Method and device for evaluating dynamic sealing performance of gas storage trap using stress field

Abstract

The present invention discloses a method and device for evaluating the dynamic sealing of a gas storage reservoir closure by using a stress field. The method includes: obtaining the geostress parameters of a single well; obtaining the spatial distribution characteristics of geostress based on a three-dimensional geological model and the geostress parameters of a single well; judging the stability of a fault based on the spatial distribution characteristics of geostress; if the fault is stable, calculating the maximum pore pressure; and evaluating the stress risk of the dynamic sealing of a gas storage reservoir fault based on the maximum pore pressure. The present invention establishes a three-dimensional geostress field model, analyzes the three-dimensional geostress field model, obtains the spatial distribution characteristics of geostress, judges whether the fault is stable, and calculates the maximum pore pressure. When the gas injection pressure of the gas storage reservoir is less than the maximum pore pressure, the stress risk of evaluating the dynamic sealing of the closure is stable. When the gas injection pressure is greater than the maximum pore pressure, the stress risk of evaluating the dynamic sealing of the closure is unstable. The system comprehensively evaluates the dynamic sealing of the gas storage reservoir closure.

Description

Technical Field

[0001] The invention belongs to the field of natural gas storage and transportation, and in particular relates to a method and a device for evaluating the dynamic sealing performance of a gas storage reservoir closure by using a stress field. Background Art

[0002] At present, both at home and abroad, great importance is attached to the evaluation of the sealing of gas storage closures. The evaluation of sealing before the construction of gas storage is increasing in both breadth and depth; more and more research is being conducted on both static sealing evaluation and dynamic sealing evaluation. The burial depth of foreign underground gas storages is generally less than 2000m, with simple structure, thick reservoir, good physical properties, good geological conditions, and easy construction. The geological conditions of the construction targets of underground gas storages in my country are relatively poor, with a large burial depth, generally greater than 3000m, relatively more faults, more complex structure, rapid sedimentary phase change, poor reservoir physical properties, and strong heterogeneity. From the current technical point of view, there are relatively mature evaluation indicators and evaluation methods for the static sealing evaluation of gas storage closures. However, in the dynamic sealing evaluation of gas storages, there are many evaluation indicators and evaluation factors, and a set of methods and technical series for dynamic sealing evaluation has not yet been formed.

[0003] In terms of the evaluation of the static sealing of gas storage closures, it mainly involves some dynamic parameter experiments and calculations. Generally, the static sealing of the closure is evaluated by analyzing the thickness of the cap rock, the degree of stable distribution, the nature, inclination, and ductility of the fault. The dynamic sealing of the cap and fault is evaluated through indoor tests such as dynamic breakthrough pressure, minimum horizontal principal stress, shear safety index, and slip index.

[0004] In the evaluation of static sealing of gas storage closures, the cap rock mainly includes static test analysis of breakthrough pressure, permeability, pore throat distribution, and porosity; the fault includes fault stress, two-disk lithology configuration analysis, smear coefficient, and sealing coefficient calculation analysis.

[0005] In the evaluation of dynamic sealing of gas storage traps, the caprock mainly includes the evaluation of capillary sealing capacity. On the basis of conventional static breakthrough pressure test, the core alternating load fatigue damage test is carried out according to the actual ground stress and the designed pressure range to obtain the critical breakthrough pressure of the caprock core after periodic injection and production, and determine the dynamic capillary sealing pressure limit of the caprock. In addition, it also includes tensile damage evaluation, using experiments such as mine hydraulic fracturing and core acoustic emission Kaiser effect to determine the current ground stress of the reservoir and caprock, and evaluate the risk of tensile damage.

[0006] During the construction of gas storage facilities, there are relatively few studies on the reactivation mechanism and evaluation of faults after cyclic loading. The following literature mainly involves sealing evaluation. Gartrell A evaluated the basins after the uplift period and found that the reactivation of faults caused the destruction of the cap rock. He discussed the role of the integrity of the cap rock on the redistribution of oil and gas, and established an oil and gas risk assessment model based on this. HRGrunau pointed out that in the study of cap rock distribution, special attention should be paid to the analysis of lateral continuity characteristics. When there are faults in the formation, the effectiveness of the cap rock will be significantly reduced. Prozorovich's research shows that the density of microcracks formed during diagenesis is negatively correlated with the thickness of the cap rock. Fu Guang et al. counted and analyzed the mudstone cap rocks in my country's major oil and gas basins and found that the active cracks in the cap rock are the only channel for oil and gas loss, and the geological time of this oil and gas loss is periodic. Lü Yanfang and others believed that faults would reduce the planar distribution area of ​​the cap layer and make it thinner. The study also found that the thickness, fault throw and dip of the cap layer are the main influencing factors of fault damage to the cap layer. The concept of the fault thickness of the cap layer was defined, and the sealing capacity of the cap layer after fault damage was quantitatively evaluated by the corresponding calculation method. The correctness of the conclusion was verified by the example of the cap layer in the Kuche Depression. Liu Anying and others evaluated the Xujiaweizi cap layer and found that the oil and gas accumulation was different when the degree of cap layer damage was different, that is, the cap layer with a large degree of damage was conducive to the accumulation of oil and gas, but the oil and gas would be lost when the degree of cap layer damage was large.

[0007] In summary, there are few studies on the dynamic sealing of gas storage closures, and most of them focus on the sealing capacity of the cap rock. Currently, there is no systematic and complete method and system for evaluating the dynamic sealing of gas storage closures. Summary of the invention

[0008] The purpose of the present invention is to propose a method and device for evaluating the dynamic sealing of gas storage closures using stress fields, so as to solve the problem that the dynamic sealing of existing gas storage closures is mainly aimed at the sealing capacity of the cap rock, and there is a lack of a systematic and complete gas storage closure dynamic sealing evaluation method and system.

[0009] In order to achieve the above-mentioned purpose, the present invention provides a method for evaluating the dynamic sealing of a gas storage reservoir closure by using a stress field, comprising: obtaining single well geostress parameters; obtaining geostress spatial distribution characteristics based on a three-dimensional geological model and the single well geostress parameters; judging the stability of a fault based on the geostress spatial distribution characteristics; if the fault is stable, calculating the maximum pore pressure; and evaluating the stress risk of the dynamic sealing of a gas storage reservoir fault based on the maximum pore pressure.

[0010] Optionally, obtaining the spatial distribution characteristics of geostress based on the three-dimensional geological model and the single well geostress parameters includes: inserting the single well geostress parameters into the three-dimensional geological model to obtain a three-dimensional geostress model; and analyzing the three-dimensional geostress model to obtain the spatial distribution characteristics of geostress.

[0011] Optionally, judging the stability of the fault based on the spatial distribution characteristics of the geostress includes: obtaining the normal stress and shear stress of the fault plane based on the spatial distribution characteristics of the geostress; and judging the stability of the fault based on the normal stress and shear stress using the Coulomb failure criterion.

[0012] Optionally, the Coulomb failure criterion is CFF = τ net -μσ n , where CFF is the evaluation coefficient, τ net is the shear stress on the fault plane, σ n is the normal stress of the fault plane, and μ is the weight; if the evaluation coefficient is less than zero, the fault is stable; if the evaluation coefficient is equal to zero, the fault is unstable.

[0013] Optionally, the single well geostress parameters include overburden formation pressure, pore pressure, minimum principal stress, maximum principal stress, geostress direction and rock mechanical property parameters.

[0014] Optionally, the shear stress of the fault plane is calculated using the following formula:

[0015] τ net =0.5(σ 1 -σ 3 )sinβ

[0016] Among them, τ net is the shear stress on the fault plane, σ 1 is the maximum principal stress, σ 3 is the minimum principal stress, and β is the angle between the fault plane and the direction of the ground stress.

[0017] Optionally, the normal stress of the fault plane is calculated using the following formula:

[0018] σ n =0.5(σ 1 +σ 3 )+0.5(σ 1 -σ 3 )cosβ

[0019] Among them, σ n is the normal stress on the fault plane, σ 1 is the maximum principal stress, σ 3 is the minimum principal stress, and β is the angle between the fault plane and the direction of the ground stress.

[0020] Optionally, if the fault is stable, calculating the maximum pore pressure includes: injecting gas into the three-dimensional geostress model multiple times; gradually increasing the pressure of the injected gas to obtain new maximum principal stress and new minimum principal stress values ​​under each gas pressure; calculating a new evaluation coefficient based on the new maximum principal stress and the new minimum principal stress values; if the new evaluation coefficient is equal to zero, using the gas pressure corresponding to the new evaluation coefficient as the maximum pore pressure.

[0021] Optionally, the stress risk of dynamic sealing of the fault of the gas storage reservoir evaluated based on the maximum pore pressure includes: establishing a fluid-solid coupling model based on the three-dimensional geostress model and in combination with a numerical simulation of the pore pressure variation of the gas storage reservoir; multiple gas injections and multiple gas productions within the fluid-solid coupling model; when the gas pressure of the injected gas is less than the maximum pore pressure, determining that the stress risk of dynamic sealing of the fault of the gas storage reservoir is stable; when the gas pressure of the injected gas is greater than or equal to the maximum pore pressure, determining that the stress risk of dynamic sealing of the fault of the gas storage reservoir is unstable.

[0022] In the second aspect, the present invention also proposes a device for evaluating the dynamic sealing of a gas storage reservoir closure by using a stress field, the device comprising: a first acquisition module for acquiring single well geostress parameters; a second acquisition module for obtaining spatial distribution characteristics of geostress based on a three-dimensional geological model and the single well geostress parameters; a judgment module for judging the stability of a fault based on the spatial distribution characteristics of geostress; a calculation module for calculating the maximum pore pressure if the fault is stable; and an evaluation module for evaluating the stress risk of the dynamic sealing of a gas storage reservoir fault based on the maximum pore pressure.

[0023] Optionally, obtaining the spatial distribution characteristics of geostress based on the three-dimensional geological model and the single well geostress parameters includes: inserting the single well geostress parameters into the three-dimensional geological model to obtain a three-dimensional geostress model; and analyzing the three-dimensional geostress model to obtain the spatial distribution characteristics of geostress.

[0024] Optionally, judging the stability of the fault based on the spatial distribution characteristics of the geostress includes: obtaining the normal stress and shear stress of the fault plane based on the spatial distribution characteristics of the geostress; and judging the stability of the fault based on the normal stress and shear stress using the Coulomb failure criterion.

[0025] Optionally, the Coulomb failure criterion is CFF = τ net -μσ n , where CFF is the evaluation coefficient, τ net is the shear stress on the fault plane, σ n is the normal stress of the fault plane, and μ is the weight; if the evaluation coefficient is less than zero, the fault is stable; if the evaluation coefficient is equal to zero, the fault is unstable.

[0026] Optionally, the single well geostress parameters include overburden formation pressure, pore pressure, minimum principal stress, maximum principal stress, geostress direction and rock mechanical property parameters.

[0027] Optionally, the shear stress of the fault plane is calculated using the following formula:

[0028] τ net =0.5(σ 1 -σ 3 )sinβ

[0029] Among them, τ net is the shear stress on the fault plane, σ 1 is the maximum principal stress, σ 3 is the minimum principal stress, and β is the angle between the fault plane and the direction of the ground stress.

[0030] Optionally, the normal stress of the fault plane is calculated using the following formula:

[0031] σ n =0.5(σ 1 +σ 3 )+0.5(σ 1 -σ 3 )cosβ

[0032] Among them, σ n is the normal stress on the fault plane, σ 1 is the maximum principal stress, σ 3 is the minimum principal stress, and β is the angle between the fault plane and the direction of the ground stress.

[0033] Optionally, if the fault is stable, calculating the maximum pore pressure includes: injecting gas into the three-dimensional geostress model multiple times; gradually increasing the pressure of the injected gas to obtain new maximum principal stress and new minimum principal stress values ​​under each gas pressure; calculating a new evaluation coefficient based on the new maximum principal stress and the new minimum principal stress values; if the new evaluation coefficient is equal to zero, using the gas pressure corresponding to the new evaluation coefficient as the maximum pore pressure.

[0034] Optionally, the stress risk of dynamic sealing of the fault of the gas storage reservoir evaluated based on the maximum pore pressure includes: establishing a fluid-solid coupling model based on the three-dimensional geostress model and in combination with a numerical simulation of the pore pressure variation of the gas storage reservoir; multiple gas injections and multiple gas productions within the fluid-solid coupling model; when the gas pressure of the injected gas is less than the maximum pore pressure, determining that the stress risk of dynamic sealing of the fault of the gas storage reservoir is stable; when the gas pressure of the injected gas is greater than or equal to the maximum pore pressure, determining that the stress risk of dynamic sealing of the fault of the gas storage reservoir is unstable.

[0035] The beneficial effects of the present invention are as follows: the method and device for evaluating the dynamic sealing of a gas storage reservoir closure by using a stress field of the present invention establish a three-dimensional geostress field model based on a three-dimensional geological model and single well geostress parameters, analyze the three-dimensional geostress field model, obtain the spatial distribution characteristics of geostress, judge whether the fault is stable based on the spatial distribution characteristics of geostress, and if the fault is stable, calculate and obtain the maximum pore pressure. When the gas injection pressure of the gas storage reservoir is less than the maximum pore pressure, the stress risk for evaluating the dynamic sealing of the closure is stable, and when the gas injection pressure is greater than the maximum pore pressure, the stress risk for evaluating the dynamic sealing of the closure is unstable. The method can systematically and completely evaluate the dynamic sealing of the gas storage reservoir closure, and the evaluation result is clear, the applicability is strong, and the cost is low.

[0036] The present invention has other features and advantages, which will be apparent from or will be described in detail in the accompanying drawings and the following specific embodiments incorporated herein, which together serve to explain the specific principles of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] The above and other objects, features and advantages of the present invention will become more apparent through a more detailed description of exemplary embodiments of the present invention in conjunction with the accompanying drawings, wherein like reference numerals generally represent like components throughout the exemplary embodiments of the present invention.

[0038] Figure 1 A flow chart of a method for evaluating dynamic sealing performance of a gas storage reservoir closure using a stress field according to an embodiment of the present invention is shown.

[0039] Figure 2 A schematic diagram of the spatial distribution of geostress in a method for evaluating the dynamic sealing performance of a gas storage reservoir closure using a stress field according to an embodiment of the present invention is shown.

[0040] Figure 3 A schematic diagram of the stability of a fault under current ground stress in a certain work area of ​​a method for evaluating the dynamic sealing performance of a gas storage trap using a stress field according to an embodiment of the present invention is shown.

[0041] Figure 4 A diagram showing the stability of a fault in a certain work area under the highest pore pressure according to a method for evaluating the dynamic sealing performance of a gas storage reservoir trap using a stress field according to an embodiment of the present invention is shown.

[0042] Figure 5 A schematic diagram of the distribution of pore pressure at a certain time in a section of a certain work area of ​​a method for evaluating dynamic sealing performance of a gas storage reservoir closure by using a stress field according to an embodiment of the present invention is shown.

[0043] Figure 6A dynamic stability analysis diagram of a fault under a digital model pore pressure variation body in a certain work area of ​​a method for evaluating the dynamic sealing performance of a gas storage reservoir closure using a stress field according to an embodiment of the present invention is shown.

[0044] Figure 7 A block diagram of a vertical well volume fracturing system combining radial wells with carbon dioxide fracturing according to an embodiment of the present invention is shown. DETAILED DESCRIPTION

[0045] The preferred embodiments of the present invention will be described in more detail below. Although the preferred embodiments of the present invention are described below, it should be understood that the present invention 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 make the present invention more thorough and complete, and to fully convey the scope of the present invention to those skilled in the art.

[0046] The present invention provides a method for evaluating the dynamic sealing performance of a gas storage reservoir closure by utilizing a stress field, comprising: obtaining a single well geostress parameter; obtaining a geostress spatial distribution characteristic based on a three-dimensional geological model and the single well geostress parameter; judging the stability of a fault based on the geostress spatial distribution characteristic; if the fault is stable, calculating the maximum pore pressure; and evaluating the stress risk of the dynamic sealing performance of a gas storage reservoir fault based on the maximum pore pressure.

[0047] Specifically, the geostress parameters of a single well mainly include overburden pressure, formation pore pressure, minimum principal stress, maximum principal stress, geostress direction and rock mechanical properties. The above parameters are mainly obtained through logging curve calculation and correction with laboratory sample experimental data. Among them, the overburden pressure is obtained by density logging integral calculation; the formation pore pressure is mainly obtained through actual measurement, conventional logging and seismic velocity calculation; the minimum principal stress is obtained by fracture pressure test, mud loss test, etc.; the maximum principal stress is obtained by wellbore collapse analysis, dipole acoustic wave analysis or tectonic movement analysis; the geostress direction is obtained by imaging logging or Cashier effect experiment. Rock mechanical properties mainly include uniaxial rock strength, Poisson's ratio, Young's modulus and other rock mechanical properties parameters, which are mainly obtained by core tests, logging, wellbore collapse analysis, etc. The above single well geostress parameter data obtained are used as the basis for geostress modeling. On the basis of three-dimensional geological modeling, the above single well geostress parameters are inserted to construct a three-dimensional geostress model. The three-dimensional geostress model is analyzed to obtain the spatial distribution characteristics of geostress, and the normal stress and shear stress of the fault are calculated, and then the evaluation coefficient is calculated. The stability of the fault is judged by the evaluation coefficient. When the evaluation coefficient is not zero, the fault is stable, and the maximum pore pressure is calculated. The gas storage is injected and produced multiple times. When the injection pressure is less than the maximum pore pressure, the stress risk of evaluating the dynamic sealing of the closure is stable. When the injection pressure is greater than the maximum pore pressure, the stress risk of evaluating the dynamic sealing of the closure is unstable. This method can systematically and completely evaluate the dynamic sealing of the gas storage closure.

[0048] According to an exemplary embodiment, a method for evaluating the dynamic sealing of a gas storage reservoir closure using a stress field is provided. Based on a three-dimensional geological model and single well geostress parameters, a three-dimensional geostress field model is established. The three-dimensional geostress field model is analyzed to obtain spatial distribution characteristics of geostress. Based on the spatial distribution characteristics of geostress, whether the fault is stable is determined. If the fault is stable, the maximum pore pressure is calculated and the gas storage reservoir is injected and produced multiple times. When the injection pressure is less than the maximum pore pressure, the stress risk for evaluating the dynamic sealing of the closure is stable. When the injection pressure is greater than the maximum pore pressure, the stress risk for evaluating the dynamic sealing of the closure is unstable. This method can systematically and completely evaluate the dynamic sealing of the gas storage reservoir closure, and the evaluation results are clear, the applicability is strong, and the cost is low.

[0049] As an optional solution, based on the three-dimensional geological model and the single well geostress parameters, obtaining the spatial distribution characteristics of geostress includes: inserting the single well geostress parameters into the three-dimensional geological model to obtain the three-dimensional geostress model; and analyzing the three-dimensional geostress model to obtain the spatial distribution characteristics of geostress.

[0050] Specifically, on the basis of 3D geological modeling, the single well geostress parameters such as overburden pressure, formation pore pressure, minimum principal stress, maximum principal stress, geostress direction and rock mechanical properties are calculated, and the structural model of the 3D geological model is used as a constraint. The single well geostress parameters are inserted into the 3D geological model through lithofacies analysis or sequential Gaussian method to construct a 3D geostress model. For the established 3D geostress model, the distribution law and change of triaxial principal stress (vertical stress, maximum horizontal stress and minimum horizontal stress) and pore pressure in the formation are analyzed, and the spatial distribution characteristics of geostress are accurately analyzed to obtain the spatial distribution characteristics of geostress.

[0051] As an optional solution, judging the stability of the fault based on the spatial distribution characteristics of the geostress includes: obtaining the normal stress and shear stress of the fault plane based on the spatial distribution characteristics of the geostress; judging the stability of the fault based on the normal stress and shear stress using the Coulomb failure criterion.

[0052] As an alternative, the Coulomb failure criterion is CFF = τ net -μσ n , where CFF is the evaluation coefficient, τ net is the shear stress on the fault plane, σ n is the normal stress of the fault plane, and μ is the weight; if the evaluation coefficient is less than zero, the fault is stable; if the evaluation coefficient is equal to zero, the fault is unstable.

[0053] Specifically, based on the spatial distribution characteristics of geostress, the stability of the fault under the current stress state is analyzed. The principle is to obtain the normal stress and shear stress of the section through the calculation of the geostress parameters of a single well, analyze the magnitude of the normal stress and shear stress at the section, and compare the magnitude of the normal stress and shear stress. When the shear stress is greater than the normal stress, the fault will slip.

[0054] Specifically, using the Coulomb failure criterion CFF = τ net -μσ n , to judge the fault stability. In this formula, CFF is the evaluation coefficient, τ net is the shear stress on the fault plane, σ n is the normal stress of the fault plane, μ is the weight, and μ is between 0.6 and 1, which can be obtained through indoor tests. When CFF is negative, the fault plane remains stable, and the shear stress is not enough to overcome the sliding resistance μσ n When CFF reaches zero, the shear stress can overcome the effective normal stress on the plane of the primary fault, resulting in slip. This evaluation method is used to evaluate the stability of each fault in the gas storage reservoir under the current ground stress state.

[0055] As an optional option, the single well geostress parameters include overburden formation pressure, pore pressure, minimum principal stress, maximum principal stress, geostress direction and rock mechanical property parameters.

[0056] Specifically, the overburden pressure is obtained by density logging integral calculation; the formation pore pressure is mainly obtained through actual measurement, conventional logging and seismic velocity calculation; the minimum principal stress is obtained by fracture pressure test, mud loss test, etc.; the maximum principal stress is obtained by wellbore collapse analysis, dipole acoustic wave analysis or tectonic movement analysis; the ground stress direction is obtained by imaging logging or Cashier effect experiment. Rock mechanical properties mainly include uniaxial rock strength, Poisson's ratio, Young's modulus and other rock mechanical property parameters, which are mainly obtained by core test, logging, wellbore collapse analysis, etc.

[0057] As an alternative, the shear stress on the fault plane is calculated using the following formula,

[0058] τ net =0.5(σ 1 -σ 3 )sinβ

[0059] Among them, τ net is the shear stress on the fault plane, σ 1 is the maximum principal stress, σ 3 is the minimum principal stress, and β is the angle between the fault plane and the direction of the ground stress.

[0060] Generally speaking, the shear stress τ acting on the fault plane is net It mainly depends on the magnitude of the principal stresses (maximum principal stress and minimum principal stress), pore pressure, and the angle β between the fault plane and the ground stress.

[0061] As an alternative, the normal stress on the fault plane is calculated using the following formula,

[0062] σ n =0.5(σ 1 +σ 3 )+0.5(σ 1 -σ 3 )cosβ

[0063] Among them, σ n is the normal stress on the fault plane, σ 1 is the maximum principal stress, σ 3 is the minimum principal stress, and β is the angle between the fault plane and the direction of the ground stress.

[0064] Generally speaking, the normal stress σ acting on the fault plane is n It mainly depends on the magnitude of the principal stresses (maximum principal stress and minimum principal stress), pore pressure, and the angle β between the fault plane and the ground stress.

[0065] As an optional solution, if the fault is stable, calculating the maximum pore pressure includes: injecting gas into the three-dimensional geostress model multiple times; gradually increasing the pressure of the injected gas to obtain new maximum principal stress and new minimum principal stress values ​​under each gas pressure; calculating a new evaluation coefficient based on the new maximum principal stress and new minimum principal stress values; if the new evaluation coefficient is equal to zero, using the gas pressure corresponding to the new evaluation coefficient as the maximum pore pressure.

[0066] Specifically, under the current ground stress state, if the fault is stable, it is necessary to analyze under which stress state the fault may slip or open. The effect of pore pressure on fault slip is through the normal stress σ n Introduce, the normal stress is S n -P p , where P p is the pore pressure, S n To decompose the normal stress on the cross section. Therefore, if the pore pressure of the cross section is increased, the normal stress will be reduced, which will cause the fault to slip. The specific method is to change the normal stress by injecting gas into the body, and continuously increase the injection pressure from small to large, which will cause the underground stress field to change, and the maximum and minimum principal stress values ​​will be redistributed. The maximum principal stress and minimum principal stress under each gas injection and each injection pressure are obtained as the new maximum principal stress and the new minimum principal stress. The new evaluation coefficient is calculated each time. Using the Coulomb criterion, if the new evaluation coefficient CFF is equal to the critical point zero value, the injection pressure corresponding to the new evaluation coefficient will be used as the maximum pore pressure P p .

[0067] As an optional scheme, based on the maximum pore pressure, the stress risk of dynamic sealing of gas storage faults is evaluated, including: establishing a fluid-solid coupling model based on a three-dimensional geostress model and combining it with the numerical simulation of pore pressure variation of the gas storage; multiple gas injections and multiple gas productions in the fluid-solid coupling model; when the gas pressure of gas injection is less than the maximum pore pressure, the stress risk of dynamic sealing of gas storage faults is determined to be stable; when the gas pressure of gas injection is greater than or equal to the maximum pore pressure, the stress risk of dynamic sealing of gas storage faults is determined to be unstable.

[0068] As an emergency peak-shaving facility, the stability of the gas storage enclosure under strong injection, strong production and alternating loads is the key to its safe operation.

[0069] During the injection and production cycle of a gas storage reservoir, changes in injection pressure lead to changes in the pore pressure field of the entire gas storage reservoir, and changes in pore pressure will lead to changes in the entire stress field, that is, changes in the maximum principal stress and minimum principal stress. Changes in the maximum principal stress and minimum principal stress will cause changes in the normal stress and shear stress of the fault, and the stability of the fault will change.

[0070] Within an injection-production cycle, the magnitude of the ground stress field at different time nodes is obtained to analyze the stability of the fault.

[0071] On the basis of the three-dimensional geological model and the three-dimensional geostress model, combined with the historical fitting and numerical simulation results of the gas storage reservoir, that is, the numerical simulation pore pressure variation body of the gas storage reservoir, a dynamic coupling model of stress-fluid is established, also known as the fluid-solid coupling model.

[0072] Multiple gas injection and gas production were carried out on the established fluid-solid coupling model to simulate the dynamic change of ground stress (effective stress) caused by the change of pore pressure during the injection and production process of the gas storage reservoir, as well as the strain (deformation) of the reservoir and caprock rocks caused by it. When the gas pressure of gas injection is less than the maximum pore pressure, the stress risk of the dynamic sealing of the gas storage fault is judged to be stable; when the gas pressure of gas injection is greater than or equal to the maximum pore pressure, the stress risk of the dynamic sealing of the gas storage fault is judged to be unstable.

[0073] Through the above calculations and evaluations, it can be determined whether the gas storage facility can operate safely under different injection and production cycles and different work systems.

[0074] The present invention also proposes a device for evaluating the dynamic sealing of a gas storage reservoir closure by using a stress field, the device comprising: a first acquisition module for acquiring single well geostress parameters; a second acquisition module for obtaining spatial distribution characteristics of geostress based on a three-dimensional geological model and single well geostress parameters; a judgment module for judging the stability of a fault based on the spatial distribution characteristics of geostress; a calculation module for calculating the maximum pore pressure if the fault is stable; and an evaluation module for evaluating the stress risk of the dynamic sealing of a gas storage reservoir fault based on the maximum pore pressure.

[0075] Specifically, the geostress parameters of a single well mainly include overburden pressure, formation pore pressure, minimum principal stress, maximum principal stress, geostress direction and rock mechanical properties. The above parameters are mainly obtained through logging curve calculation and correction with laboratory sample experimental data. Among them, the overburden pressure is obtained by density logging integral calculation; the formation pore pressure is mainly obtained through actual measurement, conventional logging and seismic velocity calculation; the minimum principal stress is obtained by fracture pressure test, mud loss test, etc.; the maximum principal stress is obtained by wellbore collapse analysis, dipole acoustic wave analysis or tectonic movement analysis; the geostress direction is obtained by imaging logging or Cashier effect experiment. Rock mechanical properties mainly include uniaxial rock strength, Poisson's ratio, Young's modulus and other rock mechanical properties parameters, which are mainly obtained by core tests, logging, wellbore collapse analysis, etc. The above single well geostress parameter data obtained are used as the basis for geostress modeling. On the basis of three-dimensional geological modeling, the above single well geostress parameters are inserted to construct a three-dimensional geostress model. The three-dimensional geostress model is analyzed to obtain the spatial distribution characteristics of geostress, and the normal stress and shear stress of the fault are calculated, and then the evaluation coefficient is calculated. The stability of the fault is judged by the evaluation coefficient. When the evaluation coefficient is not zero, the fault is stable, and the maximum pore pressure is calculated. The gas storage is injected and produced multiple times. When the injection pressure is less than the maximum pore pressure, the stress risk of evaluating the dynamic sealing of the closure is stable. When the injection pressure is greater than the maximum pore pressure, the stress risk of evaluating the dynamic sealing of the closure is unstable. This method can systematically and completely evaluate the dynamic sealing of the gas storage closure.

[0076] According to an exemplary embodiment, a device for evaluating the dynamic sealing of a gas storage reservoir closure using a stress field is used. Based on a three-dimensional geological model and single well geostress parameters, a three-dimensional geostress field model is established. The three-dimensional geostress field model is analyzed to obtain spatial distribution characteristics of geostress. Based on the spatial distribution characteristics of geostress, it is determined whether the fault is stable. If the fault is stable, the maximum pore pressure is calculated and the gas storage reservoir is injected and produced multiple times. When the injection pressure is less than the maximum pore pressure, the stress risk for evaluating the dynamic sealing of the closure is stable. When the injection pressure is greater than the maximum pore pressure, the stress risk for evaluating the dynamic sealing of the closure is unstable. This method can systematically and completely evaluate the dynamic sealing of the gas storage reservoir closure, and the evaluation results are clear, the applicability is strong, and the cost is low.

[0077] As an optional solution, based on the three-dimensional geological model and the single well geostress parameters, obtaining the spatial distribution characteristics of geostress includes: inserting the single well geostress parameters into the three-dimensional geological model to obtain the three-dimensional geostress model; and analyzing the three-dimensional geostress model to obtain the spatial distribution characteristics of geostress.

[0078] Specifically, on the basis of 3D geological modeling, the single well geostress parameters such as overburden pressure, formation pore pressure, minimum principal stress, maximum principal stress, geostress direction and rock mechanical properties are calculated, and the structural model of the 3D geological model is used as a constraint. The single well geostress parameters are inserted into the 3D geological model through lithofacies analysis or sequential Gaussian method to construct a 3D geostress model. For the established 3D geostress model, the distribution law and change of triaxial principal stress (vertical stress, maximum horizontal stress and minimum horizontal stress) and pore pressure in the formation are analyzed, and the spatial distribution characteristics of geostress are accurately analyzed to obtain the spatial distribution characteristics of geostress.

[0079] As an optional solution, judging the stability of the fault based on the spatial distribution characteristics of the geostress includes: obtaining the normal stress and shear stress of the fault plane based on the spatial distribution characteristics of the geostress; judging the stability of the fault based on the normal stress and shear stress using the Coulomb failure criterion.

[0080] As an alternative, the Coulomb failure criterion is CFF = τ net -μσ n , where CFF is the evaluation coefficient, τ net is the shear stress on the fault plane, σ n is the normal stress of the fault plane, and μ is the weight; if the evaluation coefficient is less than zero, the fault is stable; if the evaluation coefficient is equal to zero, the fault is unstable.

[0081] Specifically, based on the spatial distribution characteristics of geostress, the stability of the fault under the current stress state is analyzed. The principle is to obtain the normal stress and shear stress of the section through the calculation of the geostress parameters of a single well, analyze the magnitude of the normal stress and shear stress at the section, and compare the magnitude of the normal stress and shear stress. When the shear stress is greater than the normal stress, the fault will slip.

[0082] Specifically, using the Coulomb failure criterion CFF = τ net -μσ n , to judge the fault stability. In this formula, CFF is the evaluation coefficient, τ net is the shear stress on the fault plane, σ n is the normal stress of the fault plane, μ is the weight, and μ is between 0.6 and 1, which can be obtained through indoor tests. When CFF is negative, the fault plane remains stable, and the shear stress is not enough to overcome the sliding resistance μσ n When CFF reaches zero, the shear stress can overcome the effective normal stress on the plane of the primary fault, resulting in slip. This evaluation method is used to evaluate the stability of each fault in the gas storage reservoir under the current ground stress state.

[0083] As an optional option, the single well geostress parameters include overburden formation pressure, pore pressure, minimum principal stress, maximum principal stress, geostress direction and rock mechanical property parameters.

[0084] Specifically, the overburden pressure is obtained by density logging integral calculation; the formation pore pressure is mainly obtained through actual measurement, conventional logging and seismic velocity calculation; the minimum principal stress is obtained by fracture pressure test, mud loss test, etc.; the maximum principal stress is obtained by wellbore collapse analysis, dipole acoustic wave analysis or tectonic movement analysis; the ground stress direction is obtained by imaging logging or Cashier effect experiment. Rock mechanical properties mainly include uniaxial rock strength, Poisson's ratio, Young's modulus and other rock mechanical property parameters, which are mainly obtained by core test, logging, wellbore collapse analysis, etc.

[0085] As an alternative, the shear stress on the fault plane is calculated using the following formula,

[0086] τ net =0.5(σ 1 -σ 3 )sinβ

[0087] Among them, τ net is the shear stress on the fault plane, σ 1 is the maximum principal stress, σ 3 is the minimum principal stress, and β is the angle between the fault plane and the direction of the ground stress.

[0088] Generally speaking, the shear stress τ acting on the fault plane is net It mainly depends on the magnitude of the principal stresses (maximum principal stress and minimum principal stress), pore pressure, and the angle β between the fault plane and the ground stress.

[0089] As an alternative, the normal stress on the fault plane is calculated using the following formula,

[0090] σ n =0.5(σ 1 +σ 3 )+0.5(σ 1 -σ 3 )cosβ

[0091] Among them, σ n is the normal stress on the fault plane, σ 1 is the maximum principal stress, σ 3 is the minimum principal stress, and β is the angle between the fault plane and the direction of the ground stress.

[0092] Generally speaking, the normal stress σ acting on the fault plane is n It mainly depends on the magnitude of the principal stresses (maximum principal stress and minimum principal stress), pore pressure, and the angle β between the fault plane and the ground stress.

[0093] As an optional solution, if the fault is stable, calculating the maximum pore pressure includes: injecting gas into the three-dimensional geostress model multiple times; gradually increasing the pressure of the injected gas to obtain new maximum principal stress and new minimum principal stress values ​​under each gas pressure; calculating a new evaluation coefficient based on the new maximum principal stress and new minimum principal stress values; if the new evaluation coefficient is equal to zero, using the gas pressure corresponding to the new evaluation coefficient as the maximum pore pressure.

[0094] Specifically, under the current ground stress state, if the fault is stable, it is necessary to analyze under which stress state the fault may slip or open. The effect of pore pressure on fault slip is through the normal stress σ n Introduce, the normal stress is S n -P p , where P p is the pore pressure, S n To decompose the normal stress on the cross section. Therefore, if the pore pressure of the cross section is increased, the normal stress will be reduced, which will cause the fault to slip. The specific method is to change the normal stress by injecting gas into the body, and continuously increase the injection pressure from small to large, which will cause the underground stress field to change, and the maximum and minimum principal stress values ​​will be redistributed. The maximum principal stress and minimum principal stress under each gas injection and each injection pressure are obtained as the new maximum principal stress and the new minimum principal stress. The new evaluation coefficient is calculated each time. Using the Coulomb criterion, if the new evaluation coefficient CFF is equal to the critical point zero value, the injection pressure corresponding to the new evaluation coefficient will be used as the maximum pore pressure P p .

[0095] As an optional scheme, based on the maximum pore pressure, the stress risk of dynamic sealing of gas storage faults is evaluated, including: establishing a fluid-solid coupling model based on a three-dimensional geostress model and combining it with the numerical simulation of pore pressure variation of the gas storage; multiple gas injections and multiple gas productions in the fluid-solid coupling model; when the gas pressure of gas injection is less than the maximum pore pressure, the stress risk of dynamic sealing of gas storage faults is determined to be stable; when the gas pressure of gas injection is greater than or equal to the maximum pore pressure, the stress risk of dynamic sealing of gas storage faults is determined to be unstable.

[0096] As an emergency peak-shaving facility, the stability of the gas storage enclosure under strong injection, strong production and alternating loads is the key to its safe operation.

[0097] During the injection and production cycle of a gas storage reservoir, changes in injection pressure lead to changes in the pore pressure field of the entire gas storage reservoir, and changes in pore pressure will lead to changes in the entire stress field, that is, changes in the maximum principal stress and minimum principal stress. Changes in the maximum principal stress and minimum principal stress will cause changes in the normal stress and shear stress of the fault, and the stability of the fault will change.

[0098] Within an injection-production cycle, the magnitude of the ground stress field at different time nodes is obtained to analyze the stability of the fault.

[0099] On the basis of the three-dimensional geological model and the three-dimensional geostress model, combined with the historical fitting and numerical simulation results of the gas storage reservoir, that is, the numerical simulation pore pressure variation body of the gas storage reservoir, a dynamic coupling model of stress-fluid is established, also known as the fluid-solid coupling model.

[0100] Multiple gas injection and gas production were carried out on the established fluid-solid coupling model to simulate the dynamic change of ground stress (effective stress) caused by the change of pore pressure during the injection and production process of the gas storage reservoir, as well as the strain (deformation) of the reservoir and caprock rocks caused by it. When the gas pressure of gas injection is less than the maximum pore pressure, the stress risk of the dynamic sealing of the gas storage fault is judged to be stable; when the gas pressure of gas injection is greater than or equal to the maximum pore pressure, the stress risk of the dynamic sealing of the gas storage fault is judged to be unstable.

[0101] Through the above calculations and evaluations, it can be determined whether the gas storage facility can operate safely under different injection and production cycles and different work systems.

[0102] Embodiment 1

[0103] Figure 1 A flow chart of a method for evaluating dynamic sealing performance of a gas storage reservoir closure using a stress field according to an embodiment of the present invention is shown. Figure 2 A schematic diagram of the spatial distribution of geostress in a method for evaluating the dynamic sealing performance of a gas storage reservoir closure using a stress field according to an embodiment of the present invention is shown. Figure 3 A schematic diagram of the stability of a fault under current ground stress in a certain work area of ​​a method for evaluating the dynamic sealing performance of a gas storage trap using a stress field according to an embodiment of the present invention is shown. Figure 4 A diagram showing the stability of a fault in a certain work area under the highest pore pressure according to a method for evaluating the dynamic sealing performance of a gas storage reservoir trap using a stress field according to an embodiment of the present invention is shown. Figure 5 A schematic diagram of the distribution of pore pressure at a certain time in a section of a certain work area of ​​a method for evaluating dynamic sealing performance of a gas storage reservoir closure by using a stress field according to an embodiment of the present invention is shown. Figure 6 A dynamic stability analysis diagram of a fault under a digital model pore pressure variation body in a certain work area of ​​a method for evaluating the dynamic sealing performance of a gas storage reservoir closure using a stress field according to an embodiment of the present invention is shown.

[0104] Combination Figure 1 , Figure 2 , Figure 3 , Figure 4 , Figure 5 and Figure 6 As shown, the method for evaluating the dynamic sealing performance of a gas storage reservoir closure by using a stress field comprises:

[0105] S102: Obtaining single well geostress parameters;

[0106] Specifically, the geostress parameters of a single well mainly include overburden pressure, formation pore pressure, minimum principal stress, maximum principal stress, geostress direction and rock mechanical property parameters. The above parameters are mainly obtained through logging curve calculation and correction with laboratory sample experimental data. Among them, the overburden pressure is obtained by density logging integral calculation; the formation pore pressure is mainly obtained through actual measurement, conventional logging and seismic velocity calculation; the minimum principal stress is obtained by fracture pressure test, mud loss test, etc.; the maximum principal stress is obtained by wellbore collapse analysis, dipole acoustic wave analysis or tectonic movement analysis; the geostress direction is obtained by imaging logging or Cashier effect experiment. Rock mechanical properties mainly include uniaxial rock strength, Poisson's ratio, Young's modulus and other rock mechanical property parameters, which are mainly obtained by core test, logging, wellbore collapse analysis, etc. The above single well geostress parameter data obtained are used as the basis for geostress modeling.

[0107] S104: based on the three-dimensional geological model and the ground stress parameters of the single well, obtaining the spatial distribution characteristics of the ground stress;

[0108] Among them, based on the three-dimensional geological model and the single well geostress parameters, obtaining the spatial distribution characteristics of geostress includes: inserting the single well geostress parameters into the three-dimensional geological model to obtain the three-dimensional geostress model; analyzing the three-dimensional geostress model to obtain the spatial distribution characteristics of geostress.

[0109] Specifically, on the basis of 3D geological modeling, the single well geostress parameters such as overburden pressure, formation pore pressure, minimum principal stress, maximum principal stress, geostress direction and rock mechanical properties are calculated, and the structural model of the 3D geological model is used as a constraint. The single well geostress parameters are inserted into the 3D geological model through lithofacies analysis or sequential Gaussian method to construct a 3D geostress model. For the established 3D geostress model, the distribution law and change of triaxial principal stress (vertical stress, maximum horizontal stress and minimum horizontal stress) and pore pressure in the formation are analyzed, and the spatial distribution characteristics of geostress are accurately analyzed to obtain the spatial distribution characteristics of geostress.

[0110] S106: Determine the stability of the fault based on the spatial distribution characteristics of ground stress;

[0111] Among them, judging the stability of the fault based on the spatial distribution characteristics of the ground stress includes: obtaining the normal stress and shear stress of the fault plane based on the spatial distribution characteristics of the ground stress; judging the stability of the fault based on the normal stress and shear stress using the Coulomb failure criterion.

[0112] Among them, the Coulomb failure criterion is CFF = τ net -μσn , where CFF is the evaluation coefficient, τ net is the shear stress on the fault plane, σ n is the normal stress of the fault plane, and μ is the weight; if the evaluation coefficient is less than zero, the fault is stable; if the evaluation coefficient is equal to zero, the fault is unstable.

[0113] Specifically, based on the spatial distribution characteristics of geostress, the stability of the fault under the current stress state is analyzed. The principle is to obtain the normal stress and shear stress of the section through the calculation of the geostress parameters of a single well, analyze the magnitude of the normal stress and shear stress at the section, and compare the magnitude of the normal stress and shear stress. When the shear stress is greater than the normal stress, the fault will slip.

[0114] Specifically, using the Coulomb failure criterion CFF = τ net -μσ n , to judge the fault stability. In this formula, CFF is the evaluation coefficient, τ net is the shear stress on the fault plane, σ n is the normal stress of the fault plane, μ is the weight, and μ is between 0.6 and 1, which can be obtained through indoor tests. When CFF is negative, the fault plane remains stable, and the shear stress is not enough to overcome the sliding resistance μσ n When CFF reaches zero, the shear stress can overcome the effective normal stress on the plane of the primary fault, resulting in slip. This evaluation method is used to evaluate the stability of each fault in the gas storage reservoir under the current ground stress state.

[0115] Among them, the single well geostress parameters include overburden pressure, pore pressure, minimum principal stress, maximum principal stress, geostress direction and rock mechanical properties parameters.

[0116] The shear stress on the fault plane is calculated using the following formula:

[0117] τ net =0.5(σ 1 -σ 3 )sinβ

[0118] Among them, τ net is the shear stress on the fault plane, σ 1 is the maximum principal stress, σ 3 is the minimum principal stress, and β is the angle between the fault plane and the direction of the ground stress.

[0119] Among them, the normal stress of the fault plane is calculated using the following formula:

[0120] σ n =0.5(σ 1 +σ 3 )+0.5(σ 1 -σ 3)cosβ

[0121] Among them, σ n is the normal stress on the fault plane, σ 1 is the maximum principal stress, σ 3 is the minimum principal stress, and β is the angle between the fault plane and the direction of the ground stress.

[0122] Generally speaking, the shear stress τ acting on the fault plane is net and normal stress σ n It mainly depends on the magnitude of the principal stresses (maximum principal stress and minimum principal stress), pore pressure, and the angle β between the fault plane and the ground stress.

[0123] S108: If the fault is stable, calculate the maximum pore pressure;

[0124] Among them, if the fault is stable, calculating the maximum pore pressure includes: injecting gas into the three-dimensional geostress model multiple times; gradually increasing the pressure of the injected gas to obtain new maximum principal stress and new minimum principal stress values ​​under each gas pressure; calculating a new evaluation coefficient based on the new maximum principal stress and new minimum principal stress values; if the new evaluation coefficient is equal to zero, the gas pressure corresponding to the new evaluation coefficient is used as the maximum pore pressure.

[0125] Specifically, under the current ground stress state, if the fault is stable, it is necessary to analyze under which stress state the fault may slip or open. The effect of pore pressure on fault slip is through the normal stress σ n Introduce, the normal stress is S n -P p , where P p is the pore pressure, S n To decompose the normal stress on the cross section. Therefore, if the pore pressure of the cross section is increased, the normal stress will be reduced, which will cause the fault to slip. The specific method is to change the normal stress by injecting gas into the body, and continuously increase the injection pressure from small to large, which will cause the underground stress field to change, and the maximum and minimum principal stress values ​​will be redistributed. The maximum principal stress and minimum principal stress under each gas injection and each injection pressure are obtained as the new maximum principal stress and the new minimum principal stress. The new evaluation coefficient is calculated each time. Using the Coulomb criterion, if the new evaluation coefficient CFF is equal to the critical point zero value, the injection pressure corresponding to the new evaluation coefficient will be used as the maximum pore pressure P p .

[0126] S110: Evaluate the stress risk of dynamic sealing of gas storage faults based on maximum void pressure.

[0127] Among them, based on the maximum pore pressure, the stress risk of dynamic sealing of gas storage faults is evaluated, including: establishing a fluid-solid coupling model based on a three-dimensional geostress model and combining the pore pressure variation body of the gas storage with numerical simulation; multiple gas injections and multiple gas productions in the fluid-solid coupling model; when the gas pressure of gas injection is less than the maximum pore pressure, the stress risk of dynamic sealing of gas storage faults is judged to be stable; when the gas pressure of gas injection is greater than or equal to the maximum pore pressure, the stress risk of dynamic sealing of gas storage faults is judged to be unstable.

[0128] On the basis of the three-dimensional geological model and the three-dimensional geostress model, combined with the historical fitting and numerical simulation results of the gas storage reservoir, that is, the numerical simulation pore pressure variation body of the gas storage reservoir, a dynamic coupling model of stress-fluid is established, also known as the fluid-solid coupling model.

[0129] Multiple gas injection and gas production were carried out on the established fluid-solid coupling model to simulate the dynamic change of ground stress (effective stress) caused by the change of pore pressure during the injection and production process of the gas storage reservoir, as well as the strain (deformation) of the reservoir and caprock rocks caused by it. When the gas pressure of gas injection is less than the maximum pore pressure, the stress risk of the dynamic sealing of the gas storage fault is judged to be stable; when the gas pressure of gas injection is greater than or equal to the maximum pore pressure, the stress risk of the dynamic sealing of the gas storage fault is judged to be unstable.

[0130] Embodiment 2

[0131] Figure 7 A block diagram of a device for evaluating dynamic sealing performance of a gas storage reservoir closure using a stress field according to an embodiment of the present invention is shown.

[0132] like Figure 7 As shown, the device for evaluating the dynamic sealing performance of a gas storage reservoir closure by using a stress field comprises:

[0133] The first acquisition module 102 acquires the ground stress parameters of a single well;

[0134] A second acquisition module 104 is configured to obtain spatial distribution characteristics of geostress based on the three-dimensional geological model and the geostress parameters of the single well;

[0135] A judgment module 106, judging the stability of the fault based on the spatial distribution characteristics of the ground stress;

[0136] A calculation module 108 calculates the maximum pore pressure if the fault is stable;

[0137] The evaluation module 110 evaluates the stress risk of the dynamic sealing property of the gas storage fault based on the maximum void pressure.

[0138] Specifically, the geostress parameters of a single well mainly include overburden pressure, formation pore pressure, minimum principal stress, maximum principal stress, geostress direction and rock mechanical property parameters. The above parameters are mainly obtained through logging curve calculation and correction with laboratory sample experimental data. Among them, the overburden pressure is obtained by density logging integral calculation; the formation pore pressure is mainly obtained through actual measurement, conventional logging and seismic velocity calculation; the minimum principal stress is obtained by fracture pressure test, mud loss test, etc.; the maximum principal stress is obtained by wellbore collapse analysis, dipole acoustic wave analysis or tectonic movement analysis; the geostress direction is obtained by imaging logging or Cashier effect experiment. Rock mechanical properties mainly include uniaxial rock strength, Poisson's ratio, Young's modulus and other rock mechanical property parameters, which are mainly obtained by core test, logging, wellbore collapse analysis, etc. The above single well geostress parameter data obtained are used as the basis for geostress modeling.

[0139] Among them, based on the three-dimensional geological model and the single well geostress parameters, obtaining the spatial distribution characteristics of geostress includes: inserting the single well geostress parameters into the three-dimensional geological model to obtain the three-dimensional geostress model; analyzing the three-dimensional geostress model to obtain the spatial distribution characteristics of geostress.

[0140] Specifically, on the basis of 3D geological modeling, the single well geostress parameters such as overburden pressure, formation pore pressure, minimum principal stress, maximum principal stress, geostress direction and rock mechanical properties are calculated, and the structural model of the 3D geological model is used as a constraint. The single well geostress parameters are inserted into the 3D geological model through lithofacies analysis or sequential Gaussian method to construct a 3D geostress model. For the established 3D geostress model, the distribution law and change of triaxial principal stress (vertical stress, maximum horizontal stress and minimum horizontal stress) and pore pressure in the formation are analyzed, and the spatial distribution characteristics of geostress are accurately analyzed to obtain the spatial distribution characteristics of geostress.

[0141] Among them, judging the stability of the fault based on the spatial distribution characteristics of the ground stress includes: obtaining the normal stress and shear stress of the fault plane based on the spatial distribution characteristics of the ground stress; judging the stability of the fault based on the normal stress and shear stress using the Coulomb failure criterion.

[0142] Among them, the Coulomb failure criterion is CFF = τ net -μσ n , where CFF is the evaluation coefficient, τ net is the shear stress on the fault plane, σ n is the normal stress of the fault plane, and μ is the weight; if the evaluation coefficient is less than zero, the fault is stable; if the evaluation coefficient is equal to zero, the fault is unstable.

[0143] Specifically, based on the spatial distribution characteristics of geostress, the stability of the fault under the current stress state is analyzed. The principle is to obtain the normal stress and shear stress of the section through the calculation of the geostress parameters of a single well, analyze the magnitude of the normal stress and shear stress at the section, and compare the magnitude of the normal stress and shear stress. When the shear stress is greater than the normal stress, the fault will slip.

[0144] Specifically, using the Coulomb failure criterion CFF = τ net -μσ n , to judge the fault stability. In this formula, CFF is the evaluation coefficient, τ net is the shear stress on the fault plane, σ n is the normal stress of the fault plane, μ is the weight, and μ is between 0.6 and 1, which can be obtained through indoor tests. When CFF is negative, the fault plane remains stable, and the shear stress is not enough to overcome the sliding resistance μσ n When CFF reaches zero, the shear stress can overcome the effective normal stress on the plane of the primary fault, resulting in slip. This evaluation method is used to evaluate the stability of each fault in the gas storage reservoir under the current ground stress state.

[0145] Among them, the single well geostress parameters include overburden pressure, pore pressure, minimum principal stress, maximum principal stress, geostress direction and rock mechanical properties parameters.

[0146] The shear stress on the fault plane is calculated using the following formula:

[0147] τ net =0.5(σ 1 -σ 3 )sinβ

[0148] Among them, τ net is the shear stress on the fault plane, σ 1 is the maximum principal stress, σ 3 is the minimum principal stress, and β is the angle between the fault plane and the direction of the ground stress.

[0149] Among them, the normal stress of the fault plane is calculated using the following formula:

[0150] σ n =0.5(σ 1 +σ 3 )+0.5(σ 1 -σ 3 )cosβ

[0151] Among them, σ n is the normal stress on the fault plane, σ 1 is the maximum principal stress, σ 3 is the minimum principal stress, and β is the angle between the fault plane and the direction of the ground stress.

[0152] Generally speaking, the shear stress τ acting on the fault plane is net and normal stress σ n It mainly depends on the magnitude of the principal stresses (maximum principal stress and minimum principal stress), pore pressure, and the angle β between the fault plane and the ground stress.

[0153] Among them, if the fault is stable, calculating the maximum pore pressure includes: injecting gas into the three-dimensional geostress model multiple times; gradually increasing the pressure of the injected gas to obtain new maximum principal stress and new minimum principal stress values ​​under each gas pressure; calculating a new evaluation coefficient based on the new maximum principal stress and new minimum principal stress values; if the new evaluation coefficient is equal to zero, the gas pressure corresponding to the new evaluation coefficient is used as the maximum pore pressure.

[0154] Specifically, under the current ground stress state, if the fault is stable, it is necessary to analyze under which stress state the fault may slip or open. The effect of pore pressure on fault slip is through the normal stress σ n Introduce, the normal stress is S n -P p , where P p is the pore pressure, S n To decompose the normal stress on the cross section. Therefore, if the pore pressure of the cross section is increased, the normal stress will be reduced, which will cause the fault to slip. The specific method is to change the normal stress by injecting gas into the body, and continuously increase the injection pressure from small to large, which will cause the underground stress field to change, and the maximum and minimum principal stress values ​​will be redistributed. The maximum principal stress and minimum principal stress under each gas injection and each injection pressure are obtained as the new maximum principal stress and the new minimum principal stress. The new evaluation coefficient is calculated each time. Using the Coulomb criterion, if the new evaluation coefficient CFF is equal to the critical point zero value, the injection pressure corresponding to the new evaluation coefficient will be used as the maximum pore pressure P p .

[0155] Among them, based on the maximum pore pressure, the stress risk of dynamic sealing of gas storage faults is evaluated, including: establishing a fluid-solid coupling model based on a three-dimensional geostress model and combining the pore pressure variation body of the gas storage with numerical simulation; multiple gas injections and multiple gas productions in the fluid-solid coupling model; when the gas pressure of gas injection is less than the maximum pore pressure, the stress risk of dynamic sealing of gas storage faults is judged to be stable; when the gas pressure of gas injection is greater than or equal to the maximum pore pressure, the stress risk of dynamic sealing of gas storage faults is judged to be unstable.

[0156] On the basis of the three-dimensional geological model and the three-dimensional geostress model, combined with the historical fitting and numerical simulation results of the gas storage reservoir, that is, the numerical simulation pore pressure variation body of the gas storage reservoir, a dynamic coupling model of stress-fluid is established, also known as the fluid-solid coupling model.

[0157] Multiple gas injection and gas production were carried out on the established fluid-solid coupling model to simulate the dynamic change of ground stress (effective stress) caused by the change of pore pressure during the injection and production process of the gas storage reservoir, as well as the strain (deformation) of the reservoir and caprock rocks caused by it. When the gas pressure of gas injection is less than the maximum pore pressure, the stress risk of the dynamic sealing of the gas storage fault is judged to be stable; when the gas pressure of gas injection is greater than or equal to the maximum pore pressure, the stress risk of the dynamic sealing of the gas storage fault is judged to be unstable.

[0158] The embodiments of the present invention have been described above, and the above description is exemplary, not exhaustive, and is not limited to the disclosed embodiments. Many modifications and changes will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments.

Claims

1. A method for evaluating the dynamic sealing performance of a gas storage reservoir using a stress field, characterized in that: include: Obtaining the ground stress parameters of a single well; Based on the three-dimensional geological model and the single well geostress parameters, obtaining the spatial distribution characteristics of geostress; Based on the spatial distribution characteristics of the ground stress, determine the stability of the fault; If the fault is stable, calculate the maximum pore pressure; Based on the maximum pore pressure, evaluating the stress risk of dynamic sealing of the gas storage fault; Wherein, judging the stability of the fault based on the spatial distribution characteristics of the geostress includes: Based on the spatial distribution characteristics of the ground stress, obtaining the normal stress and shear stress of the fault plane; Based on the normal stress and shear stress, the stability of the fault is determined using the Coulomb failure criterion; Among them, the Coulomb failure criterion is CFF=-τ net -ms n Among them, CFF is the evaluation coefficient, τ net is the shear stress on the fault plane, σ n is the normal stress on the fault plane, μ is the weight; If the evaluation coefficient is less than zero, the fault is stable; If the evaluation coefficient is equal to zero, the fault is unstable; The single well geostress parameters include overburden formation pressure, pore pressure, minimum principal stress, maximum principal stress, geostress direction and rock mechanical property parameters; The shear stress of the fault plane is calculated using the following formula: t net =0.5(σ1-σ3)sinβ Among them, τ net is the shear stress on the fault plane, σ1 is the maximum principal stress, σ3 is the minimum principal stress, and β is the angle between the fault plane and the direction of the ground stress; The normal stress of the fault plane is calculated using the following formula: s n =0.5(σ1+σ3)+0.5(σ1-σ3)cosβ Among them, σ n is the normal stress of the fault plane, σ1 is the maximum principal stress, σ3 is the minimum principal stress, and β is the angle between the fault plane and the direction of the ground stress.

2. The method for evaluating the dynamic sealing performance of a gas storage reservoir by using a stress field according to claim 1, characterized in that: The obtaining of the spatial distribution characteristics of the geostress based on the three-dimensional geological model and the geostress parameters of the single well includes: Inserting the single well geostress parameter into the three-dimensional geological model to obtain a three-dimensional geostress model; The three-dimensional geostress model is analyzed to obtain the spatial distribution characteristics of the geostress.

3. The method for evaluating the dynamic sealing performance of a gas storage reservoir by using a stress field according to claim 2, characterized in that: If the fault is stable, calculating the maximum pore pressure includes: Inject gas into the three-dimensional geostress model multiple times; The pressure of the injected gas is gradually increased to obtain new maximum principal stress and new minimum principal stress values ​​under each gas pressure; Based on the new maximum principal stress and the new minimum principal stress values, a new evaluation coefficient is calculated; If the new evaluation coefficient is equal to zero, the gas pressure corresponding to the new evaluation coefficient is used as the maximum pore pressure.

4. The method for evaluating the dynamic sealing performance of a gas storage reservoir by using a stress field according to claim 3, characterized in that: The stress risk of evaluating the dynamic sealing property of the gas storage fault based on the maximum pore pressure includes: Based on the three-dimensional geostress model and in combination with the pore pressure variation body of the gas storage reservoir numerical simulation, a fluid-solid coupling model is established; Multiple gas injection and multiple gas extraction in the fluid-solid coupling model; When the gas pressure of the gas injection is less than the maximum pore pressure, the stress risk of the dynamic sealing property of the gas storage fault is determined to be stable; When the gas pressure of the injected gas is greater than or equal to the maximum pore pressure, the stress risk of the dynamic sealing property of the gas storage fault is determined to be unstable.

5. A device for evaluating the dynamic sealing performance of a gas storage reservoir by using a stress field, characterized in that: The device includes: The first acquisition module acquires the ground stress parameters of a single well; A second acquisition module obtains spatial distribution characteristics of geostress based on the three-dimensional geological model and the geostress parameters of the single well; A judgment module, judging the stability of the fault based on the spatial distribution characteristics of the ground stress; A calculation module, if the fault is stable, calculates the maximum pore pressure; An evaluation module, based on the maximum pore pressure, evaluates the stress risk of dynamic sealing of the gas storage fault; Wherein, judging the stability of the fault based on the spatial distribution characteristics of the geostress includes: Based on the spatial distribution characteristics of the ground stress, obtaining the normal stress and shear stress of the fault plane; Based on the normal stress and shear stress, the stability of the fault is determined using the Coulomb failure criterion; Among them, the Coulomb failure criterion is CFF=τ net -ms n Among them, CFF is the evaluation coefficient, τ net is the shear stress on the fault plane, σ n is the normal stress on the fault plane, μ is the weight; If the evaluation coefficient is less than zero, the fault is stable; If the evaluation coefficient is equal to zero, the fault is unstable; The single well geostress parameters include overburden formation pressure, pore pressure, minimum principal stress, maximum principal stress, geostress direction and rock mechanical property parameters; The shear stress of the fault plane is calculated using the following formula: t net =0.5(σ1-σ3)sinβ Among them, τ net is the shear stress on the fault plane, σ1 is the maximum principal stress, σ3 is the minimum principal stress, and β is the angle between the fault plane and the direction of the ground stress; The normal stress of the fault plane is calculated using the following formula: s n =0.5(σ1+σ3)+0.5(σ1-σ3)cosβ Among them, σ n is the normal stress of the fault plane, σ1 is the maximum principal stress, σ3 is the minimum principal stress, and β is the angle between the fault plane and the direction of the ground stress.

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