Evaluation method of geological fault activity risk

Abstract

The invention discloses a geological fault activity risk evaluation method, which comprises the steps of constructing a geological model of a research area, determining a distribution area of a geological fault through a three-dimensional coordinate system established on the geological model, and calculating a fault sliding coefficient according to fault point coordinates of corresponding rock sample columns on reference points and contrast points in the distribution area; calculating the overall geological structure vulnerability coefficient of the geological fault; calculating an earthquake risk coefficient of the position of the geological fault; and calculating an activity risk coefficient of the geological fault according to the calculated fault sliding coefficient, the geological structure vulnerability coefficient and the earthquake risk coefficient, and evaluating the activity risk of the geological fault. Accuracy of activity risk assessment of the geological fault is effectively improved, combination of field survey data and monitoring data is achieved, and a solution which is complete in theory, scientific in method and high in practicability is provided for fault activity risk assessment.

Description

Technical Field

[0001] The present invention relates to the field of geological activity risk research, and particularly relates to a method for evaluating the risk of geological fault activity. Background Art

[0002] Fault activity refers to the phenomenon that a pre-existing fault at a certain depth underground undergoes relative movement of the upper and lower plates due to a change in its own stress state, resulting in relative displacement of the fault. Fault activity may cause seismic activities in oil and gas production areas, thus posing potential safety hazards to production areas and the lives of local residents.

[0003] In order to minimize such risks as much as possible, currently mainly seismic monitoring means, sensor detection means, etc. are adopted. These are all oriented towards the results of events to retrospectively evaluate whether the fault is active and whether the fault activity will cause earthquakes, and the data collection is single, unable to accurately evaluate the current geological fault activity risk. For faults that are not exposed on the surface, only seismic monitoring can be used to retrospectively evaluate the fault activity based on the spatial characteristics of seismic activities, and the risk cannot be accurately evaluated. Summary of the Invention

[0004] In view of the above deficiencies of the prior art, the present invention provides a method for evaluating the risk of geological fault activity, which combines field survey data and seismic monitoring data to reasonably and accurately evaluate the activity risk of geological faults.

[0005] To achieve the above invention objective, the technical solution adopted by the present invention is as follows:

[0006] Provide a method for evaluating the risk of geological fault activity, which includes the following steps:

[0007] S1: Construct a geological model of the research area, draw geological faults on the geological model, determine the distribution area of the geological faults through a three-dimensional coordinate system established on the geological model, take a number of reference points and control points before and after the monitoring period T based on the distribution area, and calculate the fault slip coefficient according to the fault point coordinates of the corresponding rock sample columns at the reference points and control points;

[0008] S2: According to the obtained rock sample columns, calculate the geological structure vulnerability coefficients of the rock layers above and below the fault boundary respectively based on the fault boundary, and then calculate the overall geological structure vulnerability coefficient of the geological fault;

[0009] S3: Count the number of earthquakes and their corresponding magnitudes that occurred in the area where the geological fault is located during the monitoring period T, and calculate the seismic hazard coefficient of the location where the geological fault is located;

[0010] S4: Calculate the activity risk coefficient of the geological fault based on the calculated fault slip coefficient, geological structure vulnerability coefficient, and seismic hazard coefficient, and evaluate the magnitude of the activity risk of the geological fault.

[0011] Further, step S1 includes:

[0012] S11: Determine the research area of the geological fault activity, construct the geological model of the research area, and draw the detected geological fault in the geological model;

[0013] S12: Establish a three-dimensional coordinate system in the geological model. The xoy plane of the three-dimensional coordinate system is parallel to the horizontal plane. Vertically project the geological fault onto the xoy plane. The boundary of the geological fault forms a horizontal distribution area in the xoy plane. Uniformly set a number of reference points in the distribution area;

[0014] S13: Use the reference point as the perpendicular foot to make a perpendicular line perpendicular to the xoy plane, and obtain the intersection point of each perpendicular line and the upper soil layer of the geological model as the monitoring point. The staff reaches the actual location of the geological fault through the positioning of the monitoring point, and drills down to obtain the rock sample column at each monitoring point;

[0015] S14: Obtain the coordinates (x n , y n , z n ) of the fault point below the monitoring point in the three-dimensional coordinate system according to the position of the geological fault on the rock sample column, where n is the number of the reference point;

[0016] S15: After the set monitoring period T, uniformly set a number of control points in the distribution area, and make the control points not coincide with the reference points, and the number of control points is the same as that of the reference points. Execute steps S13 - S14 to obtain the coordinates (x n ′, y n ′, z′ n ) of the corresponding fault point of the control point in the three-dimensional coordinate system;

[0017] S16: Construct the coordinate set A of the reference points and the coordinate set B of the control points. According to the coordinates of the reference points and the control points in the three-dimensional coordinate system screen the two nearest reference points and control points as the fault activity control group;

[0018] S17: After obtaining the fault activity control group, delete the coordinates of the reference points and the control points in the fault activity control group from the coordinate set A and the coordinate set B, and then return to step S16 to perform the screening of the fault activity control group without replacement;

[0019] S18: Repeat step S17 until the reference point coordinates and the control point coordinates in the coordinate set A and the coordinate set B are matched, and then output all fault activity control groups, as well as the reference point a corresponding to the reference point coordinates and the control point coordinates in each fault activity control group. n and control point b n ;

[0020] S19: Using reference point a n and control point b n The coordinates of the corresponding fault point The fault slip coefficient v is calculated from the difference between them.

[0021] Furthermore, the screening objective function of the fault activity control group is;

[0022]

[0023] Furthermore, the fault slip coefficient v is calculated as follows;

[0024]

[0025] Where N is the number of reference points and control points.

[0026] Further, step S2 includes:

[0027] S21: Based on the rock sample column currently obtained at each monitoring point and the fault boundary line on the rock sample column, the compressive strength and density of each rock layer on the upper and lower sides are tested respectively to calculate the geological structural fragility coefficient of the geological fault;

[0028]

[0029] Where i is the number of the rock layer, E is the number of rock layers, is the compressive strength of the rock formation, is Poisson's ratio, is the bulk modulus, is the rock density;

[0030] S22: obtaining the geological structural fragility coefficient I1 of the rock layer above the fault boundary line and the geological structural fragility coefficient I2 of the rock layer below the fault boundary line, and calculating the geological structural fragility coefficient I0 of the entire geological fault according to the fault type;

[0031] I0=α1I1+α2I2;

[0032] Among them, α1 and α2 are the geological structure vulnerability weight coefficients of the upper rock layer and the lower rock layer respectively;

[0033] When the geological fault is a normal fault, α1<α2;

[0034] When the geological fault is a reverse fault, take α1 > α2;

[0035] When the geological fault is a smooth fault, take α1 = α2;

[0036] And both satisfy α1 + α2 = 1.

[0037] Furthermore, the calculation method of the seismic risk coefficient p is:

[0038]

[0039] Among them, J is the number of earthquakes occurring during the monitoring period T, j is the number of the earthquakes occurring during the monitoring period T, P(IM > x|m j ,r) is the attenuation relationship of ground motion intensity, m j is the earthquake intensity, r is the earthquake influence distance, v j is the number of earthquakes with magnitudes exceeding the magnitude threshold among the J earthquakes, f j is the occurrence probability of earthquakes with magnitudes exceeding the magnitude threshold among the J earthquakes, A is the area of the seismic source region around the geological fault, β j is the G-R relationship coefficient of the earthquake, m min is the upper magnitude limit of the earthquakes occurring around the geological fault, m max is the lower magnitude limit of the earthquakes occurring around the geological fault, sh(.) is the hyperbolic sine function, and Δm is the average magnitude interval among the J earthquakes.

[0040] Furthermore, step S4 includes:

[0041] S41: Calculate the activity risk coefficient W of the geological fault according to the calculated fault slip coefficient v, geological structure vulnerability coefficient I0, and seismic risk coefficient p;

[0042]

[0043] Among them, is the average value of the fault slip coefficients calculated in all historical monitoring periods, I′ is the threshold of the geological structure vulnerability coefficient, is the average value of the seismic risk coefficients calculated in all historical monitoring periods;

[0044] S42: Set the threshold W0 of the activity risk coefficient;

[0045] If W > W0, it is determined that the activity risk of the current geological fault is large;

[0046] If W ≤ W0, it is determined that the activity risk of the current geological fault is small.

[0047] The beneficial effects of the present invention are as follows: By reasonably and evenly distributing data acquisition points, the present solution comprehensively calculates the sliding data related to geological faults by comparing the positions of fault distributions at the data acquisition points, and combines the mechanical data of rock strata at the data acquisition points to calculate the relevant data for evaluating the vulnerability of geological structures. At the same time, the seismic risk coefficient is introduced, and the activity risks of geological faults are comprehensively evaluated using geological fault sliding, geological structure, and seismic data, effectively improving the accuracy of the activity risk assessment of geological faults, realizing the combination of on-site survey data and monitoring data, and providing a solution with complete theory, scientific method, and strong practicability for fault activity risk assessment. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] Figure 1 It is a flowchart of the evaluation method for the activity risk of geological faults. DETAILED DESCRIPTION OF THE INVENTION

[0049] The following is a description of the specific implementation manners of the present invention to facilitate those skilled in the art to understand the present invention. However, it should be clear that the present invention is not limited to the scope of the specific implementation manners. For those of ordinary skill in the art, as long as various changes are within the spirit and scope of the present invention defined and determined by the appended claims, these changes are obvious, and all inventions and creations using the concept of the present invention are within the scope of protection.

[0050] As Figure 1 shown, an evaluation method for the activity risk of geological faults includes the following steps:

[0051] S1: Construct a geological model of the research area, draw geological faults on the geological model, determine the distribution area of the geological faults through a three-dimensional coordinate system established on the geological model, and respectively take a number of reference points and control points before and after the monitoring period T based on the distribution area. Calculate the fault sliding coefficient according to the fault point coordinates of the corresponding rock sample columns at the reference points and control points. Step S1 specifically includes:

[0052] S11: Determine the research area of geological fault activity, construct a geological model of the research area, and draw the detected geological faults within the geological model;

[0053] S12: Establish a three-dimensional coordinate system within the geological model. The xoy plane of the three-dimensional coordinate system is parallel to the horizontal plane. Vertically project the geological faults onto the xoy plane. The boundaries of the geological faults form a horizontal distribution area within the xoy plane, and a number of reference points are evenly set within the distribution area;

[0054] S13: Use the reference point as the perpendicular foot to draw a perpendicular line perpendicular to the xoy plane, and obtain the points where each perpendicular line intersects the topsoil layer of the geological model as monitoring points. The staff reaches the actual location of the geological fault through the positioning of the monitoring points, and drills down to obtain the rock sample columns at each monitoring point;

[0055] S14: Obtain the coordinates (x n , y n , z n ) in the three-dimensional coordinate system of the fault points below the monitoring points according to the positions of the geological faults on the rock sample columns, where n is the number of the reference point;

[0056] S15: After the set monitoring period T, evenly set several control points in the distribution area, and make the control points not coincide with the reference points, and the number of control points is the same as that of the reference points. Execute steps S13 - S14 to obtain the coordinates (x n ′, y n ′, z′ n ) in the three-dimensional coordinate system of the corresponding fault points of the control points;

[0057] S16: Construct the coordinate set A of the reference points and the coordinate set B of the control points, and screen the two nearest reference points and control points according to the coordinates of the reference points and control points in the three-dimensional coordinate system as the fault activity control group. The screening objective function of the fault activity control group is;

[0058]

[0059] S17: After obtaining the fault activity control group, delete the coordinates of the reference points and control points in the fault activity control group from the coordinate sets A and B, and then return to step S16 to perform the screening of the fault activity control group without replacement;

[0060] S18: Repeat step S17 until the coordinates of the reference points and control points in the coordinate sets A and B are all paired, and then output all the fault activity control groups, as well as the reference points a n and the control points b n corresponding to the coordinates of the reference points and control points in each fault activity control group;

[0061] S19: Use the coordinates of the fault points corresponding to the reference point a n and the control point b n to calculate the fault slip coefficient v;

[0062]

[0063] ​Among them, N is the number of reference points and control points; the sliding risk of the fault is evaluated by calculating the moving speeds of the two fault points with the closest distance within the monitoring period T.

[0064] S2: Based on the obtained rock sample columns and taking the fault demarcation line as the basis, calculate the geological structure vulnerability coefficients of the rock layers above and below the fault demarcation line respectively, and then calculate the geological structure vulnerability coefficient of the overall geological fault. Step S2 specifically includes:

[0065] S21: Based on the rock sample columns obtained at each current monitoring point and taking the fault demarcation line on the rock sample column as the basis, test the compressive strength and density of each rock layer on the upper and lower sides respectively, and calculate the geological structure vulnerability coefficient of the geological fault;

[0066]

[0067] Among them, i is the number of the rock layer, E is the number of rock layers, is the compressive strength of the rock layer, is the Poisson's ratio, is the bulk modulus, is the rock layer density;

[0068] S22: Obtain the geological structure vulnerability coefficient I1 of the rock layer above the fault demarcation line and the geological structure vulnerability coefficient I2 of the rock layer below the fault demarcation line, and calculate the geological structure vulnerability coefficient I0 of the overall geological fault according to the fault type;

[0069] I0 = α1I1 + α2I2;

[0070] Among them, α1 and α2 are the geological structure vulnerability weight coefficients of the upper and lower rock layers respectively;

[0071] When the geological fault is a normal fault, take α1 < α2; during the geological change process of the normal fault geological fault, tensile forces are generated in the upper and lower rock layers, and the lower rock layer is lifted upward, and its geological structure vulnerability has a greater impact on the surface geological activities. Generally, take α1 = 0.4 and α2 = 0.6;

[0072] When the geological fault is a reverse fault, take α1 > α2; during the geological change process of the reverse fault geological fault, extrusion forces are generated in the upper and lower rock layers, and the upper rock layer is lifted upward, and its geological structure vulnerability has a greater impact on the surface geological activities. Generally, take α1 = 0.7 and α2 = 0.3;

[0073] When the geological fault is a smooth fault, take α1 = α2; there will be no lifting changes in the upper and lower rock layers;

[0074] And both satisfy α1 + α2 = 1.

[0075] The geological structure vulnerability coefficient I0 represents the vulnerability of the rock strata around the geological fault. The larger the geological structure vulnerability coefficient I0, the more stable the mechanical properties of the rock strata, and the more stable the geological fault during its activity.

[0076] S3: Statistically count the number of earthquakes and their corresponding magnitudes that occurred in the area where the geological fault is located during the monitoring period T, and calculate the seismic hazard coefficient p of the location where the geological fault is located;

[0077]

[0078] Among them, J is the number of earthquakes that occurred during the monitoring period T, j is the serial number of the number of earthquakes that occurred during the monitoring period T, P(IM>x|m j ,r) is the ground motion intensity attenuation relationship, m j is the earthquake intensity, r is the earthquake influence distance, v j is the number of earthquakes with magnitudes exceeding the magnitude threshold among the J earthquakes, f j is the occurrence probability of earthquakes with magnitudes exceeding the magnitude threshold among the J earthquakes, A is the area of the seismic source region around the geological fault, β j is the G-R relationship coefficient of the earthquake, m min is the upper magnitude limit of the earthquakes that occurred around the geological fault, m max is the lower magnitude limit of the earthquakes that occurred around the geological fault, sh(.) is the hyperbolic sine function, and Δm is the average magnitude interval among the J earthquakes;

[0079] S4: Calculate the activity risk coefficient of the geological fault based on the calculated fault slip coefficient, geological structure vulnerability coefficient, and seismic hazard coefficient, and evaluate the magnitude of the activity risk of the geological fault. Step S4 specifically includes:

[0080] S41: Calculate the activity risk coefficient W of the geological fault based on the calculated fault slip coefficient v, geological structure vulnerability coefficient I0, and seismic hazard coefficient p;

[0081]

[0082] Among them, is the average value of the fault slip coefficients calculated for all historical monitoring periods, I′ is the threshold value of the geological structure vulnerability coefficient, is the average value of the seismic hazard coefficients calculated for all historical monitoring periods;

[0083] S42: Set the threshold value W0 of the activity risk coefficient;

[0084] If W>W0, it is determined that the activity risk of the current geological fault is large;

[0085] If W≤W0, it is determined that the activity risk of the current geological fault is small.

[0086] Through reasonable and uniform distribution of data acquisition points, the present invention comprehensively calculates the sliding data related to geological faults by comparing the positions of fault distributions at the data acquisition points, and combines the mechanical data of rock strata at the data acquisition points to calculate the relevant data for evaluating the vulnerability of geological structures. At the same time, the seismic risk coefficient is introduced, and the geological fault sliding, geological structure and seismic data are used to comprehensively evaluate the activity risk of geological faults, effectively improving the accuracy of the activity risk assessment of geological faults, realizing the combination of on-site survey data and monitoring data, and providing a set of solutions with complete theory, scientific method and strong practicability for the evaluation of fault activity risk.

Claims

1. A method for evaluating the risk of geological fault activity, characterized in that, It includes the following steps: S1: Construct a geological model of the research area, draw geological faults on the geological model, determine the distribution area of the geological faults through a three-dimensional coordinate system established on the geological model, take a number of reference points and control points before and after the monitoring period T based on the distribution area, and calculate the fault slip coefficient according to the fault point coordinates of the corresponding rock sample columns at the reference points and control points; S2: According to the obtained rock sample columns, based on the fault demarcation line, calculate the geological structure vulnerability coefficients of the rock layers above and below the fault demarcation line respectively, and then calculate the geological structure vulnerability coefficient of the overall geological fault; S3: Count the number of earthquakes and their corresponding magnitudes that occurred in the area where the geological fault is located during the monitoring period T, and calculate the seismic hazard coefficient of the location where the geological fault is located; S4: Calculate the activity risk coefficient of the geological fault according to the calculated fault slip coefficient, geological structure vulnerability coefficient and seismic hazard coefficient, and evaluate the magnitude of the activity risk of the geological fault.

2. The evaluation method for geological fault activity risk according to claim 1, wherein The step S1 includes: S11: Determine the research area of the geological fault activity, construct a geological model of the research area, and draw the detected geological faults within the geological model; S12: Establish a three-dimensional coordinate system within the geological model. The xoy plane of the three-dimensional coordinate system is parallel to the horizontal plane. Vertically project the geological fault onto the xoy plane. The boundary of the geological fault forms a horizontal distribution area within the xoy plane, and a number of reference points are evenly set within the distribution area; S13: Use the reference points as the vertical points to draw perpendicular lines perpendicular to the xoy plane, and obtain the points where each perpendicular line intersects the topsoil layer on the geological model as the monitoring points. The staff reaches the actual location of the geological fault through the positioning of the monitoring points, and drills down to obtain the rock sample columns at each monitoring point; S14: Obtain the coordinates (x n , y n , z n ) of the fault point below the monitoring point in the three-dimensional coordinate system according to the position of the geological fault on the rock sample column, where n is the number of the reference point; S15: After the set monitoring period T, a number of control points are evenly set within the distribution area, and the control points do not coincide with the reference points, and the number of control points is the same as that of the reference points. Then, perform steps S13 - S14 to obtain the coordinates (x n ′, y n ′, z′ n ) of the fault points corresponding to the control points in the three-dimensional coordinate system; S16: Construct the coordinate set A of the reference points and the coordinate set B of the control points, and based on the coordinates of the reference points and the control points in the three-dimensional coordinate system Screen the two nearest reference points and control points as the fault activity control group; After obtaining the fault activity control group, delete the reference point coordinates and control point coordinates in the fault activity control group from the coordinate sets A and B, and then return to step S16 to perform the screening of the fault activity control group without replacement; S18: Repeat step S17 until the reference point coordinates and the control point coordinates in coordinate set A and coordinate set B are all paired, then output all fault activity control groups, and reference point a corresponding to the reference point coordinates and the control point coordinates in each fault activity control group n and control point b n ; S19: Utilize the reference point a n and the control point b n to calculate the fault slip coefficient v based on the difference between the coordinates of the corresponding fault points ​ 3. The evaluation method for geological fault activity risk according to claim 2, characterized in that The screening objective function of the fault activity control group is; 4. The evaluation method for geological fault activity risk according to claim 2, characterized in that The calculation method of the fault slip coefficient v is; Where N is the number of reference points and control points.

5. The evaluation method for geological fault activity risk according to claim 1, characterized in that, The step S2 includes: S21: According to the rock sample columns obtained at each current monitoring point, based on the fault demarcation line on the rock sample column, test the compressive strength and density of each rock layer on the upper and lower sides respectively, and calculate the geological structure vulnerability coefficient of the geological fault; Among them, \(i\) is the rock stratum number, \(E\) is the number of rock strata, is the compressive strength of the rock stratum, is the Poisson's ratio, is the bulk modulus, is the rock stratum density; S22: Obtain the geological structure vulnerability coefficient I1 of the rock layer above the fault demarcation line and the geological structure vulnerability coefficient I2 of the rock layer below the fault demarcation line, and calculate the geological structure vulnerability coefficient I0 of the overall geological fault according to the fault type; I0 = α1I1 + α2I2; Where α1 and α2 are the geological structure vulnerability weight coefficients of the upper and lower rock layers respectively; When the geological fault is a normal fault, take α1 < α2; When the geological fault is a reverse fault, take α1 > α2; When the geological fault is a smooth fault, take α1 = α2; And both satisfy α1 + α2 = 1.

6. The evaluation method for geological fault activity risk according to claim 1, wherein, The calculation method of the seismic hazard coefficient p is: where J is the number of earthquakes occurring during the monitoring period T, j is the number of the earthquakes occurring during the monitoring period T, P(IM>x|m j ,r) is the ground motion intensity attenuation relationship, m j is the earthquake intensity, r is the earthquake influence distance, v j is the number of earthquakes with magnitudes exceeding the magnitude threshold among the J earthquakes, f j is the occurrence probability of earthquakes with magnitudes exceeding the magnitude threshold among the J earthquakes, A is the area of the seismic source region around the geological fault, β j is the G-R relationship coefficient of the earthquake, m min is the upper magnitude limit of the earthquakes occurring around the geological fault, m max is the lower magnitude limit of the earthquakes occurring around the geological fault, sh(.) is the hyperbolic sine function, and Δm is the average magnitude interval among the J earthquakes.

7. The evaluation method for geological fault activity risk according to claim 1, characterized in that, The step S4 includes: S41: Calculate the activity risk coefficient W of the geological fault according to the calculated fault slip coefficient v, the geological structure vulnerability coefficient I0, and the seismic hazard coefficient p; Among them, is the average value of the fault slip coefficient calculated for all historical monitoring periods, and I′ is the threshold value of the geological structure vulnerability coefficient, is the average value of the seismic risk coefficient calculated for all historical monitoring periods; S42: Set the threshold value W0 of the activity risk coefficient; If W > W0, it is determined that the activity risk of the current geological fault is high; If W ≤ W0, it is determined that the activity risk of the current geological fault is low.

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