characteristic parameters of faults and natural fractures in the specified area, and the discontinuum mechanics grid can be assigned data such as normal stiffness, shear stiffness, cohesion, friction angle, shear dilation angle, and tensile strength properties obtained from indoor core experiments.

[0058] In the above step 103 , a continuum mechanical grid may be constructed according to the physical property parameters and geomechanical parameters of the designated area in the reservoir characterization data obtained in the above step 101 .

[0059] In specific implementation, a continuous mechanical grid describing reservoir physical properties can be constructed based on the physical property parameters and geomechanical parameters of the specified area. The continuous mechanical grid is endowed with parameters such as three-dimensional shale reservoir density, porosity, permeability, Young's modulus, and Poisson's ratio.

[0060] In the above step 104, an infinite formation mechanics grid model of the shale reservoir can be constructed based on the discontinuum mechanics grid established in step 102 and the continuum mechanics grid established in step 103.

[0061] The infinite formation mechanics grid model may include a plurality of mechanics grid units.

[0062] In one embodiment, the above step 104 may specifically include:

[0063] The discontinuum mechanics grid and the continuum mechanics grid are combined to obtain a formation mechanics grid model of the shale reservoir;

[0064] Obtain Young's modulus, Poisson's ratio, density, porosity and Biot coefficient of upper surrounding rock, lower surrounding rock and lateral surrounding rock;

[0065] The formation mechanics grid model of the shale reservoir is expanded outward by preset multiples in four directions: upward, downward, left and right. After expanding outward by the preset multiples, an infinite formation mechanics grid model of the shale reservoir is constructed according to the Young's modulus, Poisson's ratio, density, porosity and Biot coefficient of the upper surrounding rock, lower surrounding rock and lateral surrounding rock.

[0066] In specific implementation, the discontinuum mechanics grid and the continuum mechanics grid can be combined to construct a formation mechanics grid model of the shale reservoir. Then, the formation mechanics grid model of the shale reservoir is expanded by preset multiples (such as 3-5 times) in four directions: upward, downward, left, and right. A simulated infinite formation mechanics model including the shale reservoir, upper surrounding rock, lower surrounding rock, and lateral surrounding rock is constructed. The simulated infinite formation mechanics model is given the Young's modulus, Poisson's ratio, density, porosity, and Biot coefficient of the upper surrounding rock, lower surrounding rock, and lateral surrounding rock, so as to obtain the formation mechanics grid model of the shale reservoir.

[0067] Among them, Young's modulus, Poisson's ratio, density, porosity and Biot coefficient of the upper surrounding rock, lower surrounding rock and lateral surrounding rock can be obtained through core experiments, or calculated using seismic inversion or logging data.

[0068] In the above step 105, according to the preset pore pressure conditions and strain boundary conditions, the finite element calculation method can be used to invert the stress field distribution of the infinite formation mechanical grid model to determine the maximum horizontal principal stress, minimum horizontal principal stress, vertical stress and pore pressure of each mechanical grid unit.

[0069] During specific implementation, the pore pressure condition and the strain boundary condition may be preset.

[0070] In one embodiment, the pore pressure condition may refer to a pore pressure condition for stress initialization;

[0071] The strain boundary conditions may include the maximum horizontal principal strain, the minimum horizontal principal strain, and the strain boundary conditions of the minimum horizontal principal strain orientation.

[0072] In the specific implementation, the finite element calculation method is used to invert the stress field distribution of the infinite formation mechanical grid model and determine the maximum horizontal principal stress σ of each mechanical grid unit. H , minimum horizontal principal stress σ h , vertical stress σ z and pore pressure P p Specifically, through the finite element method, according to the above strain boundary conditions (mechanical tectonic stress coefficient) and pore pressure conditions, it is assumed that the bottom surface of the entire infinite stratum mechanical grid model is a simply supported constraint, and gravity and side boundary displacement are applied at the same time. The three-dimensional ground stress field is calculated by finite element until the displacement function of each unit converges.

[0073] In the above step 106, the maximum horizontal principal stress σ of each mechanical grid unit can be H , minimum horizontal principal stress σ h and vertical stress σ z , P determines the ground stress state of each mechanical grid unit.

[0074] In one embodiment, the above step 106 may specifically include:

[0075] For each mechanical grid unit: if the maximum horizontal principal stress is greater than the minimum horizontal principal stress, and the minimum horizontal principal stress is greater than the vertical stress, the mechanical grid unit is in a reverse fault stress state; if the vertical stress is greater than the maximum horizontal principal stress, and the maximum horizontal principal stress is greater than the minimum horizontal principal stress, the mechanical grid unit is in a normal fault stress state; if the maximum horizontal principal stress is greater than the vertical stress, and the vertical stress is greater than the minimum horizontal principal stress, the mechanical grid unit is in a strike-slip fault stress state.

[0076] In specific implementation, for each mechanical grid unit, when σ H >σ h >σ z When , the mechanical grid unit is in the reverse fault stress state; when σ z >σ H >σ h When , the mechanical grid unit is in a normal fault stress state; when σ H >σ z >σ h When , the mechanical grid unit is in the strike-slip fault stress state.

[0077] In the above step 107, the maximum effective stress S1 and the minimum effective stress S3 of each mechanical grid unit of the formation mechanics grid model of the complete shale reservoir can be calculated respectively according to the different in-situ stress state information and pore pressure of each mechanical grid unit.

[0078] In one embodiment, the above step 107 may specifically include:

[0079] For each mechanical mesh element:

[0080] If the mechanical grid unit is in a reverse fault stress state, the maximum effective stress of the mechanical grid unit is the difference between the maximum horizontal principal stress and the pore pressure; the minimum effective stress of the mechanical grid unit is the difference between the vertical stress and the pore pressure.

[0081] In one embodiment, the above step 107 may further include:

[0082] For each mechanical mesh element:

[0083] If the mechanical grid unit is in a normal fault stress state, the maximum effective stress of the mechanical grid unit is the difference between the vertical stress and the pore pressure; the minimum effective stress of the mechanical grid unit is the difference between the minimum horizontal principal stress and the pore pressure.

[0084] In one embodiment, the above step 107 may further include:

[0085] For each mechanical mesh element:

[0086] If the mechanical grid unit is in a strike-slip fault stress state, the maximum effective stress of the mechanical grid unit is the difference between the maximum horizontal principal stress and the pore pressure; the minimum effective stress of the mechanical grid unit is the difference between the minimum horizontal principal stress and the pore pressure.

[0087] In specific implementation, when the mechanical grid unit is in the reverse fault stress state, the maximum effective stress S1 = σ H -P p , minimum effective stress S3 = σ z -P p ;

[0088] When the mechanical grid unit is in a normal fault stress state, the maximum effective stress S1 = σ z -P p , minimum effective stress S3 = σ h -P p ;

[0089] When the mechanical grid unit is in the strike-slip fault stress state, the maximum effective stress S1 = σ H -P p , minimum effective stress S3 = σ h -P p .

[0090] In the above step 108, the critical injection pressure of the shale reservoir may be determined according to the maximum effective stress S1 and the minimum effective stress S3 of each mechanical grid unit.

[0091] The critical injection pressure is the minimum pore pressure increment required for shear failure of shale reservoirs under different geostress states.

[0092] In one embodiment, the above step 108 may specifically include:

[0093] Through indoor experimental tests, the internal friction angle of the core with different ground stress state information is obtained;

[0094] The critical injection pressure of each mechanical grid unit is calculated based on the internal friction angle, maximum effective stress and minimum effective stress of the core of the in-situ stress state information of each mechanical grid unit.

[0095] In one embodiment, the critical injection pressure of each mechanical grid unit is calculated according to the internal friction angle, maximum effective stress and minimum effective stress of the core of the in-situ stress state information of each mechanical grid unit, which may specifically include:

[0096] The critical injection pressure of each mechanical grid unit is calculated according to the following formula 1:

[0097]

[0098] Among them, s1 is the maximum effective stress, s3 is the minimum effective stress, and φ is the internal friction angle.

[0099] The unit of internal friction angle φ is degree.

[0100] In specific implementation, the internal friction angle of the core with different geostress state information can be obtained based on indoor experiments, such as triaxial compression tests or direct shear tests; the corresponding internal friction angle of the core is determined based on the geostress state information of each mechanical grid unit, and the internal friction angle, maximum effective stress and minimum effective stress of the core with geostress state information of each mechanical grid unit are substituted into Formula 1 to calculate the critical injection pressure △P of each mechanical grid unit. According to the critical injection pressure △P of each mechanical grid unit, the minimum pressure required for compression failure of the shale reservoir can be obtained.

[0101] In this way, through the above method, the critical injection pressure of regional shale reservoirs under different geostress states at which compression failure occurs can be obtained. According to the predicted critical injection pressure of regional shale reservoirs under different geostress states at which compression failure occurs, the quantitative assessment of the risk of regional rock instability under complex geostress field conditions can be realized, which solves the problem of judging the risk of regional rock instability caused by hydraulic fracturing injection fluid, and can be used to support the optimization and adjustment of the fluid strength used for hydraulic fracturing reservoir transformation.

[0102] In order to facilitate understanding of the above method for determining the critical injection pressure of a shale reservoir, the above method is described below with reference to a specific embodiment.

[0103] 1. Calculation of three-dimensional geostress field (maximum horizontal principal stress, minimum horizontal principal stress and vertical stress)

[0104] Collect regional reservoir physical properties, geomechanics, faults, and natural fracture data (i.e., obtain the physical property parameters, geomechanics parameters, and spatial distribution characteristic parameters of faults and natural fractures in a specified area of ​​the shale reservoir) and establish Figure 2 The discontinuum mechanics mesh containing faults and natural fractures is shown as Figure 2 The discontinuum mechanical model is assigned corresponding mechanical parameters (i.e. core experimental data) as shown in Table 1; a continuous mechanical grid is established to describe the reservoir properties.

[0105] According to the discontinuum mechanics grid and the continuum mechanics grid, the formation mechanics grid model of the shale reservoir is established, such as Figure 3As shown, the top view and side view of the formation mechanics grid model of the shale reservoir are shown. The plane accuracy of the model is 20m×20m, the vertical accuracy of the high-quality reservoir section is about 0.5m, and the total number of grids is 9 million.

[0106] exist Figure 3 Based on this, an approximate infinite formation mechanics model (infinite formation mechanics grid model of shale reservoir) is constructed, such as Figure 4 As shown in Figure 2, it is a schematic diagram of the infinite formation mechanical grid model of the shale reservoir, and the corresponding mechanical parameters of the upper surrounding rock, lower surrounding rock and lateral surrounding rock are given, see Table 2.

[0107] In addition, the pore pressure conditions and strain boundary conditions are set, and the finite element calculation method is used to invert the stress field distribution of the infinite formation mechanical grid model to determine the maximum horizontal principal stress, minimum horizontal principal stress, vertical stress and pore pressure of each mechanical grid unit. The set pore pressure conditions (i.e., initial pore pressure gradient) and strain boundary conditions are shown in Table 3.

[0108] Table 1 Discontinuum mechanics model parameter settings

[0109]

[0110] Table 2 Parameter settings of the external expansion mechanical model

[0111]

[0112] Table 3 Pore pressure conditions, strain boundary conditions

[0113]

[0114] 2. Identification of geostress state

[0115] According to the maximum horizontal principal stress, minimum horizontal principal stress and vertical stress, the regional ground stress state is judged, such as Figure 5 , which is a schematic diagram of different ground stress states provided by an embodiment of the present invention.

[0116] 3. Calculation of critical injection pressure

[0117] Input the internal friction angle data of the core with different geostress state information, and calculate the critical injection pressure of the regional shale reservoir under different geostress states for compression failure according to Formula 1, as follows: Figure 6 , which is a schematic diagram of the distribution of critical injection pressure of a regional shale reservoir provided by an embodiment of the present invention.

[0118] In summary, according to the critical injection pressure of regional shale reservoir compression failure under different geostress states, the quantitative assessment of regional rock instability risk under complex geostress field conditions can be realized, which solves the judgment of the risk of regional rock instability caused by hydraulic fracturing injection fluid, and can be used to support the optimization and adjustment of fluid strength for hydraulic fracturing reservoir transformation.

[0119] The present invention also provides a device for determining the critical injection pressure of a shale reservoir, as described in the following embodiments. Since the principle of the device to solve the problem is similar to the method for determining the critical injection pressure of a shale reservoir, the implementation of the device can refer to the implementation of the method for determining the critical injection pressure of a shale reservoir, and the repeated parts will not be repeated.

[0120] like Figure 7 FIG. 1 is a schematic diagram of a device for determining a critical injection pressure of a shale reservoir provided by an embodiment of the present invention. The device may include:

[0121] The data acquisition module 701 is used to acquire reservoir characterization data of a specified area of ​​a shale reservoir; the reservoir characterization data includes physical property parameters, geomechanical parameters, and spatial distribution characteristic parameters of faults and natural fractures in the specified area;

[0122] The first grid construction module 702 is used to construct a discontinuum mechanics grid according to pre-acquired core experimental data and spatial distribution characteristic parameters of faults and natural fractures in a specified area;

[0123] The second grid construction module 703 is used to construct a continuum mechanics grid according to the physical parameters and geomechanical parameters of the specified area;

[0124] The third grid construction module 704 is used to construct an infinite formation mechanical grid model of the shale reservoir according to the discontinuum mechanical grid and the continuum mechanical grid; the infinite formation mechanical grid model includes a plurality of mechanical grid units;

[0125] The ground stress determination module 705 is used to invert the stress field distribution of the infinite formation mechanical grid model using the finite element calculation method according to the preset pore pressure conditions and strain boundary conditions, and determine the maximum horizontal principal stress, minimum horizontal principal stress, vertical stress and pore pressure of each mechanical grid unit;

[0126] The stress state determination module 706 is used to determine the ground stress state information of each mechanical grid unit according to the maximum horizontal principal stress, the minimum horizontal principal stress and the vertical stress of each mechanical grid unit;

[0127] The effective stress calculation module 707 is used to calculate the maximum effective stress and the minimum effective stress of each mechanical grid unit according to the ground stress state information and pore pressure of each mechanical grid unit;

[0128] The critical injection pressure determination module 708 is used to determine the critical injection pressure of the shale reservoir according to the maximum effective stress and the minimum effective stress of each mechanical grid unit. The critical injection pressure is the minimum pore pressure increment required for shear failure of the shale reservoir under different ground stress states.

[0129] In one embodiment, the physical property parameters may include density, porosity and permeability of the three-dimensional shale reservoir;

[0130] The geomechanical parameters may include Young's modulus and Poisson's ratio;

[0131] The spatial distribution characteristic parameters of the faults and natural fractures may include the length, fault distance, dip and strike of the faults and natural fractures.

[0132] In one embodiment, the core test data may include: normal stiffness, shear stiffness, cohesion, friction angle, dilatancy angle and tensile strength.

[0133] In one embodiment, the third grid construction module may be specifically used for:

[0134] The discontinuum mechanics grid and the continuum mechanics grid are combined to obtain a formation mechanics grid model of the shale reservoir;

[0135] Obtain Young's modulus, Poisson's ratio, density, porosity and Biot coefficient of upper surrounding rock, lower surrounding rock and lateral surrounding rock;

[0136] The formation mechanics grid model of the shale reservoir is expanded outward by preset multiples in four directions: upward, downward, left and right. After expanding outward by the preset multiples, an infinite formation mechanics grid model of the shale reservoir is constructed according to the Young's modulus, Poisson's ratio, density, porosity and Biot coefficient of the upper surrounding rock, lower surrounding rock and lateral surrounding rock.

[0137] In one embodiment, the pore pressure condition may refer to a pore pressure condition for stress initialization;

[0138] The strain boundary conditions may include the maximum horizontal principal strain, the minimum horizontal principal strain, and the strain boundary conditions of the minimum horizontal principal strain orientation.

[0139] In one embodiment, the stress state determination module may be specifically used to:

[0140] For each mechanical grid unit: if the maximum horizontal principal stress is greater than the minimum horizontal principal stress, and the minimum horizontal principal stress is greater than the vertical stress, the mechanical grid unit is in a reverse fault stress state; if the vertical stress is greater than the maximum horizontal principal stress, and the maximum horizontal principal stress is greater than the minimum horizontal principal stress, the mechanical grid unit is in a normal fault stress state; if the maximum horizontal principal stress is greater than the vertical stress, and the vertical stress is greater than the minimum horizontal principal stress, the mechanical grid unit is in a strike-slip fault stress state.

[0141] In one embodiment, the effective stress calculation module can be specifically used for:

[0142] For each mechanical mesh element:

[0143] If the mechanical grid unit is in a reverse fault stress state, the maximum effective stress of the mechanical grid unit is the difference between the maximum horizontal principal stress and the pore pressure; the minimum effective stress of the mechanical grid unit is the difference between the vertical stress and the pore pressure.

[0144] In one embodiment, the effective stress calculation module can also be used to:

[0145] For each mechanical mesh element:

[0146] If the mechanical grid unit is in a normal fault stress state, the maximum effective stress of the mechanical grid unit is the difference between the vertical stress and the pore pressure; the minimum effective stress of the mechanical grid unit is the difference between the minimum horizontal principal stress and the pore pressure.

[0147] In one embodiment, the effective stress calculation module can also be used to:

[0148] For each mechanical mesh element:

[0149] If the mechanical grid unit is in a strike-slip fault stress state, the maximum effective stress of the mechanical grid unit is the difference between the maximum horizontal principal stress and the pore pressure; the minimum effective stress of the mechanical grid unit is the difference between the minimum horizontal principal stress and the pore pressure.

[0150] In one embodiment, the critical injection pressure determination module may be specifically used to:

[0151] Through indoor experimental tests, the internal friction angle of the core with different ground stress state information is obtained;

[0152] The critical injection pressure of each mechanical grid unit is calculated based on the internal friction angle, maximum effective stress and minimum effective stress of the core of the in-situ stress state information of each mechanical grid unit.

[0153] In one embodiment, the critical injection pressure determination module may also be used to:

[0154] The critical injection pressure of each mechanical grid unit is calculated according to the following formula:

[0155]

[0156] Among them, s1 is the maximum effective stress, s3 is the minimum effective stress, and φ is the internal friction angle.

[0157] The embodiment of the present invention also provides a computer device, such as Figure 8 As shown, it is a schematic diagram of a computer device in an embodiment of the present invention. The computer device 800 includes a memory 810, a processor 820, and a computer program 830 stored in the memory 810 and executable on the processor 820. When the processor 820 executes the computer program 830, the above-mentioned method for determining the critical injection pressure of the shale reservoir is implemented.

[0158] An embodiment of the present invention further provides a computer-readable storage medium, wherein the computer-readable storage medium stores a computer program, and when the computer program is executed by a processor, the method for determining the critical injection pressure of a shale reservoir is implemented.

[0159] An embodiment of the present invention further provides a computer program product, which includes a computer program. When the computer program is executed by a processor, the method for determining the critical injection pressure of a shale reservoir is implemented.

[0160] In the embodiment of the present invention, reservoir characterization data of a designated area of ​​a shale reservoir is obtained; the reservoir characterization data includes physical property parameters, geomechanical parameters, and spatial distribution characteristic parameters of faults and natural fractures in the designated area; a discontinuum mechanical grid is constructed based on pre-acquired core experimental data and spatial distribution characteristic parameters of faults and natural fractures in the designated area; a continuum mechanical grid is constructed based on the physical property parameters and geomechanical parameters of the designated area; an infinite formation mechanical grid model of the shale reservoir is constructed based on the discontinuum mechanical grid and the continuum mechanical grid; the infinite formation mechanical grid model includes a plurality of mechanical grid units; a finite element calculation is adopted based on the pre-set pore pressure conditions and strain boundary conditions. Methods Invert the stress field distribution of the infinite formation mechanical grid model to determine the maximum horizontal principal stress, minimum horizontal principal stress, vertical stress and pore pressure of each mechanical grid unit; determine the geostress state information of each mechanical grid unit according to the maximum horizontal principal stress, minimum horizontal principal stress and vertical stress of each mechanical grid unit; calculate the maximum effective stress and minimum effective stress of each mechanical grid unit according to the geostress state information and pore pressure of each mechanical grid unit; determine the critical injection pressure of the shale reservoir according to the maximum effective stress and minimum effective stress of each mechanical grid unit, which is the minimum pore pressure increment required for shear failure of the shale reservoir under different geostress states. In this way, according to the minimum pore pressure increment required for shear failure of the shale reservoir under different geostress states, the quantitative assessment of the risk of regional rock mass instability under complex geostress field conditions can be realized, which solves the judgment of the risk of regional rock mass instability caused by hydraulic fracturing injection fluid, and can be used to support the optimization and adjustment of the strength of hydraulic fracturing reservoir reconstruction fluid.

[0161] Those skilled in the art will appreciate that embodiments of the present invention may be provided as methods, systems, or computer program products. Therefore, the present invention may take the form of a complete hardware embodiment, a complete software embodiment, or an embodiment combining software and hardware. Moreover, the present invention may take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0162] The present invention is described with reference to flowcharts and / or block diagrams of methods, devices (systems), and computer program products according to embodiments of the present invention. It should be understood that each process and / or block in the flowchart and / or block diagram, as well as the combination of processes and / or blocks in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to produce a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the flowchart and / or block diagram. Figure 1 A process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0163] These computer program instructions may also be stored in a computer-readable memory capable of directing a computer or other programmable data processing device to operate in a specific manner, so that the instructions stored in the computer-readable memory produce an article of manufacture comprising an instruction device, which implements the process Figure 1 A process or multiple processes and / or boxes Figure 1 A function specified in one or more boxes.

[0164] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operating steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing instructions for implementing the process. Figure 1 A process or multiple processes and / or boxes Figure 1 The steps for the functions specified in one or more boxes.

[0165] The specific embodiments described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for determining the critical injection pressure of a shale reservoir, characterized in that: include: Obtaining reservoir characterization data of a designated area of ​​a shale reservoir; the reservoir characterization data includes physical property parameters, geomechanical parameters, and spatial distribution characteristic parameters of faults and natural fractures in the designated area; Construct a discontinuum mechanics grid based on pre-acquired core experimental data and spatial distribution characteristic parameters of faults and natural fractures in a specified area; Construct a continuum mechanics grid based on the physical parameters and geomechanical parameters of the specified area; An infinite formation mechanical grid model of a shale reservoir is constructed according to the discontinuum mechanical grid and the continuum mechanical grid; the infinite formation mechanical grid model includes a plurality of mechanical grid units; According to the preset pore pressure conditions and strain boundary conditions, the finite element calculation method is used to invert the stress field distribution of the infinite formation mechanical grid model to determine the maximum horizontal principal stress, minimum horizontal principal stress, vertical stress and pore pressure of each mechanical grid unit; Determine the ground stress state information of each mechanical grid unit according to the maximum horizontal principal stress, the minimum horizontal principal stress and the vertical stress of each mechanical grid unit; According to the ground stress state information and pore pressure of each mechanical grid unit, the maximum effective stress and the minimum effective stress of each mechanical grid unit are calculated; The critical injection pressure of the shale reservoir is determined according to the maximum effective stress and the minimum effective stress of each mechanical grid unit. The critical injection pressure is the minimum pore pressure increment required for shear failure of the shale reservoir under different ground stress states.

2. The method according to claim 1, characterized in that The physical property parameters include three-dimensional shale reservoir density, porosity and permeability; The geomechanical parameters include Young's modulus and Poisson's ratio; The spatial distribution characteristic parameters of the faults and natural fractures include the length, fault distance, inclination and strike of the faults and natural fractures.

3. The method according to claim 1, characterized in that The core test data include normal stiffness, shear stiffness, cohesion, friction angle, dilatancy angle and tensile strength.

4. The method according to claim 1, characterized in that Based on the discontinuum mechanics grid and the continuum mechanics grid, a formation mechanics grid model of shale reservoir is constructed, including: The discontinuum mechanics grid and the continuum mechanics grid are combined to obtain a formation mechanics grid model of the shale reservoir; Obtain Young's modulus, Poisson's ratio, density, porosity and Biot coefficient of upper surrounding rock, lower surrounding rock and lateral surrounding rock; The formation mechanics grid model of the shale reservoir is expanded outward by preset multiples in four directions: upward, downward, left and right. After expanding outward by the preset multiples, an infinite formation mechanics grid model of the shale reservoir is constructed according to the Young's modulus, Poisson's ratio, density, porosity and Biot coefficient of the upper surrounding rock, lower surrounding rock and lateral surrounding rock.

5. The method according to claim 1, characterized in that The pore pressure condition refers to the pore pressure condition used for stress initialization; The strain boundary conditions include the maximum horizontal principal strain, the minimum horizontal principal strain and the strain boundary conditions of the minimum horizontal principal strain orientation.

6. The method according to claim 1, characterized in that According to the maximum horizontal principal stress, minimum horizontal principal stress and vertical stress of each mechanical grid unit, the ground stress state information of each mechanical grid unit is determined, including: For each mechanical grid unit: if the maximum horizontal principal stress is greater than the minimum horizontal principal stress, and the minimum horizontal principal stress is greater than the vertical stress, the mechanical grid unit is in a reverse fault stress state; if the vertical stress is greater than the maximum horizontal principal stress, and the maximum horizontal principal stress is greater than the minimum horizontal principal stress, the mechanical grid unit is in a normal fault stress state; if the maximum horizontal principal stress is greater than the vertical stress, and the vertical stress is greater than the minimum horizontal principal stress, the mechanical grid unit is in a strike-slip fault stress state.

7. The method according to claim 6, characterized in that According to the ground stress state information and pore pressure of each mechanical grid unit, the maximum effective stress and minimum effective stress of each mechanical grid unit are calculated, including: For each mechanical mesh element: If the mechanical grid unit is in a reverse fault stress state, the maximum effective stress of the mechanical grid unit is the difference between the maximum horizontal principal stress and the pore pressure; the minimum effective stress of the mechanical grid unit is the difference between the vertical stress and the pore pressure.

8. The method according to claim 6, characterized in that According to the ground stress state information and pore pressure of each mechanical grid unit, the maximum effective stress and minimum effective stress of each mechanical grid unit are calculated, including: For each mechanical mesh element: If the mechanical grid unit is in a normal fault stress state, the maximum effective stress of the mechanical grid unit is the difference between the vertical stress and the pore pressure; the minimum effective stress of the mechanical grid unit is the difference between the minimum horizontal principal stress and the pore pressure.

9. The method according to claim 6, characterized in that According to the ground stress state information and pore pressure of each mechanical grid unit, the maximum effective stress and minimum effective stress of each mechanical grid unit are calculated, including: For each mechanical mesh element: If the mechanical grid unit is in a strike-slip fault stress state, the maximum effective stress of the mechanical grid unit is the difference between the maximum horizontal principal stress and the pore pressure; the minimum effective stress of the mechanical grid unit is the difference between the minimum horizontal principal stress and the pore pressure.

10. The method according to claim 1, characterized in that According to the maximum effective stress and minimum effective stress of each mechanical grid unit, the critical injection pressure of the shale reservoir is determined, including: Through indoor experimental tests, the internal friction angle of the core with different ground stress state information is obtained; The critical injection pressure of each mechanical grid unit is calculated based on the internal friction angle, maximum effective stress and minimum effective stress of the core of the in-situ stress state information of each mechanical grid unit.

11. The method according to claim 10, characterized in that According to the internal friction angle, maximum effective stress and minimum effective stress of the core of each mechanical grid unit, the critical injection pressure of each mechanical grid unit is calculated, including: The critical injection pressure of each mechanical grid unit is calculated according to the following formula: Among them, s1 is the maximum effective stress, s3 is the minimum effective stress, and φ is the internal friction angle.

12. A device for determining the critical injection pressure of a shale reservoir, characterized in that: include: A data acquisition module is used to acquire reservoir characterization data of a specified area of ​​a shale reservoir; the reservoir characterization data includes physical property parameters, geomechanical parameters, and spatial distribution characteristic parameters of faults and natural fractures in the specified area; The first grid construction module is used to construct a discontinuum mechanics grid based on pre-acquired core experimental data and spatial distribution characteristic parameters of faults and natural fractures in a specified area; The second grid construction module is used to construct a continuum mechanics grid according to the physical property parameters and geomechanical parameters of the specified area; A third grid construction module is used to construct an infinite formation mechanical grid model of the shale reservoir according to the discontinuum mechanical grid and the continuum mechanical grid; the infinite formation mechanical grid model includes a plurality of mechanical grid units; The ground stress determination module is used to invert the stress field distribution of the infinite formation mechanical grid model using the finite element calculation method according to the pre-set pore pressure conditions and strain boundary conditions, and determine the maximum horizontal principal stress, minimum horizontal principal stress, vertical stress and pore pressure of each mechanical grid unit; A stress state determination module is used to determine the ground stress state information of each mechanical grid unit according to the maximum horizontal principal stress, the minimum horizontal principal stress and the vertical stress of each mechanical grid unit; An effective stress calculation module is used to calculate the maximum effective stress and the minimum effective stress of each mechanical grid unit according to the ground stress state information and pore pressure of each mechanical grid unit; The critical injection pressure determination module is used to determine the critical injection pressure of the shale reservoir according to the maximum effective stress and the minimum effective stress of each mechanical grid unit. The critical injection pressure is the minimum pore pressure increment required for shear failure of the shale reservoir under different ground stress states.

13. The device according to claim 12, characterized in that The physical property parameters include three-dimensional shale reservoir density, porosity and permeability; The geomechanical parameters include Young's modulus and Poisson's ratio; The spatial distribution characteristic parameters of the faults and natural fractures include the length, fault distance, inclination and strike of the faults and natural fractures.

14. The device according to claim 12, characterized in that The core test data include normal stiffness, shear stiffness, cohesion, friction angle, dilatancy angle and tensile strength.

15. The device according to claim 12, characterized in that The third grid construction module is specifically used for: The discontinuum mechanics grid and the continuum mechanics grid are combined to obtain a formation mechanics grid model of the shale reservoir; Obtain Young's modulus, Poisson's ratio, density, porosity and Biot coefficient of upper surrounding rock, lower surrounding rock and lateral surrounding rock; The formation mechanics grid model of the shale reservoir is expanded outward by preset multiples in four directions: upward, downward, left and right. After expanding outward by the preset multiples, an infinite formation mechanics grid model of the shale reservoir is constructed according to the Young's modulus, Poisson's ratio, density, porosity and Biot coefficient of the upper surrounding rock, lower surrounding rock and lateral surrounding rock.

16. The device according to claim 12, characterized in that The pore pressure condition refers to the pore pressure condition used for stress initialization; The strain boundary conditions include the maximum horizontal principal strain, the minimum horizontal principal strain and the strain boundary conditions of the minimum horizontal principal strain orientation.

17. The device according to claim 12, characterized in that Stress state determination module, specifically used for: For each mechanical grid unit: if the maximum horizontal principal stress is greater than the minimum horizontal principal stress, and the minimum horizontal principal stress is greater than the vertical stress, the mechanical grid unit is in a reverse fault stress state; If the vertical stress is greater than the maximum horizontal principal stress, and the maximum horizontal principal stress is greater than the minimum horizontal principal stress, the mechanical grid unit is in a normal fault stress state; If the maximum horizontal principal stress is greater than the vertical stress, and the vertical stress is greater than the minimum horizontal principal stress, the mechanical grid unit is in a strike-slip fault stress state.

18. The device according to claim 17, characterized in that The effective stress calculation module is specifically used for: For each mechanical mesh element: If the mechanical grid unit is in a reverse fault stress state, the maximum effective stress of the mechanical grid unit is the difference between the maximum horizontal principal stress and the pore pressure; the minimum effective stress of the mechanical grid unit is the difference between the vertical stress and the pore pressure.

19. The device according to claim 17, characterized in that The effective stress calculation module is also used for: For each mechanical mesh element: If the mechanical grid unit is in a normal fault stress state, the maximum effective stress of the mechanical grid unit is the difference between the vertical stress and the pore pressure; the minimum effective stress of the mechanical grid unit is the difference between the minimum horizontal principal stress and the pore pressure.

20. The device according to claim 17, characterized in that The effective stress calculation module is also used for: For each mechanical mesh element: If the mechanical grid unit is in a strike-slip fault stress state, the maximum effective stress of the mechanical grid unit is the difference between the maximum horizontal principal stress and the pore pressure; the minimum effective stress of the mechanical grid unit is the difference between the minimum horizontal principal stress and the pore pressure.

21. The device according to claim 12, characterized in that The critical injection pressure determination module is specifically used for: Through indoor experimental tests, the internal friction angle of the core with different ground stress state information is obtained; The critical injection pressure of each mechanical grid unit is calculated based on the internal friction angle, maximum effective stress and minimum effective stress of the core of the in-situ stress state information of each mechanical grid unit.

22. The device according to claim 21, characterized in that The critical injection pressure determination module is also used for: The critical injection pressure of each mechanical grid unit is calculated according to the following formula: Among them, s1 is the maximum effective stress, s3 is the minimum effective stress, and φ is the internal friction angle.

23. A computer device comprising a memory, a processor and a computer program stored in the memory and executable on the processor, characterized in that: When the processor executes the computer program, the method according to any one of claims 1 to 11 is implemented.

24. A computer-readable storage medium, characterized in that: The computer-readable storage medium stores a computer program, and when the computer program is executed by a processor, the method according to any one of claims 1 to 11 is implemented.

25. A computer program product, characterized in that The computer program product comprises a computer program, and when the computer program is executed by a processor, the method according to any one of claims 1 to 11 is implemented.

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