Fault development gas storage operation upper limit pressure determination method considering overpressure operation condition

Abstract

The invention relates to a fault development gas storage operation upper limit pressure determination method considering an overpressure operation condition. The method comprises the following steps: 1, establishing a gas storage three-dimensional geomechanical model covering reservoir, cap strata and peripheral faults; 2, carrying out geomechanical simulation; 3, determining the shear failure resistance limit pressure bearing capacity and the tensile failure resistance limit pressure bearing capacity of the cover layer; 4, designing a gas logging permeability test experiment of the cover rock under different static confining pressures; 5, determining the gas breakthrough pressure of the cover rock under different pressure increasing coefficients; 6, determining the sealing limit pressure-bearing capacity of the capillary tube of the cover layer; 7, determining the anti-slip activation limit pressure bearing capacity and the anti-expansion fracture limit pressure bearing capacity of the fault; and 8, the operation upper limit pressure of the gas storage is determined. According to the method, the four-dimensional geomechanical model is established, the stress path of the reservoir building and gas injection process of the oil and gas reservoir is obtained through numerical simulation, and the dynamic horizontal principal stress of the reservoir building and gas injection process is calculated and determined by taking the determined reservoir top horizontal principal stress as the reference.

Description

Technical Field

[0001] This invention relates to the field of underground natural gas storage technology, and more specifically, to a method for determining the upper limit pressure of a fault-developed gas storage facility that takes into account overpressure operating conditions. Background Technology

[0002] The upper operating pressure refers to the highest reservoir pressure that a gas storage facility (UGS) can reach during injection and production operations. This upper operating pressure is a critical parameter concerning the safety and economy of the gas storage facility, and ensuring the safety of the geological structure is the most important and fundamental factor in designing the upper operating pressure. The essence of a gas storage facility is to utilize underground depleted oil and gas reservoirs, salt caverns, or aquifers to store high-pressure natural gas. Each geological structure has its inherent rock mechanics pressure bearing limit. If the operating pressure exceeds the upper limit, it may lead to caprock rupture or fault activation, compromising the gas storage facility's sealing and causing natural gas to leak into shallow layers or to the surface. This not only results in resource loss but may also cause safety accidents.

[0003] In the past, when designing the upper limit pressure for gas storage operation, the traditional view was that the original formation pressure was the maximum pressure the rock had ever withstood, therefore the upper limit pressure for gas storage operation should not exceed the original formation pressure. However, this view is not entirely accurate. The key reason is that the maximum pressure that underground rock strata can withstand is not determined by the original formation pressure, i.e., by the geostress. The benchmark for setting the upper limit pressure is the current geostress field and rock mechanical properties, not the historical original pressure. Therefore, it is feasible for the upper limit pressure of gas storage operation to exceed the original formation pressure. Moreover, gas storage is a large-scale infrastructure investment, and its operation aims for long-term economic value based on safety. The upper limit pressure determines the working gas volume of the gas storage. The higher the upper limit pressure is set, the greater the theoretical working gas volume. However, overpressure operation is not about blindly increasing the pressure; its feasibility is based on a more accurate and comprehensive evaluation of the dynamic sealing ultimate pressure bearing capacity of the geological body.

[0004] However, due to the special operating conditions of gas storage facilities, determining the dynamic sealing limit pressure bearing capacity of the gas storage geological body requires close attention to high-pressure, high-speed injection and production, and alternating load conditions. During high-speed, intensive injection and production, the formation pressure rises and falls sharply, causing periodic disturbances in the regional stress field. According to numerical simulations of CO2 overpressure storage, after the injection formation pressure exceeds the hydrostatic pressure, the horizontal principal stresses of both the reservoir and caprock show an increasing trend, but the increase in the former is much greater than that in the latter. Meanwhile, the effective horizontal principal stresses of both the reservoir and caprock show a decreasing trend, and there are abrupt changes in both the horizontal and vertical effective principal stresses on both sides of the reservoir-caprock interface. Summary of the Invention

[0005] The objective of this invention is to provide a method for determining the upper limit pressure of a fault-developed gas reservoir considering overpressure operating conditions. This invention establishes a fitted and corrected three-dimensional dynamic elastoplastic geomechanical model. Through three-dimensional geomechanical simulation, it determines the three-dimensional geostress field at different times during cyclic injection and production under overpressure conditions after the oil and gas reservoir is reconstructed. It determines the horizontal principal stress path during the formation pressure increase process. Considering the influence of the stress hysteresis effect of formation elastoplastic deformation, it accurately evaluates the ultimate pressure-bearing capacity of the gas reservoir caprock by adopting caprock tension and shear failure criteria. Simultaneously, based on the stress disturbance characteristics revealed by the three-dimensional geomechanical simulation, it guides subsequent experimental design. First, using the minimum effective horizontal principal stress value of different reservoirs obtained from the simulation as the confining pressure, a gas permeability experiment of the caprock rock is designed to determine its gas permeability after 50 cycles of axial reciprocating alternating loading. Then, based on the functional relationship between rock gas permeability and dynamic breakthrough pressure, the breakthrough pressure value of the caprock under dynamic stress conditions is determined. Finally, through normalization, a relationship diagram between the dynamic breakthrough pressure and the gas storage pressure-boosting coefficient was plotted, and a corresponding functional relationship was established to accurately determine the dynamic capillary seal ultimate pressure-bearing capacity of the caprock under cyclic loading. Based on determining the caprock's ultimate pressure-bearing capacity, the ultimate pressure-bearing capacity of the faults against mechanical failure was then investigated. Therefore, based on fault development characteristics and the spatial relationship of the gas storage layers, fault classification was first carried out. Based on the classification results, and using geomechanical simulation results, the ultimate pressure-bearing capacity of the faults against mechanical failure was determined using the shear slip index and the expansion trend index. By comprehensively comparing the calculated dynamic breakthrough pressure of the caprock with the ultimate pressure-bearing caprock and faults against mechanical failure, the minimum value was selected as the upper operating pressure limit of the gas storage.

[0006] The technical solution provided by this invention is: a method for determining the upper limit pressure of a fault-developed gas storage facility considering overpressure operating conditions, comprising the following steps:

[0007] Step (1): Establish a three-dimensional geomechanical dynamic model of the gas storage reservoir covering the reservoir, caprock and surrounding faults, and correct the model based on the measured or regional geostress evaluation results;

[0008] Step (2): Using the corrected model, conduct geomechanical simulation to determine the three-dimensional principal stress path of the reservoir during the reservoir construction and gas injection process, and calculate the dynamic three-dimensional principal stress during the reservoir construction and gas injection process;

[0009] Step (3): Based on the dynamic triaxial principal stress during the gas injection process, the shear and tensile safety indices are used to determine the ultimate bearing capacity of the caprock against shear and tensile failure, respectively.

[0010] Step (4): Based on the stress disturbance characteristics of the gas storage reservoir determined by geomechanical simulation, design and carry out gas permeability test after 50 alternating loads on the caprock under different effective stresses;

[0011] Step (5): Use the conversion relationship between rock gas permeability and gas breakthrough pressure to determine the gas breakthrough pressure of the caprock under different pressure-boosting coefficients;

[0012] Step (6): Draw a graph showing the relationship between the normalized dynamic breakthrough pressure of the caprock and the pressure boosting coefficient of the gas storage tank, establish a functional relationship, and analyze and determine the capillary seal ultimate pressure bearing capacity of the caprock;

[0013] Step (7): Based on the dynamic triaxial principal stress during the gas injection process, the slip trend index and expansion trend index are used to determine the fault's resistance to slip activation and expansion rupture ultimate bearing capacity, respectively.

[0014] Step (8): Using the pressure increase coefficient as the horizontal axis and the evaluation indices such as the capillary sealing ultimate pressure bearing capacity of the capillary layer and the mechanical damage resistance ultimate pressure bearing capacity of the capillary layer and fault as the vertical axis, draw an intersection chart to determine the upper limit pressure of the gas storage facility.

[0015] The three-dimensional dynamic geomechanical simulation mentioned in step (1) above refers to a dynamic mechanical model established on the basis of a three-dimensional geomechanical model by combining fluid-structure interaction numerical simulation, which is used to determine the characteristics of formation pressure and geostress changes during the construction, injection and production process of a gas storage facility.

[0016] The reservoir horizontal stress path during the formation pressure increase process described in step (2) above is calculated using the formula... Perform calculations;

[0017] in, This refers to the change in pore pressure during the gas storage process; The changes in the three principal stresses during the gas injection process in the gas storage facility, including the changes in the maximum horizontal principal stress. Minimum horizontal principal stress variation MPa; The horizontal principal stress paths during gas injection into the gas storage facility, including the path of maximum horizontal principal stress. and minimum horizontal principal stress path .

[0018] The dynamic triaxial principal stress during the gas injection process in the underground storage facility described in step (2) above is calculated using the formula... Perform calculations;

[0019] in, Dynamic triaxial principal stresses during the gas injection process in the gas storage facility, including the maximum horizontal principal stress. Minimum horizontal principal stress MPa; The three principal stresses prior to reservoir construction, including the maximum horizontal principal stress before reservoir construction. Minimum horizontal principal stress before reservoir construction MPa; Formation pressure at different times during the gas injection process for oil and gas reservoir construction; Formation pressure before reservoir construction in oil and gas reservoirs.

[0020] The ultimate tensile failure pressure of the cap layer mentioned in step (3) above is calculated using the formula... The calculation is performed using the formula for the cap layer tensile safety index. Iterative analysis was conducted to determine this;

[0021] in, The ultimate tensile failure pressure of the caprock is expressed in MPa. The minimum horizontal principal stress during the gas injection process in the reservoir construction of an oil and gas reservoir, in MPa; To extend the safety index, dimensionless; Formation pressure (MPa) at different times during the reservoir construction and gas injection process;

[0022] The dynamic minimum horizontal principal stress during the reservoir construction and gas injection process in the caprock is described. Using formula Perform calculations;

[0023] in, The minimum principal stress before the caprock is built is expressed in MPa. The maximum principal stress before the caprock was built is expressed in MPa. This is the minimum horizontal principal stress path; Formation pressure before reservoir construction in oil and gas reservoirs.

[0024] The ultimate shear failure pressure of the caprock mentioned in step (3) above is calculated using the formula... The calculation is performed using the cap layer shear safety index formula. Iterative analysis was conducted to determine this;

[0025] in, The ultimate shear failure pressure of the caprock, in MPa; Cohesion, MPa; It is the internal friction angle; The minimum dynamic principal stress during the gas injection process in the reservoir construction of an oil and gas reservoir, in MPa; The maximum dynamic principal stress during the reservoir construction and gas injection process, measured in MPa. The shear safety index is dimensionless. Cohesion, MPa; It is the internal friction angle; The maximum effective principal stress during the gas injection process in the reservoir construction process, measured in MPa. The minimum effective principal stress during the gas injection process in the reservoir construction is given in MPa.

[0026] The dynamic maximum principal stress during the reservoir construction and gas injection process is described above. and minimum principal stress The values ​​differ under different geostress states. Among them, ① when the geostress state at a certain moment during the reservoir construction and gas injection process is a normal fault stress state ( ), , ② When the geostress state at a certain moment during the reservoir construction and gas injection process is the reverse fault stress state ( ), , ③ When the in-situ stress state at a certain moment during the reservoir construction and gas injection process is the strike-slip fault stress state ( ), , .

[0027] in, The maximum dynamic horizontal principal stress during the gas injection process of reservoir construction in oil and gas reservoirs, in MPa; The minimum horizontal principal stress during the reservoir construction and gas injection process, measured in MPa. Dynamic vertical principal stress during reservoir construction and gas injection The maximum horizontal principal stress (MPa) at a certain moment during the reservoir construction and gas injection process is given. The minimum horizontal principal stress (MPa) at a certain moment during the reservoir construction and gas injection process is given. The vertical principal stress at a certain moment during the gas injection process of building an oil and gas reservoir.

[0028] The dynamic maximum horizontal principal stress during the reservoir construction and gas injection process is described above. and minimum horizontal principal stress Using formula and calculate;

[0029] in, The maximum horizontal principal stress before reservoir construction, MPa; The minimum horizontal principal stress before reservoir construction, in MPa; This is the path of maximum horizontal principal stress. Minimum horizontal principal stress path; Formation pressure (MPa) at different times during the reservoir construction and gas injection process; Formation pressure before reservoir construction, MPa.

[0030] In step (5) above, determining the gas breakthrough pressure of the caprock under different minimum effective principal stresses of the reservoir using the functional relationship between rock gas permeability and caprock static breakthrough pressure refers to: using the functional relationship Perform calculations;

[0031] in, Rock gas breakthrough pressure at different upper limit pressures, MPa; denoted as ρ_a, where ρ is the gas permeability; α and β are parameters of the mathematical fitting function.

[0032] The step (6) above, which involves plotting the relationship between the normalized dynamic breakthrough pressure of the caprock and the gas storage pressure-boosting coefficient, refers to plotting a relationship curve with the gas storage pressure-boosting coefficient as the abscissa and the normalized dynamic breakthrough pressure as the ordinate, and establishing a binomial, logarithmic, or exponential functional relationship. When using a binomial functional relationship, its expression is: ;

[0033] in, To achieve normalized dynamic breakthrough pressure; Rock gas breakthrough pressure at different upper limit pressures, MPa; The breakthrough pressure under hydrostatic pressure, in MPa; denoted as the gas storage pressure boosting coefficient, which is the ratio of the upper limit pressure to the hydrostatic pressure; a, b, and c are parameters of the mathematical fitting function.

[0034] The dynamic capillary seal ultimate pressure bearing capacity of the caprock mentioned in step (6) above refers to the pressure difference between the reservoir and the caprock continuously increasing during the gas injection process of the oil and gas reservoir construction, when the caprock dynamically breaks through the pressure. When the pressure difference between the reservoir and caprock is less than the pressure difference during gas injection and storage construction in an oil and gas reservoir, the caprock capillary dynamic sealing limit is reached. The pressure bearing capacity of the caprock dynamic capillary sealing limit at this point is determined using the formula... Perform calculations;

[0035] in, The ultimate pressure bearing capacity of the capillary seal under alternating load conditions, in MPa; The initial pressure of the caprock, i.e., the breakthrough pressure before the caprock pressure boosting operation, is expressed in MPa. It is the hydrostatic pressure.

[0036] The fault anti-slip activation ultimate bearing capacity mentioned in step (7) above is calculated using the formula... Perform calculations;

[0037] in, To activate the ultimate bearing capacity for fault anti-slip, MPa; The fault friction coefficient; The normal stress on the fault surface when slippage is activated, in MPa; is the cross-sectional shear stress, in MPa, when the fault is activated by slip.

[0038] The normal stress on the cross section when the fault undergoes anti-slip activation. and cross-sectional shear stress Using formula Perform iterative analysis and calculation;

[0039] in, This is a fault slip trend index; Dynamic cross-sectional normal stress during the gas injection process of oil and gas reservoir construction, MPa; Dynamic cross-sectional shear stress during the gas injection process of oil and gas reservoir construction, MPa; Formation pressure at different times during the gas injection process of oil and gas reservoir construction.

[0040] The dynamic cross-sectional normal stress mentioned above Using formula Calculations are performed; while the cross-sectional shear stress... Using formula Perform calculations;

[0041] in, , The maximum and minimum dynamic horizontal principal stresses during the gas injection process of oil and gas reservoir construction; Dynamic vertical principal stress during the gas injection process of oil and gas reservoir construction; The fault azimuth angle; This represents the fault dip angle.

[0042] The dynamic maximum horizontal principal stress during the reservoir construction and gas injection process described in the above steps is... and minimum horizontal principal stress Using formula and Perform calculations;

[0043] in, The maximum horizontal principal stress before reservoir construction, MPa; The minimum horizontal principal stress before reservoir construction, in MPa; This is the path of maximum horizontal principal stress. Minimum horizontal principal stress path; Formation pressure (MPa) at different times during the reservoir construction and gas injection process; Formation pressure before reservoir construction, MPa.

[0044] The fault's ultimate bearing capacity against expansion and rupture, as described in step (7) above, when When using the formula Perform calculations; when When using the formula Perform calculations;

[0045] in, The ultimate bearing capacity against expansion and rupture of the fault is measured in MPa. The maximum principal stress, in MPa, occurs when the fault undergoes expansion and rupture. The minimum principal stress, in MPa, is the stress required for the fault to expand and rupture. is the principal stress on the cross section when the fault undergoes expansion and rupture, in MPa; denoted as the tensile strength of the rock, in MPa.

[0046] The maximum principal stress when the fault undergoes anti-slip activation. and minimum principal stress Using formula Perform iterative analysis and calculation;

[0047] in, It is an inflation trend index; The maximum dynamic principal stress during the gas injection process in the reservoir construction process, measured in MPa. The minimum dynamic principal stress during the gas injection process in the reservoir construction of an oil and gas reservoir, in MPa;

[0048] The dynamic cross-sectional normal stress during the gas injection process of oil and gas reservoir construction, MPa.

[0049] The dynamic maximum principal stress during the reservoir construction and gas injection process is described above. and maximum principal stress The values ​​differ under different geostress states. Among them, ① when the geostress state at a certain moment during the reservoir construction and gas injection process is a normal fault stress state ( )hour, , ; ② When the geostress state at a certain moment during the reservoir construction and gas injection process is the reverse fault stress state ( )hour, , ③ When the stress state of an oil and gas reservoir is at a certain moment during the reservoir construction and gas injection process, it is the stress state of a strike-slip fault. )hour, , .

[0050] in, The maximum dynamic horizontal principal stress during the gas injection process of reservoir construction in oil and gas reservoirs, in MPa; The minimum horizontal principal stress during the reservoir construction and gas injection process, measured in MPa. Dynamic vertical principal stress during reservoir construction and gas injection The maximum horizontal principal stress (MPa) at a certain moment during the reservoir construction and gas injection process is given. The minimum horizontal principal stress (MPa) at a certain moment during the reservoir construction and gas injection process is given. The vertical principal stress at a certain moment during the gas injection process of building an oil and gas reservoir.

[0051] The dynamic maximum horizontal principal stress during the reservoir construction and gas injection process described in the above steps is... and minimum horizontal principal stress Using formula and Perform calculations;

[0052] in, The maximum horizontal principal stress before reservoir construction, MPa; The minimum horizontal principal stress before reservoir construction, in MPa; This is the path of maximum horizontal principal stress. This is the path of minimum horizontal principal stress; Formation pressure (MPa) at different times during the reservoir construction and gas injection process; Formation pressure before reservoir construction, MPa.

[0053] The beneficial effects of this invention are:

[0054] (1) Existing methods typically determine the capillary sealing limit of the caprock based on conventional gas breakthrough pressure tests of core samples. However, this testing method is difficult to accurately reflect the impact of dynamic changes in geostress during high-speed injection and production in gas reservoirs on the micropore structure and capillary sealing capacity of the caprock. In particular, it cannot evaluate the impact of significant disturbances in regional horizontal principal stress on the dynamic sealing capacity of the caprock capillary under pressurization and gas injection conditions during oil and gas reservoir reconstruction. This invention integrates four-dimensional geomechanical simulation and indoor alternating load gas permeability testing experiments. First, it clarifies the characteristics of geostress disturbance caused by injection and production, and then designs gas permeability tests under different effective stress conditions to determine and convert the gas breakthrough pressure of the caprock under dynamic stress. By establishing a quantitative relationship between dynamic breakthrough pressure and pressurization coefficient, the dynamic ultimate pressure bearing capacity of the caprock under alternating load is accurately characterized. Compared with conventional methods, this invention fully considers the fluid-structure interaction effect during injection and production, which is more consistent with the actual working conditions of gas reservoir pressurization and high-speed cyclic injection and production.

[0055] (2) Current methods are usually based on conventional static geological or geomechanical theories, using indicators such as gas breakthrough pressure of caprock, critical closure gas column height of faults, and minimum horizontal principal stress determined by field test interpretation or theoretical calculation to constrain and determine the upper limit pressure of gas storage. This method does not fully reflect the ultimate pressure bearing capacity of multiple objects such as caprock and faults during the injection and production process of gas storage in fault-developed areas, nor does it consider the impact of gas storage pressurization injection on geostress disturbance and formation deformation. It is only applicable to gas storage in areas with no fault development, small injection and production pressure amplitude, and no pressurization injection. This invention is based on fluid-structure interaction theory. Through alternating load core experiments and four-dimensional geomechanical simulation, it takes the dynamic disturbance of geostress under pressurization injection as the basis, and simultaneously adopts a comprehensive quantitative analysis of multiple factors such as caprock dynamic capillary, shear and tensile failure resistance, fault slip resistance and expansion rupture resistance. By drawing a multi-indicator intersection chart, it accurately determines the upper limit pressure of gas storage in fault-developed areas under pressurization injection, which greatly improves the scientificity and accuracy of the upper limit pressure design. Attached Figure Description

[0056] Figure 1 This is a schematic diagram of the process of the present invention;

[0057] Figure 2 This is a diagram showing the transformation relationship between dynamic and static rock mechanics parameters of the Shengping gas storage facility of the present invention.

[0058] Figure 3 The three-dimensional geomechanical model of the Shengping gas storage facility established for this invention;

[0059] Figure 4 This is a geostress distribution map of the original and pre-construction areas of the Shengping gas storage reservoir of the present invention;

[0060] Figure 5 The stress path diagram of the horizontal principal stress during the gas injection and pressurization process of the Shengping gas storage tank of the present invention;

[0061] Figure 6 This is a graph showing the functional relationship between the gas permeability of rock samples and the breakthrough pressure used in this invention.

[0062] Figure 7 This is an experimental diagram illustrating the ultimate pressure-bearing capacity of the capillary tubes in the cover layer of the Shengping gas storage tank according to the present invention.

[0063] Figure 8 This is a cross-sectional diagram of the evaluation indicators for the ultimate pressure bearing capacity of the cap layer and fault of the Shengping gas storage facility according to the present invention.

[0064] Figure 9 This is a comparison chart showing the working gas volume of a gas storage facility after determining the upper limit operating pressure using the present invention and traditional methods. Detailed Implementation

[0065] Preferred embodiments of the invention will now be described in more detail. While preferred embodiments of the invention are described below, it should be understood that the invention can be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided so that the invention will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art.

[0066] This method uses the Shengping gas storage facility as an example. The Shengping gas storage facility was converted from the Shengping gas reservoir. The Shengping gas reservoir trap type is a fault-antic composite trap with an area of ​​22.62 km². 2 The closure amplitude is 170m. Geological evaluation and development dynamic evaluation show that the Shengping gas reservoir is a marginal and bottom water gas reservoir with an original formation pressure of 32.0MPa, belonging to a normal temperature and pressure system.

[0067] A method for determining the upper limit pressure of a complex gas storage facility with fault-block development that considers overpressure operation is adopted. The specific embodiments of the present invention will be further described in detail below with reference to the accompanying drawings:

[0068] refer to Figure 1 As shown, a method for determining the upper limit pressure of a fault-bounded gas storage facility operating under overpressure includes the following steps:

[0069] Step S101: Establish a three-dimensional geomechanical dynamic model of the gas storage reservoir, encompassing the reservoir, caprock, and surrounding faults, and calibrate the model based on measured or regional geostress assessment results. Specifically:

[0070] ① A geological model was established based on seismic and well logging data. Based on the geological model, the model was expanded in the plane, vertical and horizontal directions to establish a gas reservoir geomechanical model covering caprock, reservoir, overlying strata, underlying strata and faults. A three-dimensional mechanical property model was established by combining rock mechanics experiments and well logging interpretation results.

[0071] In practical applications, the geological model of the Shengping gas storage was expanded. The horizontal expansion was multiplied by 1.5 times, extending to 3 times the storage area. The overlying strata were expanded to the surface by 1.5 times, and the underlying strata were expanded to a depth of 30,000 m by 1.5 times. The model's horizontal grid size was 50×50 m, with average grid heights of 8 m for the overlying strata and 10 m for the reservoir vertically. The total number of grids was 8.68 million. Simultaneously, combining the results of indoor rock mechanics experiments and well logging data interpretation at the Shengping gas storage, the dynamic and static rock mechanics parameters of different wells and strata were determined, and the conversion relationship between dynamic and static rock mechanics parameters was established. The relationship between dynamic and static Young's moduli was as follows: The relationship between dynamic and static Poisson ratios is: By utilizing the relationship between dynamic and static rock mechanics parameters and combining porosity and phase models to constrain the modeling of three-dimensional rock mechanical properties, a three-dimensional rock mechanical property model is established. Figure 2 A diagram showing the transformation relationship between dynamic and static rock mechanics parameters in the Shengping gas storage facility. Figure 3 A three-dimensional geomechanical model of the Shengping gas storage facility.

[0072] ②Based on the results of the seepage-stress coupling numerical simulation of the gas storage tank, a four-dimensional geomechanical model was established on the basis of the three-dimensional geomechanical model, and mechanical boundary conditions were set to conduct geomechanical simulation to determine the three-dimensional geostress disturbance characteristics of the region.

[0073] In practical applications, based on the interpretation results of logging data from the Shengping gas reservoir, the vertical principal stress gradient range was determined to be between 2.37 and 2.50 MPa / 100m, with an average of 2.44 MPa / 100m; the maximum horizontal principal stress gradient was 2.29 MPa / 100m; and the minimum horizontal principal stress gradient was 1.92 MPa / 100m. The direction of the maximum horizontal principal stress was 82.7° east of north. Based on the interpretation results, mechanical boundary conditions were set, and geomechanical simulation conditions were defined using numerical results to conduct geomechanical simulations. The results determined that the magnitude of the vertical principal stress in the initial stage of the gas reservoir ranged from 62 to 82 MPa, the maximum horizontal principal stress was distributed between 50 and 76 MPa, and the minimum horizontal principal stress was distributed between 46 and 65 MPa. Figure 4 This is a map showing the distribution of geostress in the original and pre-construction areas of the Shengping gas storage reservoir.

[0074] Step S102: Using the corrected model, conduct geomechanical simulation to determine the three-dimensional principal stress path of the reservoir during the reservoir construction and gas injection process, and calculate the dynamic three-dimensional principal stress during the reservoir construction and gas injection process.

[0075] In practical applications, based on the simulation results of the geomechanical model of the Shengping gas storage facility, stress path diagrams were plotted at four time points. To ensure the consistency and certainty of the results, October 1st was selected as the main time step, and triaxial principal stress path diagrams were plotted. The minimum horizontal principal stress path value for the Shengping gas storage facility was determined to be 0.785, and the maximum horizontal principal stress path value was determined to be 0.729, based on the horizontal principal stress path diagrams. Table 1 shows the triaxial principal stresses at the junction of the storage cap and reservoir at the Shengping gas storage facility under different pressure-boosting coefficients determined using the stress path diagrams. Figure 5 Stress path diagram of horizontal principal stress during the gas injection and pressurization process of Shengping gas storage.

[0076] Table 1. Statistical table of dynamic triaxial principal stresses at different pressure boosting coefficients in Shengping Gas Storage Facility

[0077]

[0078] Step S103: Based on the dynamic triaxial principal stress during the gas injection process, the shear and tensile safety indices are used to determine the ultimate bearing capacity of the caprock against shear and tensile failure, respectively.

[0079] In practical applications, based on the triaxial principal stresses at the reservoir-caprock interface under different pressure-boosting coefficients determined in the previous step during gas storage construction and injection, the tensile and shear safety indices of the caprock under different pressure-boosting coefficients are determined using the formulas for calculating the caprock tension and shear safety indices, as shown in Table 2. Calculations show that the formation pressure corresponding to caprock tension failure is 77 MPa, with a pressure-boosting coefficient of 2.41. At this point, the shear safety index at the reservoir-caprock interface is approximately 0.507, far exceeding the critical index of 0 for shear failure. Therefore, when the upper limit pressure is 77 MPa, the caprock experiences tensile failure but not shear failure. Based on the combined tensile and shear safety indices, the ultimate bearing capacity of the caprock is determined to be 77 MPa.

[0080] Table 2. Statistical Table of Evaluation Indicators for Ultimate Pressure Bearing Capacity of the Overburden Layer under Different Pressure Rise Coefficients at Shengping Gas Storage Facility

[0081]

[0082] Step S104: Based on the stress disturbance characteristics of the gas storage reservoir determined by geomechanical simulation, design and carry out gas permeability measurement experiments after 50 alternating loads on the caprock under different effective stresses.

[0083] In practical applications, the experimental steps are as follows:

[0084] (1) Sample preparation: The natural caprock core was taken from the reservoir-caprock transition zone of the Shengping gas storage facility, at an average depth of 2851 m, with a core diameter of 100 mm. The contents of clay minerals, quartz, and plagioclase in the caprock core of the Shengping gas storage facility were 46.6%, 28.1%, and 22.6%, respectively. A total of 42 cylindrical samples were obtained from the natural caprock core through vertical drilling, with a diameter of 25 mm and a length of 50 mm. These samples were used for caprock pressure permeability and static breakthrough pressure experiments.

[0085] (2) According to the experimental standard GB / T 29,172–2012, the permeability of the dry core was tested under the original geostress conditions. After the core samples were saturated with formation water, the static breakthrough pressure under the original geostress conditions was measured according to the experimental standard SY / T5748-2013.

[0086] (3) The specific experimental scheme is shown in Table 3. To simulate the gas injection and production process of the gas storage tank, triaxial effective stress was applied to the sample. The maximum injection pressure was set as a multiple of the initial formation pressure, and the minimum production pressure was determined by a combination of design parameters such as the single-well production capacity and effective storage space. Deviatoric stress was applied to the sample in the axial direction to simulate the effective stress during the injection-production process. The loading and unloading frequency was 0.05 Hz. The confining pressure was taken as the minimum effective horizontal principal stress under each pressure coefficient (Pmax / Pi). During the experiment, nitrogen was used to measure the permeability of the sample simultaneously using the steady-state method, and the circumferential and axial strains of the sample and the permeability at the end of the loading and unloading stress were recorded throughout the process.

[0087] Table 3. Test scheme for pressure permeability and static breakthrough pressure

[0088]

[0089] Step S105: Using the conversion relationship between rock gas permeability and gas breakthrough pressure, the gas breakthrough pressure of the caprock under different pressure-boosting coefficients is determined.

[0090] In practical applications, the rock gas permeability *k* and breakthrough pressure of the caprock core of the Shengping gas storage facility are determined according to step S104, as shown in Table 4. Based on the experimental results, a graph showing the relationship between rock sample gas permeability and breakthrough pressure is plotted, and the functional relationship between the rock sample breakthrough pressure and gas permeability is determined as follows: . Figure 6 This is a graph showing the functional relationship between gas permeability of rock samples and breakthrough pressure.

[0091] Table 4. Statistical Table of Rock Gas Permeability and Breakthrough Pressure Experiment Results

[0092]

[0093] Step S106: Draw a graph showing the relationship between the normalized dynamic breakthrough pressure of the caprock and the pressure-boosting coefficient of the gas storage tank, establish a functional relationship, and analyze and determine the capillary sealing ultimate pressure bearing capacity of the caprock.

[0094] In practical applications, based on the functional relationship between rock sample gas permeability and breakthrough pressure determined in steps S104 and S105, the corresponding dynamic breakthrough pressure is obtained. Finally, the difference between the pressure difference between the reservoir and caprock of the Shengping gas storage facility and the dynamic breakthrough pressure is calculated as the upper limit pressure increases, and a cross-plot is plotted, as shown below. Figure 7 As shown. From Figure 7It can be seen that as the pressure boosting coefficient increases, the pressure difference between the reservoir and the caprock continuously increases because the pore pressure of the caprock remains constant, but the dynamic breakthrough pressure of the caprock rock continuously decreases. When the dynamic breakthrough pressure depletes to the same level as the pressure difference between the reservoir and the caprock, the caprock capillary dynamic sealing critical state is reached. According to mathematical fitting, when the pressure boosting coefficient of the Shengping gas storage is 1.42, the caprock capillary dynamic sealing critical state is reached, and the corresponding caprock capillary dynamic sealing ultimate pressure bearing capacity is 41.2 MPa. Figure 7 Experimental diagram for the ultimate pressure bearing capacity of the capillary tubes in the cover layer of the Shengping gas storage facility.

[0095] Step S107: Based on the dynamic triaxial principal stress during the gas injection process, the slip trend index and expansion trend index are used to determine the fault's resistance to slip activation and expansion rupture ultimate bearing capacity, respectively.

[0096] In practical applications, according to geomechanical numerical simulations, among the three faults that pierce the reservoir and caprock, the F11 fault has the highest risk of slip activation, with an average ultimate bearing capacity against slip activation of 43.58 MPa in the reservoir section. Regarding the evaluation of the fault's ultimate bearing capacity against expansion and rupture, indoor rock mechanics experiments show that the average tensile strength of the Shengping gas storage reservoir rocks is 3.5 MPa, while the difference between the maximum and minimum principal stresses in the reservoir is approximately 16 MPa, satisfying the formula... Based on the application conditions, and according to the fault expansion trend index, the probability of fault expansion occurring in F2, F5, and F11 is relatively low. When fault slip activation occurs, the fault expansion trend index is approximately 0.9, less than 1.0.

[0097] Table 5. Statistical Table of Evaluation Indicators for Fault Ultimate Pressure Bearing Capacity under Different Pressure Rise Coefficients at Shengping Gas Storage Facility

[0098]

[0099] Step S108: Using the pressure increase coefficient as the abscissa and the evaluation indices such as the capillary sealing ultimate pressure bearing capacity of the capillary layer and the mechanical damage resistance ultimate pressure bearing capacity of the capillary layer and fault as the ordinate, draw an intersection chart to determine the upper limit pressure of the gas storage facility.

[0100] In practical applications, the caprock's ultimate pressure-bearing capacity against mechanical failure was determined to be 77 MPa based on caprock tension and shear safety indices. The dynamic breakthrough pressure of the caprock, determined using a new method, was 41.2 MPa. Combining the caprock breakthrough pressure and the ultimate pressure-bearing capacity against mechanical failure, the dynamic ultimate pressure-bearing capacity of the caprock was indeed 41.2 MPa. The dynamic ultimate pressure-bearing capacity of the fault, determined using fault slip tendency and expansion tendency indices, was 43.8 MPa. By comprehensively comparing the dynamic ultimate pressure-bearing caprock and fault, the ultimate pressure-bearing capacity of the gas storage geological body was determined to be 41.2 MPa. Therefore, the ultimate pressure-bearing capacity of the geological body was taken as the upper limit pressure of the Shengping gas storage, i.e., 41.2 MPa. Figure 8 This is a cross-sectional diagram of the evaluation indicators for the ultimate bearing capacity against mechanical failure of caprock and fault.

[0101] Comparison of the effects and advantages of the new method of this invention with existing methods:

[0102] Based on the mass balance method, the effective storage capacity is estimated to be 74.3 MPa when the upper limit pressure of the gas storage facility is the original formation pressure of 32.0 MPa. 10 8 m 3 When the upper pressure is increased to 41.2 MPa, the effective storage capacity is 79.9. 10 8 m 3 When the lower limit pressure of the gas storage facility is maintained at 20 MPa, compared with the upper limit pressure of 32.0 MPa, the working gas volume is estimated to increase by 5.57 at an upper limit pressure of 41.2 MPa. 10 8 m 3 The increase was 22.9%, and the comparison results are as follows: Figure 9 As shown.

[0103] Compared to existing methods, this invention fundamentally breaks through the traditional static, single-object evaluation framework, constructing a dynamic, multi-factor coupled comprehensive evaluation system for the sealing performance and operational upper limit pressure of gas storage caprock. Existing methods generally rely on static geological parameters such as conventional gas breakthrough pressure tests in core samples, or use a single index (such as minimum horizontal principal stress) for constraint based on simplified geomechanical theory. Their core flaw lies in failing to fully consider the actual operation of gas storage facilities, especially the dynamic changes caused by the intense fluid-structure interaction under high-speed cyclic injection and pressurized gas injection conditions. To address these limitations, the innovation of this invention is reflected in the following two aspects: First, methodologically, it achieves a leap from "static characterization" to "dynamic response." This invention abandons isolated static testing, creatively integrating four-dimensional geomechanical simulation with indoor alternating load gas permeability testing experiments. By simulating the entire injection and production process to clarify the characteristics of geostress disturbance, and based on this, designing core permeability experiments covering different effective stress paths, the gas breakthrough pressure of the caprock under dynamic stress is obtained, establishing a quantitative relationship between dynamic breakthrough pressure and pressure-boosting coefficient, and achieving accurate characterization of the dynamic ultimate pressure-bearing capacity of the caprock under alternating loads. Secondly, in terms of evaluation dimensions, it expands from a "single object" to a "system synergy." Based on fluid-structure interaction theory, this invention expands the evaluation object from the single caprock capillary sealing capacity to include multiple geological elements, including the caprock (resistance to shear failure, tensile failure) and faults (resistance to slippage failure, expansion fracture). By integrating the results of multi-factor quantitative analysis and drawing multi-index cross-plots for comprehensive judgment, the overall upper limit pressure of the entire caprock-fault system under complex geological conditions such as pressurized gas injection and fault development can be scientifically determined. Finally, in terms of engineering applicability, it achieves a close fit from an "ideal model" to "real working conditions."

Claims

1. A method for determining the upper limit pressure of a fault-developed gas storage facility considering overpressure operating conditions, the method comprising the following steps: Step (1): Establish a three-dimensional geomechanical dynamic model of the gas storage reservoir covering the reservoir, caprock and surrounding faults, and correct the model based on the measured or regional geostress evaluation results; Step (2): Using the corrected model, conduct geomechanical simulation to determine the three-dimensional principal stress path of the reservoir during the reservoir construction and gas injection process, and calculate the dynamic three-dimensional principal stress during the reservoir construction and gas injection process; Step (3): Based on the dynamic triaxial principal stress during the gas injection process, the shear and tensile safety indices are used to determine the ultimate bearing capacity of the caprock against shear and tensile failure, respectively. Step (4): Based on the stress disturbance characteristics of the gas storage reservoir determined by geomechanical simulation, design and carry out gas permeability test after 50 alternating loads on the caprock under different effective stresses; Step (5): Use the conversion relationship between rock gas permeability and gas breakthrough pressure to determine the gas breakthrough pressure of the caprock under different pressure-boosting coefficients; Step (6): Draw a graph showing the relationship between the normalized dynamic breakthrough pressure of the caprock and the pressure boosting coefficient of the gas storage tank, establish a functional relationship, and analyze and determine the capillary seal ultimate pressure bearing capacity of the caprock; Step (7): Based on the dynamic triaxial principal stress during the gas injection process, the slip trend index and expansion trend index are used to determine the fault's resistance to slip activation and expansion rupture ultimate bearing capacity, respectively. Step (8): Using the pressure increase coefficient as the horizontal axis and the evaluation indices such as the capillary sealing ultimate pressure bearing capacity of the capillary layer and the mechanical damage resistance ultimate pressure bearing capacity of the capillary layer and fault as the vertical axis, draw an intersection chart to determine the upper limit pressure of the gas storage facility.

2. The method for determining the upper limit pressure of a fault-developed gas storage facility considering overpressure operating conditions according to claim 1, characterized in that, The three-dimensional dynamic geomechanical simulation mentioned in step (1) refers to the dynamic mechanical model established by combining fluid-structure interaction numerical simulation on the basis of the three-dimensional geomechanical model, which is used to determine the characteristics of formation pressure and geostress changes during the construction, injection and production process of the gas storage facility.

3. The method for determining the upper limit pressure of a fault-developed gas storage facility considering overpressure operating conditions according to claim 1, characterized in that, The reservoir horizontal stress path during the formation pressure increase process described in step (2) is calculated using the formula... Perform calculations; in, This refers to the change in pore pressure during the gas storage process; The changes in the three principal stresses during the gas injection process in the gas storage facility, including the changes in the maximum horizontal principal stress. Minimum horizontal principal stress variation MPa; The horizontal principal stress paths during gas injection into the gas storage facility, including the path of maximum horizontal principal stress. and minimum horizontal principal stress path .

4. The method for determining the upper limit pressure of a fault-developed gas storage facility considering overpressure operating conditions according to claim 1, characterized in that, The dynamic triaxial principal stress during the gas injection process in step (2) is calculated using the formula... Perform calculations; in, Dynamic triaxial principal stresses during the gas injection process in the gas storage facility, including the maximum horizontal principal stress. Minimum horizontal principal stress MPa; The three principal stresses prior to reservoir construction, including the maximum horizontal principal stress before reservoir construction. Minimum horizontal principal stress before reservoir construction MPa; Formation pressure at different times during the gas injection process for oil and gas reservoir construction; Formation pressure before reservoir construction in oil and gas reservoirs.

5. The method for determining the upper limit pressure of a fault-developed gas storage facility considering overpressure operating conditions according to claim 1, characterized in that, The ultimate tensile failure pressure of the cap layer mentioned in step (3) is calculated using the formula... The calculation is performed using the formula for the cap layer tensile safety index. Iterative analysis was conducted to determine this; in, The ultimate tensile failure pressure of the caprock is expressed in MPa. The minimum horizontal principal stress during the gas injection process in the reservoir construction of an oil and gas reservoir, in MPa; To extend the safety index, dimensionless; Formation pressure (MPa) at different times during the reservoir construction and gas injection process; The dynamic minimum horizontal principal stress during the reservoir construction and gas injection process in the caprock is described. Using formula Perform calculations; in, The minimum principal stress before the caprock is built is expressed in MPa. The maximum principal stress before the caprock was built is expressed in MPa. This is the minimum horizontal principal stress path; Formation pressure before reservoir construction in oil and gas reservoirs.

6. The method for determining the upper limit pressure of a fault-developed gas storage facility considering overpressure operating conditions according to claim 1, characterized in that, The ultimate shear failure pressure of the caprock mentioned in step (3) is calculated using the formula... The calculation is performed using the cap layer shear safety index formula. Iterative analysis was conducted to determine this; in, The ultimate shear failure pressure of the caprock, in MPa; Cohesion, MPa; It is the internal friction angle; The minimum dynamic principal stress during the gas injection process in the reservoir construction of an oil and gas reservoir, in MPa; The maximum dynamic principal stress during the reservoir construction and gas injection process, measured in MPa. The shear safety index is dimensionless. Cohesion, MPa; It is the internal friction angle; The maximum effective principal stress during the gas injection process in the reservoir construction process, measured in MPa. The minimum effective principal stress during the gas injection process in the reservoir construction of an oil and gas reservoir, in MPa; The dynamic maximum principal stress during the reservoir construction and gas injection process is described above. and minimum principal stress The values ​​differ under different geostress states; among them, ① when the geostress state at a certain moment during the reservoir construction and gas injection process is a normal fault stress state ( ), , ② When the geostress state at a certain moment during the reservoir construction and gas injection process is the reverse fault stress state ( ), , ③ When the in-situ stress state at a certain moment during the reservoir construction and gas injection process is the strike-slip fault stress state ( ), , ; in, The maximum dynamic horizontal principal stress during the gas injection process of reservoir construction in oil and gas reservoirs, in MPa; The minimum horizontal principal stress during the reservoir construction and gas injection process, measured in MPa. Dynamic vertical principal stress during reservoir construction and gas injection The maximum horizontal principal stress (MPa) at a certain moment during the reservoir construction and gas injection process is given. The minimum horizontal principal stress (MPa) at a certain moment during the reservoir construction and gas injection process is given. The vertical principal stress at a certain moment during the gas injection process of building a reservoir for oil and gas; The dynamic maximum horizontal principal stress during the reservoir construction and gas injection process is described above. and minimum horizontal principal stress Using formula and calculate; in, The maximum horizontal principal stress before reservoir construction, MPa; The minimum horizontal principal stress before reservoir construction, in MPa; This is the path of maximum horizontal principal stress. Minimum horizontal principal stress path; Formation pressure (MPa) at different times during the reservoir construction and gas injection process; Formation pressure before reservoir construction, MPa.

7. The method for determining the upper limit pressure of a fault-developed gas storage facility considering overpressure operating conditions according to claim 1, characterized in that, The step (5) mentioned above, which uses the functional relationship between rock gas permeability and caprock static breakthrough pressure to determine the caprock gas breakthrough pressure under different minimum effective principal stresses of the reservoir, refers to: using the functional relationship... Perform calculations; in, Rock gas breakthrough pressure at different upper limit pressures, MPa; denoted as ρ_a, where ρ is the gas permeability; α and β are parameters of the mathematical fitting function.

8. The method for determining the upper limit pressure of a fault-developed gas storage facility considering overpressure operating conditions according to claim 1, characterized in that, The step (6) of plotting the relationship between the normalized dynamic breakthrough pressure of the caprock and the gas storage pressure-boosting coefficient refers to: plotting a relationship curve with the gas storage pressure-boosting coefficient as the abscissa and the normalized dynamic breakthrough pressure as the ordinate, and establishing a binomial, logarithmic, or exponential functional relationship; when using a binomial functional relationship, its expression is: ; in, To achieve normalized dynamic breakthrough pressure; Rock gas breakthrough pressure at different upper limit pressures, MPa; The breakthrough pressure under hydrostatic pressure, in MPa; denoted as the gas storage pressure boosting coefficient, which is the ratio of the upper limit pressure to the hydrostatic pressure; a, b, and c are parameters of the mathematical fitting function.

9. The method for determining the upper limit pressure of a fault-developed gas storage facility considering overpressure operating conditions according to claim 1, characterized in that, The dynamic capillary seal ultimate pressure bearing capacity of the caprock mentioned in step (6) refers to the pressure difference between the reservoir and the caprock continuously increasing during the gas injection process of the oil and gas reservoir construction, when the caprock dynamically breaks through the pressure. When the pressure difference between the reservoir and caprock is less than the pressure difference during gas injection and storage construction in an oil and gas reservoir, the caprock capillary dynamic sealing limit is reached. The pressure bearing capacity of the caprock dynamic capillary sealing limit at this point is determined using the formula... Perform calculations; in, The ultimate pressure bearing capacity of the capillary seal under alternating load conditions, in MPa; The initial pressure of the caprock, i.e., the breakthrough pressure before the caprock pressure boosting operation, is expressed in MPa. It is the hydrostatic pressure.

10. The method for determining the upper limit pressure of a fault-developed gas storage facility considering overpressure operating conditions according to claim 1, characterized in that, The fault anti-slip activation ultimate bearing capacity mentioned in step (7) is calculated using the formula... Perform calculations; in, To activate the ultimate bearing capacity for fault anti-slip, MPa; The fault friction coefficient; The normal stress on the fault surface when slippage is activated, in MPa; The shear stress at the fault surface when slippage is activated, in MPa; The normal stress on the cross section when the fault undergoes anti-slip activation. and cross-sectional shear stress Using formula Perform iterative analysis and calculation; in, This is a fault slip trend index; Dynamic cross-sectional normal stress during reservoir construction and gas injection process, MPa; Dynamic cross-sectional shear stress during the gas injection process of oil and gas reservoir construction, MPa; The formation pressure at different times during the reservoir construction and gas injection process; and the dynamic cross-sectional normal stress mentioned above. Using formula Calculations are performed; while the cross-sectional shear stress... Using formula Perform calculations; in, , The maximum and minimum dynamic horizontal principal stresses during the gas injection process of oil and gas reservoir construction; Dynamic vertical principal stress during the gas injection process of oil and gas reservoir construction; The fault azimuth angle; The fault dip angle; The dynamic maximum horizontal principal stress during the reservoir construction and gas injection process described in the above steps is... and minimum horizontal principal stress Using formula and Perform calculations; in, The maximum horizontal principal stress before reservoir construction, MPa; The minimum horizontal principal stress before reservoir construction, in MPa; This is the path of maximum horizontal principal stress. Minimum horizontal principal stress path; Formation pressure (MPa) at different times during the reservoir construction and gas injection process; Formation pressure before reservoir construction, MPa.

11. The method for determining the upper limit pressure of a fault-developed gas storage facility considering overpressure operating conditions according to claim 1, characterized in that, The ultimate bearing capacity against expansion and rupture of the fault described in step (7), when When using the formula Perform calculations; when When using the formula Perform calculations; in, The ultimate bearing capacity against expansion and rupture of the fault is measured in MPa. The maximum principal stress, in MPa, occurs when the fault undergoes expansion and rupture. The minimum principal stress, in MPa, is the stress required for the fault to expand and rupture. is the principal stress on the cross section when the fault undergoes expansion and rupture, in MPa; The tensile strength of the rock is given in MPa. The maximum principal stress when the fault undergoes anti-slip activation. and minimum principal stress Using formula Perform iterative analysis and calculation; in, It is an inflation trend index; The maximum dynamic principal stress during the gas injection process in the reservoir construction process, measured in MPa. The minimum dynamic principal stress during the gas injection process in the reservoir construction of an oil and gas reservoir, in MPa; Dynamic cross-sectional normal stress during reservoir construction and gas injection process, MPa; The dynamic maximum principal stress during the reservoir construction and gas injection process is described above. and maximum principal stress The values ​​differ under different geostress states; among them, ① when the geostress state at a certain moment during the reservoir construction and gas injection process is the normal fault stress state ( )hour, , ; ② When the geostress state at a certain moment during the reservoir construction and gas injection process is the reverse fault stress state ( )hour, , ③ When the stress state of an oil and gas reservoir is at a certain moment during the reservoir construction and gas injection process, it is the stress state of a strike-slip fault. )hour, , ; in, The maximum dynamic horizontal principal stress during the gas injection process of reservoir construction in oil and gas reservoirs, in MPa; The minimum horizontal principal stress during the reservoir construction and gas injection process, measured in MPa. Dynamic vertical principal stress during reservoir construction and gas injection The maximum horizontal principal stress (MPa) at a certain moment during the reservoir construction and gas injection process is given. The minimum horizontal principal stress (MPa) at a certain moment during the reservoir construction and gas injection process is given. The vertical principal stress at a certain moment during the gas injection process of building a reservoir for oil and gas; The dynamic maximum horizontal principal stress during the reservoir construction and gas injection process described in the above steps is... and minimum horizontal principal stress Using formula and Perform calculations; in, The maximum horizontal principal stress before reservoir construction, MPa; The minimum horizontal principal stress before reservoir construction, in MPa; This is the path of maximum horizontal principal stress. This is the path of minimum horizontal principal stress; Formation pressure (MPa) at different times during the reservoir construction and gas injection process; Formation pressure before reservoir construction, MPa.

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