Quantitative evaluation method and system for premature senility fracture opening capability

Abstract

The invention relates to a quantitative evaluation method and system for premature senility fracture opening capability, and belongs to the technical field of oil-gas exploration, and the method comprises the steps: obtaining fracture related parameters in a research area; the fracture surface positive pressure in the fracture reservoir forming period is calculated according to the fracture related parameters; calculating the plastic deformation ultimate pressure of the fractured mudstone according to the fracture related parameters; according to the section positive pressure and the mudstone plastic deformation ultimate pressure, the opening capacity index of the fracture reservoir forming period is calculated; and dividing fracture opening capability evaluation grades according to the fracture reservoir forming period opening capability index so as to evaluate the premature senility fracture opening capability. According to the method, by calculating the section positive pressure and the mudstone plastic deformation ultimate pressure, quantitative calculation of the opening capacity index is achieved, the fault conduction opening capacity is converted from traditional experience-dependent interpretation into a computable, sortable and comparable quantitative index, and objectivity and consistency of evaluation results are improved.

Description

Technical Field

[0001] This application relates to the field of oil and gas exploration technology, and in particular to a quantitative evaluation method and system for the ability to initiate premature aging fractures. Background Technology

[0002] In traditional hydrocarbon accumulation theories, early-fading faults are generally considered closed faults because they cease activity before the critical accumulation period and their surfaces gradually close due to the overlying strata and tectonic stresses, thus lacking late-stage vertical transport capacity. However, recent deep exploration practices have shown that some early-fading faults may still partially reopen during the accumulation period, providing pathways for secondary hydrocarbon migration and significantly impacting deep hydrocarbon enrichment.

[0003] Since these types of faults ceased activity before the hydrocarbon accumulation period, traditional evaluation methods are mostly based on fault activity or static closure parameters (such as infill material, mud content, and segment morphology), which are insufficient to effectively reflect their potential for reopening under the coupled effects of fluid pressure and formation stress during the hydrocarbon accumulation period. Existing methods only select some factors for qualitative or semi-quantitative analysis, failing to comprehensively consider key mechanical and temporal parameters such as cross-sectional normal pressure, mudstone plastic deformation limit, and hydrocarbon accumulation time. This results in significant uncertainty in determining whether early-aging faults possess the ability to reopen during the hydrocarbon accumulation period.

[0004] Therefore, the current lack of an evaluation system that can quantitatively couple multiple mechanical factors, achieve visualized output, and provide ranked comparisons limits the accuracy of screening deep oil and gas migration paths and favorable zones. Summary of the Invention

[0005] This application addresses, to at least some extent, one of the technical problems in the related art.

[0006] Therefore, this application aims to provide a quantitative evaluation method and system for the opening capacity of early-aging faults. By calculating the normal pressure of the fault section and the ultimate pressure of plastic deformation of mudstone, the opening capacity index can be quantitatively calculated, transforming the fault conduction opening capacity from the traditional reliance on empirical interpretation into a calculable, sortable, and comparable quantitative indicator, thereby improving the objectivity and consistency of the evaluation results.

[0007] To achieve the above objectives, in a first aspect, this application provides a method for quantitatively evaluating the ability to initiate premature aging fractures, comprising: Obtain fracture-related parameters in the study area; Calculate the normal pressure on the fracture surface and the ultimate pressure of mudstone plastic deformation during the fracture formation period based on fracture-related parameters; The fracture opening capacity index during the hydrocarbon accumulation period is calculated based on the cross-sectional normal pressure and the ultimate pressure of mudstone plastic deformation. The ability to open premature aging faults is evaluated based on the index of ability to open faults during the reservoir formation period.

[0008] In this embodiment, the cross-sectional normal pressure and the ultimate pressure of mudstone plastic deformation are calculated based on fracture-related parameters, thereby incorporating the influence of time on fracture into the calculation of the fracture opening capacity index. This realizes the transformation of fracture opening trend from qualitative empirical judgment to quantitative model calculation, greatly improving the consistency and objectivity of the evaluation results and providing direct data support for decision-making.

[0009] In conjunction with the first aspect, in some implementations of the first aspect, the fault-related parameters include the depth at which the present source rock is displaced, the thickness of the strata deposited during and after the hydrocarbon accumulation period, the density of the overlying strata, the density of the formation water, the fault dip angle, and the burial depth of the strata.

[0010] In this embodiment, the effective stress is calculated using the density of the overlying strata and the density of the formation water, and the magnitude of the vertical stress decomposed onto the fault surface is calculated using the fault dip angle; the influence of time on the fault is introduced into the calculation of the opening capacity index by using the thickness and burial depth of the strata deposited during the hydrocarbon accumulation period and the later period; the spatial location of the fault point is determined by the depth of the fault where the current source rock is displaced; and the opening capacity index is calculated using the above-mentioned fault-related parameters that include static and dynamic evolution elements.

[0011] In conjunction with the first aspect, in some implementations of the first aspect, the formula for calculating the normal pressure on the fault section during the hydrocarbon accumulation period is as follows: ; in, This refers to the cross-sectional normal pressure, expressed in MPa. This represents the stress coefficient during the hydrocarbon accumulation period. This represents the depth of the faulted section in the present-day source rock, in meters. The thickness of the strata deposited during the hydrocarbon accumulation period and the later period is shown in meters. This refers to the density of the overlying strata, expressed in g / cm³. 3 ; This refers to the density of formation water, expressed in g / cm³. 3 ; The value is the fault dip angle, expressed in degrees.

[0012] In this embodiment, the thickness of the strata deposited during the reservoir formation period and the later stage of reservoir formation is used as a variable to accurately locate the additional closing pressure exerted by the sedimentary strata on the fault during the critical period from the cessation of fault activity to reservoir formation. This gives the entire calculation model the characteristics of time evolution, making it more realistic than traditional calculations based on purely static parameters.

[0013] In conjunction with the first aspect, in some implementations of the first aspect, the formula for calculating the ultimate pressure of mudstone plastic deformation is: ; in, This represents the ultimate pressure for plastic deformation of mudstone, expressed in MPa. and All are the plasticity coefficients of mudstone; The depth of the stratum is expressed in meters (m).

[0014] In this embodiment of the application, by introducing the burial depth, the change in the ultimate pressure of mudstone plastic deformation with increasing depth is reflected, and the abstract concept of mudstone plastic deformation is transformed into a specific calculable value to represent the ability of mudstone in the fault zone to resist pressure and maintain a closed state, laying the foundation for the calculation of the opening capacity index below.

[0015] In conjunction with the first aspect, in some implementations of the first aspect, the formula for calculating the fault-based hydrocarbon accumulation capacity index is as follows: ; in, This is an index representing the capacity to initiate hydrocarbon accumulation during fault formation.

[0016] In the embodiments of this application, by calculating and comparing the magnitude of the cross-sectional normal pressure and the ultimate pressure of mudstone plastic deformation, two states are objectively presented: when the cross-sectional normal pressure is dominant, the cross-section tends to close, and when the ultimate pressure of mudstone plastic deformation is dominant, the cross-section tends to open. This eliminates the traditional reliance on experience-based judgment and makes the judgment of the cross-section opening capacity more objective.

[0017] In conjunction with the first aspect, in some implementations of the first aspect, the numerical range of the reservoir opening capability index is divided into a first evaluation level and a second evaluation level; or the numerical range of the reservoir opening capability index is divided into a first evaluation level, a second evaluation level, and a third evaluation level.

[0018] In this embodiment of the application, by dividing the cross-section opening capability index into two evaluation levels, the evaluation results can be used to directly determine whether premature aging fractures have the potential to open, thereby improving the efficiency of the preliminary evaluation of premature aging fractures.

[0019] In conjunction with the first aspect, some implementations of the first aspect include methods for evaluating the opening capacity of premature aging faults based on the hydrocarbon accumulation period opening capacity index, such as: Determine whether the reservoir-forming capacity index is greater than or equal to the first preset value; If so, the premature aging fracture is judged as the first evaluation level, and it does not have the ability to be reopened during the reservoir formation period; if not, the premature aging fracture is judged as the second evaluation level, and it has the ability to be reopened during the reservoir formation period.

[0020] In this embodiment, the ability to open a premature aging fracture is determined by comparing the opening capability index with a first preset value. This transforms the complex evaluation model into a clear binary discrimination tool, ensuring the objectivity of the conclusion. At the same time, the use of a single judgment logic improves the efficiency of rapid screening and opening judgment of fractures during exploration.

[0021] In conjunction with the first aspect, some implementations of the first aspect include methods for evaluating the opening capacity of premature aging faults based on the hydrocarbon accumulation period opening capacity index, such as: Determine whether the reservoir-forming capacity index is greater than or equal to the first preset value; If yes, then the premature aging fracture is judged as the first evaluation level, and it does not have the ability to reopen during the reservoir formation period; if no, then it is judged whether the reservoir formation period opening ability index is greater than or equal to the second preset value, wherein the second preset value is less than the first preset value. If yes, the premature aging fault is judged as a second-level evaluation, with low capacity for opening up reservoirs during the reservoir formation period; if no, the premature aging fault is judged as a third-level evaluation, with high capacity for opening up reservoirs during the reservoir formation period.

[0022] In this embodiment, by dividing the fault opening capacity index into three evaluation levels, the evaluation results become more intuitive and operable, allowing non-experts to quickly understand and draw relevant geological conclusions. This achieves visualized zoning and rapid ranking of fault opening capacity within the study area, which is beneficial for improving the efficiency of regional analysis of oil and gas migration paths. Simultaneously, by setting a second evaluation level, the robustness of the evaluation system is enhanced, avoiding misjudgments of faults near critical values ​​and improving the accuracy of the evaluation.

[0023] Secondly, this application provides a quantitative evaluation system for the ability to initiate premature aging fractures, including: The geological parameter input module is used to obtain fault-related parameters in the study area; The parameter calculation module is used to calculate the normal pressure of the fracture section and the ultimate pressure of mudstone plastic deformation during the fracture formation period based on the number of fracture-related parameters. The fracture opening capacity index calculation module is used to calculate the fracture opening capacity index during the hydrocarbon accumulation period based on the cross-sectional normal pressure and the ultimate pressure of mudstone plastic deformation. The evaluation output module is used to evaluate the opening capacity of early-aging faults based on the fault reservoir opening capacity index.

[0024] In this embodiment, a quantitative evaluation system for the reopening capacity of prematurely aging faults effectively solves the problem of traditional techniques being unable to quantitatively assess the reopening potential of prematurely aging faults during hydrocarbon accumulation. The system achieves full-process standardization and automation from data acquisition to conclusion output through geological parameter input modules, parameter calculation modules, fault reopening capacity index calculation modules, and evaluation output modules. It transforms the fault reopening trend from qualitative empirical analysis into a classification of reopening capacity indices, thereby achieving calculable quantitative analysis and improving evaluation efficiency. Furthermore, the system can replace parameters according to the conditions of different study areas, making it flexible and applicable to fault systems under different tectonic backgrounds, with a wide range of applicability and strong practicality.

[0025] As can be seen from the above technical solutions, additional aspects and advantages of this application will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of this application. Attached Figure Description

[0026] Figure 1 This is a flowchart illustrating a quantitative evaluation method for the ability to initiate premature aging fractures according to an embodiment of this application. Figure 2 This is a flowchart illustrating an embodiment of the method for evaluating the opening capacity of premature aging fractures based on the hydrocarbon accumulation period opening capacity index. Figure 3 This is a flowchart illustrating another embodiment of the method for evaluating the opening capacity of premature aging fractures based on the reservoir opening capacity index. Figure 4 This is a diagram showing the relationship between the ultimate pressure of mudstone plastic deformation and the burial depth in an embodiment of this application; Figure 5 This is a histogram showing the distribution of the C-value of the main reservoir-forming capacity index of the Class II oil source fracture in this application. Figure 6 This is a histogram showing the distribution of the C-values ​​of the main hydrocarbon accumulation capacity index during the adjustment of faults in this application embodiment; Figure 7 This is a schematic diagram of the architecture of a quantitative evaluation system for the ability to initiate premature aging fractures according to an embodiment of this application; In the above figures: 100, Quantitative evaluation system for the opening capacity of premature aging faults; 101, Geological parameter input module; 102, Parameter calculation module; 103, Fault opening capacity index calculation module; 104, Evaluation output module. Detailed Implementation

[0027] In the description of this application, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc., indicating the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this application.

[0028] In this application, unless otherwise expressly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection, an electrical connection, or a connection that allows communication between components; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication between two components or the interaction between two components, unless otherwise expressly limited. Those skilled in the art can understand the specific meaning of the above terms in this application based on the specific circumstances.

[0029] In this application, unless otherwise expressly specified and limited, "above" or "below" the second feature can mean that the first feature is in direct contact with the second feature, or that the first feature is in indirect contact with the second feature through an intermediate medium. Furthermore, "above," "on top of," and "over" the second feature can mean that the first feature is directly above or diagonally above the second feature, or simply that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature can mean that the first feature is directly below or diagonally below the second feature, or simply that the first feature is at a lower horizontal level than the second feature.

[0030] In this application, the terms "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., refer to a specific feature, structure, material, or characteristic described in connection with that embodiment or example, which is included in at least one embodiment or example of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0031] The present application will now be described in detail through exemplary embodiments. However, it should be understood that, without further description, elements, structures, and features in one embodiment may be advantageously incorporated into other embodiments.

[0032] In the existing technology, the traditional view is that early-aging faults are unlikely to play a vertical transport role in the late-stage hydrocarbon accumulation process. Although these faults have a certain vertical extension depth, they have ceased activity before the hydrocarbon accumulation period and the fault surface gradually closes, so they are regarded as closed faults.

[0033] However, exploration practice has shown that some early-aging faults may still partially reopen during the hydrocarbon accumulation period, becoming channels for oil and gas migration. Because the tendency of fault closure is dynamically influenced by multiple factors such as mudstone plastic deformation, fluid pressure, and hydrocarbon accumulation time, existing static evaluation methods cannot accurately reflect the reopening capacity of early-aging faults as they dynamically change during hydrocarbon accumulation.

[0034] Based on this, this application proposes a quantitative evaluation method for the ability to open premature aging faults, so as to achieve a comprehensive judgment on their dynamic opening potential during the hydrocarbon accumulation period.

[0035] Figure 1 This is a schematic flowchart of a method for quantitatively evaluating the ability to initiate premature aging fractures, provided in the first aspect of this application. The method includes the following steps.

[0036] S1. Obtain fracture-related parameters in the study area.

[0037] Specifically, in the study area, fault-related parameters include the depth of the faulted sections of the present-day source rocks. Thickness of strata deposited during the hydrocarbon accumulation period and the later stages of hydrocarbon accumulation Density of overlying strata Formation water density Fault dip angle and burial depth .

[0038] Among them, the density of the overlying strata and formation water density The depth of the faulted section of the current source rock can be directly measured through direct density logging and water sample analysis. Thickness of sedimentary strata during the hydrocarbon accumulation period and the later stages of hydrocarbon accumulation Fault dip angle and burial depth It is mainly obtained through seismic data and well logging calibration.

[0039] It should be noted that all fault-related parameters are standard basic data used in oil and gas exploration and development in the study area. For any block that has undergone seismic exploration and has some drilling data, fault parameters can be directly obtained or reasonably estimated.

[0040] S2. Calculate the normal pressure on the fracture surface and the ultimate pressure of mudstone plastic deformation during the formation of reservoirs based on the relevant parameters of the fracture.

[0041] Specifically, the formula for calculating the normal pressure on the fault section during the hydrocarbon accumulation period is as follows: .

[0042] in, This refers to the cross-sectional normal pressure, expressed in MPa. This represents the stress coefficient during the hydrocarbon accumulation period. This represents the depth of the faulted section in the present-day source rock, in meters. The thickness of the strata deposited during the hydrocarbon accumulation period and the later period is shown in meters. This refers to the density of the overlying strata, expressed in g / cm³. 3 ; This refers to the density of formation water, expressed in g / cm³. 3 ; The value is the fault dip angle, expressed in degrees.

[0043] Specifically, in the evaluation of premature aging fracture initiation capacity, the normal stress of the fracture section... This represents the compressive stress perpendicular to the fracture surface, mainly derived from the gravity of the overlying strata and tectonic stress. The greater the pressure, the stronger the tendency for the fracture surface to close, and the less likely it is to reopen; conversely, a smaller pressure indicates that the fracture surface still has some activity potential. Therefore, calculating the normal pressure of the fracture surface is crucial. It is a necessary step to determine whether the fracture has the potential to be reopened.

[0044] By establishing a calculation formula, the cross-sectional normal pressure is... Calculation of stratigraphic thickness during the hydrocarbon accumulation period and the later stages of hydrocarbon accumulation. The connection is due to the thickness of the strata deposited during the hydrocarbon accumulation period and the later stages of hydrocarbon accumulation. It increases with time, thus leading to cross-sectional normal pressure. The greater the increase, the stronger the closing trend, thus quantifying the key dynamic factor of "activity time" to facilitate the calculation of cross-sectional normal pressure at different periods. .

[0045] It should be noted that the stress coefficient during the hydrocarbon accumulation period... Related to the geomechanical factors of the study block. For example, in an embodiment of this application, =0.009876.

[0046] The formula for calculating the ultimate pressure of mudstone under plastic deformation is: ; in, This represents the ultimate pressure for plastic deformation of mudstone, expressed in MPa. and All are the plasticity coefficients of mudstone; The depth of the stratum is expressed in meters (m).

[0047] Specifically, the ultimate pressure of plastic deformation in mudstone This represents the ultimate effective normal pressure required for mudstone (or fault gouge) in a fault zone to undergo plastic flow and lose its sealing ability; the burial depth of the strata. This indicates the depth of a point on the fault surface during the hydrocarbon accumulation period, rather than the current depth, by establishing the ultimate pressure of mudstone plastic deformation. With burial depth The relationship between the plastic deformation limit pressure of mudstone and the ... plastic deformation limit pressure of mudstone. By converting it into a continuous intensity variable, the evaluation loss caused by the traditional method of simply classifying fractures into "closed" and "open" states is avoided.

[0048] It should be noted that the plasticity coefficient of mudstone and As an adjustable parameter, it can be determined through experiments using mudstone samples of different burial depths and lithologies, or it can be obtained from the ultimate plastic deformation pressure of mudstone in well logging data. Establish a relationship diagram with confining pressure, and then determine the relationship between confining pressure and stratum depth. A relationship diagram was established, and finally, using confining pressure as a bridge, the ultimate pressure for plastic deformation of mudstone was determined. With burial depth The relationship diagram was used to calculate the plasticity coefficient of mudstone through univariate linear regression. and The value of .

[0049] S3. Based on the cross-sectional normal pressure and the ultimate pressure of mudstone plastic deformation. Calculate the index of the ability to open up the fault formation period.

[0050] Specifically, the formula for calculating the fault-based hydrocarbon accumulation capacity index is as follows: .

[0051] in, This is an index representing the capacity to initiate hydrocarbon accumulation during fault formation.

[0052] By establishing cross-sectional normal pressure Ultimate pressure of plastic deformation of mudstone The ratio is the ratio of the external combined pressure acting on the fracture surface to keep it closed to the internal strength force of the fracture zone resisting reopening. By comparing the magnitude of the opposing forces, it can be indicated whether the fracture has the ability to reopen.

[0053] Capacity index during fault formation period In the calculation formula, the dimensionless value is obtained by dividing two physical quantities with the same dimension (unit of pressure). This eliminates the influence of absolute dimensions, making the evaluation results independent of specific pressure values, increasing the universality of the calculation formula, and achieving direct comparability across different fractures and regions. This is achieved through the use of the opening capacity index... This indicates the fault opening capacity, transforming the fault conduction capacity from an empirically-dependent interpretation into a calculable, rankable, and comparable quantitative indicator, thereby improving the objectivity and consistency of the evaluation results.

[0054] S4. Evaluate the opening capacity of early-aging faults based on the fault reservoir opening capacity index.

[0055] In one embodiment of this application, the evaluation level is divided into a first evaluation level and a second evaluation level based on the numerical range of the reservoir opening capability index. For example... Figure 2 As shown, the method for evaluating the opening capacity of premature aging faults based on the hydrocarbon accumulation period opening capacity index is as follows.

[0056] S411. Determine whether the reservoir opening capacity index is greater than or equal to the first preset value.

[0057] S412. If yes, then the premature aging fracture is judged to be of the first evaluation level, and it does not have the ability to be reopened during the reservoir formation period; if no, then the premature aging fracture is judged to be of the second evaluation level, and it has the ability to be reopened during the reservoir formation period.

[0058] Specifically, by classifying the opening capacity of premature aging fractures into first and second evaluation levels, the evaluation results can be used to distinguish between the opening and closing segments of fractures. This can be applied to a single fracture or the entire reservoir area within a fracture zone, providing a basis for predicting oil and gas migration paths and selecting favorable zones.

[0059] In one embodiment of this application, the evaluation level is divided into a first evaluation level, a second evaluation level, and a third evaluation level based on the numerical range of the reservoir opening capability index. For example... Figure 3 As shown, the method for evaluating the opening capacity of premature aging faults based on the hydrocarbon accumulation period opening capacity index is as follows.

[0060] S421. Determine whether the reservoir opening capacity index is greater than or equal to the first preset value.

[0061] S422. If yes, then the premature aging fracture is judged to be of the first evaluation level, and it does not have the ability to be reopened during the reservoir formation period; if no, then it is judged whether the reservoir formation period opening ability index is greater than or equal to the second preset value, wherein the second preset value is less than the first preset value.

[0062] S423. If yes, then the premature aging fault is judged to be of the second evaluation level, with low opening capacity during the reservoir formation period; if no, then the premature aging fault is judged to be of the third evaluation level, with high opening capacity during the reservoir formation period.

[0063] Specifically, when the fault-based hydrocarbon accumulation period opening capacity index is greater than or equal to the first preset value, the premature aging fault is in the first evaluation level, at which point the normal pressure on the fault surface... Greater than the ultimate pressure of plastic deformation of mudstone The fracture tends to close due to plastic deformation in mechanics, so the fracture has a strong sealing ability and basically does not have the ability to reopen during the hydrocarbon accumulation period.

[0064] When the fault's ability to open during the hydrocarbon accumulation period is less than the first preset value but greater than or equal to the second preset value, the premature aging fault is in the second evaluation level. This indicates that the fault has a moderate ability to close and has some potential to reopen during the hydrocarbon accumulation period. Since the ability to open during the hydrocarbon accumulation period is still less than 1 at this time, the fault still has the ability to open, but it has tended to be in a transitional state of closure.

[0065] When the fault-induced hydrocarbon accumulation capacity index is less than the second preset value, the premature aging fault is classified as the third evaluation level, at which point the normal pressure on the fault surface... Much less than the ultimate pressure for plastic deformation of mudstone The fracture has a strong mechanical ability to resist closure, so the fracture closure ability is weak and it has a high possibility of reopening during the hydrocarbon accumulation period.

[0066] By dividing the fault opening capacity index into three evaluation levels, the evaluation results become more intuitive and operable, allowing non-experts to quickly understand and draw relevant geological conclusions. This enables visualized zoning and rapid ranking of fault opening capacity within the study area, improving the efficiency of regional analysis of oil and gas migration paths. Furthermore, the inclusion of a second evaluation level enhances the robustness of the evaluation system, preventing misjudgments of faults near critical values ​​and improving the accuracy of the evaluation.

[0067] The aforementioned quantitative evaluation method for the ability to initiate premature aging fractures is based on the depth of the faulted sections in the current source rocks. Thickness of strata deposited during the hydrocarbon accumulation period and the later stages of hydrocarbon accumulation Density of overlying strata Formation water density Fault dip angle and burial depth Calculate the normal pressure of the fault section during the hydrocarbon accumulation period. and the ultimate pressure of plastic deformation of fractured mudstone Then, based on the cross-sectional normal pressure and the ultimate pressure of mudstone plastic deformation... Calculate the fracture opening capability index An evaluation level is established based on the opening capability index, and the cross-sectional normal pressure is also considered in the establishment of the evaluation level. Ultimate pressure of plastic deformation of mudstone The study considers three controlling factors, including the time of hydrocarbon accumulation, to comprehensively reflect the reactivation trend of faults during the hydrocarbon accumulation period. It quantifies the fault's ability to activate during the hydrocarbon accumulation period, providing a directly usable data basis for subsequent fault conduction capacity assessment. Furthermore, it effectively addresses the shortcomings of existing technologies in determining the late-stage conduction capacity of such faults.

[0068] For example, the ability to initiate premature aging faults at a level three evaluation grade will be used as an example. Fault-related parameters are obtained in the study area, located in the southern part of Lufeng. The parameters are based on the stratigraphic depth collected in the study area. Confining pressure and ultimate pressure of mudstone plastic deformation As shown in Table 1.

[0069] Based on the stratigraphic depth collected in the study area Confining pressure and ultimate pressure of mudstone plastic deformation As shown in the table.

[0070] Table 1 shows the confining pressure and ultimate pressure for plastic deformation of mudstone corresponding to drilling depths in the Lufeng South area.

[0071] The data in the table shows that the higher the confining pressure, the higher the pressure required for the mudstone to undergo plastic deformation, and vice versa. Figure 4 As shown, the confining pressure applied based on the plastic deformation of mudstone and the burial depth of the sample strata... The relationship between these factors can be used to deduce the ultimate pressure of mudstone plastic deformation. With burial depth The relationship diagram is shown. Based on the data in the univariate linear regression fitting table, the following can be derived from the examples. =0.003957, =1.087604.

[0072] The first preset value is set to 1.0, and the second preset value is set to 0.5. That is, the first evaluation level is the fault-forming hydrocarbon accumulation period opening capacity index. <0.5; the second evaluation level is the fault-forming hydrocarbon accumulation period opening capacity index. ≥0.5, <1.0; the third evaluation level is the fault-based hydrocarbon accumulation period opening capacity index. ≥1.0.

[0073] By analyzing the cross-sectional normal pressure of the Class II source faults during the reservoir formation period and the regulating faults during the main reservoir formation period in the Lufeng Depression within the study area... and the ultimate pressure of plastic deformation of fractured mudstone The opening capacity index of the Class II oil source fracture during the reservoir formation period and the opening capacity index of the regulating fracture during the main reservoir formation period of the Lufeng Depression were calculated and obtained, as shown in Tables 2 and 3 below.

[0074] Table 2. Calculation of the Opening Capacity Index of Level II Oil Source Faults during the Reservoir Formation Period in the Lufeng Depression.

[0075] Table 3. Calculation of the index of the opening capacity of regulating faults during the main reservoir formation period in the Lufeng Depression.

[0076] The opening capacity index was established to quantitatively analyze the opening capacity of Class II oil source fractures and regulating fractures, such as... Figure 5 As shown, the fracture opening capacity index of Class II oil-source faults during the main reservoir formation period. The value range is 0.3~0.85, and the average opening capability index is... =0.49. For example... Figure 6 As shown, the opening capacity index of the regulating fault during the main hydrocarbon accumulation period ranges from 1.0 to 1.6, with an average opening capacity index of... =1.37. This means that the opening capacity of the Class II oil-source fault during the main reservoir formation period is rated at level three, indicating a high probability of opening; the opening capacity of the regulating fault during the main reservoir formation period is rated at level one, indicating a near-zero capacity for reopening. In summary, by comparing the opening capacity indices at different locations... They can be directly and quantitatively evaluated and compared for their relative opening and conduction capabilities.

[0077] This application provides a quantitative evaluation system 100 for the ability to initiate premature aging fractures, referring to... Figure 7 The quantitative evaluation system 100 for the ability to initiate premature aging fractures includes: Geological parameter input module 101 is used to acquire fault-related parameters in the study area; The parameter calculation module 102 is used to calculate the normal pressure of the fracture section and the ultimate pressure of mudstone plastic deformation during the fracture formation period based on fracture-related parameters. The fracture opening capacity index calculation module 103 is used to calculate the fracture opening capacity index during the hydrocarbon accumulation period based on the cross-sectional normal pressure and the ultimate pressure of mudstone plastic deformation. Evaluation output module 104 is used to evaluate the opening capacity of premature aging faults based on the reservoir opening capacity index.

[0078] By establishing a quantitative evaluation system 100 for the reopening capacity of early-aging fractures, the problem of traditional techniques being unable to quantitatively assess the reopening potential of early-aging fractures during hydrocarbon accumulation is effectively solved. The system achieves full-process standardization and automation from data acquisition to conclusion output through a geological parameter input module 101, a parameter calculation module 102, a fracture reopening capacity index calculation module 103, and an evaluation output module 104. It transforms the fracture reopening trend from qualitative empirical analysis into a classification of reopening capacity indices, thereby achieving calculable quantitative analysis and improving evaluation efficiency. Furthermore, the system can replace parameters according to the conditions of different study areas, making it flexible and applicable to fracture systems under different tectonic backgrounds, with a wide range of applicability and strong practicality. In summary, this application constructs a calculable quantitative evaluation system for fracture reopening capacity, which is of significant value for deepening the understanding of deep hydrocarbon accumulation and the exploration practice of hydrocarbon migration paths.

[0079] Although embodiments of this application have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting this application. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of this application.

Claims

1. A quantitative evaluation method for the ability to initiate premature aging fractures, characterized in that, include: Obtain fracture-related parameters in the study area; Calculate the normal pressure on the fracture surface and the ultimate pressure of plastic deformation of the fractured mudstone based on fracture-related parameters; The fracture opening capacity index during the hydrocarbon accumulation period is calculated based on the cross-sectional normal pressure and the ultimate pressure of mudstone plastic deformation. The ability to open early-aging faults is evaluated based on the fault-accumulation period opening capacity index.

2. The quantitative evaluation method for premature aging fracture initiation capability according to claim 1, characterized in that, The fault-related parameters include the depth of the fault where the present source rock is displaced, the thickness of the strata deposited during the hydrocarbon accumulation period and the later period, the density of the overlying strata, the density of the formation water, the fault dip angle, and the burial depth of the strata.

3. The quantitative evaluation method for the ability to initiate premature aging fractures according to claim 2, characterized in that, The formula for calculating the normal pressure on the fault section during the hydrocarbon accumulation period is: ; in, This refers to the cross-sectional normal pressure, expressed in MPa. This represents the stress coefficient during the hydrocarbon accumulation period. This represents the depth of the faulted section in the present-day source rock, in meters. The thickness of the strata deposited during the hydrocarbon accumulation period and the later period is shown in meters. This refers to the density of the overlying strata, expressed in g / cm³. 3 ; This refers to the density of formation water, expressed in g / cm³. 3 ; The value is the fault dip angle, expressed in degrees.

4. The quantitative evaluation method for the ability to initiate premature aging fractures according to claim 3, characterized in that, The formula for calculating the ultimate pressure of mudstone under plastic deformation is: ; in, This represents the ultimate pressure for plastic deformation of mudstone, expressed in MPa. and All are the plasticity coefficients of mudstone; The depth of the stratum is expressed in meters (m).

5. The quantitative evaluation method for the ability to initiate premature aging fractures according to claim 4, characterized in that, The formula for calculating the capacity index of early-aging fault reservoir formation period is: ; in, This is an index representing the capacity to initiate hydrocarbon accumulation during fault formation.

6. The quantitative evaluation method for the ability to initiate premature aging fractures according to claim 1, characterized in that, The evaluation level is divided into a first evaluation level and a second evaluation level based on the numerical range of the reservoir opening capacity index; or the numerical range of the reservoir opening capacity index is divided into a first evaluation level, a second evaluation level, and a third evaluation level.

7. The quantitative evaluation method for the ability to initiate premature aging fractures according to claim 6, characterized in that, Methods for evaluating the opening capacity of premature aging faults based on the hydrocarbon accumulation period opening capacity index include: Determine whether the reservoir-forming capacity index is greater than or equal to the first preset value; If so, the premature aging fracture is judged as the first evaluation level, and it does not have the ability to be reopened during the reservoir formation period; if not, the premature aging fracture is judged as the second evaluation level, and it has the ability to be reopened during the reservoir formation period.

8. The quantitative evaluation method for premature aging fracture initiation capability according to claim 6, characterized in that, Methods for evaluating the opening capacity of premature aging faults based on the hydrocarbon accumulation period opening capacity index include: Determine whether the reservoir-forming capacity index is greater than or equal to the first preset value; If yes, then the premature aging fracture is judged as the first evaluation level, and it does not have the ability to reopen during the reservoir formation period; if no, then it is judged whether the reservoir formation period opening ability index is greater than or equal to the second preset value, wherein the second preset value is less than the first preset value. If yes, the premature aging fault is judged as a second-level evaluation, with low capacity for opening up reservoirs during the reservoir formation period; if no, the premature aging fault is judged as a third-level evaluation, with high capacity for opening up reservoirs during the reservoir formation period.

9. A quantitative evaluation system for the ability to initiate premature aging fractures, characterized in that, include: The geological parameter input module is used to obtain fault-related parameters in the study area; The parameter calculation module is used to calculate the normal pressure on the fracture surface and the ultimate pressure of mudstone plastic deformation during the fracture formation period based on fracture-related parameters. The fracture opening capacity index calculation module is used to calculate the fracture opening capacity index during the hydrocarbon accumulation period based on the cross-sectional normal pressure and the ultimate pressure of mudstone plastic deformation. The evaluation output module is used to evaluate the opening capacity of early-aging faults based on the fault reservoir opening capacity index.

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