A quantitative characterization method for determining the segmentation of underground fault space

Abstract

The present invention relates to a quantitative characterization method for determining the segmentation of underground fault space, comprising the following steps: selecting a target underground fault in a three-dimensional seismic work area and using a one-dimensional survey line method to arrange the survey line, while measuring the fault distance of the target underground fault to obtain a fault distance value; determining the quantitative characterization of the fault strike segmentation and the quantitative characterization of the fault dip segmentation of the target underground fault; constructing a section-fault distance contour map using the quantitative characterization of the fault strike segmentation, the quantitative characterization of the fault dip segmentation and the fault distance values ​​of all fault distance points; using the section-fault distance contour map as a quantitative characterization of the segmentation of the target underground fault space. The method of the present invention can clarify the role of faults in the oil and gas migration and accumulation process and reduce the risk of oil and gas exploration.

Description

Technical Field

[0001] The invention relates to the fields of structural geology and petroleum geology, and in particular to a quantitative characterization method for determining the segmentation of underground fault space. Background Art

[0002] Faults in rift basins are usually complex three-dimensional structures, consisting of multiple subparallel segments separated by intact or damaged transition zones. Segmented growth is common and can develop in faults of various scales. Faults, as common geological elements, play a role throughout the entire oil and gas accumulation process, especially in the oil and gas migration stage. Faults can be channels for oil and gas migration, but also obstacles to oil and gas flow. The existence of faults increases the risk of oil and gas exploration.

[0003] A fault segment refers to a section in the same fault or fracture zone that has independent characteristics in terms of geometric structure, structural features, slip behavior and rupture conditions. The sections are connected together through transition zones in a soft or hard connection manner.

[0004] The internal configuration of faults, especially the quantitative analysis technology of fault segmentation, has become the top priority in solving oil and gas exploration and development problems. However, there are still the following problems in this field: ① Only the characteristics of fault segmentation have been qualitatively described, but it is impossible to quantitatively control the laws of underground oil and gas enrichment through qualitative description alone. ② The method of determining the segmentation of faults by using the distribution of fault throws, but the choice of survey line direction in this method has an important influence on the reading results of fault throws, and is affected by the low resolution of seismic data and the lack of field outcrop examples. ③ The research on fault segmentation is mostly focused on the strike, ignoring the fault dip segmentation, and lacks quantitative analysis of the complete three-dimensional spatial segmentation of the underground.

[0005] Faced with the increasingly sophisticated oil and gas exploration process, it is far from enough to qualitatively characterize the segmentation characteristics of faults. Only by clearly and quantitatively characterizing the segmentation laws of faults can we better clarify the role of faults in the oil and gas migration and accumulation process and reduce the risks of oil and gas exploration. Summary of the invention

[0006] In view of the above problems existing in the prior art, the technical problem to be solved by the present invention is: how to determine the segmentation of underground faults by a three-dimensional quantitative characterization method.

[0007] In order to solve the above technical problems, the present invention adopts the following technical solutions:

[0008] A quantitative characterization method for determining the segmentation of underground fault space includes the following steps:

[0009] S100: selecting a target underground fault in the three-dimensional seismic work area and arranging a survey line using a one-dimensional survey line method, and measuring the fault distance of the target underground fault, wherein the fault distance refers to the distance between the two sides of the fault;

[0010] S200: quantitatively characterizing the segmentation of the target underground fault, wherein the quantitative characterization of the segmentation of the target underground fault includes quantitative characterization of the segmentation of the fault strike and quantitative characterization of the segmentation of the fault dip;

[0011] S300: selecting a fault point on the fault strike, and using the selected fault point to determine a quantitative representation of the segmentation of the fault strike;

[0012] S400: selecting a fault point on the fault dip, and using the selected fault point to determine a quantitative representation of the segmented nature of the fault dip;

[0013] S500: constructing a section-fault distance contour map using the quantitative characterization of the fault strike segmentation, the quantitative characterization of the fault dip segmentation and the fault distance values ​​of all fault distance points;

[0014] S600: Using the section-fault distance contour map as a segmented quantitative representation of the target underground fault space.

[0015] Specifically, the specific steps of determining the quantitative characterization of the fault strike segmentation in S300 are as follows:

[0016] S310: Draw fault strike displacement curve:

[0017] S311: Establish a coordinate system, with the fault strike line number as the horizontal coordinate and the fault distance as the vertical coordinate;

[0018] S312: along the strike of the target underground fault, multiple fault throws on the fault reflection axis are selected at equal intervals, and the selected fault throws are marked with fault strike line numbers in sequence, where the fault strike line number is numbered as n, where n is a natural number, and the fault throw value of each fault throw is measured at the same time, and each fault strike line number corresponds to the fault throw value at that location one by one;

[0019] S313: projecting the strike line number of each fault throw and the corresponding fault throw value into the coordinate system established in S411 in sequence to obtain strike throw displacement points, and connecting the strike throw displacement points in sequence, and obtaining a curve after connecting the lines as a fault strike displacement curve, wherein the fault throw value of the fault throw is used as the displacement value of the fault throw point; and recording the trough point on the fault strike displacement curve as a fault strike segmented growth connection point;

[0020] S320: Draw the fault strike, fault throw and stripping curve:

[0021] S321: Determine the displacement propagation mode of the target underground fault activity by using the following method: determine the maximum fault displacement as the starting point, and then propagate from the fault displacement point with the largest displacement value to the fault displacement point with the smallest displacement value. If a segmented growth connection point appears on the fault strike displacement curve, it is a segmented propagation mode; if no segmented growth connection point appears on the fault strike displacement curve, it is an isolated propagation mode;

[0022] S322: According to the displacement propagation mode of the target underground fault activity and the fault strike displacement curve, the ancient fault distance of the target historical period is "back-stripped" by using the adjacent fault distance subtraction method and the maximum fault distance subtraction method to obtain the fault strike fault distance back-stripping curve; the ancient fault distance refers to the fault distance of the underground fault at that location in the target historical period;

[0023] S330: The obtained fault strike displacement curve and fault strike throw back curve are used as quantitative representations of the segmentation of the fault strike; the trough points of the fault strike displacement curve and the trough points of the fault strike throw back curve are determined, and these trough points represent the segmentation positions of the underground fault; the displacement values ​​recorded at the trough points of the underground fault strike throw back curve in each period can represent the magnitude of the throw displacement at the underground fault segment in each period.

[0024] Specifically, the fault distance in S311 is the fault distance at the repair point, and the repair point refers to the intersection of the formation reflection axis extending parallel to the section along the trajectory and the section. The fault distance at the repair point refers to the distance between the repair points in the same set of formations on both sides of the fault in the seismic profile.

[0025] At this time, if the trimming point is used to read the fault throw, it will often be smaller than the actual fault throw value, because the total fault throw includes both the fault throw specified by the trimming point and the deformation fault throw provided by the ductile deformation of the stratum within the trimming distance and the subseismic fault close to the fault plane; in order to obtain the fault throw more accurately, the fault throw at the patch point should be used instead of the fault throw at the trimming point; among them, the formation reflection axis is extended along the trajectory parallel to the section, and the intersection with the section after extension is called the patch point (patch points), the length of the trajectory along which each fault disk is extended is called the patch width (patch width), which is close to the trimming distance. In the seismic profile, the seismic wave resistance close to the fault plane bends toward the section. At this time, the intersection of the formation reflection axis and the section is called the trim point (trim points), and the distance between the bending of the formation reflection axis of the two fault disks is called the trim distance (trim distance).

[0026] Specifically, the specific content of using the adjacent fault distance subtraction method and the maximum fault distance subtraction method to "backstrip" the ancient fault distances of different periods in S322 is: if the ancient fault distance belongs to a fault grown under the "fixed length" model, the adjacent fault distance subtraction method is used; if the ancient fault distance belongs to a fault grown under the "fault propagation" model, the maximum fault distance subtraction method is used.

[0027] The growth connection process along the fault strike includes a "fixed length" model and a "fault propagation" model. The "fixed length" model means that the length of the fault is determined early and the displacement is gradually accumulated in subsequent slip events; the "fault propagation" model means that the length and displacement of the fault increase at the same time. This classification can accurately use different methods to deal with different situations and improve the accuracy of the results.

[0028] Specifically, the specific steps of determining the quantitative characterization of the fault dip segmentation in S400 are as follows:

[0029] S410: Draw fault dip displacement curve:

[0030] S411: establishing a coordinate system, with the fault distance as the horizontal coordinate and the fault burial depth as the vertical coordinate, wherein the fault burial depth refers to the underground depth of the fault;

[0031] S412: along the target underground fault dip, multiple fault throws are selected at equal intervals and fault depth numbers are marked on the selected fault throws in sequence, where the fault depth number is denoted as m, where m is a natural number; and at the same time, the fault throw value of each fault throw is measured, where each fault depth number corresponds to the fault throw value at that location;

[0032] S413: projecting the fault depth sequence number of each fault throw and the corresponding fault throw value into the coordinate system established in S511 in sequence to obtain the dip fault throw displacement points, and connecting the dip fault throw displacement points in sequence, and the curve obtained after connecting the lines is used as the fault dip displacement curve, wherein the value of the fault throw is used as the displacement value of the fault throw point; the trough point on the fault dip displacement curve is defined as a low value point in the coordinate system, and the low value point is recorded as the fault dip segment growth connection point;

[0033] S420: The obtained fault dip displacement curve is used as a quantitative representation of the fault dip segmentation; the depth of the trough point of the fault dip displacement curve represents the growth period of the fault segmentation; the displacement value recorded at the trough point can represent the size of the displacement at the fault segmentation.

[0034] Specifically, the specific steps of constructing the section-fault distance contour map in S500 are as follows:

[0035] S510: The fault offset points along the fault strike and the fault offset points along the fault dip are taken as the fault offset point set A, and the expression is as follows:

[0036] ;

[0037] Among them, i represents the i-th break point, Indicates the total number of break points. The horizontal coordinate of the break point, The vertical coordinate of the break point, Indicates the fault value of the fault point;

[0038] S520: Project the horizontal and vertical coordinates of all the fault distance points in A onto the same plane, use the fault distance value corresponding to each fault distance point as the value of the fault distance point in the plane coordinate system, and generate contour lines according to the horizontal and vertical coordinates of all the fault distance points and the values ​​in the corresponding coordinate system to obtain a section-fault distance contour line map.

[0039] The section-fault throw contour map can more intuitively show the fault throw distribution and provide additional information such as the location where the fault segment starts to grow. The abnormally low value points of the fault throw contour line represent the segmented growth location, and the spacing and density of the contour lines represent the fault throw gradient at that location. Small spacing and dense arrangement mean that the fault throw changes significantly and the fault throw gradient is large.

[0040] Compared with the prior art, the present invention has at least the following advantages:

[0041] 1. Select the target underground fault in the three-dimensional seismic work area and use the one-dimensional survey line method to arrange the survey line. In the process of reading the target underground fault data in different strike segments, change the survey line direction to ensure that the survey line direction is perpendicular to the strike of the target underground fault to reduce the fault reading error; measure the basic information of the target underground fault, and the information such as the fault position, fault nature, fault length and fault attitude obtained by measuring the basic information can complete the understanding of the basic conditions of the underground fault; then, by determining the quantitative characterization of the fault strike, the quantitative characterization of the fault dip and all fault point values, the quantitative characterization of the spatial segmentation of the underground fault is obtained.

[0042] 2. The method of determining the segmentation of underground fault space in the present invention combines the fault strike segmentation and the dip segmentation together for the first time, and is dedicated to clarifying the phenomenon of the segmentation of fault space, from the original two-dimensional curve to three-dimensional space.

[0043] 3. The present invention can not only quantitatively characterize the spatial segmentation of underground faults, but also determine the fault displacement propagation mode according to the displacement changes, providing a geological basis for analyzing the effectiveness of fault-related closures, the vertical closure of faults, and the lateral closure of faults. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] Figure 1 Schematic diagram of fault distribution in an embodiment of the present invention.

[0045] Figure 2 Schematic diagram of distance reading in an embodiment of the present invention.

[0046] Figure 3 It is the fault strike displacement curve in the embodiment of the present invention.

[0047] Figure 4 It is the fault strike, fault throw and stripping curve in the embodiment of the present invention.

[0048] Figure 5 It is the fault dip displacement curve in the embodiment of the present invention.

[0049] Figure 6 It is a fault section-fault distance contour map in an embodiment of the present invention.

[0050] Figure 7 This is a schematic diagram of the prediction of the extension length of the fault strike in the case of the present invention.

[0051] Figure 8 This is a schematic diagram of the prediction of the fault dip extension length in the case of the present invention. DETAILED DESCRIPTION

[0052] The present invention is described in further detail below.

[0053] Example 1: See Figure 1-6 , a quantitative characterization method for determining the segmentation of underground fault space, comprising the following steps:

[0054] S100: Select the target underground fault and arrange the survey line in the 3D seismic work area: Take the Fa fault in Nanpu Sag as an example. The Fa fault is located in the southwest of Nanpu Sag. Through the investigation of the geological background of the study area, it is known that the Fa fault has obvious changes in its strike direction. It vertically penetrates the fault depression and depression layer. There are good oil and gas shows in the footwall of the fault. It is the main oil source fault in Nanpu Sag. Use the one-dimensional survey line method to arrange the survey line perpendicular to the strike direction of the fault. After determining the starting point of the survey line at the western end of the fault, according to the accuracy of the seismic data, gradually arrange the survey line at intervals of 16 CDPs to the other end; in the process of reading fault data in different strike segments, change the survey line direction to ensure that the survey line direction is perpendicular to the fault strike to reduce the fault distance reading error, see Figure 1 .

[0055] Measurement of basic fault information: The fault location described is as follows: Figure 1As shown, the fault is a normal fault, with an overall strike of NE and dip of SE, with a total length of 24,180 m. According to the change in the strike of the fault at the bottom interface of the Minghuazhen Formation, it is preliminarily divided into the western section and the eastern section, wherein the western section has a strike of NNE, dips to SE, is about 14,200 m long, and has a dip angle of 52°; the eastern section has a strike of NE, dips to SE, is about 10,000 m long, and has a dip angle of 58°. Based on this information, it is preliminarily determined that the strike of the Fa fault is segmented; basic information measurement is performed on the target underground fault, and the basic information measurement includes measuring the fault position, fault nature, fault length, and fault dip using existing technology;

[0056] The fault position includes the geodetic coordinate position and the regional structural position; the fault property is a normal fault, a reverse fault or a strike-slip fault; the fault length includes the length of each segment of the fault and the total length of the fault The fault attitude includes the strike of each fault segment, the inclination of each fault segment and the dip angle of each fault segment. The nature of the fault is determined by the marker layers on both sides of the fault, the length, strike and dip of the fault are measured by reading the geological map, and the dip angle of each fault segment is measured by using a protractor on a seismic section perpendicular to the fault strike with a fixed CDP spacing and the average value is obtained.

[0057] S200: Quantitative characterization of fault spatial segmentation: The accuracy of fault distance reading is crucial to the quantitative characterization of fault segmentation. Figure 2 The data at the patching point, not the trimming point;

[0058] S300: selecting a fault point on the fault strike, and using the selected fault point to determine a quantitative representation of the segmentation of the fault strike;

[0059] The specific steps of determining the quantitative characterization of the fault strike segmentation in S300 are as follows:

[0060] S310: Draw fault strike displacement curve:

[0061] S311: Establish a coordinate system, with the fault strike line number as the horizontal coordinate and the fault distance as the vertical coordinate;

[0062] The fault distance in S311 is the fault distance at the repair point, and the repair point refers to the intersection of the formation reflection axis extending parallel to the section along the trajectory and the section. The fault distance at the repair point refers to the distance between the repair points in the same set of formations on both sides of the fault in the seismic profile.

[0063] S312: along the strike of the target underground fault, multiple fault throws on the fault reflection axis are selected at equal intervals, and the selected fault throws are marked with fault strike line numbers in sequence, where the fault strike line number is numbered as n, where n is a natural number, and the fault throw value of each fault throw is measured at the same time, and each fault strike line number corresponds to the fault throw value at that location one by one;

[0064] S313: projecting the strike line number of each fault throw and the corresponding fault throw value into the coordinate system established in S411 in sequence to obtain strike fault throw displacement points, and connecting the strike fault throw displacement points in sequence, and the curve obtained after connecting the lines is used as the fault strike displacement curve, wherein the fault throw value of the fault throw is used as the displacement value of the fault throw point, and the curve after connecting the lines can intuitively show the change of the fault throw of each layer on the fault strike; the trough point on the fault strike displacement curve is recorded as the fault strike segmented growth connection point;

[0065] ① Strike displacement curve: With the strike line number as the horizontal coordinate and the fault distance as the vertical coordinate, the fault distances of 16 layers, Nm, Ng, Ed1, Ed3, Es1, and Es3, are taken at equal intervals in a certain direction on the strike of the fault and projected into the coordinate axis. Then, a curve is used to connect the points together to intuitively show the changes in the fault distances of the six layers on the strike of the Fa fault. See Figure 3 A low-value area is observed at the survey line L1200, which is the connection point of the fault segment growth.

[0066] Taking the fault Fa as an example, in the strike displacement curve ( Figure 3 ), the fault segmentation point is at L1180; according to the fault strike and fault throw back curve, during the deposition period of the Shahejie Formation, the fault throw at the segmentation point was 0 (indicating that the fault had not yet been connected); during the deposition period of the Dongying Formation, the fault throws at the segmentation point from deep to shallow were 95m (Es3), 76m (Es1), 46m (Ed3) and 25m (Ed1); during the deposition period of the Minghuazhen Formation, the fault throws at the segmentation point from deep to shallow were 117m (Es3), 104m (Es1), 85m (Ed3), 50m (Ed1), 47m (Ng) and 123m (Nm).

[0067] S320: Draw the fault strike, fault throw and stripping curve:

[0068] S321: The displacement propagation mode of the target underground fault activity is determined by the following method: by determining the maximum fault displacement as the starting point, and then propagating from the fault displacement point with the largest displacement value to the fault displacement point with the smallest displacement value. If a segmented growth connection point appears on the fault strike displacement curve, it is a segmented propagation mode; if no segmented growth connection point appears on the fault strike displacement curve, it is an isolated propagation mode; the maximum fault displacement generally represents the fault coincidence point, that is, the initial rupture point. If the middle is the maximum value and the two sides are the minimum values, it means that the propagation is from the middle to the two sides, and so on, it will be from left to right, or from right to left.

[0069] S322: According to the displacement propagation mode of the target underground fault activity and the fault strike displacement curve, the adjacent fault distance subtraction method and the maximum fault distance subtraction method are used to "backstrip" the ancient fault distance of the target historical period to obtain the fault strike fault distance backstripping curve; the ancient fault distance refers to the fault distance of the underground fault at that location in the target historical period, and the adjacent fault distance subtraction method and the maximum fault distance subtraction method are both existing technologies. The adjacent fault distance subtraction method refers to the fault distance of all lower layers minus the corresponding uppermost layer in the fault extension direction; the maximum fault distance subtraction method refers to the fault distance of all lower layers minus the corresponding maximum fault distance of each fault segment in the uppermost layer in the fault extension direction;

[0070] The specific content of using the adjacent fault distance subtraction method and the maximum fault distance subtraction method to "backstrip" the ancient fault distances of different periods in S322 is: if the ancient fault distance belongs to a fault grown under the "fixed length" model, the adjacent fault distance subtraction method is used; if the ancient fault distance belongs to a fault grown under the "fault propagation" model, the maximum fault distance subtraction method is used.

[0071] ②Strike-fault-displacement stripping curve: Based on the strike segmentation of the Fa fault, the position and length of the ancient fault segment can be more clearly determined by fault-displacement stripping. When performing fault-displacement stripping, the maximum fault-displacement subtraction method should be used to "strip" the ancient fault distances of different periods. The section with a fault distance greater than zero on the fault strike represents the ancient fault segment, see Figure 4 In this case, Fa was backstripped twice, in the depression period (Nm+Ng) and the second episode of rifting (Ed). The backstripping results showed that there were two unrelated faults in Fa during the deposition of the Shahejie Formation. The fault throw of the western section continued to increase westward, indicating that it came from the basement structure. The eastern section was an isolated small fault of the Shahejie Formation, and during the deposition of the Dongying Formation, the L1145-L1161 sections were "hard connected" to become a large fault.

[0072] S330: The obtained fault strike displacement curve and fault strike throw back curve are used as quantitative representations of the segmentation of the fault strike; the trough points of the fault strike displacement curve and the trough points of the fault strike throw back curve are determined, and these trough points represent the segmentation positions of the underground fault; the displacement values ​​recorded at the trough points of the underground fault strike throw back curve in each period can represent the magnitude of the throw displacement at the underground fault segment in each period.

[0073] S400: selecting a fault point on the fault dip, and using the selected fault point to determine a quantitative representation of the segmented nature of the fault dip;

[0074] S410: Draw fault dip displacement curve:

[0075] S411: establishing a coordinate system, with the fault distance as the horizontal coordinate and the fault burial depth as the vertical coordinate, wherein the fault burial depth refers to the underground depth of the fault;

[0076] S412: along the target underground fault dip, multiple fault throws are selected at equal intervals and fault depth numbers are marked on the selected fault throws in sequence, where the fault depth number is denoted as m, where m is a natural number; and at the same time, the fault throw value of each fault throw is measured, where each fault depth number corresponds to the fault throw value at that location;

[0077] S413: projecting the fault depth sequence number of each fault throw and the corresponding fault throw value into the coordinate system established in S511 in sequence to obtain the dip fault throw displacement points, and connecting the dip fault throw displacement points in sequence, and the curve obtained after connecting is used as the fault dip displacement curve, which can intuitively show the change of the fault throw of each layer on the fault dip, wherein the value of the fault throw is used as the displacement value of the fault throw point; the trough point on the fault dip displacement curve is defined as a low value point in the coordinate system, and the low value point is recorded as the fault dip segment growth connection point;

[0078] Dip displacement curve: In this case, the dip displacement curve uses fault throw as the horizontal coordinate and burial depth as the vertical coordinate. Two points are selected from the west and east sections of Fa, and multiple fault throws are projected from bottom to top on the fault dip into the coordinate axis. Then a curve is used to connect the points together. See Figure 5 , which directly shows the change of fault distance in the fault dip. Figure 5 It can be seen that the fault throw of the western section of Fa decreases continuously from bottom to top, and the fault throw gradient is always positive. However, a low-value area appears in the Dongying Formation in the eastern section of Fa, and the fault throw gradient is negative at this location, which is the segmented growth connection point of the eastern section of Fa fault. For example, the fault Fa, see Figure 5 , a trough appears in the dip displacement curve of the eastern section of Fa, and the depth of the trough is the stratum of the eastern third section. Therefore, the eastern third section is the period of segmented growth of the fault, and the fault throw is 75m at this time.

[0079] S420: The obtained fault dip displacement curve is used as a quantitative representation of the fault dip segmentation; the depth of the trough point of the fault dip displacement curve represents the growth period of the fault segmentation; the displacement value recorded at the trough point can represent the size of the displacement at the fault segmentation.

[0080] S500: constructing a section-fault distance contour map by using the quantitative characterization of the fault strike segmentation, the quantitative characterization of the fault dip segmentation and the fault distance values ​​of all fault distance points;

[0081] The specific steps of constructing the section-fault distance contour map in S500 are as follows:

[0082] S510: The fault offset points along the fault strike and the fault offset points along the fault dip are taken as the fault offset point set A, and the expression is as follows:

[0083] ;

[0084] Among them, i represents the i-th break point, Indicates the total number of break points. The horizontal coordinate of the break point, The vertical coordinate of the break point, Indicates the fault value of the fault point;

[0085] S520: Project the horizontal and vertical coordinates of all the fault distance points in A onto the same plane, use the fault distance value corresponding to each fault distance point as the value of the fault distance point in the plane coordinate system, and generate contour lines according to the horizontal and vertical coordinates of all the fault distance points and the values ​​in the corresponding coordinate system to obtain a section-fault distance contour line map.

[0086] Section-fault distance contour map: also known as fault displacement projection map, refers to the projection of fault displacement onto the fault plane. The distribution of its displacement on the fault plane can more intuitively show the distribution of fault distance, and can also provide additional information about the location where the fault segment begins to grow. The abnormally low value area of ​​the fault distance contour line represents the segment growth location, and the spacing and density of the contour lines represent the fault distance gradient at that location. Small spacing and dense arrangement mean that the fault distance changes significantly and the fault distance gradient is large. Use the fault distance information to make a fault section-fault distance contour map, see Figure 6; Read the fault value and longitude and latitude coordinate information of the data points in the seismic data, import the processed data into the "conventional contour mapping" module in the Double Fox software, and complete the contour mapping according to the guided steps. It can be seen from the figure that the Fa fault is divided into two parts with the local minimum in the middle part as the boundary. The fault value of the Fa west section is large and the contour lines are densely arranged. When the depth decreases, the fault begins to extend to the side; the fault distance contour line of the Fa east section consists of two parts, each of which is an ellipse with the maximum fault value as the concentric contour line. The maximum value of the fault distance contour line represents the approximate area of ​​the fault distance nucleation point, and the position of the minimum fault distance in the middle represents the dip connection part. In addition, the long axis of the fault distance contour line in the lower part of the fault is approximately horizontal, indicating that the lateral connection of the fault occurs before the dip connection.

[0087] In addition, after determining the quantitative characterization of the segmentation of underground fault space, other applications can be carried out:

[0088] 1. Determination of fault growth connection mode:

[0089] After identifying the spatial segmentation points of the fault using the strike and dip displacement curves and the section fault throw contour map, the growth connection mode was analyzed in detail. The figure shows that during the Es1 period, the Fa West segment continued to grow and propagate in the "up and down propagation type" as the inherited structure of the basement fault. The Fa East segment was nucleated at this time and was two non-interfering faults with the Fa West segment. During the Ed3 period, the Fa West segment and the Fa East segment grew upward and were hard connected together as a whole to grow and propagate upward, indicating that the Fa fault existed in the "fault propagation model" during the Es period, with displacement and length increasing simultaneously; after the Ed period, the west segment and the east segment were connected together, and displacement continued to accumulate in the "fixed length model". During the Nm period, a small fault developed above the Fa East segment and grew downward to connect with the Fa East segment in a dip manner. The dip displacement reached a minimum value, and the fault throw gradient showed a negative gradient. The fault propagation mode was a "dip connection type".

[0090] 2. Quantitative prediction of fault extension length:

[0091] ① Determination of the fault end distance: The fault end distance includes two parts: strike and dip. Through observation, it is found that the fault distance value of the left side of the Fa West section in strike continues to increase, and the fault distance of the eastern section shows a downward trend, indicating that the end of the Fa East section does not interact with other geological structures; in terms of dip, the fault distance of the Fa West section continues to grow from the basement upward, and the fault distance continues to decrease upward, while in the eastern section, the fault developed in the late stage propagates downward and connects with the pre-existing fault in dip. The nucleation position of the late fault has not yet been determined. Therefore, the fault distance of the Fa East section in strike and the Fa West section in dip can be predicted by the fault distance gradient method. Figure 3 The fault distance Dh at the end of the Nm layer fault strike is read as 46ms. Figure 5The middle shows that the fault throw Dv of the end of the Nm group fault in the western section of Fa is 99ms;

[0092] ② Fault throw gradient at the end of the fault: The fault throw gradient is the rate of change of the fault throw, which refers to the displacement of the fault per unit length, and is expressed as the slope of each point on the displacement curve. Using the strike and dip displacement curve data obtained in steps c② and c④, calculate the strike throw gradient and dip throw gradient at the end of the fault. In terms of strike, the fault throw gradient at the eastern end of Fa is γh=(D2-D1) / (L2-L1)=(70-46) / (1471-1447)=1; in terms of dip, the fault throw gradient at the western end of Fa is γv=(D2-D1) / (H2-H1)=(152-99) / (2072-1423)=0.08;

[0093] ③ Determination of the final length of the fault: In terms of strike, the final length of the fault (Lfh) = original length (Lih) + uncertain fault segment length (Luh), where Luh = D / γh, then Lfh = Lih + D / γh = 24180 + 46 / 1 = 24226m, such as Figure 7 As shown; in terms of inclination, the final extension length of the fault (Lfv) = target interface fault depth (Liv) - uncertain fault segment length (Luv), where Luv = D / γv, then Lfv = Liv-D / γv = 1423-99 / 0.08 = 185.5ms.

[0094] In general, Fa can extend 46m eastward in strike direction, and the total length of the fault should be 24226m. In dip direction, the western section of Fa can propagate upward to 185.5ms, see Figure 8 .

[0095] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solution of the present invention can be modified or replaced by equivalents without departing from the purpose and scope of the technical solution of the present invention, which should be included in the scope of the claims of the present invention.

Claims

1. A quantitative characterization method for determining the segmentation of underground fault space, characterized in that: The steps include: S100: selecting a target underground fault in the three-dimensional seismic work area and arranging a survey line using a one-dimensional survey line method, and measuring the fault distance of the target underground fault, wherein the fault distance refers to the distance between the two sides of the fault; S200: quantitatively characterizing the segmentation of the target underground fault, wherein the quantitative characterization of the segmentation of the target underground fault includes quantitative characterization of the segmentation of the fault strike and quantitative characterization of the segmentation of the fault dip; S300: selecting a fault point on the fault strike, and using the selected fault point to determine a quantitative representation of the segmentation of the fault strike; S400: Selecting a fault point on the fault dip, and using the selected fault point to determine the quantitative representation of the fault dip segmentation; the specific steps of determining the quantitative representation of the fault dip segmentation are as follows: S410: Draw fault dip displacement curve: S411: establishing a coordinate system, with the fault distance as the horizontal coordinate and the fault burial depth as the vertical coordinate, wherein the fault burial depth refers to the underground depth of the fault; S412: along the target underground fault dip, multiple fault throws are selected at equal intervals and fault depth numbers are marked on the selected fault throws in sequence, where the fault depth number is denoted as m, where m is a natural number; and at the same time, the fault throw value of each fault throw is measured, where each fault depth number corresponds to the fault throw value at that location; S413: projecting the fault depth sequence number of each fault throw and the corresponding fault throw value into the coordinate system established in S411 in sequence to obtain the dip fault throw displacement points, and connecting the dip fault throw displacement points in sequence, and the curve obtained after connecting the lines is used as the fault dip displacement curve, wherein the value of the fault throw is used as the displacement value of the fault throw point; the trough point on the fault dip displacement curve is defined as a low value point in the coordinate system, and the low value point is recorded as the fault dip segment growth connection point; S420: using the obtained fault dip displacement curve as a quantitative representation of the fault dip segmentation; the depth of the trough point of the fault dip displacement curve represents the growth period of the fault segmentation; the displacement value recorded at the trough point represents the magnitude of the displacement at the fault segmentation; S500: constructing a section-fault distance contour map using the quantitative characterization of the fault strike segmentation, the quantitative characterization of the fault dip segmentation and the fault distance values ​​of all fault distance points; S600: Using the section-fault distance contour map as a segmented quantitative representation of the target underground fault space.

2. A quantitative characterization method for determining the segmentation of underground fault space according to claim 1, characterized in that: The specific steps of determining the quantitative characterization of the fault strike segmentation in S300 are as follows: S310: Draw fault strike displacement curve: S311: Establish a coordinate system, with the fault strike line number as the horizontal coordinate and the fault distance as the vertical coordinate; S312: along the strike of the target underground fault, multiple fault throws on the fault reflection axis are selected at equal intervals, and the selected fault throws are marked with fault strike line numbers in sequence, where the fault strike line number is numbered as n, where n is a natural number, and the fault throw value of each fault throw is measured at the same time, and each fault strike line number corresponds to the fault throw value at that location one by one; S313: projecting the strike line number of each fault throw and the corresponding fault throw value into the coordinate system established in S411 in sequence to obtain strike throw displacement points, and connecting the strike throw displacement points in sequence, and obtaining a curve after connecting the lines as a fault strike displacement curve, wherein the fault throw value of the fault throw is used as the displacement value of the fault throw point; and recording the trough point on the fault strike displacement curve as a fault strike segmented growth connection point; S320: Draw the fault strike, fault throw and stripping curve: S321: Determine the displacement propagation mode of the target underground fault activity by using the following method: determine the maximum fault displacement as the starting point, and then propagate from the fault displacement point with the largest displacement value to the fault displacement point with the smallest displacement value. If a segmented growth connection point appears on the fault strike displacement curve, it is a segmented propagation mode; if no segmented growth connection point appears on the fault strike displacement curve, it is an isolated propagation mode; S322: According to the displacement propagation mode of the target underground fault activity and the fault strike displacement curve, the ancient fault distance of the target historical period is "back-stripped" by using the adjacent fault distance subtraction method and the maximum fault distance subtraction method to obtain the fault strike fault distance back-stripping curve; the ancient fault distance refers to the fault distance of the underground fault at that location in the target historical period; S330: The obtained fault strike displacement curve and fault strike throw back-stripping curve are used as quantitative representations of the segmentation of the fault strike; the trough points of the fault strike displacement curve and the trough points of the fault strike throw back-stripping curve are determined, and these trough points represent the segmentation positions of the underground fault; the displacement values ​​recorded at the trough points of the underground fault strike throw back-stripping curves in each period represent the magnitude of the throw displacement at the underground fault segment in each period.

3. A quantitative characterization method for determining the segmentation of underground fault space as claimed in claim 2, characterized in that: The fault distance in S311 is the fault distance at the repair point, and the repair point refers to the intersection of the formation reflection axis extending parallel to the section along the trajectory and the section. The fault distance at the repair point refers to the distance between the repair points in the same set of formations on both sides of the fault in the seismic profile.

4. A quantitative characterization method for determining the segmentation of underground fault space according to claim 3, characterized in that: The specific content of "stripping back" the ancient fault distances of different periods by using the adjacent fault distance subtraction method and the maximum fault distance subtraction method in S322 is: if the ancient fault distance belongs to a fault grown under the "fixed length" model, the adjacent fault distance subtraction method is used; if the ancient fault distance belongs to a fault grown under the "fault propagation" model, the maximum fault distance subtraction method is used.

5. A quantitative characterization method for determining the segmentation of underground fault space according to claim 4, characterized in that: The specific steps of constructing the section-fault distance contour map in S500 are as follows: S510: The fault offset points along the fault strike and the fault offset points along the fault dip are taken as the fault offset point set A, and the expression is as follows: A={x i ,y i ,d i |i=1,2,...,f n }; Among them, i represents the i-th break point, f n =n+m represents the total number of break points, x i Indicates the horizontal coordinate of the break point, y i The vertical coordinate of the break point, d i Indicates the fault value of the fault point; S520: Project the horizontal and vertical coordinates of all the fault distance points in A onto the same plane, use the fault distance value corresponding to each fault distance point as the value of the fault distance point in the corresponding plane coordinate system, and generate contour lines according to the horizontal and vertical coordinates of all the fault distance points and the values ​​in the corresponding coordinate system to obtain a section-fault distance contour line map.

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