Four-dimensional ground stress simulation method and system for rock mechanical property change

Abstract

The invention provides a four-dimensional ground stress simulation method and system for rock mechanical property changes. The simulation method comprises the steps that S1, a fine reservoir geologic model, a geomechanical model and a natural fracture model are established; s2, ground stress simulation is carried out, and a ground stress model is established; s3, fracturing simulation is carried out, and an artificial hydraulic fracture network model is established; s4, acquiring mechanical properties of the fractured rock; s5, establishing a combined fracture network model after fracturing; s6, oil reservoir flow simulation is carried out, and fluid distribution and pressure distribution after fracturing are simulated; and S7, carrying out four-dimensional crustal stress simulation considering the mechanical property change of the fractured rock. According to the method, the mechanical property change after the rock is broken and the interaction between the matrix rock and the artificial hydraulic seam are considered, so that the rock crustal stress simulation is comprehensively considered, and the depicting precision of the inter-well seam net is improved.

Description

Technical Field

[0001] The invention relates to the technical field of reservoir numerical simulation, and in particular to a four-dimensional geostress simulation method and system for rock mechanical property changes. Background Art

[0002] Numerical reservoir simulation is an important technology in petroleum engineering and one of the core technologies for the integrated development of shale oil geology and engineering. The purpose of numerical reservoir simulation is to predict the migration characteristics of the reservoir and predict the oil production and reserves of the reservoir, providing a scientific basis for oil production decisions. Numerical reservoir simulation technology includes two main aspects: one is to establish an accurate and comprehensive numerical reservoir model; the other is to solve the model equation through numerical calculation to simulate and predict the migration characteristics of the reservoir.

[0003] Fracturing technology in oil reservoir development is a technology that uses high-pressure liquid to expand and connect the fissures or natural cracks in the oil and gas reservoir to form a fracture network, so as to improve the physical properties of the oil and gas reservoir and increase the permeability and oil production capacity of the reservoir. During the fracturing process, the rock is subjected to huge pressure, which causes the mechanical properties of the rock to change, thus affecting the formation and distribution of rock cracks, crack permeability and permeability. Summary of the invention

[0004] In view of the above problems, the present invention is proposed to provide a four-dimensional geostress simulation method and system for changes in rock mechanical properties that overcome the above problems or at least partially solve the above problems.

[0005] According to one aspect of the present invention, a four-dimensional geostress simulation method for changes in rock mechanical properties is provided, the simulation method comprising:

[0006] Step S1: Establish a detailed reservoir geological model, a geomechanical model and a natural fracture model;

[0007] Step S2: Conduct geostress simulation and establish a geostress model;

[0008] Step S3: Conducting fracturing simulation and establishing an artificial hydraulic fracture network model;

[0009] Step S4: obtaining mechanical properties of rock after fracture;

[0010] Step S5: establishing a combined fracture network model after fracturing;

[0011] Step S6: conducting reservoir flow simulation to simulate fluid distribution and pressure distribution after fracturing;

[0012] Step S7: Conduct a four-dimensional geostress simulation that takes into account changes in rock mechanical properties after fracturing.

[0013] Optionally, the simulation method further includes: Step S8: Based on Step S7, conducting a fracturing simulation of the well section to be fractured, and simulating the expansion and distribution of artificial fractures.

[0014] Optionally, the step S1: establishing a detailed reservoir geological model, geomechanical model and natural fracture model specifically includes: based on actual block data, through basic geological research and reservoir numerical simulation requirements, using relevant software to establish a reservoir geological model, geomechanical model and natural fracture model.

[0015] Optionally, the step S2: conducting geostress simulation and establishing a geostress model specifically includes:

[0016] On the basis of step S1, a finite element simulation method is used to carry out a geostress simulation and establish a geostress model using a finite element simulator.

[0017] Optionally, the step S3: conducting fracturing simulation and establishing an artificial hydraulic fracture network model specifically includes:

[0018] On the basis of step S2, the fracturing process is fitted by fracturing simulation software to establish an artificial hydraulic fracture network model.

[0019] Optionally, the step S4: obtaining mechanical properties of rock after fracture specifically includes:

[0020] The mechanical parameters of rock after fracture are obtained through indoor compression test and shear test results.

[0021] Optionally, the mechanical parameters include stiffness, shear stiffness, cohesion, internal friction angle, and expansion angle.

[0022] Optionally, the step S5: establishing a combined fracture network model after fracturing specifically includes:

[0023] On the basis of step S3 and step S1, a geological model is established for finely characterizing the physical property changes after fracturing and the spatial distribution of the combined fracture network using an unstructured grid, and multiple groups of artificial hydraulic fracture network models and multiple groups of natural fracture models are characterized, so that different fracture mechanical parameters can be defined for different groups of fracture models when performing four-dimensional geostress simulation.

[0024] Optionally, the step S6: conducting reservoir flow simulation, simulating fluid distribution and pressure distribution after fracturing specifically includes:

[0025] On the basis of step S3 and step S1, a reservoir flow simulation is carried out based on a reservoir numerical simulator, the process of fracturing fluid entering the well during the fracturing process is simulated by injection method, and the fluid distribution and pressure distribution after fracturing are simulated.

[0026] Optionally, the step S7: carrying out a four-dimensional geostress simulation considering changes in rock mechanical properties after fracturing specifically includes:

[0027] On the basis of step S3, step S5 and step S6, the ground stress model is recalculated by a finite element simulator, the basic geological model after fracturing is obtained by the calculation of step 3, the combined fracture network model and rock mechanics parameter model after fracturing are obtained by the calculation of step S5, and the fluid model and reservoir pressure model after fracturing are obtained by the calculation of step S6.

[0028] The present invention also provides a four-dimensional geostress simulation system for rock mechanical property changes, using any one of the above-mentioned four-dimensional geostress simulation methods for rock mechanical property changes, the simulation system comprising:

[0029] Model building module, used to build detailed reservoir geological model, geomechanical model and natural fracture model;

[0030] The geostress model building module is used to carry out geostress simulation and build a geostress model;

[0031] Artificial hydraulic fracture network model building module, used to carry out fracturing simulation and build artificial hydraulic fracture network model;

[0032] Mechanical property acquisition module, used to obtain the mechanical properties of rock after fracture;

[0033] Fracture network model building module, used to build a combined fracture network model after fracturing;

[0034] Reservoir flow simulation module, used to carry out reservoir flow simulation and simulate fluid distribution and pressure distribution after fracturing;

[0035] The Siwei geostress simulation module is used to carry out four-dimensional geostress simulation considering the changes in rock mechanical properties after fracturing.

[0036] The present invention provides a four-dimensional geostress simulation method and system for the change of rock mechanical properties, the simulation method comprising: step S1: establishing a fine reservoir geological model, a geomechanical model and a natural fracture model; step S2: conducting geostress simulation and establishing a geostress model; step S3: conducting fracturing simulation and establishing an artificial hydraulic fracture network model; step S4: obtaining the mechanical properties of the rock after fracture; step S5: establishing a combined fracture network model after fracturing; step S6: conducting reservoir flow simulation, simulating the fluid distribution and pressure distribution after fracturing; step S7: conducting a four-dimensional geostress simulation considering the change of rock mechanical properties after fracturing. By considering the change of mechanical properties after rock fracture and the interaction between matrix rock and artificial hydraulic fractures, a comprehensive consideration of rock geostress simulation is achieved, thereby improving the accuracy of the characterization of the inter-well fracture network.

[0037] The above description is only an overview of the technical solution of the present invention. In order to more clearly understand the technical means of the present invention, it can be implemented according to the contents of the specification. In order to make the above and other purposes, features and advantages of the present invention more obvious and easy to understand, the specific implementation methods of the present invention are listed below. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other accompanying drawings can be obtained based on these accompanying drawings without paying creative work.

[0039] Figure 1 A flowchart of a four-dimensional geostress simulation method for changes in rock mechanical properties provided by an embodiment of the present invention;

[0040] Figure 2 The pre-fracturing ground stress model provided by the embodiment of the present invention - taking the minimum horizontal principal stress attribute model as an example;

[0041] Figure 3 A natural fracture model provided by an embodiment of the present invention;

[0042] Figure 4 An artificial hydraulic fracture model provided by an embodiment of the present invention;

[0043] Figure 5 A combined fracture network model provided by an embodiment of the present invention;

[0044] Figure 6 Mechanical properties of rock after fracture provided by the embodiments of the present invention;

[0045] Figure 7 A post-fracture reservoir pressure field model provided by an embodiment of the present invention;

[0046] Figure 8 Comparison results of conventional four-dimensional geostress simulation provided in the embodiment of the present invention and four-dimensional geostress simulation under the combined influence of pore pressure rise and rock fracture after fracturing - taking the minimum horizontal principal stress attribute model as an example;

[0047] Fig. 9 The embodiment of the present invention provides a comparison between the method and conventional four-dimensional geostress simulation results on the impact of crack propagation simulation. DETAILED DESCRIPTION

[0048] The exemplary embodiments of the present disclosure will be described in more detail below with reference to the accompanying drawings. Although the exemplary embodiments of the present disclosure are shown in the accompanying drawings, it should be understood that the present disclosure can be implemented in various forms and should not be limited by the embodiments set forth herein. On the contrary, these embodiments are provided to enable a more thorough understanding of the present disclosure and to fully convey the scope of the present disclosure to those skilled in the art.

[0049] The terms "comprises" and "having" and any variations thereof in the description embodiments, claims and drawings of the present invention are intended to cover non-exclusive inclusions, for example, including a series of steps or units.

[0050] The technical solution of the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments.

[0051] Example 1

[0052] The present invention relates to a four-dimensional geostress simulation method that considers the change of rock mechanical properties after reservoir fracturing, which is mainly used in the integrated development of shale oil geology and engineering. The method establishes a fine reservoir geological model, a geomechanical model and a numerical simulation model, and combines the reference indoor test results to consider the change of mechanical properties after rock fracture, as well as the interaction between matrix rock and artificial hydraulic fractures, so as to achieve a comprehensive consideration of rock geostress simulation, thereby improving the accuracy of the inter-well fracture network characterization and providing support for the integrated development of shale oil geology and engineering.

[0053] The technical solution of the present invention is achieved through the following technical steps:

[0054] Step S1: Establish a detailed reservoir geological model, geomechanical model and natural fracture model

[0055] This step is the basis of geostress simulation. Through basic geological research and reservoir numerical simulation requirements, relevant software is used to establish reservoir geological model, geomechanical model and natural fracture model.

[0056] Step S2: Conduct geostress simulation and establish geostress model

[0057] The model established in step S1 is used to carry out geostress simulation and establish a geostress model, which is the premise and basis for fracturing simulation.

[0058] Step S3: Conduct fracturing simulation and establish an artificial hydraulic fracture network model

[0059] Based on the results of step S1 and step S2, a fracturing simulation is carried out to establish an artificial hydraulic fracture network model, and a post-fracturing basic geological model is established based on the artificial hydraulic fracture network model, including porosity, permeability, etc.

[0060] Step S4: Obtaining mechanical properties of rock after fracture

[0061] Through the results of indoor compression tests and shear tests, the mechanical parameters of rock after fracture are obtained, including stiffness, shear stiffness, cohesion, internal friction angle, expansion angle, etc.

[0062] Step S5: Establishing a combined fracture network model after fracturing

[0063] Based on the artificial hydraulic fracture network model in step S3 and the natural fracture model in step S1, a combined fracture network model after fracturing is established.

[0064] Step S6: Conduct reservoir flow simulation to simulate fluid distribution and pressure distribution after fracturing

[0065] Based on the combined fracture network model established in step S4, reservoir flow simulation is carried out to simulate the fluid distribution and pressure distribution after fracturing.

[0066] Step S7: Conduct four-dimensional geostress simulation considering the changes in rock mechanical properties after fracturing

[0067] Based on the matrix rock mechanics model in step S1, the combined fracture network model in step S5, and the post-fracture fluid field model and pressure field model in step S6, a four-dimensional geostress simulation after fracturing is carried out, wherein the mechanical parameters of the rock after fracture obtained in step S4 are defined for the artificial hydraulic fracture model in the combined fracture network model;

[0068] Step S8: Based on the results of step S7, the next step of fracturing simulation is carried out to further improve the accuracy of the characterization of the inter-well fracture network.

[0069] Example 2

[0070] (1) Figure 2 Establish the reservoir geological model and geostress model of the target block. The specific model parameters are as follows:

[0071] ① The grid step size is 10×10 meters,

[0072] ②The number of grid nodes is 258×281×390=28274220,

[0073] ③Complete attribute modeling and reserve calculation fitting;

[0074] (2) Figure 3 Establish a natural fracture model based on well logging interpretation and seismic interpretation data;

[0075] (3) Figure 4 For the fracturing simulation of actual mine fracturing construction, an artificial hydraulic fracture model is established;

[0076] (4) Figure 5Based on the natural fracture model and artificial hydraulic fracture model, a combined fracture network model is established;

[0077] (5) Figure 6 Define the mechanical parameters of rock after fracture obtained from indoor core tests for artificial hydraulic fractures;

[0078] (6) Figure 7 Based on the combined fracture network model, numerical reservoir simulation is carried out to simulate the reservoir pressure field and fluid field after fracturing fluid injection;

[0079] (7) Figure 8 Based on the results of steps 1-6, the 4D geostress simulation after fracturing was carried out. It was found that this method takes more comprehensive factors into consideration. The 4D geostress after fracturing does not simply increase, but is affected by the combined effects of rock mechanics changes and reservoir pressure changes.

[0080] (8) Fig. 9 By comparing the effects of this method and the conventional four-dimensional geostress simulation method on fracture propagation simulation, it is found that this method takes more factors into consideration and can more precisely characterize the distribution of artificial hydraulic fractures between wells.

[0081] Beneficial effects: 1. Comprehensive consideration of rock in-situ stress simulation

[0082] The present invention establishes a fine reservoir geological model, a geomechanical model and a numerical simulation model, combines reference indoor test results, considers the changes in mechanical properties after rock fracture, and the interaction between matrix rock and artificial hydraulic fractures, and achieves comprehensive consideration of rock in situ stress simulation.

[0083] 2. Improve the accuracy of the inter-well fracture network

[0084] The present invention improves the accuracy of depicting the inter-well fracture network by taking into account factors such as changes in mechanical properties after rock fracture, and provides support for the integrated development of shale oil geology and engineering.

[0085] 3. Improve the level of integrated development of shale oil geology and engineering

[0086] The present invention provides a reliable numerical simulation method for the integrated development of shale oil geology and engineering, improves the research level in this field, and provides technical guarantee for achieving high-efficiency, low-cost and high-yield shale oil development.

[0087] The above specific implementation methods further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above are only specific implementation methods of the present invention and are not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A four-dimensional geostress simulation method for changes in rock mechanical properties, characterized in that: The simulation method comprises: Step S1: Establish a detailed reservoir geological model, a geomechanical model and a natural fracture model; Step S2: Conduct geostress simulation and establish a geostress model; Step S3: Conducting fracturing simulation and establishing an artificial hydraulic fracture network model; Step S4: obtaining mechanical properties of rock after fracture; Step S5: establishing a combined fracture network model after fracturing; Step S6: conducting reservoir flow simulation to simulate fluid distribution and pressure distribution after fracturing; Step S7: Conduct a four-dimensional geostress simulation that takes into account changes in rock mechanical properties after fracturing.

2. A four-dimensional geostress simulation method for rock mechanical property changes according to claim 1, characterized in that: The simulation method further comprises: step S8: based on step S7, conducting a fracturing simulation of the well section to be fractured, and simulating the expansion and distribution of artificial fractures.

3. A four-dimensional geostress simulation method for rock mechanical property changes according to claim 1, characterized in that: The step S1: establishing a fine reservoir geological model, a geomechanical model and a natural fracture model specifically includes: based on actual block data, through basic geological research and reservoir numerical simulation requirements, using relevant software to establish a reservoir geological model, a geomechanical model and a natural fracture model.

4. A four-dimensional geostress simulation method for rock mechanical property changes according to claim 1, characterized in that: The step S2: conducting geostress simulation and establishing a geostress model specifically includes: On the basis of step S1, a finite element simulation method is used to carry out a geostress simulation and establish a geostress model using a finite element simulator.

5. A four-dimensional geostress simulation method for rock mechanical property changes according to claim 1, characterized in that: The step S3: carrying out fracturing simulation and establishing an artificial hydraulic fracture network model specifically includes: On the basis of step S2, the fracturing process is fitted by fracturing simulation software to establish an artificial hydraulic fracture network model.

6. A four-dimensional geostress simulation method for rock mechanical property changes according to claim 1, characterized in that: The step S4: obtaining the mechanical properties of the rock after fracture specifically includes: The mechanical parameters of rock after fracture are obtained through indoor compression test and shear test results.

7. A four-dimensional geostress simulation method for rock mechanical property changes according to claim 6, characterized in that: The mechanical parameters include stiffness, shear stiffness, cohesion, internal friction angle, and expansion angle.

8. A four-dimensional geostress simulation method for rock mechanical property changes according to claim 1, characterized in that: The step S5: establishing a combined fracture network model after fracturing specifically includes: On the basis of step S3 and step S1, a geological model is established for finely characterizing the physical property changes after fracturing and the spatial distribution of the combined fracture network using an unstructured grid, and multiple groups of artificial hydraulic fracture network models and multiple groups of natural fracture models are characterized, so that different fracture mechanical parameters can be defined for different groups of fracture models when performing four-dimensional geostress simulation.

9. A four-dimensional geostress simulation method for rock mechanical property changes according to claim 1, characterized in that: The step S6: conducting reservoir flow simulation, simulating fluid distribution and pressure distribution after fracturing specifically includes: On the basis of step S3 and step S1, a reservoir flow simulation is carried out based on a reservoir numerical simulator, the process of fracturing fluid entering the well during the fracturing process is simulated by injection method, and the fluid distribution and pressure distribution after fracturing are simulated.

10. A four-dimensional geostress simulation method for rock mechanical property changes according to claim 1, characterized in that: The step S7: carrying out a four-dimensional geostress simulation considering the change of rock mechanical properties after fracturing specifically includes: On the basis of step S3, step S5 and step S6, the ground stress model is recalculated by a finite element simulator, the basic geological model after fracturing is obtained by the calculation of step 3, the combined fracture network model and rock mechanics parameter model after fracturing are obtained by the calculation of step S5, and the fluid model and reservoir pressure model after fracturing are obtained by the calculation of step S6.

11. A four-dimensional geostress simulation system for rock mechanical property changes, using a four-dimensional geostress simulation method for rock mechanical property changes as described in any one of claims 1 to 10, characterized in that: The simulation system comprises: Model building module, used to build detailed reservoir geological model, geomechanical model and natural fracture model; The geostress model building module is used to carry out geostress simulation and build a geostress model; Artificial hydraulic fracture network model building module, used to carry out fracturing simulation and build artificial hydraulic fracture network model; Mechanical property acquisition module, used to obtain the mechanical properties of rock after fracture; Fracture network model building module, used to build a combined fracture network model after fracturing; Reservoir flow simulation module, used to carry out reservoir flow simulation and simulate fluid distribution and pressure distribution after fracturing; The Siwei geostress simulation module is used to carry out four-dimensional geostress simulation considering the changes in rock mechanical properties after fracturing.

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