Numerical simulation method, device and equipment for water injection induced fracture prediction

Abstract

The invention provides a numerical simulation method, device and equipment for water injection induced fracture prediction, and relates to the technical field of numerical simulation. The method comprises the following steps: acquiring basic parameters of a research area; the basic parameters comprise oil reservoir geologic characteristic parameters, rock physical property parameters and fracture development conditions; obtaining a crack distribution index according to the crack density; according to the oil reservoir geologic characteristic parameters, the rock physical property parameters, the fracture development condition and the fracture distribution index, the equivalent permeability is obtained; and dynamically predicting the crack according to the equivalent permeability. According to the method, the basic parameters and the fracture distribution index of the research area are input as variables, the equivalent permeability is obtained, the equivalent permeability distribution is calculated and updated, and the problem that simulation repeatability is poor due to manual control is solved.

Description

Technical Field

[0001] The present application relates to the field of numerical simulation technology, and in particular to a numerical simulation method, device and equipment for predicting water injection-induced fractures. Background Art

[0002] In the extraction of oil and gas, water injection-induced fractures are an effective way to enhance oil and gas fluidity and improve oil recovery efficiency. Water injection-induced fractures can significantly improve the permeability of the reservoir. By creating a fracture network, the fluid can move more smoothly in the underground rock formation, which makes the oil and gas that were originally difficult to flow easier to be produced, thereby increasing the recovery rate of oil and gas; in low-permeability reservoirs, the fractures formed by the water injection process can help push more crude oil to the production wells, thereby optimizing the oil recovery process. The dynamic expansion of water injection-induced fractures has an important impact on scheme design and parameter optimization. Therefore, it is crucial to study the numerical simulation method for predicting the dynamic expansion of water injection-induced fractures.

[0003] In the existing numerical simulation methods, the expansion direction of water injection-induced fractures is manually specified based on the preset stress distribution. This method requires the simulator to judge the possible expansion area and direction of the fracture based on the flow field conditions, which relies on personal experience. Therefore, the judgment of the crack expansion direction using the existing numerical simulation method is subjective, and different people may get different results, resulting in poor simulation repeatability. Summary of the invention

[0004] The present application provides a numerical simulation method, device and equipment for predicting water injection-induced fractures, which are used to solve the problem of poor repeatability caused by using existing numerical simulation methods to judge the direction of fracture expansion.

[0005] A first aspect of an embodiment of the present invention provides a numerical simulation method for predicting water injection-induced fractures, comprising:

[0006] Obtaining basic parameters of the study area; the basic parameters include reservoir geological characteristic parameters, rock physical parameters and fracture development;

[0007] The crack distribution index is obtained according to the crack density;

[0008] Obtaining equivalent permeability according to the reservoir geological characteristic parameters, the rock physical property parameters, the fracture development conditions and the fracture distribution index;

[0009] The fracture dynamics are predicted based on the equivalent permeability.

[0010] In a possible design, the reservoir geological characteristic parameters include maximum horizontal principal stress, minimum horizontal principal stress, overburden formation pressure and formation pressure;

[0011] The rock physical parameters include Poisson's ratio and tensile strength;

[0012] The fracture development conditions include fracture inclination angles.

[0013] In a possible design, obtaining the equivalent permeability according to the reservoir geological characteristic parameters, the rock physical property parameters, the fracture development conditions and the fracture distribution index includes:

[0014] Obtaining an activation pressure threshold according to the Poisson's ratio, the overburden pressure, the formation pressure, the maximum horizontal principal stress, the minimum horizontal principal stress and the fracture dip;

[0015] Obtaining a fracture pressure threshold according to the maximum horizontal principal stress, the minimum horizontal principal stress, the overburden formation pressure and the tensile strength;

[0016] Obtaining a water injection-induced fracture pressure threshold under a mixed mechanism according to the fracture distribution index, the activation pressure threshold and the fracturing pressure threshold;

[0017] The equivalent permeability is obtained according to the water injection induced fracture pressure threshold under the mixed mechanism.

[0018] In a possible design, obtaining the water injection-induced fracture pressure threshold under a mixed mechanism according to the fracture distribution index, the activation pressure threshold and the fracturing pressure threshold includes:

[0019] The pressure threshold formula is used to obtain the water injection-induced fracture pressure threshold under the mixed mechanism according to the fracture distribution index, the activation pressure threshold and the fracture pressure threshold. The pressure threshold formula is:

[0020] p s =(A f p i +(1-A f ) f ) 1-cosγ

[0021] Among them, the p s is the water injection induced fracture pressure threshold under the mixed mechanism, and the A f is the crack distribution index, the p i is the activation pressure threshold, the p f is the rupture pressure threshold, and γ is the angle between the main flow line and the maximum horizontal principal stress.

[0022] In a possible design, obtaining the equivalent permeability according to the water injection-induced fracture pressure threshold under the mixed mechanism includes:

[0023] The equivalent permeability is obtained by using an equivalent permeability modification function according to the water injection induced fracture pressure threshold under the mixed mechanism; the equivalent permeability modification function is:

[0024]

[0025] Among them, the K f (p) is the equivalent permeability, and K i is the initial permeability, c1 is a preset dimensionless parameter, c2 is a preset dimensionless parameter, p is the formation pressure, and p s is the pressure threshold of water injection-induced fractures under the hybrid mechanism.

[0026] In a possible design, obtaining the crack distribution index according to the crack density includes:

[0027] According to the crack density, a crack density field map is obtained by using a Kriging interpolation method;

[0028] The crack density field map is normalized to obtain the crack distribution index.

[0029] In a possible design, obtaining the activation pressure threshold according to the Poisson's ratio, the overburden pressure, the formation pressure, the maximum horizontal principal stress, the minimum horizontal principal stress and the fracture dip angle includes:

[0030] The activation pressure threshold is obtained by the activation pressure formula according to the Poisson's ratio, the overburden pressure, the formation pressure, the maximum horizontal principal stress, the minimum horizontal principal stress and the fracture dip angle; the activation pressure formula is:

[0031]

[0032] Among them, the p i is the activation pressure threshold, v is the Poisson's ratio, and p o is the overburden pressure, the p p is the formation pressure, the σ H is the maximum horizontal principal stress, the σ h is the minimum horizontal principal stress, θ is the crack inclination, and β is the angle between the maximum horizontal principal stress direction and the crack direction.

[0033] In a possible design, obtaining the fracture pressure threshold according to the maximum horizontal principal stress, the minimum horizontal principal stress, the overburden formation pressure and the tensile strength includes:

[0034] The fracture pressure threshold is obtained by using the fracture pressure formula according to the maximum horizontal principal stress, the minimum horizontal principal stress, the overburden pressure and the tensile strength; the fracture pressure formula is:

[0035] p f =3σ h -σ H +σ f -p o

[0036] Among them, the p f is the rupture pressure threshold, the σ h is the minimum horizontal principal stress, the σ H is the maximum horizontal principal stress, the p o is the overburden pressure, the σ f is the tensile strength.

[0037] A second aspect of an embodiment of the present invention provides a numerical simulation device for predicting water injection-induced fractures, comprising:

[0038] A basic parameter acquisition module is used to obtain basic parameters of the study area; the basic parameters include reservoir geological characteristic parameters, rock physical parameters and fracture development conditions;

[0039] A crack distribution index acquisition module, used to obtain the crack distribution index according to the crack density;

[0040] An equivalent permeability acquisition module, used to obtain the equivalent permeability according to the reservoir geological characteristic parameters, the rock physical property parameters, the fracture development conditions and the fracture distribution index;

[0041] The dynamic prediction module is used to perform dynamic prediction of fractures according to the equivalent permeability.

[0042] A third aspect of an embodiment of the present invention provides an electronic device, comprising: a processor and a memory communicatively connected to the processor;

[0043] The memory stores computer-executable instructions;

[0044] The processor executes the computer-executable instructions stored in the memory to implement the numerical simulation method for predicting water injection-induced fractures provided in the first aspect of the embodiment of the present invention.

[0045] A fourth aspect of an embodiment of the present invention provides a computer-readable storage medium, in which computer-executable instructions are stored to implement the numerical simulation method for predicting water injection-induced fractures provided in the first aspect of an embodiment of the present invention.

[0046] A fifth aspect of an embodiment of the present invention provides a computer program product, including a computer program, which, when executed by a processor, implements the numerical simulation method for predicting water injection-induced fractures provided in the first aspect of an embodiment of the present invention.

[0047] The present application provides a numerical simulation method, device and equipment for predicting water injection-induced fractures, and the numerical simulation method for predicting water injection-induced fractures includes: obtaining basic parameters of the study area; the basic parameters include reservoir geological characteristic parameters, rock physical parameters and fracture development; obtaining fracture distribution index according to fracture density; obtaining equivalent permeability according to reservoir geological characteristic parameters, rock physical parameters, fracture development and fracture distribution index; and predicting fracture dynamics according to equivalent permeability. Based on the above method, the following technical effects are achieved: studying the numerical simulation method for predicting the dynamic expansion of water injection-induced fractures, considering the influence of water injection-induced fractures in scheme design and parameter optimization, providing an effective adjustment method for the development of later fractured tight oil reservoirs, guiding and controlling the moderate expansion of water injection-induced fractures, improving oil recovery efficiency, and guiding the further exploitation of remaining oil; taking the basic parameters and fracture distribution index as variable inputs to obtain equivalent permeability, and updating the induced fracture distribution through equivalent permeability, avoiding inaccurate results that may occur due to human control; considering the influence of streamlines, it is suitable for a variety of well networks and different production conditions, with a wide range of applications and easy to use. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] 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 description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0049] Figure 1 Schematic diagram of the numerical simulation method for predicting water injection-induced fractures provided in the embodiment of the present application Figure 1 ;

[0050] Figure 2 Schematic diagram of the numerical simulation method for predicting water injection-induced fractures provided in the embodiment of the present application Figure 2 ;

[0051] Figure 3 A distribution diagram of high permeability areas in the 10th cycle of the numerical simulation method for predicting water injection-induced fractures provided in an embodiment of the present application;

[0052] Figure 4 A distribution diagram of high permeability areas in the 20th cycle of the numerical simulation method for predicting water injection-induced fractures provided in an embodiment of the present application;

[0053] Figure 5 A schematic diagram of the structure of a numerical simulation device for predicting water injection-induced fractures provided in an embodiment of the present application;

[0054] Figure 6 A schematic diagram of the structure of an electronic device provided in an embodiment of the present application. DETAILED DESCRIPTION

[0055] In the embodiments of the present application, words such as "first" and "second" are used to distinguish between identical or similar items with substantially the same functions and effects. Those skilled in the art will understand that words such as "first" and "second" do not limit the quantity and execution order, and words such as "first" and "second" do not necessarily limit the difference. It should be noted that in the embodiments of the present application, words such as "exemplary" or "for example" are used to indicate examples, illustrations or explanations. Any embodiment or design described as "exemplary" or "for example" in this application should not be interpreted as being more preferred or more advantageous than other embodiments or design. Specifically, the use of words such as "exemplary" or "for example" is intended to present related concepts in a specific way. In the embodiments of the present application, "at least one" refers to one or more, and "more" refers to two or more.

[0056] It should be noted that the "at..." in the embodiments of the present application can be the instant when a certain situation occurs, or can be a period of time after a certain situation occurs, and the embodiments of the present application do not specifically limit this. In addition, the numerical simulation method for predicting water injection-induced fractures provided in the embodiments of the present application is only used as an example, and the numerical simulation method for predicting water injection-induced fractures can also include more or less content.

[0057] In order to clearly describe the technical solutions of the embodiments of the present application, some of the terms and technologies involved in the embodiments of the present application are briefly introduced:

[0058] Water injection induced fractures: refers to the process of injecting liquid (usually water) into underground rock layers or geological bodies, causing cracks in the underground rock layers or geological bodies due to increased pressure or expanding existing cracks. This process is widely used in the following scenarios: 1) Oil and gas extraction, by injecting high-pressure liquid into underground rock formations, cracks can be generated in the rocks, thereby releasing oil or natural gas; 2) Geothermal energy development, by inducing fractures through water injection, the permeability of geothermal reservoirs can be enhanced, the circulation efficiency of geothermal fluids can be improved, and thus the amount of geothermal energy extracted can be increased; 3) Groundwater resource management, in the process of reservoir and groundwater recharge, groundwater reserves can be increased by inducing fractures through water injection.

[0059] The pressure threshold of water injection-induced fractures refers to the maximum injection pressure that the underground rock layer or geological body can withstand during the water injection-induced fracture process. When this pressure threshold is reached, the underground rock layer or geological body will crack and cause the fracture to expand. This scheme links the pressure threshold of water injection-induced fractures with the equivalent permeability to perform dynamic prediction of fractures.

[0060] Fracture distribution index of water injection-induced fractures: refers to the parameter that describes the expansion mode of water injection-induced fractures. It indicates the distribution law of fractures in space, including information on the density, direction and morphology of fractures. This scheme combines the fracture distribution index with the pressure threshold of a single mechanism of fracture formation to obtain a unified pressure threshold.

[0061] Exemplary embodiments will be described in detail herein, examples of which are shown in the accompanying drawings. When the following description refers to the drawings, the same numbers in different drawings represent the same or similar elements unless otherwise indicated. The implementations described in the following exemplary embodiments do not represent all implementations consistent with the present application. Instead, they are merely examples of devices and methods consistent with some aspects of the present application as detailed in the appended claims.

[0062] The technical solution of the present invention is described in detail with specific embodiments below. The following specific embodiments can be combined with each other, and the same or similar concepts or processes may not be repeated in some embodiments. The embodiments of the present invention will be described below in conjunction with the accompanying drawings.

[0063] In order to clearly understand the technical solution of the present application, the solution of the prior art is first introduced in detail.

[0064] The existing numerical simulation method manually specifies the expansion direction of water injection-induced fractures based on stress distribution. This requires the simulator to judge the area and orientation of the water injection-induced fractures that may be caused by the flow field. This judgment is subjective and different people may get different results. Therefore, the repeatability of the numerical simulation of water injection-induced fractures using the existing technology is poor.

[0065] In the prior art, the following problems exist in parallel with this problem: the pressure-sensitive formula of equivalent permeability is not directly linked to the pressure threshold, so it is necessary to manually divide the equivalent area and the sensitive parameter table; a unified pressure threshold is not constructed through the activation pressure threshold of natural fractures and the rupture pressure threshold of forming new fractures, so the fracture network formed by multiple natural fractures or hydraulic fractures communicating with each other is not considered; a parameter that can describe the expansion mode of water injection-induced fractures, namely the fracture distribution index, is not defined according to the fracture density, so the description of the fracture expansion mode is relatively complicated.

[0066] Therefore, in order to solve the problem of poor repeatability of numerical simulation for water injection-induced fracture prediction using existing technologies, the study found that ① the basic parameters and fracture distribution index of the study area should be obtained; ② the equivalent permeability should be obtained based on the basic parameters and fracture distribution index; ③ the fracture dynamics should be predicted based on the equivalent permeability.

[0067] Specifically, basic parameters of the study area are obtained; basic parameters include reservoir geological characteristic parameters, rock physical parameters and fracture development;

[0068] The crack distribution index is obtained according to the crack density;

[0069] The equivalent permeability is obtained based on reservoir geological characteristic parameters, rock physical parameters, fracture development and fracture distribution index;

[0070] Fracture dynamics prediction is performed based on equivalent permeability.

[0071] The numerical simulation method for predicting water injection-induced cracks in an embodiment of the present invention is based on the principle of the above-mentioned working condition preset conditions. The present invention uses the basic parameters and crack distribution index of the study area as variable inputs to obtain an equivalent permeability modification function, and updates the induced crack distribution through the equivalent permeability modification function, thereby avoiding the problem of poor repeatability caused by human subjective judgment.

[0072] Based on the above creative findings, the technical solution of the present application is proposed.

[0073] The following introduces the application scenarios of the numerical simulation method for predicting water injection-induced fractures provided by an embodiment of the present invention.

[0074] The numerical simulation method for water injection-induced fracture prediction in this scheme is applicable to a variety of well networks and different production conditions, has a wide range of applications, and is simple and easy to use. First, the activation pressure threshold of natural fractures and the fracture pressure threshold for forming new fractures are obtained using basic parameters. Then, a unified pressure threshold is established through the activation pressure threshold of natural fractures, the fracture pressure threshold for forming new fractures, and the fracture distribution index, that is, the water injection-induced fracture pressure threshold under the mixed mechanism. Finally, an equivalent permeability modification function is established in combination with the water injection-induced fracture pressure threshold under the mixed mechanism, and the equivalent permeability modification function is used to predict fracture dynamics. The numerical simulation method for water injection-induced fracture prediction in this scheme directly links the equivalent permeability with a unified pressure threshold, thereby avoiding the permeability pressure-sensitive zoning of the entire oilfield area.

[0075] The embodiments of the present application are introduced below in conjunction with the drawings in the specification.

[0076] Figure 1 Schematic diagram of the numerical simulation method for predicting water injection-induced fractures provided in the embodiment of the present application Figure 1, the numerical simulation method for predicting water injection-induced fractures provided in this embodiment includes the following steps:

[0077] S101. Obtain basic parameters of the study area; basic parameters include reservoir geological characteristic parameters, rock physical property parameters and fracture development.

[0078] In this embodiment, the basic parameters of the study area refer to the parameters that can describe the geological structure and physical characteristics of the study area; the reservoir geological characteristic parameters refer to the parameters that can provide information such as the geometric shape, structural characteristics, and sedimentary environment of the reservoir; the rock physical property parameters refer to the parameters that can provide the porosity, permeability, saturation and other physical properties of the rock; the fracture development situation refers to the parameters that can provide information such as the existence, distribution, direction, density of fractures in the rock and their influence on fluid flow.

[0079] Obtaining the basic parameters of the study area is crucial for the subsequent numerical simulation of water injection-induced fracture prediction. These parameters determine the accuracy and reliability of the simulation, which in turn affects the simulation results' reflection of actual underground conditions. Through detailed geological surveys and experimental tests, researchers can ensure that the simulation fully considers the various factors that affect fracture propagation, thereby providing more valuable predictions and suggestions, which helps optimize the design of water injection operations and improve the efficiency of resource extraction.

[0080] S102. Obtain a crack distribution index according to the crack density.

[0081] In this embodiment, water injection-induced fractures are usually a fracture network formed by multiple natural fractures or hydraulic fractures communicating with each other. In order to establish a unified water injection-induced fracture pressure threshold expression, this method defines the fracture distribution index A f , used to describe the density of fractures in a formation.

[0082] S103. Obtain equivalent permeability based on reservoir geological characteristic parameters, rock physical parameters, fracture development and fracture distribution index.

[0083] In this embodiment, equivalent permeability is a key function. Equivalent permeability is a parameter that describes the flow capacity of fluid in a fracture network and is obtained by comprehensively considering the overall permeability of the fracture and the surrounding rock.

[0084] S104. Predict fracture dynamics based on equivalent permeability.

[0085] In this embodiment, equivalent permeability plays an important role in predicting water injection-induced fracture growth, and it can reflect the fracture growth rate and the formation of fracture network.

[0086] The numerical simulation method for predicting water injection-induced fractures provided in the present application comprises: obtaining basic parameters of the study area, including reservoir geological characteristic parameters, rock physical parameters and fracture development; obtaining fracture distribution index according to fracture density; obtaining equivalent permeability according to reservoir geological characteristic parameters, rock physical parameters, fracture development and fracture distribution index; and predicting fracture dynamics according to equivalent permeability. Based on the above method, the following technical effects are achieved: studying the numerical simulation method for predicting the dynamic expansion of water injection-induced fractures, considering the influence of water injection-induced fractures in scheme design and parameter optimization, providing an effective adjustment method for the development of later fractured tight oil reservoirs, guiding and controlling the moderate expansion of water injection-induced fractures, improving oil recovery efficiency, and guiding the further exploitation of remaining oil; taking the basic parameters and fracture distribution index as variable inputs to obtain equivalent permeability, and updating the induced fracture distribution through equivalent permeability, avoiding inaccurate results that may occur in human control; considering the influence of streamlines, it is applicable to a variety of well networks and different production conditions, with a wide range of applications and easy to use.

[0087] Based on the numerical simulation method for predicting water injection-induced cracks provided in the previous embodiment of the present invention, this embodiment provides a numerical simulation method for predicting water injection-induced cracks, which specifically includes the following steps:

[0088] S201. Obtain basic parameters of the study area; basic parameters include reservoir geological characteristic parameters, rock physical property parameters and fracture development.

[0089] Specifically, in this embodiment, reservoir geological characteristic parameters include maximum horizontal principal stress, minimum horizontal principal stress, overburden pressure and formation pressure; rock physical property parameters include Poisson's ratio and tensile strength; and fracture development conditions include fracture inclination.

[0090] Rock physical parameters also include rock fracture pressure, porosity and permeability; fracture development conditions also include fracture density and artificial fracture distribution.

[0091] In this embodiment, the effect of S201 and the meaning of each basic parameter are similar to the effect of S101 and the definition of each basic parameter in the previous embodiment of the present invention, and are not repeated here.

[0092] S202. Obtain a crack distribution index according to the crack density.

[0093] In this embodiment, the meaning of the crack distribution index in S202 and the effect of the index are similar to the meaning of the crack distribution index in S102 in the previous embodiment of the present invention and the effect of the index, which will not be repeated here.

[0094] S203, obtaining an activation pressure threshold according to the Poisson's ratio, the overburden pressure, the formation pressure, the maximum horizontal principal stress, the minimum horizontal principal stress and the fracture inclination.

[0095] In this embodiment, Poisson's ratio refers to an indicator of the ratio of the strain of a material in one direction to the strain in the vertical direction, overburden pressure refers to the pressure exerted by all rock layers above the rock on the lower rock layer, formation pressure refers to the pressure exerted by fluid (such as oil, gas or water) in the underground rock layer on the rock, maximum horizontal principal stress refers to the maximum pressure exerted on the horizontal plane, minimum horizontal principal stress refers to the minimum pressure exerted on the horizontal plane, fracture dip refers to the inclination angle of the fracture plane relative to the horizontal plane, and activation pressure threshold refers to the critical pressure for inducing a natural fracture that was originally in a closed state. Poisson's ratio, overburden pressure, formation pressure, maximum horizontal principal stress, minimum horizontal principal stress and fracture dip are all basic parameters.

[0096] According to the above basic parameters, the activation pressure threshold can be obtained in a variety of ways, including experiments, formula calculations, and empirical estimates.

[0097] The pressure around the water injection well is built up, thus activating the natural fractures that were originally closed. This is the first formation mechanism of water injection-induced fractures. In ultra-low permeability reservoirs, the development degree of natural micro fractures is usually relatively high. As the water injection progresses, when the formation pressure reaches the opening pressure of the natural micro fractures, the natural fractures that were originally closed will be induced.

[0098] The opening order of cracks at different inclination angles is different. As the angle between the streamline (direction of fluid flow) and the maximum horizontal principal stress (the maximum direction of underground stress) decreases, the opening pressure of the natural fracture decreases. After the natural fracture opens, the water absorption rate around the well increases directionally, and the injected water moves along the natural fracture in the direction of the maximum principal stress.

[0099] S204. Obtain a fracture pressure threshold value according to the maximum horizontal principal stress, the minimum horizontal principal stress, the overburden stratum pressure and the tensile strength.

[0100] In this embodiment, the maximum horizontal principal stress, the minimum horizontal principal stress and the overburden pressure are described in step S203, the tensile strength refers to the maximum bearing capacity of the rock under tensile stress, and the fracture pressure threshold refers to the critical pressure for inducing the formation of new cracks. The maximum horizontal principal stress, the minimum horizontal principal stress, the overburden pressure and the tensile strength are all basic parameters.

[0101] Based on the above basic parameters, the rupture pressure threshold can be obtained in a variety of ways, including experiments, formula calculations, and empirical estimates.

[0102] When there are neither natural fractures nor artificial fractures in the formation around the injection well, and water is continuously injected at an injection pressure close to or higher than the formation fracture pressure, an induced layer along the maximum horizontal principal stress will be formed around the injection well.

[0103] The second formation mechanism of water injection-induced fractures is the formation of new fractures in the fractured rock formation. The new fractures not only affect the stability of the rock formation, but also may become channels for fluid flow, which has an important impact on the development and utilization of underground resources.

[0104] S205. Obtain a water injection-induced fracture pressure threshold under a mixed mechanism according to the fracture distribution index, the activation pressure threshold, and the fracture pressure threshold.

[0105] In this embodiment, the water injection-induced fracture pressure threshold under the hybrid mechanism is directly linked to the activation pressure threshold and the fracture pressure threshold, thereby avoiding the manual division of equivalent regions and sensitive parameter tables.

[0106] In this embodiment, according to the fracture distribution index, the activation pressure threshold and the fracture pressure threshold, the water injection-induced fracture pressure threshold under the hybrid mechanism can be obtained by a variety of methods, including experiments, formula calculations and empirical estimation.

[0107] S206. Obtain equivalent permeability according to the water injection-induced fracture pressure threshold under the mixed mechanism.

[0108] In this embodiment, according to the water injection-induced fracture pressure threshold under the hybrid mechanism, the equivalent permeability can be obtained by a variety of methods, including experiments, formula calculations, and empirical estimates.

[0109] After water injection-induced fractures are formed, a high permeability fracture zone is usually created in the formation. The presence of these fracture zones allows fluids (such as water or oil) to pass through more easily, which increases the permeability of the formation and makes the fluid flow more smoothly within the fracture zone.

[0110] During oil field development, such highly permeable fracture zones may form between oil wells and water wells. Fracture zones formed during water injection may connect oil wells and water wells, causing the injected water to push oil molecules more effectively or causing the interaction between water and oil to be more significant.

[0111] Equivalent permeability is a parameter used to describe the effect of fractures on the overall permeability of the formation. In areas where water injection induces fractures, the presence of these fractures will change the overall permeability of the formation. An equivalent permeability modification function is established, which calculates the permeability change of the entire area based on the number, direction, size and distribution of fractures.

[0112] S207. Predict fracture dynamics based on equivalent permeability.

[0113] In this embodiment, the effect of S207 is similar to the effect of S104 in the previous embodiment of the present invention, and will not be described in detail here.

[0114] Based on the numerical simulation method for predicting water injection-induced cracks provided in the first and second embodiments of the present invention, this embodiment provides a numerical simulation method for predicting water injection-induced cracks, which specifically includes the following steps:

[0115] S301. Obtain basic parameters of the study area; basic parameters include reservoir geological characteristic parameters, rock physical property parameters and fracture development conditions.

[0116] In this embodiment, the effect of S301 and the meaning of each basic parameter are similar to the effect of S201 and the definition of each basic parameter in the previous embodiment of the present invention, and will not be repeated here.

[0117] S302. Obtain a crack distribution index according to the crack density.

[0118] In this embodiment, the definition of the crack distribution index in S302 and the effect of the index are similar to the definition of the crack distribution index in S202 in the previous embodiment of the present invention and the effect of the index, and will not be repeated here.

[0119] S303, obtaining an activation pressure threshold according to the Poisson's ratio, the overburden pressure, the formation pressure, the maximum horizontal principal stress, the minimum horizontal principal stress and the fracture inclination.

[0120] In this embodiment, the meanings of the Poisson's ratio, overburden pressure, formation pressure, maximum horizontal principal stress, minimum horizontal principal stress, fracture inclination and activation pressure threshold in S303, the method for obtaining the activation pressure threshold and the corresponding effects are similar to the meanings of the Poisson's ratio, overburden pressure, formation pressure, maximum horizontal principal stress, minimum horizontal principal stress, fracture inclination and activation pressure threshold in S203 in the previous embodiment of the present invention, the method for obtaining the activation pressure threshold and the corresponding effects, and are not repeated here.

[0121] S304, obtaining a fracture pressure threshold according to the maximum horizontal principal stress, the minimum horizontal principal stress, the overburden stratum pressure and the tensile strength.

[0122] In this embodiment, the meanings of the maximum horizontal principal stress, the minimum horizontal principal stress, the overburden pressure, the tensile strength and the fracture pressure threshold in S304, the method for obtaining the fracture pressure threshold and the corresponding effects are similar to the meanings of the maximum horizontal principal stress, the minimum horizontal principal stress, the overburden pressure, the tensile strength and the fracture pressure threshold in S204 in the previous embodiment of the present invention, the method for obtaining the fracture pressure threshold and the corresponding effects, and are not repeated here.

[0123] S305. Obtain a water injection-induced fracture pressure threshold under a mixed mechanism according to the fracture distribution index, the activation pressure threshold, and the fracture pressure threshold.

[0124] Optionally, in this embodiment, the pressure threshold formula is used to obtain the water injection-induced fracture pressure threshold under the mixed mechanism according to the fracture distribution index, the activation pressure threshold and the fracture pressure threshold; the pressure threshold formula is:

[0125] p s =(A f p i +(1-A f ) f ) 1-cosγ

[0126] Among them, p s is the pressure threshold of water injection-induced fractures under the mixed mechanism, A f is the crack distribution index, p i is the activation pressure threshold, p f is the fracture pressure threshold, and γ is the angle between the main flow line and the maximum horizontal principal stress. This formula reflects that in formations with the same fracture development state, water injection-induced fractures are more likely to form between injection wells and production wells.

[0127] In this embodiment, a specific calculation formula is provided to directly link the water injection-induced fracture pressure threshold under the hybrid mechanism with the activation pressure threshold and the fracture pressure threshold, thereby avoiding the manual division of equivalent areas and sensitive parameter tables.

[0128] During water flooding development, the rock mechanical parameters and geostress field of the reservoir are constantly changing, resulting in changes in the formation conditions of water injection-induced fractures, which is the third formation mechanism of water injection-induced fractures. During the water injection process, the reservoir properties change, and the speed of water injection-induced fracture formation gradually accelerates. When the formation pressure is greater than the threshold pressure of water injection-induced fractures, the reservoir permeability here is updated, thereby achieving the effect of reservoir property change.

[0129] For the crack distribution index A f Specifically, when there are no natural cracks and hydraulic cracks, A f is 0; the higher the degree of development of natural fractures or hydraulic fractures, the higher the f The closer the value is to 1; in areas where hydraulic fracturing is carried out, A f The value of is 1.

[0130] S306. Obtain equivalent permeability according to the water injection-induced fracture pressure threshold under the mixed mechanism.

[0131] In this embodiment, the meaning, function and method of obtaining the equivalent permeability in S306 are similar to those of S206 in the previous embodiment of the present invention, and will not be repeated here.

[0132] S307. Predict fracture dynamics based on equivalent permeability.

[0133] In this embodiment, the effect of S307 is similar to the effect of S207 in the previous embodiment of the present invention, and will not be described in detail here.

[0134] Based on the numerical simulation method for predicting water injection-induced cracks provided in the previous embodiment of the present invention, this embodiment provides a numerical simulation method for predicting water injection-induced cracks, which specifically includes the following steps:

[0135] S401. Obtain basic parameters of the study area; basic parameters include reservoir geological characteristic parameters, rock physical property parameters and fracture development.

[0136] In this embodiment, the effect of S401 and the meaning of each basic parameter are similar to the effect of S301 and the definition of each basic parameter in the previous embodiment of the present invention, and are not repeated here.

[0137] S402. Obtain a crack distribution index according to the crack density.

[0138] In this embodiment, the definition of the crack distribution index in S402 and the effect of the index are similar to the definition of the crack distribution index in S302 in the previous embodiment of the present invention and the effect of the index, and are not repeated here.

[0139] S403, obtaining an activation pressure threshold according to the Poisson's ratio, the overburden pressure, the formation pressure, the maximum horizontal principal stress, the minimum horizontal principal stress and the fracture inclination.

[0140] In this embodiment, the meanings of the Poisson's ratio, overburden pressure, formation pressure, maximum horizontal principal stress, minimum horizontal principal stress, fracture inclination and activation pressure threshold in S403, the method for obtaining the activation pressure threshold and the corresponding effects are similar to the meanings of the Poisson's ratio, overburden pressure, formation pressure, maximum horizontal principal stress, minimum horizontal principal stress, fracture inclination and activation pressure threshold in S303 in the previous embodiment of the present invention, and are not repeated here.

[0141] S404, obtaining a fracture pressure threshold according to the maximum horizontal principal stress, the minimum horizontal principal stress, the overburden stratum pressure and the tensile strength.

[0142] In this embodiment, the meanings of the maximum horizontal principal stress, the minimum horizontal principal stress, the overburden pressure, the tensile strength and the fracture pressure threshold in S404, the method for obtaining the fracture pressure threshold and the corresponding effects are similar to the meanings of the maximum horizontal principal stress, the minimum horizontal principal stress, the overburden pressure, the tensile strength and the fracture pressure threshold in S304 in the previous embodiment of the present invention, and are not repeated here.

[0143] S405. Obtain a water injection-induced fracture pressure threshold under a mixed mechanism according to the fracture distribution index, the activation pressure threshold, and the fracture pressure threshold.

[0144] In this embodiment, the method of obtaining the water injection induced fracture pressure threshold under the hybrid mechanism and the corresponding effect in S405 are similar to the method of obtaining the water injection induced fracture pressure threshold under the hybrid mechanism and the corresponding effect in S305 in the previous embodiment of the present invention, and will not be repeated here.

[0145] S406. Obtain equivalent permeability according to the water injection-induced fracture pressure threshold under the mixed mechanism.

[0146] Optionally, in this embodiment, an equivalent permeability modification function is used to obtain an equivalent permeability according to the water injection-induced fracture pressure threshold under the hybrid mechanism; the equivalent permeability modification function is:

[0147]

[0148] Among them, K f (p) is the equivalent permeability, K i is the initial permeability, c1 is the preset dimensionless parameter, c2 is the preset dimensionless parameter, p is the formation pressure, p s is the pressure threshold of water injection-induced fractures under the mixed mechanism.

[0149] In this embodiment, the values ​​of c1 and c2 are determined by experiments.

[0150] In this embodiment, a specific calculation formula is provided to link the water injection-induced fracture pressure threshold under the mixed mechanism with the equivalent permeability, and the fracture dynamics are predicted by updating the equivalent permeability, which has good repeatability.

[0151] During the water injection process, the formation pressure will continue to change. As the formation pressure changes, the equivalent permeability will continue to change, thereby updating the equivalent permeability distribution.

[0152] S407. Predict fracture dynamics based on equivalent permeability.

[0153] In this embodiment, the effect of S407 is similar to the effect of S307 in the previous embodiment of the present invention, and will not be described in detail here.

[0154] Figure 2 Schematic diagram of the numerical simulation method for predicting water injection-induced fractures provided in the embodiment of the present application Figure 2 .like Figure 2 As shown, the numerical simulation method for predicting water injection-induced cracks provided in this embodiment is a further refinement of the numerical simulation method for predicting water injection-induced cracks provided in the previous embodiment of the present invention. The numerical simulation method for predicting water injection-induced cracks provided in this embodiment includes the following steps:

[0155] S501. Obtain basic parameters of the study area; basic parameters include reservoir geological characteristic parameters, rock physical property parameters and fracture development conditions.

[0156] In this embodiment, the effect of S501 and the meaning of each basic parameter are similar to the effect of S401 and the definition of each basic parameter in the previous embodiment of the present invention, and will not be repeated here.

[0157] S502. Obtain a crack distribution index according to the crack density.

[0158] Optionally, in this embodiment, a crack density field map is obtained according to the crack density by using the Kriging interpolation method; the crack density field map is normalized to obtain a crack distribution index.

[0159] In this embodiment, the definition of the crack distribution index in S502 and the effect of the index are similar to the definition of the crack distribution index in S402 in the previous embodiment of the present invention and the effect of the index, and will not be repeated here.

[0160] S503, obtaining an activation pressure threshold according to the Poisson's ratio, the overburden pressure, the formation pressure, the maximum horizontal principal stress, the minimum horizontal principal stress and the fracture inclination.

[0161] Optionally, in this embodiment, the activation pressure threshold is obtained by using the activation pressure formula according to Poisson's ratio, overburden pressure, formation pressure, maximum horizontal principal stress, minimum horizontal principal stress and fracture inclination; the activation pressure formula is:

[0162]

[0163] Among them, p i is the activation pressure threshold, v is the Poisson's ratio, p o is the overburden pressure, p p is the formation pressure, σ H is the maximum horizontal principal stress, σ his the minimum horizontal principal stress, θ is the crack inclination, and β is the angle between the maximum horizontal principal stress direction and the crack direction.

[0164] In this embodiment, the meanings and corresponding effects of Poisson's ratio, overburden pressure, formation pressure, maximum horizontal principal stress, minimum horizontal principal stress, fracture inclination and activation pressure threshold in S503 are similar to the meanings and corresponding effects of Poisson's ratio, overburden pressure, formation pressure, maximum horizontal principal stress, minimum horizontal principal stress, fracture inclination and activation pressure threshold in S403 in the previous embodiment of the present invention, and are not repeated here.

[0165] S504, obtaining a fracture pressure threshold according to the maximum horizontal principal stress, the minimum horizontal principal stress, the overburden stratum pressure and the tensile strength.

[0166] Optionally, in this embodiment, the fracture pressure threshold is obtained by using the fracture pressure formula according to the maximum horizontal principal stress, the minimum horizontal principal stress, the overburden pressure and the tensile strength; the fracture pressure formula is:

[0167] p f =3σ h -σ H +σ f -p o

[0168] Among them, p f is the rupture pressure threshold, σ h is the minimum horizontal principal stress, σ H is the maximum horizontal principal stress, p o is the overburden pressure, σ f For tensile strength.

[0169] In this embodiment, the meanings and corresponding effects of the maximum horizontal principal stress, minimum horizontal principal stress, overburden pressure, tensile strength and fracture pressure threshold in S504 are similar to the meanings and corresponding effects of the maximum horizontal principal stress, minimum horizontal principal stress, overburden pressure, tensile strength and fracture pressure threshold in S404 in the previous embodiment of the present invention, and are not repeated here.

[0170] S505. Obtain a water injection-induced fracture pressure threshold under a mixed mechanism according to the fracture distribution index, the activation pressure threshold, and the fracture pressure threshold.

[0171] In this embodiment, the method of obtaining the water injection induced fracture pressure threshold under the hybrid mechanism and the corresponding effect in S505 are similar to the method of obtaining the water injection induced fracture pressure threshold under the hybrid mechanism and the corresponding effect in S405 in the previous embodiment of the present invention, and will not be repeated here.

[0172] S506. Obtain equivalent permeability according to the water injection-induced fracture pressure threshold under the mixed mechanism.

[0173] In this embodiment, the method of obtaining the equivalent permeability in S506 and the corresponding effect are similar to the method of obtaining the equivalent permeability in S406 in the previous embodiment of the present invention and the corresponding effect, and will not be repeated here.

[0174] S507. Predict fracture dynamics based on equivalent permeability.

[0175] In this embodiment, the effect of S507 is similar to the effect of S407 in the previous embodiment of the present invention, and will not be described in detail here.

[0176] First, a geological model of the study area is established, the injection and production parameters of the wells are set, and then a numerical simulation of water injection-induced fracture prediction is performed. The geological model is designed to describe the geological structure and physical characteristics of the study area and input relevant parameters for numerical simulation.

[0177] Taking the Triassic Yanchang Formation Chang 6 in the Heshui area as an example, the practicality of the present invention in simulating the dynamic expansion of water injection-induced fractures was verified. The oil field is located in the southwest of the Ordos Basin. The original formation pressure in the well area is 14.5MPa, and it has the characteristics of natural fractures in the northeast 70° direction. The maximum horizontal principal stress is 36MPa, the minimum horizontal principal stress is 28MPa, the overburden pressure is 21MPa, the maximum horizontal principal stress direction is NEE-SWW, the Poisson's ratio is 0.25, and the initial average permeability is 3.6×10 -3 μm 2 The development well pattern is a five-point mixed vertical and horizontal well pattern. This experiment simulates the dynamic characteristics of water injection-induced fractures under the condition of periodic asynchronous injection and production. The two unit production wells used for simulation are already in the high water content stage, and long-term water injection under conditions close to the fracture pressure has led to the formation of water injection-induced fractures in the area.

[0178] According to step S503, the natural fracture activation pressure (p i ) is 29.8MPa, and the rupture pressure (p f ) is 37MPa, the crack distribution index (A f ) is between 0 and 1. 20 cycles of numerical simulation were performed, during which the reservoir equivalent permeability was updated according to step S506.

[0179] Through simulation experiments, it can be found that in the surrounding areas of two unit production wells in the high water content stage, the water injection-induced fracture pressure threshold is low, and as the distance from the two unit production wells increases, the water injection-induced fracture pressure threshold in the area gradually increases. It can be concluded that in the surrounding areas of the two unit production wells in the high water content stage, water injection operations are more likely to induce fractures; the difficulty of water injection-induced fractures will increase with the increase of the distance from the two unit production wells, that is, in the areas far away from the two unit production wells, greater pressure needs to be applied to induce fractures. Therefore, the above conclusions are of great significance for the optimization and risk assessment of water injection operations. When performing water injection operations in the area near the production wells in the high water content stage, special attention should be paid to the risk of low water injection-induced fracture pressure threshold; and in the areas far away from the production wells in the high water content stage, higher pressure requirements need to be considered.

[0180] When conducting experimental observations on the hypertonic area, focus on monitoring the hypertonic area distribution map every 5 cycles to obtain more accurate data. Figure 3 This is a high permeability area distribution diagram of the 10th cycle of the numerical simulation method for predicting water injection-induced fractures provided in an embodiment of the present application, Figure 4 The distribution map of high permeability areas in the 20th cycle of the numerical simulation method for predicting water injection-induced fractures provided in the embodiment of the present application. The experimental results clearly show that the permeability around the injection-production flow line is significantly higher than that in other areas, which indicates that water injection-induced fractures are more likely to form near the injection-production flow line; the permeability characteristics of the high permeability area of ​​water injection-induced fractures have obvious directionality, which is the same as the direction of the maximum horizontal principal stress. During the long-term water injection process, interconnected channels will gradually form between water injection-induced fractures and hydraulic fractures. If these cracks are directly connected to the water injection well, water channeling may occur, thereby affecting the efficiency and safety of the water injection operation. Therefore, when designing and implementing water injection operations, the directionality and permeability of the fractures should be fully considered to optimize the water injection strategy and reduce the risk of water channeling.

[0181] The numerical simulation method for predicting water injection-induced fractures provided in this embodiment includes: obtaining basic parameters of the study area, the basic parameters including reservoir geological characteristic parameters, rock physical parameters and fracture development; obtaining a fracture distribution index according to fracture density; obtaining an activation pressure threshold according to Poisson's ratio, overburden pressure, formation pressure, maximum horizontal principal stress, minimum horizontal principal stress and fracture inclination; obtaining a fracture pressure threshold according to maximum horizontal principal stress, minimum horizontal principal stress, overburden pressure and tensile strength; obtaining a water injection-induced fracture pressure threshold under a mixed mechanism according to the fracture distribution index, the activation pressure threshold and the fracture pressure threshold; and obtaining a fracture dynamic prediction according to the water injection-induced fracture pressure threshold under the mixed mechanism. Based on the above method, the following effects are achieved: a numerical simulation method for predicting the dynamic expansion of water injection-induced fractures is studied, and the influence of water injection-induced fractures is considered in scheme design and parameter optimization, which provides an effective adjustment method for the development of fractured tight oil reservoirs in the later stage, guides the control of moderate expansion of water injection-induced fractures, improves oil recovery efficiency, and guides the further exploitation of remaining oil; basic parameters and fracture distribution index are used as variable inputs to obtain equivalent permeability, and the distribution of induced fractures is updated by equivalent permeability, avoiding inaccurate results that may occur due to human control; considering the influence of streamlines, it is suitable for a variety of well networks and different production conditions, with a wide range of applications and easy to use; the pressure-sensitive formula of equivalent permeability is directly linked to the pressure threshold, thereby avoiding the manual division of equivalent areas and sensitive parameter tables; according to the natural fracture activation pressure and the new fracture rupture pressure, the water injection-induced fracture pressure threshold under the mixed mechanism is calculated, and a parameter sensitivity table related to the pressure threshold is constructed, which realizes the prediction of water injection-induced fractures and reservoir parameter modification in different well networks, injection-production conditions and formation conditions, and the required parameters are simple and easy to obtain, with strong versatility.

[0182] The embodiment of the present invention can divide the electronic device or the main control device into functional modules according to the above method example. For example, each functional module can be divided according to each function, or two or more functions can be integrated into one processing unit. The above integrated unit can be implemented in the form of hardware or in the form of software functional modules. It should be noted that the division of modules in the embodiment of the present invention is schematic and is only a logical function division. There may be other division methods in actual implementation.

[0183] Figure 5 This is a schematic diagram of the structure of a numerical simulation device for predicting water injection-induced cracks provided in an embodiment of the present application. Figure 5 As shown, in this embodiment, the numerical simulation device 500 for predicting water injection-induced cracks can be located in an electronic device. The numerical simulation device 500 for predicting water injection-induced cracks includes:

[0184] Basic parameter acquisition module 501: used to obtain basic parameters of the study area; basic parameters include reservoir geological characteristic parameters, rock physical parameters and fracture development conditions;

[0185] The crack distribution index acquisition module 502 is used to obtain the crack distribution index according to the crack density;

[0186] Equivalent permeability acquisition module 503: used to obtain equivalent permeability according to reservoir geological characteristic parameters, rock physical parameters, fracture development and fracture distribution index;

[0187] Dynamic prediction module 504: used to perform dynamic prediction of fractures according to equivalent permeability.

[0188] The numerical simulation device for predicting water injection-induced fractures provided in this embodiment can be executed Figure 1 The technical solution of the numerical simulation method embodiment of water injection induced fracture prediction shown in the figure has the same implementation principle and technical effect as Figure 1 The embodiments of the numerical simulation method for predicting water injection-induced fractures are similar and will not be described in detail here.

[0189] Meanwhile, the numerical simulation device for predicting water injection-induced fractures provided by the present invention further refines the numerical simulation device for predicting water injection-induced fractures 500 based on the numerical simulation device for predicting water injection-induced fractures provided by the previous embodiment.

[0190] Optionally, in this embodiment, the reservoir geological characteristic parameters, rock physical parameters and fracture development conditions in the basic parameter acquisition module 501 include:

[0191] The reservoir geological characteristic parameters include the maximum horizontal principal stress, the minimum horizontal principal stress, the overburden rock pressure and the formation pressure; the rock physical property parameters include Poisson's ratio and tensile strength; the fracture development conditions include the fracture dip angle.

[0192] Optionally, in this embodiment, the crack distribution index acquisition module 502 is specifically used for:

[0193] According to the crack density, the crack density field map is obtained by Kriging interpolation method;

[0194] The crack density field map is normalized to obtain the crack distribution index.

[0195] Optionally, in this embodiment, the equivalent permeability acquisition module 503 is specifically used for:

[0196] The activation pressure threshold is obtained according to Poisson's ratio, overburden pressure, formation pressure, maximum horizontal principal stress, minimum horizontal principal stress and fracture inclination;

[0197] The fracture pressure threshold is obtained according to the maximum horizontal principal stress, the minimum horizontal principal stress, the overburden pressure and the tensile strength;

[0198] The water injection-induced fracture pressure threshold under the mixed mechanism is obtained according to the fracture distribution index, activation pressure threshold and fracture pressure threshold.

[0199] The equivalent permeability is obtained according to the pressure threshold of water injection-induced fractures under the mixed mechanism.

[0200] Optionally, when the equivalent permeability acquisition module 503 obtains the activation pressure threshold according to the Poisson's ratio, the overburden pressure, the formation pressure, the maximum horizontal principal stress, the minimum horizontal principal stress and the fracture inclination, the activation pressure threshold is obtained according to the activation pressure formula based on the Poisson's ratio, the overburden pressure, the formation pressure, the maximum horizontal principal stress, the minimum horizontal principal stress and the fracture inclination; the activation pressure formula is:

[0201]

[0202] Among them, p i is the activation pressure threshold, v is the Poisson's ratio, p o is the overburden pressure, p p is the formation pressure, σ H is the maximum horizontal principal stress, σ h is the minimum horizontal principal stress, θ is the crack inclination, and β is the angle between the maximum horizontal principal stress direction and the crack direction.

[0203] Optionally, when the equivalent permeability acquisition module 503 obtains the fracture pressure threshold according to the maximum horizontal principal stress, the minimum horizontal principal stress, the overburden pressure and the tensile strength, the fracture pressure threshold is obtained according to the maximum horizontal principal stress, the minimum horizontal principal stress, the overburden pressure and the tensile strength through the fracture pressure formula; the fracture pressure formula is:

[0204] p f =3σ h -σ H +σ f -p o

[0205] Among them, p f is the rupture pressure threshold, σ h is the minimum horizontal principal stress, σ H is the maximum horizontal principal stress, p o is the overburden pressure, σ f For tensile strength.

[0206] Optionally, when the equivalent permeability acquisition module 503 obtains the water injection induced fracture pressure threshold under the hybrid mechanism according to the fracture distribution index, the activation pressure threshold and the fracture pressure threshold, the water injection induced fracture pressure threshold under the hybrid mechanism is obtained according to the fracture distribution index, the activation pressure threshold and the fracture pressure threshold through a pressure threshold formula; the pressure threshold formula is:

[0207] p s =(A f p i +(1-A f ) f ) 1-cosγ

[0208] Among them, p s is the pressure threshold of water injection-induced fractures under the mixed mechanism, A f is the crack distribution index, p i is the activation pressure threshold, p f is the rupture pressure threshold, and γ is the angle between the main flow line and the maximum horizontal principal stress.

[0209] Optionally, when obtaining the equivalent permeability according to the water injection induced fracture pressure threshold under the hybrid mechanism, the equivalent permeability acquisition module 503 obtains the equivalent permeability according to the water injection induced fracture pressure threshold under the hybrid mechanism through an equivalent permeability modification function; the equivalent permeability modification function is:

[0210]

[0211] Among them, K f (p) is the equivalent permeability, K i is the initial permeability, c1 is the preset dimensionless parameter, c2 is the preset dimensionless parameter, p is the formation pressure, p s is the pressure threshold of water injection-induced fractures under the mixed mechanism.

[0212] The numerical simulation device for predicting water injection-induced fractures provided in this embodiment can be executed Figure 1 and Figure 2 The technical solution of the numerical simulation method embodiment of water injection induced fracture prediction shown in the figure has the same implementation principle and technical effect as Figure 1 and Figure 2 The numerical simulation method for predicting water injection-induced fractures shown in the embodiment is similar and will not be described in detail here.

[0213] According to an embodiment of the present invention, the present invention also provides a numerical simulation electronic device for water injection induced fracture prediction, a computer readable storage medium and a computer program product.

[0214] Figure 6A schematic diagram of the structure of an electronic device provided in an embodiment of the present application. The electronic device for numerical simulation of water injection induced fracture prediction is intended to be used for various electronic devices that can perform the numerical simulation method for water injection induced fracture prediction, such as microcomputers, single chip microcomputers and other suitable computers. The components shown herein, their connections and relationships, and their functions are merely examples and are not intended to limit the implementation of the present invention described and / or claimed herein.

[0215] like Figure 6 As shown, the electronic device 60 includes: at least one processor 601 and a memory 602. The electronic device 60 also includes a communication component 603. The processor 601, the memory 602 and the communication component 603 are connected via a bus 604.

[0216] In a specific implementation process, at least one processor 601 executes the computer execution instructions stored in the memory 602, so that at least one processor 601 executes the numerical simulation method for water injection induced fracture prediction executed by the electronic device side as above.

[0217] The specific implementation process of the processor 601 can refer to the above-mentioned embodiment of the numerical simulation method for predicting water injection-induced fractures. The implementation principle and technical effect are similar, and this embodiment will not be repeated here.

[0218] In the above embodiment, it should be understood that the processor 601 can be a central processing unit (CPU), or other general-purpose processors, digital signal processors (DSP), application-specific integrated circuits (ASIC), etc. The general-purpose processor 601 can be a microprocessor or any conventional processor, etc. The steps of the method disclosed in the invention can be directly embodied as being executed by a hardware processor, or can be executed by a combination of hardware and software modules in the processor.

[0219] The memory 602 may include a high-speed RAM memory, and may also include a non-volatile storage NVM, such as at least one disk storage.

[0220] The bus 604 may be an Industry Standard Architecture (ISA) bus, a Peripheral Component Interconnect (PCI) bus, or an Extended Industry Standard Architecture (EISA) bus, etc. The bus 604 may be divided into an address bus, a data bus, a control bus, etc. For ease of representation, the bus 604 in the drawings of the present application is not limited to only one bus or one type of bus.

[0221] The above-mentioned functions implemented by the electronic device and the main control device introduce the scheme provided by the embodiment of the present invention. It can be understood that in order to implement the above-mentioned functions, the electronic device or the main control device includes a hardware structure and / or software module corresponding to the execution of each function. In combination with the units and algorithm steps of each example described in the embodiment disclosed in the embodiment of the present invention, the embodiment of the present invention can be implemented in the form of hardware or a combination of hardware and computer software. Whether a function is executed in the form of hardware or computer software driving hardware depends on the specific application and design constraints of the technical solution. Those skilled in the art can use different methods to implement the described functions for each specific application, but such implementation should not be considered to exceed the scope of the technical solution of the embodiment of the present invention.

[0222] The present application also provides a computer-readable storage medium, in which computer-executable instructions are stored. When a processor executes the computer-executable instructions, the numerical simulation method for predicting water injection-induced fractures as described above is implemented.

[0223] The computer-readable storage medium mentioned above can be implemented by any type of volatile or non-volatile storage device or a combination thereof, such as static random access memory (SRAM), electrically erasable programmable read-only memory (EEPROM), erasable programmable read-only memory (EPROM), programmable read-only memory (PROM), read-only memory (ROM), magnetic memory, flash memory, magnetic disk or optical disk. The readable storage medium can be any available medium that can be accessed by a general or special-purpose computer.

[0224] An exemplary readable storage medium is coupled to a processor so that the processor can read information from the readable storage medium and write information to the readable storage medium. The readable storage medium can also be a component of the processor. The processor and the readable storage medium can be located in an application specific integrated circuit (ASIC). The processor and the readable storage medium can also exist as discrete components in an electronic device or a main control device.

[0225] The memory 602 is a non-transient computer-readable storage medium provided by the present invention. The non-transient computer-readable storage medium of the present invention stores computer instructions, which are used to enable a computer to execute the numerical simulation method for water injection-induced fracture prediction provided by the present invention.

[0226] The memory 602 is a non-transient computer-readable storage medium that can be used to store non-transient software programs, non-transient computer executable programs and modules, such as program instructions / modules corresponding to the numerical simulation method for water injection-induced fracture prediction in an embodiment of the present invention (for example, Figure 5 The processor 601 executes various functional applications and data processing by running the non-transient software programs, instructions and modules stored in the memory 602, that is, the numerical simulation method for water injection induced fracture prediction in the above method embodiment is implemented.

[0227] At the same time, this embodiment also provides a computer program product. When the instructions in the computer program product are executed by a processor, the numerical simulation method for predicting water injection-induced fractures of the above embodiment can be executed.

[0228] Those skilled in the art will readily appreciate other implementations of the embodiments of the present invention after considering the specification and practicing the invention disclosed herein. The present invention is intended to cover any variations, uses, or adaptations of the embodiments of the present invention that follow the general principles of the embodiments of the present invention and include common knowledge or customary technical means in the art that are not disclosed in the embodiments of the present invention. The specification and examples are to be regarded as exemplary only, and the true scope and spirit of the embodiments of the present invention are indicated by the claims.

[0229] It should be understood that the embodiments of the present invention are not limited to the precise structures described above and shown in the drawings, and various modifications and changes may be made without departing from the scope thereof. The scope of the embodiments of the present invention is limited only by the appended claims.

Claims

1. A numerical simulation method for predicting water injection-induced fractures, characterized in that: include: Obtaining basic parameters of the study area; the basic parameters include reservoir geological characteristic parameters, rock physical parameters and fracture development; The crack distribution index is obtained according to the crack density; Obtaining equivalent permeability according to the reservoir geological characteristic parameters, the rock physical property parameters, the fracture development conditions and the fracture distribution index; The fracture dynamics are predicted based on the equivalent permeability.

2. The numerical simulation method for predicting water injection-induced cracks according to claim 1, characterized in that: The reservoir geological characteristic parameters include maximum horizontal principal stress, minimum horizontal principal stress, overburden stratum pressure and formation pressure; The rock physical parameters include Poisson's ratio and tensile strength; The fracture development conditions include fracture inclination angles.

3. The numerical simulation method for predicting water injection-induced cracks according to claim 2, characterized in that: The obtaining of equivalent permeability according to the reservoir geological characteristic parameters, the rock physical property parameters, the fracture development conditions and the fracture distribution index comprises: Obtaining an activation pressure threshold according to the Poisson's ratio, the overburden pressure, the formation pressure, the maximum horizontal principal stress, the minimum horizontal principal stress and the fracture dip; Obtaining a fracture pressure threshold according to the maximum horizontal principal stress, the minimum horizontal principal stress, the overburden formation pressure and the tensile strength; Obtaining a water injection-induced fracture pressure threshold under a mixed mechanism according to the fracture distribution index, the activation pressure threshold and the fracturing pressure threshold; The equivalent permeability is obtained according to the water injection induced fracture pressure threshold under the mixed mechanism.

4. The numerical simulation method for predicting water injection-induced fractures according to claim 3, characterized in that: The step of obtaining the water injection induced fracture pressure threshold under the mixed mechanism according to the fracture distribution index, the activation pressure threshold and the fracturing pressure threshold comprises: The pressure threshold formula is used to obtain the water injection-induced fracture pressure threshold under the mixed mechanism according to the fracture distribution index, the activation pressure threshold and the fracture pressure threshold. The pressure threshold formula is: p s =(A f p i +(1-A f )p f )e 1-cosγ Among them, the p s is the water injection induced fracture pressure threshold under the mixed mechanism, and the A f is the crack distribution index, the p i is the activation pressure threshold, the p f is the rupture pressure threshold, and γ is the angle between the main flow line and the maximum horizontal principal stress.

5. The numerical simulation method for predicting water injection-induced fractures according to claim 4, characterized in that: The obtaining of the equivalent permeability according to the water injection induced fracture pressure threshold under the mixed mechanism comprises: The equivalent permeability is obtained by using an equivalent permeability modification function according to the water injection induced fracture pressure threshold under the mixed mechanism; the equivalent permeability modification function is: Among them, the K f (p) is the equivalent permeability, and K i is the initial permeability, c1 is a preset dimensionless parameter, c2 is a preset dimensionless parameter, p is the formation pressure, and p s is the pressure threshold of water injection-induced fractures under the hybrid mechanism.

6. The numerical simulation method for predicting water injection-induced cracks according to claim 1, characterized in that: The method of obtaining the crack distribution index according to the crack density includes: According to the crack density, a crack density field map is obtained by using a Kriging interpolation method; The crack density field map is normalized to obtain the crack distribution index.

7. The numerical simulation method for predicting water injection-induced fractures according to claim 3, characterized in that: The obtaining of the activation pressure threshold according to the Poisson's ratio, the overburden pressure, the formation pressure, the maximum horizontal principal stress, the minimum horizontal principal stress and the fracture dip angle comprises: The activation pressure threshold is obtained by the activation pressure formula according to the Poisson's ratio, the overburden pressure, the formation pressure, the maximum horizontal principal stress, the minimum horizontal principal stress and the fracture dip angle; the activation pressure formula is: Among them, the p i is the activation pressure threshold, v is the Poisson's ratio, and p o is the overburden pressure, the p p is the formation pressure, the σ H is the maximum horizontal principal stress, the σ h is the minimum horizontal principal stress, θ is the crack inclination, and β is the angle between the maximum horizontal principal stress direction and the crack direction.

8. The numerical simulation method for predicting water injection-induced fractures according to claim 3, characterized in that: The obtaining of the fracture pressure threshold according to the maximum horizontal principal stress, the minimum horizontal principal stress, the overburden formation pressure and the tensile strength comprises: The fracture pressure threshold is obtained by using the fracture pressure formula according to the maximum horizontal principal stress, the minimum horizontal principal stress, the overburden pressure and the tensile strength; the fracture pressure formula is: p f =3σ h -s H +s f -p o Among them, the p f is the rupture pressure threshold, the σ h is the minimum horizontal principal stress, the σ H is the maximum horizontal principal stress, the p o is the overburden pressure, the σ f is the tensile strength.

9. A numerical simulation device for predicting water injection-induced fractures, characterized in that: include: A basic parameter acquisition module is used to obtain basic parameters of the study area; the basic parameters include reservoir geological characteristic parameters, rock physical parameters and fracture development conditions; A crack distribution index acquisition module, used to obtain the crack distribution index according to the crack density; An equivalent permeability acquisition module, used to obtain the equivalent permeability according to the reservoir geological characteristic parameters, the rock physical property parameters, the fracture development conditions and the fracture distribution index; The dynamic prediction module is used to perform dynamic prediction of fractures according to the equivalent permeability.

10. An electronic device, characterized in that: include: A processor, and a memory communicatively connected to the processor; The memory stores computer-executable instructions; The processor executes the computer-executable instructions stored in the memory to implement the numerical simulation method for predicting water injection-induced fractures according to any one of claims 1 to 8.

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