Quantitative evaluation method and system for fault disturbance of current crustal stress field of tight reservoir

Abstract

The invention discloses a quantitative evaluation method and system for fault disturbance of a current crustal stress field of a tight reservoir, and belongs to the technical field of petroleum and natural gas development. The method comprises the following steps: S1, obtaining an actually measured crustal stress value I of a target interval of a target fault and an actually measured crustal stress value II under a non-disturbance condition; s2, obtaining a theoretical ground stress value of a target interval of the target fault under a non-disturbance condition; s3, establishing an average principal stress and shear stress intensity calculation model, and calculating to obtain the average principal stress and shear stress intensity under actual measurement and non-disturbance conditions; s4, a crustal stress fault comprehensive disturbance index calculation model is established, a crustal stress fault comprehensive disturbance index is obtained through calculation, and the larger the index value is, the stronger the fault disturbance is. According to the method, the quantitative characterization of the force-fracture coupling relationship can be realized, and the problems of poor repeatability and lack of unified quantitative standards caused by a qualitative method as a main method are effectively solved, and the technical problem that the geomechanical environment around the well near the fault is not matched with the engineering response is effectively solved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of oil and gas development, in particular to a method and system for quantitatively evaluating fault disturbance of present-day stress field in tight reservoirs. BACKGROUND

[0002] Faults and associated induced fractures are not only important reservoir spaces for oil and gas, but also key seepage channels for oil and gas. Such faults and fractures are widely developed in underground reservoirs and constitute an important geological phenomenon. Under the action of present-day stress field, stress release or concentration often occurs near the faults, resulting in significant redistribution of the stress field. At the same time, the stress state directly affects the effectiveness and activity of the faults and fractures, controls the opening and closing behavior of the faults and the fluid transmission capacity, and forms a relatively independent "force-fracture" coupling system, which has an important influence on the exploration and development of unconventional resources such as tight oil and gas.

[0003] At present, although it is recognized that faults have a disturbance effect on the stress field, the disturbance law of the present-day stress field is not clear, and the disturbance mechanism research is mostly limited to qualitative or semi-quantitative research level, which makes it difficult to accurately predict the heterogeneous distribution of the stress near the faults, and seriously restricts the efficient development of the fault and fracture zones, especially the decision accuracy in well location optimization, fracturing stimulation measure development, and engineering risk control. SUMMARY

[0004] In view of the above problems, the present application aims to provide a method and system for quantitatively evaluating fault disturbance of present-day stress field in tight reservoirs.

[0005] The technical solution of the present application is as follows: On the one hand, a method for quantitatively evaluating fault disturbance of present-day stress field in tight reservoirs is provided, comprising the following steps: S1: obtaining measured stress value one of a target fault in a target layer and measured stress value two of the same layer as the target layer under non-disturbance condition near the target fault, the measured stress value including measured maximum horizontal principal stress, measured minimum horizontal principal stress and measured vertical principal stress; S2: obtaining theoretical stress value under non-disturbance condition of the target fault in the target layer according to the measured stress value two; S3: establishing an average principal stress calculation model, and calculating the measured average principal stress and the theoretical average principal stress under non-disturbance condition respectively by combining the measured stress value one and the theoretical stress value under non-disturbance condition; establishing a shear stress intensity calculation model, and calculating the measured shear stress intensity and the theoretical shear stress intensity under non-disturbance condition respectively by combining the measured stress value one and the theoretical stress value under non-disturbance condition; S4: a comprehensive disturbance index calculation model of the crustal stress fault is established, and the average principal stress and shear stress intensity calculated in step S3 are combined to obtain the comprehensive disturbance index of the crustal stress fault; the greater the comprehensive disturbance index of the crustal stress fault is, the stronger the fault disturbance is.

[0006] As preferred, step S2 specifically comprises the following sub-steps: S21: determining the fault type of the target fault, and determining the calculation model of the principal stress of the critical state theory according to the fault type; S22: substituting the measured crustal stress value into the calculation model of the principal stress of the critical state theory to obtain the unknown of the calculation model of the principal stress of the critical state theory; S23: calculating the theoretical crustal stress value of the target fault under the non-disturbance condition of the target fault according to the calculation model of the principal stress of the critical state theory after determining the unknown.

[0007] As preferred, in step S21, when the fault type of the target fault is normal fault, the calculation model of the principal stress of the critical state theory is: (1) (2) In the formula: is the maximum horizontal principal stress, MPa; is the minimum horizontal principal stress, MPa; is the vertical principal stress, MPa; is the pore pressure of the stratum, MPa; is the critical stress coefficient of the minimum principal stress under the non-disturbance condition, dimensionless; When the fault type of the target fault is strike-slip fault, the calculation model of the principal stress of the critical state theory is: (3) (4) In the formula: is the critical stress coefficient of the maximum principal stress under the non-disturbance condition, dimensionless; When the fault type of the target fault is reverse fault, the calculation model of the principal stress of the critical state theory is: (3) (5) In step S22, the unknown of the calculation model of the principal stress of the critical state theory is the critical stress coefficient of the maximum principal stress under the non-disturbance condition and the critical stress coefficient of the minimum principal stress under the non-disturbance condition .

[0008] As preferred, in step S23, the unknowns in the calculation model of the critical state theory principal stress after the unknowns are determined are obtained by averaging the multiple unknowns obtained in step S22.

[0009] As preferred, in step S3, the average principal stress calculation model is: (6) In the formula: is the average principal stress, MPa; , , are the maximum horizontal principal stress, the minimum horizontal principal stress, and the vertical principal stress, respectively, in descending order, MPa; The shear stress intensity calculation model is: (7) In the formula: is the shear stress intensity, MPa.

[0010] As preferred, in step S4, the comprehensive disturbance index calculation model of the in-situ stress and fault is: (8) In the formula: is the comprehensive disturbance index of the in-situ stress and fault, dimensionless; is the measured average principal stress, MPa; is the theoretical average principal stress under non-disturbance conditions, MPa; is the measured shear stress intensity, MPa; is the theoretical shear stress intensity under non-disturbance conditions, MPa.

[0011] As preferred, the method further comprises the following steps: S5: Obtain the comprehensive disturbance index of the in-situ stress and fault of different single wells and different target intervals, and obtain the normal distance of different single wells and different target intervals from the fault; S6: According to the comprehensive disturbance index of the in-situ stress and fault and the normal distance obtained in step S5, a fitting model of the comprehensive disturbance index of the in-situ stress and fault and the well spacing is fitted; S7: According to the fitting model of the comprehensive disturbance index of the in-situ stress and fault and the well spacing, the comprehensive disturbance index of the in-situ stress and fault of any target interval is calculated.

[0012] As preferred, in step S5, when only the horizontal distance L of a target interval from the fault is known, the normal distance of the target interval from the fault is calculated by the following formula: (9) In the formula: is the normal distance of the target interval from the fault for the known horizontal distance, m; is the horizontal distance of the target interval from the fault, m; is the fault dip angle, °; When the well location is on the hanging wall of the fault, the normal distances of the target intervals above and below the target interval at the known horizontal distance from the fault are calculated by the following formulas, respectively: (10) (11) When the well location is on the hanging wall of the fault, the normal distances of the target intervals above and below the target interval at the known horizontal distance from the fault are calculated by the following formulas, respectively: (12) (13) In the formulas, d is the normal distance of the target interval above the target interval at the known horizontal distance from the fault, m; is the normal distance of the target interval from the fault for the known horizontal distance, m; is the reservoir mid-depth of the target interval at the known horizontal distance, m; is the reservoir mid-depth of the target interval above the target interval at the known horizontal distance, m; is the normal distance of the target interval from the fault for the known horizontal distance, m; is the reservoir mid-depth of the target interval below the target interval at the known horizontal distance, m.

[0013] Preferably, in step S6, the fitting model of the geostress fault comprehensive disturbance index and the well distance is fitted by an exponential decay function, which is as follows: (14) In the formula, d is the normal distance of the target interval from the fault, m. is the geostress fault comprehensive disturbance index of the ith target interval, dimensionless; , , are all fitting coefficients, dimensionless; is the normal distance of the ith target interval from the fault, m.

[0014] In another aspect, the present application also provides a quantitative evaluation system for the fault disturbance of the present geostress field of a tight reservoir, comprising: The measured stress value acquisition module is used for acquiring a measured stress value one of a target fault target layer and a measured stress value two of a same layer as the target layer under a non-disturbance condition near the target fault, and the measured stress value comprises a measured maximum horizontal principal stress, a measured minimum horizontal principal stress and a measured vertical principal stress; The theoretical stress value acquisition module under the non-disturbance condition is used for acquiring a theoretical stress value under the non-disturbance condition of the target fault target layer according to the measured stress value two; The average principal stress module is used for establishing an average principal stress calculation model, and respectively calculating a measured average principal stress and a theoretical average principal stress under the non-disturbance condition by combining the measured stress value one and the theoretical stress value under the non-disturbance condition; The shear stress intensity module is used for establishing a shear stress intensity calculation model, and respectively calculating a measured shear stress intensity and a theoretical shear stress intensity under the non-disturbance condition by combining the measured stress value one and the theoretical stress value under the non-disturbance condition; The stress fault comprehensive disturbance index module is used for establishing a stress fault comprehensive disturbance index calculation model, and calculating a stress fault comprehensive disturbance index by combining the calculated average principal stress and shear stress intensity; the greater the stress fault comprehensive disturbance index is, the stronger the fault disturbance is.

[0015] The present application has the following advantages: 1. The present application can be quantitatively evaluated: the traditional evaluation of fault disturbance is mostly qualitative or semi-quantitative, and mostly uses qualitative description such as "strong disturbance" and "weak disturbance", the present application firstly proposes a comprehensive quantitative index (stress fault comprehensive disturbance index T), which can quantitatively describe the disturbance degree of the fault to the stress field, and is free from the dependence on subjective experience. Further, the present application can further obtain a fitting function in combination with the fault normal distance, and accurately sort and compare the disturbance degrees of different regions and different faults by using the fitting function.

[0016] 2. The evaluation index elements of the present application are complete and comprehensive: the stress fault comprehensive disturbance index (T) not only comprehensively considers each stress component, but also considers the change of the stress direction, can more comprehensively reflect the change of the stress state, and each parameter has clear physical meaning and is scientific and reliable.

[0017] 3. The present application has strong operability and good universality: the method of the present application can be calculated by using conventional stress data (such as logging and seismic) and fault information, the process can be replicated and is easy to popularize. Meanwhile, the present application is based on the relative change of stress invariant, and can be applied to fault disturbance analysis of different types and different geological environments, and is widely applied in engineering practice. BRIEF DESCRIPTION OF DRAWINGS

[0018] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or prior art description. Obviously, the drawings in the following description only constitute some embodiments of the present application, and for those skilled in the art, other drawings can also be obtained from these drawings without creative labor.

[0019] Figure 1 Fig. 1 is a schematic diagram for calculating the normal distance between the reservoir and the fault; wherein a is a schematic diagram for calculating the well located on the hanging wall of the fault, and b is a schematic diagram for calculating the well located on the footwall of the fault; Figure 2 Fig. 2 is a rock mechanics and present-day stress interpretation profile of a single well in a specific embodiment; Figure 3 Fig. 3 is a present-day stress and comprehensive disturbance index profile of a single well in a specific embodiment; Figure 4 Fig. 4 is a fitting diagram of the exponential decay function of the present-day stress fault comprehensive disturbance index and well distance in a specific embodiment; Figure 5 Fig. 5 is a normality test diagram of the residual of the exponential decay function in a specific embodiment. DETAILED DESCRIPTION

[0020] The present application will be further described below in conjunction with the drawings and embodiments. It should be noted that the embodiments in the present application and the technical features in the embodiments can be combined with each other without conflict. It should be noted that unless otherwise specified, all technical and scientific terms used in the present application have the same meaning as generally understood by those skilled in the art to which the present application belongs. The present application discloses that the "including" or "containing" and similar words mean that the elements or objects before the words cover the elements or objects listed after the words and their equivalents, and do not exclude other elements or objects.

[0021] In one aspect, the present application provides a quantitative evaluation method for the fault disturbance of the present-day stress field in a tight reservoir, comprising the following steps: S1: obtaining the measured stress value one of the target fault in the target layer and the measured stress value two of the same layer as the target layer under non-disturbance condition near the target fault, wherein the measured stress value includes the measured maximum horizontal principal stress, the measured minimum horizontal principal stress and the measured vertical principal stress.

[0022] In one specific embodiment, the measured in-situ stress value can be obtained by integrating rock mechanics experimental data, calculation results of in-situ stress size by fracturing method, and single-well in-situ stress interpretation using logging data to obtain single-well results of profile rock mechanics and present in-situ stress size. The method has the advantages of continuous in-situ stress values in the vertical direction and high accuracy. For different types of reservoirs, the interpretation models of in-situ stress are different. For example, for tight sandstone reservoirs, the three-dimensional stress values of well profile are obtained by using the Huang model for interpretation.

[0023] It should be noted that the method for obtaining the measured in-situ stress value in the above embodiment is only a preferred embodiment of the present application. In addition to the method used in the above embodiment, other methods for obtaining the measured in-situ stress value in the prior art can also be applied to the present application.

[0024] S2: obtaining a theoretical in-situ stress value of a target fault purpose layer under non-disturbance conditions according to the measured in-situ stress value two.

[0025] In one specific embodiment, step S2 specifically comprises the following sub-steps: S21: determining the fault type of the target fault, and determining the calculation model of the critical state theoretical principal stress according to the fault type; S22: substituting the measured in-situ stress value two into the calculation model of the critical state theoretical principal stress to obtain the unknown number of the calculation model of the critical state theoretical principal stress; S23: calculating the theoretical in-situ stress value of the target fault purpose layer under non-disturbance conditions according to the calculation model of the critical state theoretical principal stress after determining the unknown number.

[0026] In one specific embodiment, in step S21, when the fault type of the target fault is a normal fault, the calculation model of the critical state theoretical principal stress is: (1) (2) In the formula: is the maximum horizontal principal stress, MPa; is the minimum horizontal principal stress, MPa; is the vertical principal stress, MPa; is the formation pore pressure, MPa; is the minimum principal stress critical stress coefficient under non-disturbance conditions (i.e. in a gently sloping area), dimensionless; When the fault type of the target fault is a strike-slip fault, the calculation model of the critical state theoretical principal stress is: (3) (4) In the formula, is the critical stress coefficient of the maximum principal stress under non-disturbed condition, dimensionless; When the fault type of the target fault is a reverse fault, the calculation model of the principal stress of the critical state theory is: (3) (5) In step S22, the unknowns of the calculation model of the principal stress of the critical state theory are the critical stress coefficient of the maximum principal stress under non-disturbed condition and the critical stress coefficient of the minimum principal stress under non-disturbed condition .

[0027] In the above embodiment, the fault type of the target fault can be determined according to the Anderson theory, which is prior art and specific steps are not repeated here. The above calculation models are based on the Coulomb rupture criterion. For a strike-slip fault, and the critical rupture state of the stratum (i.e., the cohesion is approximately equal to 0) is reasonably assumed to derive.

[0028] In a specific embodiment, in step S23, after the unknowns are determined, the calculation model of the principal stress of the critical state theory is obtained by averaging the multiple unknowns obtained in step S22.

[0029] S3: Establish an average principal stress calculation model, and calculate the measured average principal stress and the theoretical average principal stress under non-disturbed condition respectively by combining the measured in-situ stress value and the theoretical in-situ stress value under non-disturbed condition. Establish a shear stress intensity calculation model, and calculate the measured shear stress intensity and the theoretical shear stress intensity under non-disturbed condition respectively by combining the measured in-situ stress value and the theoretical in-situ stress value under non-disturbed condition.

[0030] In a specific embodiment, the average principal stress calculation model is: (6) In the formula, is the average principal stress, MPa; , , are the three in-situ stress values in descending order, MPa; The shear stress intensity calculation model is: (7) In the formula, is the shear stress intensity, MPa.

[0031] In the above embodiment, the average principal stress can reflect the change of rock volume, and the shear stress intensity can reflect the change of rock shape.

[0032] S4: establishing a geostress fault comprehensive disturbance index calculation model, combining the average principal stress and the shear stress intensity calculated in step S3 to obtain the geostress fault comprehensive disturbance index; the greater the geostress fault comprehensive disturbance index is, the stronger the fault disturbance is.

[0033] In a specific embodiment, the geostress fault comprehensive disturbance index calculation model is: (8) In the formula: is the geostress fault comprehensive disturbance index, dimensionless; is the measured average principal stress, MPa; is the theoretical average principal stress under non-disturbance condition, MPa; is the measured shear stress intensity, MPa; is the theoretical shear stress intensity under non-disturbance condition, MPa.

[0034] In the above embodiment, the average principal stress and the shear stress intensity are used to comprehensively represent the disturbance index, wherein: the disturbance representing the volume transformation ability describes to what extent the fault disturbance changes the volume compression or expansion state of the rock; the disturbance representing the shape change ability describes to what extent the fault disturbance changes the shear deformation or damage potential of the rock; the value of the average principal stress change rate measures the change rate of the compressive stress, when , it indicates that the observation point is subjected to stronger extrusion than the regional stress field; when , it indicates that the observation point has stress release; when , it indicates that the observation point has no obvious disturbance; the value of the shear stress change rate measures the change rate of the shear stress, when , it indicates that the observation point is subjected to stronger shear strength than the regional stress field, and the rock is more prone to shear failure and wellbore instability; when , it indicates that the shear strength of the observation point is weakened, and the rock is more stable.

[0035] It can be seen that the geostress fault comprehensive disturbance index calculation model comprehensively considers the change of the geostress direction, can more comprehensively reflect the change of the stress state, and has clear and scientific physical meanings.

[0036] In one specific embodiment, the quantitative evaluation method of the present application for fault disturbance of the present-day stress field of the compact reservoir further comprises the following steps: S5: obtaining the comprehensive fault disturbance index of the ground stress of different single wells and different target intervals, and obtaining the normal distance between different single wells, different target intervals and faults.

[0037] In one specific embodiment, when obtaining the normal distance between different single wells, different target intervals and faults, if only the horizontal distance L between a target interval and a fault is known, the normal distance between the target interval and the fault is calculated by the following formula: (9) In the formula: is the normal distance between the target interval and the fault with the known horizontal distance, m; is the horizontal distance between the target interval and the fault, m; is the dip angle of the fault, °; As shown in Figure 1 , when the well location is on the hanging wall of the fault, the normal distances between the target intervals above and below the target interval with the known horizontal distance and the fault are calculated by the following formulas, respectively: (10) (11) When the well location is on the hanging wall of the fault, the normal distances between the target intervals above and below the target interval with the known horizontal distance and the fault are calculated by the following formulas, respectively: (12) (13) In the formula: is the normal distance between the target interval above the target interval with the known horizontal distance and the fault, m; is the reservoir middle depth of the target interval with the known horizontal distance, m; is the reservoir middle depth of the target interval above the target interval with the known horizontal distance, m; is the normal distance between the target interval below the target interval with the known horizontal distance and the fault, m; is the reservoir middle depth of the target interval below the target interval with the known horizontal distance, m.

[0038] In the above embodiment, when only the horizontal distance L of a target layer segment from the fault is known, the normal distance L0 of the target layer segment can be used to calculate the normal distance of the target layer segment from the fault according to the position of the well site and the fault (hanging wall or footwall), in combination with the reservoir mid-depth of the target layer segment and the fault dip angle. If the horizontal distance of each target layer segment from the fault is known, formula (9) is directly used for calculation.

[0039] S6: A fitting model of the comprehensive disturbance index of the in-situ stress fault and the well spacing is fitted according to the comprehensive disturbance index of the in-situ stress fault and the normal distance obtained in step S5.

[0040] In a specific embodiment, the fitting model of the comprehensive disturbance index of the in-situ stress fault and the well spacing is fitted by an exponential decay function, which is as follows: (14) In the formula, is the comprehensive disturbance index of the in-situ stress fault of the i th target layer segment, dimensionless; , , are fitting coefficients, dimensionless; is the normal distance of the i th target layer segment from the fault, m.

[0041] In the above embodiment, is the maximum disturbance at the fault, is the decay rate, is the far-field stress disturbance intensity (theoretically 0, but actually disturbed by other factors). The present application can more accurately obtain the comprehensive disturbance index of the in-situ stress fault that is more consistent with the actual working condition by considering the far-field stress disturbance intensity.

[0042] S7: The comprehensive disturbance index of the in-situ stress fault of any target layer segment is calculated according to the fitting model of the comprehensive disturbance index of the in-situ stress fault and the well spacing.

[0043] In the above embodiment, the present application fits the comprehensive disturbance index of the in-situ stress fault and the well spacing to obtain a fitting model, which can calculate the comprehensive disturbance index of the in-situ stress fault of any target layer segment. This can provide important support for subsequent scientific research or engineering practice, and the specific effects are as follows: a. Support for reservoir reconstruction and engineering sweet spot prediction. The high disturbance area of the fault is often accompanied by a fault-derived fracture zone, and the complex stress state is helpful for the formation of a complex fracture network system in artificial fracturing reconstruction. By matching and analyzing production data, a high-yield engineering sweet spot can be circled.

[0044] b. Guidance drilling engineering optimization and risk early warning. In the well trajectory design stage, the disturbance index profile is predicted, and after coupling analysis with wellbore instability, pipe sticking and other factors, high disturbance area is actively bypassed as the early warning index of drilling engineering risk.

[0045] In another aspect, the present application also provides a quantitative evaluation system for fault disturbance of present in-situ stress field in tight reservoirs, comprising: A measured in-situ stress value acquisition module is configured to acquire a measured in-situ stress value one of a target fault target layer and a measured in-situ stress value two of a same layer as the target layer under non-disturbance conditions near the target fault, wherein the measured in-situ stress value includes a measured maximum horizontal principal stress, a measured minimum horizontal principal stress and a measured vertical principal stress; A theoretical in-situ stress value acquisition module under non-disturbance conditions is configured to acquire a theoretical in-situ stress value under non-disturbance conditions of the target fault target layer according to the measured in-situ stress value two; An average principal stress module is configured to establish an average principal stress calculation model and calculate a measured average principal stress and a theoretical average principal stress under non-disturbance conditions respectively in combination with the measured in-situ stress value one and the theoretical in-situ stress value under non-disturbance conditions; A shear stress intensity module is configured to establish a shear stress intensity calculation model and calculate a measured shear stress intensity and a theoretical shear stress intensity under non-disturbance conditions respectively in combination with the measured in-situ stress value one and the theoretical in-situ stress value under non-disturbance conditions; An in-situ stress fault comprehensive disturbance index module is configured to establish an in-situ stress fault comprehensive disturbance index calculation model and calculate an in-situ stress fault comprehensive disturbance index in combination with the calculated average principal stress and shear stress intensity; the greater the in-situ stress fault comprehensive disturbance index, the more intense the fault disturbance.

[0046] In a specific embodiment, the quantitative evaluation system for fault disturbance of present in-situ stress field in tight reservoirs also comprises: A normal distance module is configured to acquire normal distances of different single wells, different target layers and faults; A fitting module is configured to fit a fitting model of the in-situ stress fault comprehensive disturbance index and well spacing according to the obtained in-situ stress fault comprehensive disturbance index and normal distance, and calculate the in-situ stress fault comprehensive disturbance index of any target layer according to the fitting model of the in-situ stress fault comprehensive disturbance index and well spacing.

[0047] In a specific embodiment, the quantitative evaluation method for fault disturbance of present in-situ stress field in tight reservoirs is used to quantitatively evaluate the Northeast Sichuan A block. In this embodiment, the rock mechanics and present in-situ stress interpretation profile of a certain single well is as shown in Figure 2As shown, the maximum principal stress critical stress coefficient of the region is calculated according to the measured stress values of a single well near a structure which is flat and has no fault (i.e. the single well in non-disturbance condition) The minimum principal stress critical stress coefficient is 1.57 0.21, and the theoretical stress values of each single well in the non-disturbance condition are calculated by the calculation model of the critical state theory stress after the coefficient is determined. The stress fault comprehensive disturbance index of each layer of each well is calculated by combining formulas (6)-(8), wherein the profile fault disturbance profile comprehensive column chart of a single well profile is as shown in Figure 3 .

[0048] The normal distance between each target layer and the fault is calculated, and the comprehensive data table of the stress fault comprehensive disturbance index and the normal distance is obtained, and the results are shown in Table 1: Table 1 Stress fault comprehensive disturbance index and fault distance table of each single well

[0049] According to the data in Table 1, the scatter plot of the stress fault comprehensive disturbance index and the normal distance is drawn, and the data is regressed and fitted, and the fitting graph and the residual normality test graph of the exponential decay function shown in formula (14) are as shown in Figure 4 and Figure 5 . As can be seen from Figure 4 and Figure 5 , the fitting model conforms to the exponential decay function, and the residual is approximately linearly distributed along the reference line, indicating that the residual is subject to normal distribution, and the model normal assumption is reasonable. The results show that the maximum disturbance degree of the fault position is 44.8%, and the disturbance tends to be flat at 400m from the fault, and the far-field stress is mainly affected by the disturbance of other factors such as structure.

[0050] In summary, the present application can quantitatively evaluate the fault disturbance of the present-day stress field of the tight reservoir. Compared with the prior art, the present application has significant progress.

[0051] The above is only a preferred embodiment of the present application, and does not limit the present application in any form. Although the present application has been disclosed as above, it is not intended to limit the present application. Any skilled person in the art can make some changes or modifications to the above disclosed technical content without departing from the scope of the technical solution of the present application, and any simple modification, equivalent change and modification of the above embodiments according to the technical essence of the present application are still within the scope of the technical solution of the present application.

Claims

1. A quantitative evaluation method for fault disturbance in the present geostress field of tight reservoirs, characterized in that, Includes the following steps: S1: Obtain the measured in-situ stress value one of the target fault target segment and the measured in-situ stress value two of the same segment near the target fault under undisturbed conditions. The measured in-situ stress values ​​include the measured maximum horizontal principal stress, the measured minimum horizontal principal stress and the measured vertical principal stress. S2: Based on the measured ground stress value 2, obtain the theoretical ground stress value of the target fault segment under undisturbed conditions; S3: Establish a mean principal stress calculation model, and calculate the measured mean principal stress and the theoretical mean principal stress under the unperturbed conditions by combining the measured ground stress value and the theoretical ground stress value under the unperturbed conditions respectively. A shear stress strength calculation model is established, and the measured shear stress strength and the theoretical shear stress strength under the undisturbed conditions are calculated by combining the measured ground stress value and the theoretical ground stress value under the undisturbed conditions. S4: Establish a comprehensive disturbance index calculation model for geostress faults, and calculate the comprehensive disturbance index of geostress faults by combining the average principal stress and shear stress intensity obtained in step S3; the larger the comprehensive disturbance index of geostress faults, the stronger the fault disturbance.

2. The quantitative evaluation method for fault disturbance of the present geostress field in tight reservoirs according to claim 1, characterized in that, Step S2 specifically includes the following sub-steps: S21: Determine the fault type of the target fault, and determine the calculation model of the critical state theoretical principal stress based on the fault type; S22: Substitute the measured ground stress value into the calculation model of the critical state theoretical principal stress to obtain the unknowns of the calculation model of the critical state theoretical principal stress; S23: Based on the calculation model of the critical state theoretical principal stress after determining the unknowns, calculate the theoretical geostress value of the target fault segment under undisturbed conditions.

3. The quantitative evaluation method for fault disturbance of the present geostress field in tight reservoirs according to claim 2, characterized in that, In step S21, when the target fault is a normal fault, the calculation model for the critical state theoretical principal stress is as follows: （1） （2） In the formula: The maximum horizontal principal stress is expressed in MPa. The minimum horizontal principal stress is 1 MPa. The vertical principal stress is MPa; Formation pore pressure, MPa; is the minimum principal stress critical stress coefficient under undisturbed conditions, and is dimensionless; When the target fault is a strike-slip fault, the calculation model for the critical state theoretical principal stress is as follows: （3） （4） In the formula: is the critical stress coefficient of the maximum principal stress under undisturbed conditions, and is dimensionless; When the target fault is a reverse fault, the calculation model for the critical state theoretical principal stress is as follows: （3） （5） In step S22, the unknowns in the calculation model of the theoretical principal stress of the critical state are the critical stress coefficients of the maximum principal stress under the non-disturbance condition. and the minimum principal stress critical stress coefficient under the aforementioned non-disturbance conditions .

4. The quantitative evaluation method for fault disturbance of the present geostress field in tight reservoirs according to claim 3, characterized in that, In step S23, the calculation model for the theoretical principal stress of the critical state after determining the unknowns is obtained by averaging the multiple unknowns obtained in step S22.

5. The quantitative evaluation method for fault disturbance of the present geostress field in tight reservoirs according to claim 1, characterized in that, In step S3, the average principal stress calculation model is as follows: （6） In the formula: The mean principal stress is expressed in MPa. , , The three geostress values, in MPa, are the maximum horizontal principal stress, the minimum horizontal principal stress, and the vertical principal stress, ordered from largest to smallest. The shear stress strength calculation model is as follows: （7） In the formula: is the shear stress strength, MPa.

6. The quantitative evaluation method for fault disturbance of the present geostress field in tight reservoirs according to claim 1, characterized in that, In step S4, the calculation model for the comprehensive disturbance index of the geostress fault is as follows: （8） In the formula: The comprehensive disturbance index of geostress faults is dimensionless. The measured average principal stress is expressed in MPa. ρ is the theoretical average principal stress under undisturbed conditions, in MPa; The measured shear stress strength is in MPa. ρ represents the theoretical shear stress intensity under undisturbed conditions, in MPa.

7. The quantitative evaluation method for fault disturbance of the present geostress field in tight reservoirs according to any one of claims 1-6, characterized in that, It also includes the following steps: S5: Obtain the comprehensive disturbance index of geostress faults for different single wells and different target sections, and obtain the normal distance between different single wells, different target sections and faults; S6: Based on the comprehensive disturbance index of the geostress fault and the normal distance obtained in step S5, fit the fitting model of the comprehensive disturbance index of the geostress fault and the well spacing. S7: Calculate the comprehensive stress fault disturbance index for any target segment based on the fitting model of the comprehensive stress fault disturbance index and well spacing.

8. The quantitative evaluation method for fault disturbance of the present geostress field in tight reservoirs according to claim 7, characterized in that, In step S5, when obtaining the normal distances between different single wells, different target segments, and faults, if only the horizontal distance L between a target segment and the fault is known, the normal distance between that target segment and the fault is calculated using the following formula: （9） In the formula: The normal distance between the target segment and the fault, given horizontal distance, is in meters (m). The horizontal distance between the target segment and the fault, in meters (m). The fault dip angle is expressed in °. When the well location is on the hanging wall of a fault, the normal distances between the target segment above and below the target segment at the known horizontal distance and the fault are calculated using the following formulas: （10） （11） When the well location is in the footwall of a fault, the normal distances between the target segment above and below the target segment at the known horizontal distance and the fault are calculated using the following formulas: （12） （13） In the formula: The normal distance, in meters, is the distance between the target layer above the target layer at the known horizontal distance and the fault. The depth of the reservoir midpoint within the target section, at a known horizontal distance, is in meters (m). The depth of the reservoir midpoint of the target layer located above the target layer at the known horizontal distance, in meters; The normal distance, in meters, is the distance between the target layer below the target layer at the known horizontal distance and the fault. The depth in meters (m) is the central reservoir depth of the target layer located below the target layer at the known horizontal distance.

9. The quantitative evaluation method for fault disturbance of the present geostress field in tight reservoirs according to claim 7, characterized in that, In step S6, the fitting model of the comprehensive disturbance index of the geostress fault and the well spacing is fitted using an exponential decay function, which is: （14） In the formula: Let be the comprehensive stress-fault disturbance index of the i-th target segment, which is dimensionless; , , All are fitting coefficients, dimensionless; Let m be the normal distance between the i-th target segment and the fault.

10. A quantitative evaluation system for fault disturbance in the present geostress field of tight reservoirs, characterized in that, include: The measured in-situ stress value acquisition module is used to acquire the measured in-situ stress value one of the target fault target segment and the measured in-situ stress value two of the same segment as the target segment under undisturbed conditions near the target fault. The measured in-situ stress values ​​include the measured maximum horizontal principal stress, the measured minimum horizontal principal stress and the measured vertical principal stress. The module for obtaining theoretical geostress values ​​under undisturbed conditions is used to obtain the theoretical geostress values ​​of the target segment of the target fault under undisturbed conditions based on the measured geostress value 2. The mean principal stress module is used to establish a mean principal stress calculation model, and to calculate the measured mean principal stress and the theoretical mean principal stress under the unperturbed conditions by combining the measured geostress value and the theoretical mean principal stress under the unperturbed conditions, respectively. The shear stress strength module is used to establish a shear stress strength calculation model, and to calculate the measured shear stress strength and the theoretical shear stress strength under the unperturbed conditions by combining the measured ground stress value and the theoretical ground stress value under the unperturbed conditions. The geostress fault comprehensive disturbance index module is used to establish a calculation model for the geostress fault comprehensive disturbance index, and to calculate the geostress fault comprehensive disturbance index by combining the calculated average principal stress and shear stress intensity; the larger the geostress fault comprehensive disturbance index, the stronger the fault disturbance.

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