A method, system, device, medium, and product for fracture effectiveness evaluation

Abstract

The present application belongs to the technical field of oil and gas field exploration and development, and discloses a fracture effectiveness evaluation method, system, device, medium and product; the method comprises the following steps: obtaining well logging data of a target well; determining a present horizontal maximum principal stress direction based on the well logging data, and calculating the angle between the present horizontal maximum principal stress of the target well and the direction of each natural fracture; calculating the horizontal principal stress difference of each fracture of the target well; and evaluating the fracture effectiveness based on the difference between the angle between the present horizontal maximum principal stress of the target well and the direction of each natural fracture and the difference between the in-fracture critical pressure value of the opening of each natural fracture of the target well and the in-fracture critical pressure value of the mechanical condition of shear slip. The present application can realize the quantitative calculation and classification of the mechanical expansion type of a single fracture, and can develop the fracture effectiveness evaluation, so as to achieve the purpose of supporting the optimization of the oil testing interval.

Description

Technical Field

[0001] This invention belongs to the field of oil and gas field exploration and development technology, specifically relating to a method, system, equipment, medium and product for evaluating the effectiveness of fractures. Background Technology

[0002] Fractures directly impact the exploration and development of fractured oil and gas reservoirs, and fracture effectiveness evaluation is a crucial aspect of fracture assessment. Existing fracture effectiveness methods primarily utilize data from core samples, thin sections, logging, imaging, dipole shear wave logging, and analytical tests to analyze fracture development characteristics and quantitatively characterize reservoir fracture parameters (fracture occurrence, fracture filling degree, fracture density, fracture length, fracture width, and fracture porosity, etc.) to comprehensively evaluate fracture effectiveness. This type of method is mainly based on near-wellbore static geological characteristics and does not consider the actual effects of fractures during reservoir stimulation under strong compressional tectonic conditions. This often leads to a contradiction between a statically assessed fracture effectiveness and poor reservoir stimulation results (the production profile shows some stimulated sections with no actual fluid supply capacity), making it difficult to meet the actual production needs of optimized testing sections and providing insufficient support for selective stimulation. Inefficient selective stimulation methods can sometimes cause huge economic losses, even for ultra-deep reservoirs where stimulation costs can easily reach tens of millions of dollars.

[0003] Chinese Patent Publication No. CN114183121A, entitled "Quantitative Evaluation Method, Device, Electronic Equipment, and Storage Medium for Fracture Effectiveness," outlines the following steps: Measurement Step: Measuring electrical imaging logging data of the well section to be evaluated; Fracture Picking Step: Preprocessing the electrical imaging logging data to obtain clear electrical imaging image data along the wellbore direction, and picking fractures within the target section based on the image variation patterns on the electrical imaging; Fracture Classification Step: Comparing the picked fractures with image feature maps of different types of fractures, classifying the picked fractures into five types: dissolution fractures, continuous fractures, partial fractures, high-resistivity fractures, and induced fractures; Fracture Screening Step: Removing high-resistivity fractures and induced fractures; Parameter Calculation Step: Calculating the parameters for dissolution fractures, continuous fractures, partial fractures, high-resistivity fractures, and induced fractures. The patent application includes the following steps for calculating the comprehensive fracture width and density: assigning weights a1 to the width of dissolution fractures, a2 to the width of continuous fractures, and a3 to the width of partial fractures, where 1>a1>a2>a3>0. Calculating the geometric mean of the comprehensive fracture width within a 1-meter window length based on these weights involves calculating the cubic geometric mean of the comprehensive fracture width within the tested formation section. The fracture effectiveness evaluation index is calculated by multiplying the calculated geometric mean by the calculated fracture density. The parameter solution involves establishing a response equation between the fracture effectiveness evaluation index and the gas production from the drill pipe formation test, and solving this response equation to obtain the gas production. While this patent application can quantitatively evaluate fracture effectiveness, it fails to address the shortcomings of static fracture effectiveness evaluation. Summary of the Invention

[0004] To overcome the problems existing in the prior art, the present invention aims to provide a method, system, equipment, medium and product for evaluating the effectiveness of cracks. The present invention proposes a quantitative calculation method for the mechanical propagation of cracks under ultra-deep and strong extrusion stress conditions, realizing the quantitative calculation and classification of the mechanical propagation type of a single crack, and carrying out crack effectiveness evaluation, thereby supporting the optimization of the test oil layer.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows: In a first aspect, the present invention provides a method for evaluating the effectiveness of cracks, comprising the following steps: Obtain logging data from the target well; Based on well logging data, the current horizontal maximum principal stress orientation is determined, and the angle between the current horizontal maximum principal stress of the target well and the orientation of each natural fracture is calculated. Calculate the difference in horizontal principal stress in each fracture of the target well; The critical pressure values ​​within each natural fracture in the target well that cause it to open and the critical pressure values ​​within each fracture that cause shear slip are calculated based on the difference in horizontal principal stress. The effectiveness of the fractures is evaluated based on the angle between the current maximum principal stress of the target well and the orientation of each natural fracture, and the difference between the critical pressure value within the fracture at which each natural fracture opens and the critical pressure value within the fracture under mechanical conditions of shear slip.

[0006] Optionally, the orientation of the current horizontal maximum principal stress can be determined by collecting the occurrence of each fracture in the area where the target well is located.

[0007] Optionally, the formula for calculating the critical pressure value within a natural crack at which it opens is: The formula for calculating the critical pressure value within a natural crack under the mechanical conditions for shear slip is: Where pt is the critical pressure value inside the natural crack when it opens; pb is the critical pressure value inside the natural crack under mechanical conditions of shear slip; XY is the difference in horizontal principal stresses; θ is the force-crack angle. The coefficient of friction of the natural crack surface; It is the cohesive force of rocks within natural fissures.

[0008] Optionally, a theoretical chart for identifying fracture effectiveness is drawn based on the angle between the current maximum principal stress and the orientation of each natural fracture, and the difference between the critical pressure value within the fracture when each natural fracture in the target well opens and the critical pressure value within the fracture under mechanical conditions of shear slip. The chart is then used to establish a classification standard for reservoir stimulation geomechanical models and to evaluate fracture effectiveness.

[0009] Optionally, the classification of fractures based on geomechanics includes parallel opening type, oblique shear slip type, high permeability expansion type, and orthogonal opening type.

[0010] Optionally, when the critical pressure value inside the crack under the mechanical condition of shear slippage is ≤0, it is determined to be a high-permeability expansion type crack; When the critical pressure value inside the crack is greater than 0 and the critical net pressure difference inside the crack is greater than or equal to 0, it is determined to be an oblique shear slip crack. When the critical pressure value inside the crack is >0 and the critical net pressure difference inside the crack is <0, and the force-crack angle is less than or equal to 45°, it is determined to be a parallel opening type crack. When the critical pressure value inside a natural crack is greater than 0 and the critical net pressure difference inside the crack is less than 0, and the force-crack angle is greater than 45°, it is determined to be an orthogonal opening type crack.

[0011] Secondly, the present invention provides a crack effectiveness evaluation system, comprising: The data acquisition module is used to acquire logging data from the target well. The first calculation module is used to determine the current horizontal maximum principal stress orientation based on well logging data, and to calculate the angle between the current horizontal maximum principal stress of the target well and the orientation of each natural fracture. The second calculation module is used to calculate the difference in horizontal principal stress in each fracture of the target well. The third calculation module is used to calculate the critical pressure value inside the fracture when each natural fracture in the target well opens and the critical pressure value inside the fracture under the mechanical conditions of shear slip, as well as the difference between the two, based on the difference in horizontal principal stress. The evaluation module is used to evaluate fracture effectiveness based on the angle between the current maximum principal stress of the target well and the orientation of each natural fracture, and the difference between the critical pressure value within the fracture at which each natural fracture opens and the critical pressure value within the fracture under mechanical conditions of shear slip.

[0012] Thirdly, the present invention provides an electronic device, including a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor executes the computer program to implement the crack effectiveness evaluation method.

[0013] Fourthly, the present invention provides a computer-readable storage medium storing a computer program that, when executed by a processor, implements the crack effectiveness evaluation method.

[0014] Fifthly, the present invention provides a computer program product including a computer-readable medium, wherein computer-readable program code is included on the computer-readable medium, and the program code executes the crack effectiveness evaluation method.

[0015] Compared with the prior art, the present invention has the following beneficial effects: The fracture effectiveness evaluation method proposed in this invention is a fracture effectiveness evaluation method that can effectively make up for the shortcomings of static fracture effectiveness evaluation. The key innovation of this invention is to propose a quantitative calculation method for the mechanical propagation of fractures under ultra-deep and strong extrusion stress conditions. It realizes the quantitative calculation and classification of the mechanical propagation type of a single fracture, and carries out fracture effectiveness evaluation, thereby supporting the optimization of oil testing sections. Through practical application, it is shown that the fracture effectiveness evaluation based on dynamics can more scientifically and rationally select oil testing sections, and has a significant impact on the reservoir stimulation effect, bringing a brand-new solution to the fracture effectiveness evaluation of strong extrusion stress fractured reservoirs.

[0016] Furthermore, by establishing a classification standard for reservoir stimulation geomechanical models and a fracture effectiveness identification chart, this invention can facilitate the classification and evaluation of fracture effectiveness.

[0017] This invention uses rock mechanics, geostress, fractures, and their interrelationships as basic elements. By optimizing the fracture criteria applicable to strong compressional tectonic settings, it classifies and establishes standards for reservoir stimulation geomechanical models based on the mechanical propagation mechanism of natural fractures, and invents a fracture effectiveness identification chart based on dynamic analysis methods. Through quantitative calculation of mechanical parameters of a single natural fracture and classification of propagation types, it evaluates fracture effectiveness, thereby supporting the optimization of oil testing intervals.

[0018] As a force-fracture coupling sweet spot prediction method, the fracture effectiveness evaluation method of this invention improves upon the problem that conventional fracture effectiveness evaluation methods based on near-wellbore static geological characteristics cannot effectively support the selection and stimulation of fractured reservoirs under ultra-deep and high-stress conditions. The key technical point of this invention is to propose a quantitative calculation method for fracture mechanical propagation under ultra-deep and high-compression stress conditions, establish a classification standard for reservoir stimulation geomechanical models and a fracture effectiveness identification chart, realize the quantitative calculation and classification of the mechanical propagation type of a single fracture, carry out fracture effectiveness evaluation, and make the optimization of oil testing sections more scientific and meet the actual production needs.

[0019] This invention was used to evaluate the effectiveness of fractures in multiple wells in relevant blocks. The calculation results provide significant technical support for various aspects of fracture mechanical propagation type classification and reservoir stimulation selection, thereby improving reservoir stimulation effectiveness. Attached Figure Description

[0020] The accompanying drawings described herein are for illustrative purposes only and are not intended to limit the scope of the invention in any way.

[0021] In the attached diagram: Figure 1 This is a flowchart for evaluating the effectiveness of cracks, provided as an embodiment of the present invention.

[0022] Figure 2 This is a schematic diagram illustrating the calculation of the force-fracture angle using electrical imaging logging data in well XX, as described in an embodiment of the present invention.

[0023] Figure 3 This is a schematic diagram illustrating the state of a natural crack opening or shear slip under normal circumstances in this invention.

[0024] Figure 4 This is a schematic diagram showing the decomposed process of the intersection of hydraulic cracks and natural cracks under normal circumstances in this invention.

[0025] Figure 5 This is a schematic diagram illustrating the theoretical variation law of the starting pressure for the opening of natural cracks under different stress difference conditions in this invention.

[0026] Figure 6This is a schematic diagram illustrating the theoretical variation law of the initiation pressure for shear slippage of natural cracks under different stress difference conditions in this invention.

[0027] Figure 7 (a), (b), and (c) are classification diagrams of crack mechanical propagation modes under different stress differences of 20 MPa, 30 MPa, and 40 MPa, respectively, in this invention.

[0028] Figure 8 This is a theoretical classification diagram of crack mechanical propagation modes under different stress difference conditions in this invention.

[0029] Figure 9 This is a classification and statistical diagram of the mechanical propagation mode of fractures in well XX of this invention.

[0030] Figure 10 This is a diagram showing the evaluation results of fracture effectiveness in well XX according to an embodiment of the present invention. Detailed Implementation

[0031] To enable those skilled in the art to better understand the technical solutions of this invention, the technical solutions of the embodiments of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this invention, and not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of this invention.

[0032] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0033] It should be noted that any reference signs placed between parentheses in the claims should not be construed as limiting the claims. The word "comprising" does not exclude the presence of components or steps not listed in the claims. The word "a" or "an" preceding a component does not exclude the presence of a plurality of such components. This application can be implemented by means of hardware comprising several different components and by means of a suitably programmed computer. In a unit claim enumerating several means, several of these means may be embodied by the same item of hardware. The use of the words first, second, and third, etc., does not indicate any order. These words can be interpreted as names. Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this application, "multiple" means two or more, unless otherwise explicitly specified. The present invention will now be described in detail with reference to the accompanying drawings.

[0034] The present invention provides a method for evaluating the effectiveness of cracks, comprising the following steps: Obtain logging data from the target well; Based on well logging data, the current horizontal maximum principal stress orientation is determined, and the angle between the current horizontal maximum principal stress of the target well and the orientation of each natural fracture is calculated. Calculate the difference in horizontal principal stress in each fracture of the target well; The critical pressure values ​​within each natural fracture in the target well that cause it to open and the critical pressure values ​​within each fracture that cause shear slip are calculated based on the difference in horizontal principal stress. The effectiveness of the fractures is evaluated based on the angle between the current maximum principal stress of the target well and the orientation of each natural fracture, and the difference between the critical pressure value within the fracture at which each natural fracture opens and the critical pressure value within the fracture under mechanical conditions of shear slip.

[0035] The fracture effectiveness evaluation method proposed in this invention is a method that can effectively compensate for the shortcomings of static fracture effectiveness evaluation. The key innovation of this invention is to propose a quantitative calculation method for fracture mechanical propagation under ultra-deep, high-compression stress conditions, establish a classification standard for reservoir stimulation geomechanical models and a fracture effectiveness identification chart, realize the quantitative calculation and classification of the mechanical propagation type of a single fracture, and carry out fracture effectiveness evaluation, thereby supporting the optimization of oil testing sections. Through practical application, it is shown that the fracture effectiveness evaluation based on dynamics can more scientifically and rationally select oil testing sections, significantly affecting the reservoir stimulation effect, and bringing a brand-new solution to the fracture effectiveness evaluation of high-compression stress fractured reservoirs.

[0036] Example 1 The specific embodiments of the present invention will be further described below, and the specific calculation methods and effects of each step are shown as follows: Step 1: Well logging data acquisition, obtaining acoustic, density, and electrical imaging data.

[0037] P-wave, S-wave, density, and electrical imaging data of the downhole formation in well XX (Example XX) were obtained using dipole shear wave, density, and electrical imaging instruments.

[0038] Step 2: Crack orientation is captured, ground stress orientation is determined, and force-crack angle is determined.

[0039] By processing and interpreting the electrical imaging logging data of well XX in Example 1, information on stratigraphy, natural fractures, induced fractures, and wellbore collapse is obtained, and the occurrence (dip, strike, dip angle) of stratigraphy, natural fractures, induced fractures, and wellbore collapse is clarified.

[0040] The location of the current horizontal maximum principal stress is determined using the wellbore collapse method, the drill-induced fracture method, or the fast shear wave azimuth method. Based on this, the angle between the current horizontal maximum principal stress and the location of the natural fracture is calculated.

[0041] Wellbore collapse method: Utilizing well logging data such as formation dip, resistivity, and sonic logging, a wellbore imaging map is generated through processing. A symmetrical strip-shaped image of a certain width is identified as a wellbore collapse. The azimuth shown in the image is the azimuth of the minimum horizontal principal stress, and its vertical direction is the azimuth of the maximum horizontal principal stress. Extracting data from the formation dip, well inclination, wellbore azimuth, boom diameter, electrode azimuth, and relative azimuth angle from the imaging data, the azimuth of the enlarged wellbore diameter portion is statistically analyzed using a rose diagram. The resulting azimuth is the azimuth of the minimum horizontal principal stress, and its vertical direction is the azimuth of the maximum horizontal principal stress.

[0042] Drilling-induced fracture method: Identify the figure-eight shaped, symmetrical or straight, symmetrical fractures from the formation dip angle and acoustic-electric imaging map. These are stress-relieving induced fractures in the well. Read their orientation angle value from the map header scale, which is the orientation of the maximum horizontal principal stress.

[0043] Fast shear wave azimuth method: The fast shear wave azimuth of the formation is obtained by processing the sonic logging data of the dipole array, and the azimuth with the highest frequency is obtained by statistical analysis using rose diagrams. This azimuth is the azimuth of the maximum horizontal principal stress.

[0044] In this embodiment, specifically: 1) By processing and interpreting the electrical imaging data of the example well, 96 natural fractures were picked out, and the occurrence information (dip, dip angle and strike) of each fracture was clarified; taking the fracture at 7315.11 meters as an example, its strike is 68.75°.

[0045] 2) By processing and interpreting the electrical imaging data of the example well, information on wellbore collapse was obtained, and the location of the current maximum horizontal principal stress was determined by the wellbore collapse method. It was determined that the location of the maximum horizontal principal stress in this well is 45° east of north.

[0046] 3) Determine the force-joint angle θ of a single crack by the crack direction and the orientation of the maximum horizontal principal stress; taking the crack at 7315.11 meters as an example, its force-joint angle is 23.75°.

[0047] Step 3: Calculation of rock mechanical parameters and current geostress parameters.

[0048] Rock mechanics parameters include basic reservoir rock mechanics parameters (Young's modulus, Poisson's ratio).

[0049] Current geostress parameters include pore pressure, vertical stress, and horizontal principal stress.

[0050] Formula for calculating formation pore pressure using the Eaton method:

[0051] In the formula: The pressure of the overlying strata is MPa; Normal formation pore pressure, MPa; To predict the actual acoustic transit time in deep strata, ; C represents the regional index; The value represents the abnormal formation pore pressure, in MPa.

[0052] Calculate the vertical stress using the following formula:

[0053] In the formula: This refers to the pressure of the overlying strata, measured in MPa. This refers to the average formation density at depths where no well logging density values ​​are available, in g / cm³. 3 ; This refers to the density of the formation, measured in g / cm³. 3 ; H0 refers to the starting depth of density logging, in meters (m). H refers to the depth of the calculation point, in meters (m).

[0054] Using well logging data, the horizontal principal stresses were determined using the models in Table 1 below. A combined spring model was selected for evaluating the horizontal principal stresses of fractured, low-porosity sandstone oil and gas reservoirs.

[0055] Table 1

[0056] In the table, This is the maximum principal stress; Pp is the uniaxial compressive strength; Pp is the pore pressure. The minimum principal stress (confining pressure); It is the triaxial stress coefficient; ,in, It is the internal friction angle; The minimum horizontal principal stress; This represents the maximum horizontal principal stress. It is the vertical principal stress; α is Poisson's ratio; α is Biot coefficient; and These are the structural stress coefficients in the two horizontal directions; E is the elastic modulus. and These are the strains in the directions of maximum and minimum stress, respectively; and These are the effective stress coefficients in the vertical and horizontal directions, respectively; and These are the strains in the directions of maximum and minimum principal stress, respectively.

[0057] The rock mechanics parameters and current geostress parameters of well XX in Example 3 were calculated using the method described in step 3.

[0058] In this embodiment, the rock mechanics parameters and current geostress parameters of the example well are calculated using the method described in step three to determine the magnitude of the horizontal principal stress difference for each natural fracture. Taking the fracture at 7315.11 meters as an example, its horizontal principal stress difference (the difference between the maximum and minimum horizontal principal stresses) is 25.66 MPa (Poisson's ratio: 0.2038; Young's modulus: 22970.54 MPa; maximum horizontal principal stress: 158.00 MPa; minimum horizontal principal stress: 132.34 MPa).

[0059] Step 4: Quantitatively calculate the critical pressure value inside the crack under the mechanical conditions of natural crack opening and shear slip.

[0060] The quantitative calculation method for crack mechanical propagation provided by this invention quantitatively calculates the critical pressure value (P) within a natural crack under mechanical conditions for crack opening. t The critical pressure value within the crack under mechanical conditions of shear slip (P) b The values ​​of the crack at 7315.11 meters and the difference between them (ΔP) are calculated. For example, the values ​​for the crack at 7315.11 meters are 4.16 MPa, 5.06 MPa, and -0.90 MPa, respectively. The calculation process is as follows:

[0061]

[0062] Step 5: Establish classification criteria and draw a fracture effectiveness identification chart: Establish classification criteria for reservoir stimulation geomechanical models and draw a theoretical chart for fracture effectiveness identification.

[0063] Using stress difference and force-fracture angle parameters, the critical pressure value and its difference within the fracture are calculated for the mechanical conditions under which each natural fracture in an example well will open or shear slip.

[0064] We select the Warpinski-Teufel fracture criterion, which is applicable to ultra-deep, strongly compressive structural backgrounds, propose a quantitative calculation method for fracture mechanical propagation under ultra-deep, strongly compressive stress conditions, establish a classification standard for reservoir stimulation geomechanical models, and draw a fracture effectiveness identification chart.

[0065] The intersection of hydraulic fractures and natural fractures is a complex and orderly process, consisting of three stages: When a hydraulic fracture approaches a natural fracture, due to the fluid hysteresis effect, the fracture tip will reach the interface earlier than the fracturing fluid tip. Figure 4 As shown in Figure a, the fluid pressure at the intersection point is 0, while a local stress field is generated at the crack tip, leading to two possible outcomes: the natural crack either undergoes shear slip or stops, as shown in Figure a. Figure 4 As shown in b, the hydraulic fracture passes through the natural fracture, such as Figure 4 As shown in c.

[0066] When the fracturing fluid tip reaches the natural fracture, the fluid pressure at the intersection gradually increases. Under shear slip conditions in the natural fracture, the fluid may drive the natural fracture to open, causing the hydraulic fracture to change direction and extend along the natural fracture. Figure 4 As shown in d; however, when a hydraulic fracture passes through a natural fracture, two scenarios may occur: the natural fracture remains closed, as shown in d. Figure 4 As shown in diagram e, fluid flows into the natural cracks, and multiple cracks extend simultaneously, such as... Figure 4 As shown in f.

[0067] As pumping continues, the crack propagation behavior will continue to evolve. For example, in Figure 4 In case d, hydraulic fractures may deviate from the path of natural fractures, at the intersection point, such as... Figure 4 In the case shown by g, along as Figure 4 A weak point or end of the natural crack shown in h, along as... Figure 4 The direction of maximum horizontal stress, as shown in i, begins to extend again; in Figure 4 In equation e, as the fluid pressure at the intersection point increases further, the natural crack may open and extend further, such as... Figure 4 As shown in f.

[0068] When the normal stress on the walls of a natural crack is insufficient to prevent relative sliding between the walls, shear slip occurs in the crack; when the fluid pressure inside the crack is greater than the normal stress on the walls of the natural crack, the natural crack opens.

[0069] According to the Warpinski-Teufel criterion, when the horizontal stress difference is large, natural cracks will open and break at low and high approach angles, and shear slip cracks can occur at intermediate angles. When the horizontal stress difference is low, natural cracks will only open and break. The greater the horizontal stress difference, the greater the required net construction pressure and the larger the range of natural cracks that will develop shear slip, which is a positive factor in the formation of complex crack networks.

[0070] The criterion for shear slip in natural cracks is:

[0071] The criterion for determining whether a natural crack has opened is:

[0072] In the formula, The net pressure inside the crack is expressed in MPa. and These are the maximum and minimum horizontal principal stresses, respectively, in MPa; The approximation angle is the angle between the direction of the natural crack and the direction of the maximum horizontal principal stress, expressed in degrees. is the friction coefficient of the natural crack surface, which is dimensionless; The cohesive force of the rock within the natural fissure, expressed in MPa.

[0073] Based on the characteristics of fracture development in ultra-deep reservoirs and the strong in-situ stress of ultra-deep strata, this invention proposes a reservoir stimulation geomechanical model based on the mechanical propagation mechanism of natural fractures during reservoir stimulation. This classification model considers the influence of horizontal stress difference, approach angle, natural fracture cohesion, sliding friction coefficient, and fracturing parameters on the mechanical propagation mode of natural fractures, unifying the research scale and classifying reservoir stimulation geomechanical models. Overall, strongly compressive stress fractured reservoirs can be classified into four geomechanical models: parallel opening type, oblique shear-slip type, high-permeability swelling type, and orthogonal opening type.

[0074] Based on this, a classification chart for crack propagation under different horizontal stress differences was invented. Figure 8 ), used for crack effectiveness evaluation.

[0075]

[0076]

[0077] In the formula, The critical net pressure difference within the crack, in MPa; The critical net pressure within the crack at the point of opening, in MPa; X is the critical net pressure within the crack when shear slip occurs, in MPa; XY is the horizontal stress difference, in MPa. and These represent the maximum and minimum horizontal principal stresses, in MPa. Step 6: Use charts to classify crack propagation patterns and evaluate crack effectiveness.

[0078] Based on the fracture propagation classification criteria, the fracture propagation patterns of each natural fracture in the example well were classified using a classification chart, and the relevant results were statistically analyzed to evaluate the effectiveness of the fractures. See details below. Figure 9 .

[0079] The criteria for discrimination are as follows, see Table 2 for details: when At that time, it was determined to be a high-permeability expansion type crack; when ,and At that time, it was determined to be an oblique shear slip crack; when ,and At that time, it was determined to be a parallel opening type crack; when ,and At that time, it was determined to be an orthogonal opening type crack.

[0080] Table 2

[0081] Based on the above calculation results, using the fracture propagation classification criteria provided by this invention, the fracture propagation patterns of each natural fracture in the example well were classified using a classification chart. Taking the fracture at 7315.11 meters as an example, the mechanical propagation pattern of this fracture is parallel opening type. Similarly, each fracture was classified, and the results are shown in Table 3 below. Figure 9 As shown.

[0082] Table 3

[0083] The consensus of this well is based on 96 natural fractures. The method provided by this invention is used to identify and evaluate the propagation type and effectiveness of natural fractures in the example well. The mechanical type of natural fractures is mainly oblique shear slip fractures (65 fractures), accounting for 66.7%, followed by parallel opening fractures (22 fractures), accounting for 22.9%.

[0084] Example 2 Based on the crack effectiveness evaluation method of Example 1, a crack effectiveness evaluation system is disclosed, including: The data acquisition module is used to acquire logging data from the target well. The first calculation module is used to determine the current horizontal maximum principal stress orientation based on well logging data, and to calculate the angle between the current horizontal maximum principal stress of the target well and the orientation of each natural fracture. The second calculation module is used to calculate the difference in horizontal principal stress in each fracture of the target well. The third calculation module is used to calculate the critical pressure value inside the fracture when each natural fracture in the target well opens and the critical pressure value inside the fracture under the mechanical conditions of shear slip, as well as the difference between the two, based on the difference in horizontal principal stress. The evaluation module is used to evaluate fracture effectiveness based on the angle between the current maximum principal stress of the target well and the orientation of each natural fracture, and the difference between the critical pressure value within the fracture at which each natural fracture opens and the critical pressure value within the fracture under mechanical conditions of shear slip.

[0085] Example 3 The purpose of this embodiment is to provide an electronic device, including a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor executes the computer program to implement the crack effectiveness evaluation method.

[0086] Example 4 The purpose of this embodiment is to provide a computer-readable storage medium storing a computer program that, when executed by a processor, implements the crack effectiveness evaluation method.

[0087] Example 5 The purpose of this embodiment is to provide a computer program product including a computer-readable medium, wherein the computer-readable medium contains computer-readable program code that executes the crack effectiveness evaluation method.

[0088] The steps and methods involved in the apparatus of the above embodiments 2, 3, 4 and 5 correspond to those in embodiment 1. For specific implementation methods, please refer to the relevant description section of embodiment 1.

[0089] Those skilled in the art will understand that embodiments of this application can be provided as methods, systems, or computer program products. Therefore, this application can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, this application can take the form of a computer program product embodied 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. This application is described with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of this application. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, generate instructions for implementing the flowchart... Figure 1 One or more processes and / or boxes Figure 1 A device that provides the functions specified in one or more boxes. These computer program instructions may also be stored in a computer-readable storage medium that can direct a computer or other programmable data processing device to function in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including instruction means, which are implemented in a process Figure 1 One or more processes and / or boxes Figure 1 The function specified in one or more boxes. These computer program instructions may also be loaded onto a computer or other programmable data processing equipment to cause a series of operational steps to be performed on the computer or other programmable equipment to produce a computer-implemented process, thereby providing instructions that execute on the computer or other programmable equipment for implementing the process. Figure 1 One or more processes and / or boxes Figure 1 The steps of the function specified in one or more boxes.

[0090] Unless otherwise specified, the working methods or control methods involved in the above embodiments are conventional working methods or control methods in the art.

[0091] Although preferred embodiments of this application have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments as well as all changes and modifications falling within the scope of this application. Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Any other modifications or equivalent substitutions made by those skilled in the art to the technical solutions of the present invention, as long as they do not depart from the spirit and scope of the technical solutions of the present invention, should be covered within the scope of the claims of the present invention.

Claims

1. A method for evaluating the effectiveness of cracks, characterized in that, Includes the following steps: Obtain logging data from the target well; Based on well logging data, the current horizontal maximum principal stress orientation is determined, and the angle between the current horizontal maximum principal stress of the target well and the orientation of each natural fracture is calculated. Calculate the difference in horizontal principal stress in each fracture of the target well; The critical pressure values ​​within each natural fracture in the target well that cause it to open and the critical pressure values ​​within each fracture that cause shear slip are calculated based on the difference in horizontal principal stress. The effectiveness of the fractures is evaluated based on the angle between the current maximum principal stress of the target well and the orientation of each natural fracture, and the difference between the critical pressure value within the fracture at which each natural fracture opens and the critical pressure value within the fracture under mechanical conditions of shear slip.

2. The method for evaluating the effectiveness of cracks according to claim 1, characterized in that, By collecting data on the occurrence of each fracture in the area where the target well is located, the orientation of the current maximum principal stress at the horizontal level can be determined.

3. The method for evaluating the effectiveness of cracks according to claim 1, characterized in that, The formula for calculating the critical pressure value within a natural crack during its opening is as follows: The formula for calculating the critical pressure value within a natural crack under the mechanical conditions for shear slip is as follows: ; where p t p is the critical pressure value within a natural crack before it opens. b XY represents the critical pressure value within the crack under the mechanical conditions for shear slippage in a natural crack; XY represents the difference in horizontal principal stresses; θ represents the force-crack angle. The coefficient of friction of the natural crack surface; It is the cohesive force of rocks within natural fissures.

4. The method for evaluating the effectiveness of cracks according to claim 1, characterized in that, Based on the angle between the current maximum principal stress and the orientation of each natural fracture, and the difference between the critical pressure value within the fracture at which each natural fracture in the target well opens and the critical pressure value within the fracture under mechanical conditions of shear slip, a theoretical chart for fracture effectiveness identification is drawn. The chart is then used to establish a classification standard for reservoir stimulation geomechanical models to evaluate fracture effectiveness.

5. The method for evaluating the effectiveness of cracks according to claim 4, characterized in that, Geomechanical classification of fractures includes parallel opening type, oblique shear slip type, high permeability expansion type, and orthogonal opening type.

6. The method for evaluating the effectiveness of cracks according to claim 5, characterized in that, When the critical pressure value inside a natural crack is ≤0 under the mechanical condition of shear slip, it is identified as a high-permeability expansion type crack. When the critical pressure value inside the crack is greater than 0 and the critical net pressure difference inside the crack is greater than or equal to 0, it is determined to be an oblique shear slip crack. When the critical pressure value inside the crack is >0 and the critical net pressure difference inside the crack is <0, and the force-crack angle is less than or equal to 45°, it is determined to be a parallel opening type crack. When the critical pressure value inside a natural crack is greater than 0 and the critical net pressure difference inside the crack is less than 0, and the force-crack angle is greater than 45°, it is determined to be an orthogonal opening type crack.

7. A crack effectiveness evaluation system, characterized in that, include: The data acquisition module is used to acquire logging data from the target well. The first calculation module is used to determine the current horizontal maximum principal stress orientation based on well logging data, and to calculate the angle between the current horizontal maximum principal stress of the target well and the orientation of each natural fracture. The second calculation module is used to calculate the difference in horizontal principal stress in each fracture of the target well. The third calculation module is used to calculate the critical pressure value inside the fracture when each natural fracture in the target well opens and the critical pressure value inside the fracture under the mechanical conditions of shear slip, as well as the difference between the two, based on the difference in horizontal principal stress. The evaluation module is used to evaluate fracture effectiveness based on the angle between the current maximum principal stress of the target well and the orientation of each natural fracture, and the difference between the critical pressure value within the fracture at which each natural fracture opens and the critical pressure value within the fracture under mechanical conditions of shear slip.

8. An electronic device, characterized in that, It includes a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor, when executing the computer program, implements the crack effectiveness evaluation method according to any one of claims 1-6.

9. A computer-readable storage medium, characterized in that, The computer-readable storage medium stores a computer program that, when executed by a processor, implements the crack effectiveness evaluation method according to any one of claims 1-6.

10. A computer program product comprising a computer-readable medium, characterized in that, The computer-readable medium contains computer-readable program code that performs the crack effectiveness evaluation method according to any one of claims 1-6.

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