Wrinkle amplitude determination method

Abstract

The invention relates to a wrinkle amplitude determination method, and belongs to the technical field of oil and gas field exploration and development. According to the method for determining the wrinkle amplitude, a standard well point is selected from target well points, and then sensitive trend lines which can distinguish the inner anticline and the inclined direction of a target wrinkle horizon and approach a wrinkle middle line are screened out from wrinkle middle surface trend lines corresponding to the standard well point under different sampling parameters; and finally, selecting an optimal trend line closest to the actual amplitude of different segments in each target area from the sensitive trend lines, and taking an amplitude calculation value obtained by calculation based on the optimal trend line or a correction value thereof as the amplitude of the target fold layer. The method for determining the wrinkle amplitude is simple to operate, and the calculated amplitude is close to the actual amplitude, so that the method for determining the wrinkle amplitude has high accuracy.

Description

Technical Field

[0001] The invention relates to a method for determining fold amplitude, and belongs to the technical field of oil and gas field exploration and development. Background Art

[0002] Anticline oil and gas reservoirs are one of the main types of oil and gas reservoirs, accounting for more than three-quarters of the reserves of oil and gas fields. According to the anticline structure, they can be divided into compression anticline oil and gas reservoirs, basement lifting oil and gas reservoirs, drape anticline oil and gas reservoirs, plastic arch anticline oil and gas reservoirs, and reverse traction anticline oil and gas reservoirs. Among them, compression anticline oil and gas reservoirs mainly occur in the fold deformation zone of the formation formed by compression, and are often accompanied by positive anticline structures and negative syncline structures. Since the density of natural gas is 0.72g / cm 3 The density of petroleum is 0.85~1.00g / cm 3 , the density of water is 1.00g / cm 3 Therefore, according to the density, it can be determined that water is in the low part of the fold structure, and oil and gas are located upwards. Due to the supporting effect of water, the oil in the larger space below will be lifted by water to the smaller space above. Therefore, anticlines are good oil and gas storage structures, and synclines are good water storage structures. Identifying the distribution of anticlines and synclines will help determine favorable exploration target areas within the study area.

[0003] Positive anticlines are not only favorable targets for oil and gas migration and accumulation, but the fractures generated during fold formation also serve as important reservoir spaces. Fractures can improve the storage capacity and permeability of permeable reservoirs and transform low-porosity, low-permeability, tight layers into reservoirs with space for oil and gas. Fractures in tight sandstone formations form dual-medium reservoirs with matrix pore structures. Fracture-cavity networks generated in carbonate formations create favorable conditions for the development of dolomitization and karst reservoirs. Folds primarily form under compressive stress environments. The nature of the forces acting on different parts of a fold structure varies, leading to variations in the types of fractures produced. Areas with significant changes in structural curvature are optimal for fracture development. The crest of a fold anticline experiences tensional cracking, resulting in the development of fold-associated fractures (section shear fractures) and fold-derived fractures (tension fractures), making it a favorable area for the development of large-scale fractures. The trough of a syncline, however, is subject to compression and has a solid material structure. The rocks flanking fold-derived fractures (oblique conjugate shear fractures) are tightly closed, resulting in fewer fractures.

[0004] Folds are formed by the compression or shear dislocation of adjacent rock blocks. They are a series of continuous bends in rock formations caused by stress and deformation, also known as folds. The basic types of folds are anticlines and synclines. An anticline is an upward convex bend of originally horizontal rock formations under stress, while a syncline is a downward concave bend. The geometric elements of a fold include the core, limbs, inflection point, interlimb angle, turning point, fold axis, hinge, axis (axis trace), arc tip, and limb angle. The core refers to the central part of a fold anticline or syncline in plane or section; the wings refer to the strata on both sides of the fold core, which appear as the two slopes of the fold rock layer on the fold section; the inflection point is the dividing point between the convex and concave parts of a continuous periodic waveform curve, that is, the point where the curvature of the fold wing is zero (the dividing point between anticline and syncline); the wing angle refers to the angle between the tangents of the inflection points of the same fold surface constituting the two wings, and also refers to the minimum angle between the two wings. The wing angle of an arc-shaped fold refers to the angle between the tangents passing through the two inflection points on the two wings; the turning end refers to the curved part of the fold surface where it transitions from one wing to the other; for cylindrical folds, the fold axis refers to a straight line that moves parallel to itself and can depict the curved shape of the fold surface; the hinge is the line connecting the maximum curvature points of a single layer, or the line connecting the arc tips on the same layer; the axis (axis trace) is the intersection of the axis plane and the horizontal plane or the ground; the arc tip refers to the maximum curvature point on the layer; the wing angle refers to the angle between the rock layers on the two wings and the horizontal plane.

[0005] Current research on fold structures primarily focuses on their geological characteristics, structural deformation, formation mechanisms, and impacts on stratigraphy and oil and gas exploration. There are two main methods for characterizing fold size and amplitude. The first method uses the length, width, and height of a fold to characterize its size and scale. Fold length is the length of the fold hinge, fold width is the distance between two adjacent anticline (or syncline) arc tips in a transverse section (a plane perpendicular to the hinge), and fold height is the distance between adjacent anticline and syncline arc tips in a transverse section, measured along the axial plane. Using the length-to-width ratio, folds are classified as linear folds (length-to-width ratio > 10) and short-axis folds (length-to-width ratio between 3 and 10). This method only reflects the characteristics and morphology of folds and cannot distinguish and confirm the planar distribution of anticlines and synclines. It is difficult to reflect the amplitude of folds or characterize the degree of fracture development in different fold locations within the same fold structure. The second method uses parameters such as the mid-plane, half-wavelength, and amplitude to characterize the scale and size of folds. The inflection point in fold geometry is the dividing point between anticlines and synclines. The line connecting the inflection points of adjacent anticlines and synclines is the mid-plane between the two. The convex curve above the mid-plane is an anticline, and the concave curve below the mid-plane is a syncline. The half-wavelength (W) of a fold is the length of 1 / 2 cycle, which is equal to the distance between the two inflection points of an anticline or syncline. The amplitude (A) is the difference between the depth of a point on the fold and the depth of a point on the mid-plane with the same geodetic coordinates as that point on the fold. In order to more clearly characterize folds and calculate the amplitude, folds are generally represented in the form of a cross-sectional diagram. A cross section perpendicular to the target fold structure is cut out in the three-dimensional fold diagram to obtain a fold profile. The fold layer in the fold profile is the fold line, and the line connecting the inflection points corresponding to the fold line is the middle line. The difference between the depth of a certain position on the fold line and the depth of a position on the middle line with the same geodetic coordinates as the position is the amplitude of the position.

[0006] Fold structures are not only important oil and gas-bearing structures, but fractures generated during tectonic activity also play a crucial role in controlling the accumulation and accumulation of oil and gas in tight sandstones and carbonates. Fractures generated by fold deformation enhance reservoir space and permeability. To study the patterns of oil and gas accumulation in tight sandstones and characterize the development of large-scale fractures, fold severity is used as a metric in exploration research. Fold severity is the ratio of fold amplitude to fold half-wavelength. Fold amplitude reflects the degree of longitudinal curvature of the folded layer, fold width reflects the degree of lateral compression, and the ratio of fold amplitude to half-wavelength reflects the degree of folding and the development of fractures in the formation. Generally, higher fold severity indicates greater fold curvature, more developed fractures in imaging logging interpretations, and higher drilling gas production. Determining fold severity requires obtaining both fold amplitude and half-wavelength, but currently, there is no accurate and simple method for obtaining fold amplitude.

[0007] Therefore, there is an urgent need to provide a method to accurately obtain the wrinkle amplitude. Summary of the Invention

[0008] The purpose of the present invention is to provide a method for determining the wrinkle amplitude, which can solve the current problem that the wrinkle amplitude cannot be accurately and simply obtained.

[0009] In order to achieve the above objectives, the technical solution adopted by the method for determining the wrinkle amplitude of the present invention is:

[0010] A method for determining wrinkle amplitude comprises the following steps:

[0011] S1, selecting a standard well point from the target well points based on the screening criteria of having the largest number of anticline and syncline segments and the largest anticline-syncline depth difference in the fold line passing through the target well point; the target well point is a well point that has been drilled into the target fold layer; the anticline-syncline depth difference is equal to the difference between the maximum value of the depths at the arc tips of all syncline segments in the fold line and the minimum value of the depths at the arc tips of all anticline segments in the fold line;

[0012] S2, obtaining the intermediate trend lines corresponding to the standard well points under different sampling parameters, and then screening out sensitive trend lines from all the intermediate trend lines based on the ability to distinguish anticlines and synclines in the target fold layer and being close to the intermediate line as the preferred criteria; the intermediate trend lines are determined by method A or method B, wherein method A comprises the following steps: selecting sampling points on the fold line passing through the standard well point using different sampling parameters, and then performing line fitting on the sampling points under each sampling parameter, where the fitted line is the intermediate trend line corresponding to the standard well point under each sampling parameter; and method B comprises the following steps: selecting sampling points in the target fold layer using different sampling parameters, and then performing surface fitting on the sampling points under each sampling parameter, where the fitted surface is the intermediate trend surface corresponding to the standard well point under each sampling parameter, and the line connecting the position points on the intermediate trend surface under a certain sampling parameter that have the same geodetic coordinates as the data points in the fold line passing through the standard well point is the intermediate trend line corresponding to the standard well point under that sampling parameter;

[0013] S3, based on the selection criterion of the amplitude calculated based on each sensitive trend line being closest to the actual amplitude, the optimal trend line of different segments in each target area is selected from the sensitive trend lines, and the amplitude calculated based on the optimal trend line or its corrected value is used as the amplitude of the target fold layer.

[0014] The method for determining the fold amplitude of the present invention first selects a standard well point from the target well points. The standard well point best reflects the magnitude of the fold amplitudes of different scales in the fold structural area. Then, from the intermediate trend lines corresponding to the standard well points under different sampling parameters, a sensitive trend line close to the intermediate line that can distinguish anticlines and synclines within the target fold layer is screened. Finally, the optimal trend line closest to the actual amplitude in different segments within each target area is selected from the sensitive trend lines. The amplitude calculated based on the optimal trend line or its corrected value is used as the amplitude of the target fold layer. The method for determining the fold amplitude of the present invention is simple to operate, and the calculated amplitude is relatively close to the actual amplitude, indicating that the method for determining the fold amplitude of the present invention has high accuracy.

[0015] Preferably, in step S2, the sampling parameter is a sampling interval.

[0016] Preferably, in step S2, performing line fitting on the sampling points under each sampling parameter means performing line fitting according to the position coordinates of the sampling points under each sampling parameter; performing surface fitting on the sampling points under each sampling parameter means performing surface fitting according to the position coordinates of the sampling points under each sampling parameter; the position coordinates include depth coordinates.

[0017] Preferably, in step S2, screening out sensitive trend lines from all intermediate trend lines means screening out sensitive trend lines of anticline areas in the target fold horizon and sensitive trend lines of syncline areas in the target fold horizon from all intermediate trend lines.

[0018] Preferably, in step S2, the principle for determining the sensitive trend line is as follows: when the calculated amplitude values ​​of each arc tip position in the anticline section of the target fold layer calculated based on a certain intermediate trend line are all greater than half of the actual amplitude, then the intermediate trend line is determined as the sensitive trend line of the anticline area in the target fold layer; when the calculated amplitude values ​​of each arc tip position in the syncline section of the target fold layer calculated based on a certain intermediate trend line are all less than half of the actual amplitude, then the intermediate trend line is determined as the sensitive trend line of the syncline area in the target fold layer.

[0019] Preferably, in step S3, the amplitude calculation value is equal to EF, where E is the depth of a certain position, and F is the depth of a position in the sensitive trend line that has the same geodetic coordinates as the certain position.

[0020] Preferably, in step S3, the target area includes anticline areas within the large-amplitude structural area, syncline areas within the large-amplitude structural area, anticline areas within the small-amplitude structural area, and syncline areas within the small-amplitude structural area; the large-amplitude structural area refers to anticline segments and syncline segments in the fold line passing through the standard well point whose half-wavelength is greater than the target value, and the small-amplitude structural area refers to anticline segments and syncline segments in the fold line passing through the standard well point whose half-wavelength is not greater than the target value; the target value satisfies the following conditions: when the half-wavelength is greater than the target value, the difference between the maximum value of the actual amplitude at the arc tip position in the syncline segment in the fold line passing through the standard well point and the minimum value of the actual amplitude at the arc tip position in the anticline segment in the fold line passing through the standard well point is not less than 170m, and when the half-wavelength is not greater than the target value, the difference between the maximum value of the actual amplitude at the arc tip position in the syncline segment in the fold line passing through the standard well point and the minimum value of the actual amplitude at the arc tip position in the anticline segment in the fold line passing through the standard well point is less than 170m.

[0021] Preferably, in step S3, the method for selecting the optimal trend line of different segments in each target area includes the following steps: selecting a number of target position points from each target area, and then comparing the calculated amplitude value of the target position point with the actual amplitude, and selecting the optimal trend line of different segments in each target area from the sensitive trend line based on the closest selection criterion between the calculated amplitude value and the actual amplitude; the number of target position points is not less than 4.

[0022] When comparing the calculated amplitude value and the actual amplitude of the target position point, it can be done in the form of a list or a drawing. For example, the calculated amplitude value and the actual amplitude of the target position point can be compared in the form of an intersection analysis diagram. The selection criterion is that the calculated amplitude value is closest to the actual amplitude, and the optimal trend line of different segments in each target area is selected from the sensitive trend line.

[0023] Preferably, in step S3, the amplitude of a certain position in a certain segment within a certain target area is equal to XY, wherein X is the depth of the certain position, and Y is the depth of a position in the optimal trend line of the certain segment within the certain target area that has the same geodetic coordinates as the certain position.

[0024] In order to simplify the calculation and improve the calculation accuracy, preferably, in step S3, when the maximum value of the difference between the amplitude calculation value calculated based on the optimal trend line and the actual amplitude of all target position points in a certain segment within a certain target area is greater than 20m, the correction value of the amplitude calculation value calculated based on the optimal trend line is used as the amplitude of each position in a certain segment within the certain target area; the correction value of the amplitude calculation value is determined by the following method: first determine the corresponding relationship between the amplitude correction value of all target position points in a certain segment within the certain target area and the amplitude calculation value calculated based on the optimal trend line, and then Then, based on the amplitude calculation value of a certain position in a certain segment within the certain target area calculated based on the optimal trend line, the amplitude correction value of the certain position is calculated, and the calculated amplitude correction value is used as the correction value of the amplitude calculation value. The amplitude correction value of the target position point is the actual amplitude of the target position point; the correspondence between the amplitude correction values ​​of all target position points in a certain segment within the certain target area and the amplitude calculation value calculated based on the optimal trend line refers to the linear correspondence between the amplitude correction values ​​of all target position points in a certain segment within the certain target area and the amplitude calculation value calculated based on the optimal trend line.

[0025] The method for determining the fold amplitude of the present invention is suitable for fold structures that meet the following conditions: a series of fold structure development areas with weak fault activity and small fault throw. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 Schematic diagram of a fold cross section containing the target well point Well7 in an embodiment of the present invention;

[0027] Figure 2 Schematic diagram of a fold line passing through the standard well point Well4 and its corresponding middle line, and a middle trend line based on various equal sampling intervals (calculated radii) in an embodiment of the present invention;

[0028] Figure 3 This is a schematic diagram of the results of an intersection analysis using half the wavelength as the abscissa and the actual amplitude at the arc tip position in the anticline and syncline segments as the ordinate in an embodiment of the present invention;

[0029] Figure 4 Schematic diagram of the actual amplitude of each target well point and the calculated amplitude value of each target well point when it is located in a large-amplitude anticline area at each sensitive trend line in an embodiment of the present invention;

[0030] Figure 5 Schematic diagram of the results of intersection analysis of the deviation between the actual amplitude of each target well point and the amplitude calculated value calculated based on the sensitive trend line when the sampling interval is 600m, and the amplitude calculated value calculated based on the sensitive trend line when the sampling interval is 600m in an embodiment of the present invention;

[0031] Figure 6 Schematic diagram of the results of intersection analysis of the deviation between the actual amplitude of each target well point and the amplitude calculated value calculated based on the sensitive trend line when the sampling interval is 500m, and the amplitude calculated value calculated based on the sensitive trend line when the sampling interval is 500m in an embodiment of the present invention;

[0032] Figure 7 This is a schematic diagram of the results of the fold line passing through the control point XJ-4 and its corresponding middle line, and various sensitive trend lines in the large-amplitude syncline area in an embodiment of the present invention;

[0033] Figure 8 Schematic diagram of the actual amplitude of each control point and the calculated amplitude value of each control point calculated based on each sensitive trend line in the large-amplitude syncline region in an embodiment of the present invention;

[0034] Figure 9 Schematic diagram of the result of intersection analysis of the amplitude calculation value of each control point calculated based on the sensitive trend line when the sampling interval is 300m and the actual amplitude of each control point in an embodiment of the present invention;

[0035] Figure 10 Schematic diagram of the fold line, the middle line and the sensitive trend line based on the small-amplitude structural area passing through the control point Dfdbx-5 in an embodiment of the present invention;

[0036] Figure 11 Schematic diagram of the actual amplitude of each control point and the calculated amplitude value of each control point calculated based on each sensitive trend line in the small amplitude structural area in an embodiment of the present invention;

[0037] Figure 12 Schematic diagram of the result of intersection analysis of the amplitude calculated value obtained by calculating the sensitive trend line when the sampling interval is 200m and the actual amplitude of each control point in an embodiment of the present invention;

[0038] Figure 13 This is a fold structure diagram of the target fold layer in the embodiment of the present invention. DETAILED DESCRIPTION

[0039] The method for determining the fold amplitude of the present invention first selects a standard well point from the target well points. The standard well point best reflects the magnitude of the fold amplitudes of different scales in the fold structural area. Then, from the intermediate trend lines corresponding to the standard well points under different sampling parameters, a sensitive trend line close to the intermediate line that can distinguish anticlines and synclines within the target fold layer is screened. Finally, the optimal trend line closest to the actual amplitude in different segments within each target area is selected from the sensitive trend lines. The amplitude calculated based on the optimal trend line or its corrected value is used as the amplitude of the target fold layer. The method for determining the fold amplitude of the present invention is simple to operate, and the calculated amplitude is relatively close to the actual amplitude, indicating that the method for determining the fold amplitude of the present invention has high accuracy.

[0040] The method for determining the wrinkle amplitude of the present invention comprises the following steps:

[0041] S1, selecting a standard well point from the target well points based on the screening criteria of having the largest number of anticline and syncline segments and the largest anticline-syncline depth difference in the fold line passing through the target well point; the target well point is a well point that has been drilled into the target fold layer; the anticline-syncline depth difference is equal to the difference between the maximum value of the depths at the arc tips of all syncline segments in the fold line and the minimum value of the depths at the arc tips of all anticline segments in the fold line;

[0042] S2, obtaining the intermediate trend lines corresponding to the standard well points under different sampling parameters, and then screening out sensitive trend lines from all the intermediate trend lines based on the ability to distinguish anticlines and synclines in the target fold layer and being close to the intermediate line as the preferred criteria; the intermediate trend lines are determined by method A or method B, wherein method A comprises the following steps: selecting sampling points on the fold line passing through the standard well point using different sampling parameters, and then performing line fitting on the sampling points under each sampling parameter, where the fitted line is the intermediate trend line corresponding to the standard well point under each sampling parameter; and method B comprises the following steps: selecting sampling points in the target fold layer using different sampling parameters, and then performing surface fitting on the sampling points under each sampling parameter, where the fitted surface is the intermediate trend surface corresponding to the standard well point under each sampling parameter, and the line connecting the position points on the intermediate trend surface under a certain sampling parameter that have the same geodetic coordinates as the data points in the fold line passing through the standard well point is the intermediate trend line corresponding to the standard well point under that sampling parameter;

[0043] S3, based on the selection criterion of the amplitude calculated based on each sensitive trend line being closest to the actual amplitude, the optimal trend line of different segments in each target area is selected from the sensitive trend lines, and the amplitude calculated based on the optimal trend line or its corrected value is used as the amplitude of the target fold layer.

[0044] In the present invention, the actual amplitude of a certain position in the target fold horizon is equal to the difference between the depth of the position and the depth of a position on the middle surface of the target fold horizon with the same geodetic coordinates as the position.

[0045] In step S2, the sampling parameter is the sampling interval; performing line fitting on the sampling points under each sampling parameter means performing line fitting according to the position coordinates of the sampling points under each sampling parameter; performing surface fitting on the sampling points under each sampling parameter means performing surface fitting according to the position coordinates of the sampling points under each sampling parameter; the position coordinates include depth coordinates.

[0046] In step S2, screening out sensitive trend lines from all intermediate trend lines means screening out sensitive trend lines of the anticline region and the syncline region in the target fold layer from all intermediate trend lines.

[0047] In step S2, the principle for determining the sensitive trend line is as follows: when the amplitude calculation values ​​of each arc tip position in the anticline section of the target fold horizon calculated based on a certain intermediate trend line are all greater than half of the actual amplitude, then the intermediate trend line is determined as the sensitive trend line of the anticline area in the target fold horizon; when the amplitude calculation values ​​of each arc tip position in the syncline section of the target fold horizon calculated based on a certain intermediate trend line are all less than half of the actual amplitude, then the intermediate trend line is determined as the sensitive trend line of the syncline area in the target fold horizon.

[0048] In step S3, the amplitude calculation value is equal to EF, where E is the depth of a certain position and F is the depth of a position in the sensitive trend line that has the same geodetic coordinates as the certain position.

[0049] In step S3, the target area includes anticline areas within the large-amplitude structural area, syncline areas within the large-amplitude structural area, anticline areas within the small-amplitude structural area, and syncline areas within the small-amplitude structural area; the large-amplitude structural area refers to anticline segments and syncline segments in the fold line passing through the standard well point whose half-wavelength is greater than the target value, and the small-amplitude structural area refers to anticline segments and syncline segments in the fold line passing through the standard well point whose half-wavelength is not greater than the target value; the target value satisfies the following conditions: when the half-wavelength is greater than the target value, the difference between the maximum value of the actual amplitude at the arc tip position in the syncline segment in the fold line passing through the standard well point and the minimum value of the actual amplitude at the arc tip position in the anticline segment in the fold line passing through the standard well point is not less than 170m, and when the half-wavelength is not greater than the target value, the difference between the maximum value of the actual amplitude at the arc tip position in the syncline segment in the fold line passing through the standard well point and the minimum value of the actual amplitude at the arc tip position in the anticline segment in the fold line passing through the standard well point is less than 170m.

[0050] In step S3, the method for selecting the optimal trend line of different segments in each target area includes the following steps: selecting a number of target position points from each target area, and then comparing the calculated amplitude value of the target position point with the actual amplitude, and selecting the optimal trend line of different segments in each target area from the sensitive trend line based on the closest selection criterion between the calculated amplitude value and the actual amplitude; the number of target position points is not less than 4.

[0051] When comparing the calculated amplitude value and the actual amplitude of the target position point, it can be done in the form of a list or a drawing. For example, the calculated amplitude value and the actual amplitude of the target position point can be compared in the form of an intersection analysis diagram. The selection criterion is that the calculated amplitude value is closest to the actual amplitude, and the optimal trend line of different segments in each target area is selected from the sensitive trend line.

[0052] In step S3, the amplitude of a certain position in a certain segment within a certain target area is equal to XY, where X is the depth of the certain position, and Y is the depth of a position in the optimal trend line of the certain segment within the certain target area that has the same geodetic coordinates as the certain position.

[0053] In order to simplify the calculation and improve the calculation accuracy, in step S3, when the maximum value of the difference between the amplitude calculation value calculated based on the optimal trend line and the actual amplitude of all target position points in a certain segment within a certain target area is greater than 20m, the correction value of the amplitude calculation value calculated based on the optimal trend line is used as the amplitude of each position in a certain segment within the certain target area; the correction value of the amplitude calculation value is determined by the following method: first determine the corresponding relationship between the amplitude correction value of all target position points in a certain segment within the certain target area and the amplitude calculation value calculated based on the optimal trend line, and then According to the amplitude calculation value of a certain position within a certain segment within a certain target area calculated based on the optimal trend line, the amplitude correction value of the certain position is obtained, and the obtained amplitude correction value is used as the correction value of the amplitude calculation value. The amplitude correction value of the target position point is the actual amplitude of the target position point; the correspondence between the amplitude correction values ​​of all target position points within a certain segment within a certain target area and the amplitude calculation value calculated based on the optimal trend line refers to the linear correspondence between the amplitude correction values ​​of all target position points within a certain segment within a certain target area and the amplitude calculation value calculated based on the optimal trend line.

[0054] The technical solution of the present invention will be further described below with reference to specific embodiments.

[0055] Example

[0056] This example uses a block in a certain basin as an example. The block has a series of fold anticlines and synclines. Image logging has been performed on six wells to interpret fractures. Exploration practice has shown that fractures are closely related to tight sandstone reservoirs and gas testing results. The method for determining the fold amplitude in this example specifically includes the following steps:

[0057] (1) The well location data of six drilled wells in the target area, seismic interpretation grid data with a density of CDP16×16 (interpretation spacing of 400m×400m), and three-dimensional seismic data with a CDP spacing of 25m (file format SGY) were collected to create a geological seismic analysis database for fold structure research; the structural location and coordinate statistics of the six drilled wells in the target area are shown in Table 1;

[0058] Table 1 Statistics of structural locations and coordinates of 6 wells drilled in the target area

[0059] hashtag Y-axis X(m) Horizontal axis Y (m) Structural parts 3 18715220 3552560 anticline area 4 18711297 3557198 anticline area 5 18721287 3553510 anticline area 6 18712953 3547303 anticline area 7 18708928.8 3565521 anticline area 10 18705910.9 3556866 anticline area

[0060] (2) Interpolate the interpretation grid data in step (1) to obtain high-precision seismic interpretation grid data with an interpretation spacing of 25m×25m. At the same time, the data of each position in the target fold layer can be obtained (including x-axis, y-axis and z-axis coordinates, x-axis and y-axis coordinates are collectively referred to as geodetic coordinates, and z-axis coordinates are depth data). Then, according to the depth (z-axis coordinate value) of each target well point in the target fold layer and the layer data of each target point in the intermediate surface of the target fold layer (including x-axis, y-axis and z-axis coordinates, x-axis and y-axis coordinates are collectively referred to as geodetic coordinates, and z-axis coordinates are depth data), the target well point is located in the middle surface of the target fold layer. Degree data) to obtain the actual amplitude of each target well point. The target well point is the well point that has been drilled and encountered the target fold layer. The target point is the position point on the middle plane of the target fold layer that has the same geodetic coordinates as the target well point. The actual amplitude of a target well point is equal to the difference between the depth of the target well point and the depth of the target point with the same geodetic coordinates as the target well point. In this embodiment, the target well points corresponding to the wells with well numbers 3, 4, 5, 6, 7, and 10 are named Well3, Well4, Well5, Well6, Well7, and Well10 respectively.

[0061] In order to determine the actual amplitude of each target well point, a cross section perpendicular to the target fold structure can be intercepted in the high-precision seismic interpretation grid data to obtain a fold profile. The target fold layer in the fold profile is defined as the fold line, and the line connecting the inflection points corresponding to the fold line is the middle line. Then, based on the fold line and the middle line in the fold profile, the actual amplitude of each target well point is calculated. Taking Well 7 as an example, the fold profile containing the target well point Well 7 is as follows: Figure 1As shown, the amplitude data at the middle line is zero, the area above the middle line is the anticline structure area, and the corresponding amplitude data is greater than zero, and the area below the middle line is the syncline structure area, and the corresponding amplitude data is less than zero. Then, the difference between the depth of the target well point Well7 and the depth of the target point (the target point is the position point on the middle line with the same geodetic coordinates as the target well point Well7) is calculated to obtain the actual amplitude of the target well point Well7. The actual amplitudes of each target well point are shown in Table 2.

[0062] Table 2 Actual amplitude of each target well point

[0063] Target well point Actual amplitude (m) Well3 123 Well4 305 Well5 195 Well6 128 Well7 243 Well10 35

[0064] (3) Selecting a standard well point from the target well points, the selection principle is as follows: if the number of anticline segments and syncline segments in the fold line passing through a target well point is the largest and the depth difference between the anticline and syncline is the largest, then the target well point is the standard well point; wherein the fold line is the target fold layer passing through the target well point and located in the fold section; the depth difference between the anticline and syncline is equal to the difference between the maximum value of the depths at the arc tip positions of all syncline segments in the fold line and the minimum value of the depths at the arc tip positions of all anticline segments in the fold line (that is, the difference between the maximum value of the depths at the arc tip positions of the syncline segments in the fold line on the well section and the minimum value of the depths at the arc tip positions of the anticline segments in the fold line); the anticline segment in the fold line refers to the curved segment portion of the fold line located above the middle line, and the syncline segment in the fold line refers to the curved segment portion of the fold line located below the middle line; the middle line is the line connecting the inflection points in the fold line;

[0065] In this embodiment, the number of anticline and syncline segments in the fold line passing through each target well point and the depth difference between the anticline and syncline are shown in Table 3;

[0066] Table 3 The number of anticline and syncline segments in the fold line passing through each target well point and the depth difference between anticline and syncline

[0067]

[0068] As shown in Table 3, the number of anticline and syncline segments in the fold line passing through the target well point Well4 is the largest and the depth difference between the anticline and syncline is the largest. Therefore, the target well point Well4 is the standard well point;

[0069] Then, sample points are selected from the target fold layer at equal intervals along the x-axis and y-axis, and the sampling intervals along the x-axis and y-axis are equal. Then, surface fitting is performed on the sampling points under each equal sampling interval (the fitting method is the smoothing fitting method, specifically, sampling at equal intervals on both wings of the fold through the fold axis, and connecting and smoothing the sampling points into a curved surface). The fitted surface is the intermediate trend surface at each equal sampling interval. In this embodiment, since the interpretation density of the high-precision interpretation grid data of the target area is 25m×25m, the sampling interval values ​​in this embodiment are all multiples of 25m, namely 100m, 200m, 300m, 400m, 500m, 600m, 700m, and 1600m. The sampling interval values ​​are set within the above range, with different scales and sizes in the target area. The folds of different amplitudes all have the beneficial effect of the intermediate trend line adjacent to the intermediate surface of the fold; then, a cross section passing through the standard well point and perpendicular to the target fold structure is intercepted in the seismic grid data to obtain a fold profile containing a fold line, an intermediate line and an intermediate trend line based on each equal sampling interval, wherein the intermediate trend line based on a certain equal sampling interval is a line connecting the position points on the intermediate trend surface at the same sampling interval that have the same geodetic coordinates as the data points in the fold line passing through the standard point; the intermediate trend lines with sampling intervals of 100m, 200m, 300m, 400m, 500m, 600m, 700m and 1600m are named J1 trend line, J2 trend line, J3 trend line, J4 trend line, J5 trend line, J6 trend line, J7 trend line and J8 trend line respectively;

[0070] In this embodiment, sampling points can also be directly selected at equal intervals from the fold line passing through the standard point, and then line fitting is performed on the sampling points at each equal sampling interval (the fitting method is a smoothing fitting method, specifically, sampling at equal intervals on both wings of the fold through the fold axis, and connecting and smoothing the sampling points into a curve). The fitted line is the middle trend line corresponding to each equal sampling interval.

[0071] The fold line passing through the standard well point Well4 and its corresponding middle line, as well as the middle trend line based on the sampling intervals are shown in Figure 2. Figure 2 The half-wavelength of the anticline and syncline segments in the fold line passing through the standard well point Well4, the actual amplitude of the arc tip position in the anticline and syncline segments, and the calculated amplitude values ​​of the arc tip position in the anticline and syncline segments calculated based on the intermediate trend line at each equal sampling interval are shown in Table 4. The calculated amplitude value of the arc tip position at a certain equal sampling interval is equal to AB, where A is the depth of the arc tip position and B is the depth of the position point on the intermediate trend line at a certain equal sampling interval with the same geodetic coordinates as the arc tip position.

[0072] Table 4. Half-wavelength of the anticline and syncline segments in the fold line passing through the standard well point Well 4, actual amplitudes at the arc tips in the anticline and syncline segments, and calculated amplitudes at the arc tips in the anticline and syncline segments calculated based on the intermediate trend lines at each equal sampling interval.

[0073]

[0074]

[0075] As shown in Table 4, when the half wavelength is greater than 440m, the difference between the calculated amplitude at the arc tip position calculated based on the J3 trend line, J4 trend line, J5 trend line, and J6 trend line and the actual amplitude at the arc tip position is no more than 10%. Therefore, the calculated amplitude at the arc tip position calculated based on the J3 trend line, J4 trend line, J5 trend line, and J6 trend line is close to the actual amplitude at the arc tip position, which can better distinguish anticlines and synclines with a half wavelength greater than 440m. When the half wavelength is ≤440m, the calculated amplitude at the arc tip position calculated based on the J2 trend line is close to the actual amplitude at the arc tip position. The difference between the calculated amplitude at the arc tip calculated based on the trend line and the J3 trend line and the actual amplitude at the arc tip is no more than 15%. Therefore, the calculated amplitude at the arc tip calculated based on the J2 trend line and the J3 trend line is close to the actual amplitude at the arc tip, which can better distinguish anticlines and synclines with a half-wavelength of ≤440m. Comparative analysis based on the amplitude at the arc tip can distinguish the sampling parameters of large-amplitude anticlines, large-amplitude synclines, small-amplitude anticlines, and small-amplitude synclines, and has the beneficial effect of improving the accuracy of amplitude calculation.

[0076] At the same time, we use half wavelength as the horizontal coordinate and the actual amplitude of the arc tip in the anticline and syncline segments as the vertical coordinate to conduct intersection analysis. The results are as follows: Figure 3 shown by Figure 3 It can be seen that when the half wavelength is greater than 440m, the difference between the maximum actual amplitude at the arc tip position in the syncline segment and the minimum actual amplitude at the arc tip position in the anticline segment is not less than 170m, indicating that the amplitude difference between the anticline and syncline is large, the mutual influence is small, the calculation error is small, and the anticline and syncline are easy to distinguish. When the half wavelength is less than or equal to 440m, the difference between the maximum actual amplitude at the arc tip position in the syncline segment and the minimum actual amplitude at the arc tip position in the anticline segment is less than 170m, indicating that the amplitude difference between the anticline and syncline is small, the mutual influence is large, and the calculation error is small. The error is relatively large, and it is relatively difficult to distinguish between anticlines and synclines. Therefore, in order to more accurately calculate the amplitude of different areas, the area with a half-wavelength greater than 440m in the target fold layer is defined as a large-amplitude structural area, and the area with a half-wavelength less than 440m in the target fold layer is defined as a small-amplitude structural area. The anticline structure in the large-amplitude structural area is a large-amplitude anticline, the syncline structure in the large-amplitude structural area is a large-amplitude syncline, the anticline structure in the small-amplitude structural area is a small-amplitude anticline, and the syncline structure in the small-amplitude structural area is a small-amplitude syncline.

[0077] Therefore, it can be seen from Table 4 that in this embodiment, the J3 trend line, the J4 trend line, the J5 trend line, and the J6 trend line are closer to the middle line of the large-amplitude structural area, and the J3 trend line, the J4 trend line, the J5 trend line, and the J6 trend line have higher accuracy when used to calculate the amplitude of the large-amplitude structural area; the J2 trend line and the J3 trend line are closer to the middle line of the small-amplitude structural area, and the J2 trend line and the J3 trend line have higher accuracy when used to calculate the amplitude of the small-amplitude structural area;

[0078] In order to more accurately select the sensitive trend lines suitable for large-amplitude anticline area, large-amplitude syncline area, small-amplitude anticline area and small-amplitude syncline area from J1 trend line, J2 trend line, J3 trend line, J4 trend line, J5 trend line, J6 trend line, J7 trend line and J8 trend line, according to Figure 2 The determination is based on the following principles: when the amplitude calculation values ​​of each arc tip position in the anticline segment (including large-amplitude anticlines and small-amplitude anticlines) calculated based on a certain intermediate trend line are all greater than 0 and greater than half of the actual amplitude, it indicates that the intermediate trend line is close to the intermediate line of the anticline area. Therefore, the intermediate trend line is determined as the sensitive trend line in the anticline area. When the amplitude calculation values ​​of each arc tip position in the syncline segment (including large-amplitude synclines and small-amplitude synclines) calculated based on a certain intermediate trend line are all less than 0 and less than half of the actual amplitude, it indicates that the intermediate trend line is close to the intermediate line of the syncline area. Therefore, the intermediate trend line is determined as the sensitive trend line in the syncline area.

[0079] In this embodiment, the amplitude calculation values ​​of each arc tip position in the large-amplitude anticline area calculated based on the J5 trend line and the J6 trend line are all greater than 0 and greater than half of the actual amplitude. Therefore, the J5 trend line and the J6 trend line can be used as sensitive trend lines in the large-amplitude anticline area; the amplitude calculation values ​​of each arc tip position in the large-amplitude syncline area calculated based on the J3 trend line and the J4 trend line are all less than 0 and less than half of the actual amplitude. Therefore, the J3 trend line and the J4 trend line can be used as sensitive trend lines in the large-amplitude syncline area. The calculated amplitude values ​​of each arc tip position in the small-amplitude anticline area calculated based on the J2 trend line and the J3 trend line are all greater than 0 and greater than half of the actual amplitude. Therefore, the J2 trend line and the J3 trend line can be used as sensitive trend lines in the small-amplitude anticline area. The calculated amplitude values ​​of each arc tip position in the small-amplitude syncline area calculated based on the J2 trend line and the J3 trend line are all less than 0 and less than half of the actual amplitude. Therefore, the J2 trend line and the J3 trend line can be used as sensitive trend lines in the small-amplitude syncline area.

[0080] (4) In this embodiment, each target well point is located in the anticline area within the large-scale structural area. According to the depth data of each target well point in the anticline area within the large-scale structural area of ​​the target fold and each sensitive trend line in the large-scale anticline area, the amplitude calculation value of each target well point at each sensitive trend line in the large-scale anticline area is calculated. The amplitude calculation value of the target well point i at a certain sensitive trend line is equal to CD, where C is the depth of the target well point i, and D is the depth of the position point with the same geodetic coordinates as the target well point i in a certain sensitive trend line; the amplitude calculation values ​​of each target well point at each sensitive trend line in the large-scale anticline area are shown in Table 5. The actual amplitude of each target well point and the amplitude calculation value of each target well point at each sensitive trend line in the large-scale anticline area are shown in Table 5. Figure 4 As shown in Table 6, the deviations of the actual amplitudes of each target well point from the amplitudes calculated when the sampling intervals are 500m and 600m (the difference between the actual amplitudes and the amplitudes calculated) are shown in Table 6.

[0081] Table 5 Calculated amplitude values ​​of each target well point at each sensitive trend line in the large-amplitude anticline area

[0082]

[0083] Table 6 Deviation between the actual amplitude and the calculated amplitude at each target well point

[0084]

[0085] Comparing the actual amplitude of each target well point with the amplitude calculated based on each sensitive trend line, it can be seen that when the amplitude calculated value is ≤110m, the amplitude calculated value calculated using the sensitive trend line with a sampling interval of 600m has the smallest difference with the actual amplitude of the target well point, which can more accurately reflect the inflection point position of the target fold. This shows that when the amplitude calculated value is ≤110m, the middle trend surface with a sampling interval of 600m is closest to the actual middle surface. Therefore, when the amplitude calculated value is ≤110m, the sampling interval of 600m is used. The sensitive trend line is the optimal trend line of the anticline area in the large-amplitude structural zone of the target fold layer; when the amplitude calculation value is greater than 110m, the amplitude approximate value calculated by using the sensitive trend line with a sampling interval of 500m has the smallest difference with the actual amplitude of the target well point, indicating that when the amplitude calculation value is greater than 110m, the intermediate trend surface with a sampling interval of 500m is closest to the actual intermediate surface. Therefore, when the amplitude calculation value is greater than 110m, the sensitive trend line with a sampling interval of 500m is the optimal trend line of the anticline area in the large-amplitude structural zone of the target fold layer;

[0086] Therefore, by combining the portion of the sensitive trend line with an approximate amplitude of ≤110m when the sampling interval is 600m and the portion of the sensitive trend line with an approximate amplitude of >110m when the sampling interval is 500m, the optimal trend line of the anticline area within the large-amplitude structural zone of the entire target fold horizon can be obtained; based on the determined optimal trend line and the depth of each position in the target fold horizon, the amplitude of each position can be calculated. The amplitude of a certain position is equal to OP, where O is the depth of the certain position and P is the depth of the position on the optimal trend line that has the same geodetic coordinates as the certain position;

[0087] In order to more intuitively reflect the deviation between the actual amplitude of each target well point and the amplitude calculated by the sensitive trend line with a sampling interval of 500m and 600m, the deviation between the actual amplitude of each target well point and the amplitude calculated value and the amplitude calculated value are intersected and analyzed. When the intersection analysis is performed, the deviation between the actual amplitude and the amplitude calculated value is used as the vertical coordinate, and the amplitude calculated value is used as the horizontal coordinate. The intersection diagram is shown in the figure below. Figure 5-6 As shown, Figure 5 This is the intersection diagram when the sampling interval is 600m. Figure 6 is the intersection diagram when the sampling interval is 500m; Figure 5 It can be seen that when the amplitude calculation value is ≤110m, the difference (absolute error) between the amplitude calculation value and the actual amplitude of the target well point when the sampling interval is 600m is less than 2m; Figure 6 It can be seen that when the amplitude calculation value is greater than 110m, the difference (absolute error) between the amplitude calculation value when the sampling interval is 500m and the actual amplitude of the target well point is small, but the maximum absolute error still reaches 30m. In order to further improve the calculation accuracy, the amplitude calculation value when the sampling interval is 500m is linearly fitted with the actual amplitude of the target well point, and the linear relationship between the amplitude correction value and the amplitude calculation value is obtained. The relationship is: A0i( J5 )=Ai( J5 )+(-0.0515×Ai( J5 )+20.6), where A0i( J5 ) is the amplitude correction value, Ai( J5 ) is the approximate amplitude when the sampling interval is 500m;

[0088] In this embodiment, there are a total of 430,650 grid data points in the high-precision seismic interpretation grid data for the anticline region within the target fold horizon's large-amplitude structural zone, of which 320,870 grid data points have calculated amplitude values ​​≤110 m, and 109,780 grid data points have calculated amplitude values ​​>110 m. The calculated amplitude values ​​of the 109,780 grid data points with calculated amplitude values ​​>110 m are corrected using the above-mentioned linear relationship to obtain corrected amplitude values ​​for each grid data point. The corrected amplitude values ​​of the 109,780 grid data points with calculated amplitude values ​​>110 m are aggregated and combined with the calculated amplitude values ​​of the 320,870 grid data points with calculated amplitude values ​​≤110 m to obtain an amplitude data volume for the anticline region within the target fold horizon's large-amplitude structural zone (i.e., a collection of amplitude data at different positions in the anticline region within the target fold horizon's large-amplitude structural zone).

[0089] (5) Since there are no well points in the present embodiment that have been drilled into the syncline area within the large-scale structural area of ​​the target fold layer, a number of data points (the number of data points is not less than 4) are selected from the syncline area within the large-scale structural area of ​​the target fold layer as control points. In the present embodiment, there are 8 control points selected from the syncline area within the large-scale structural area. The names, horizontal and vertical coordinates and structural positions of each control point in the syncline area within the large-scale structural area are shown in Table 7. Then, according to the method in step (2), the actual amplitude of each control point in the syncline area within the large-scale structural area is determined. The actual amplitude of each control point in the syncline area within the large-scale structural area is shown in Table 8.

[0090] Table 7 Names, horizontal and vertical coordinates and areas of control points in the syncline area within the large-scale structural zone

[0091] Control point name Y-axis X(m) Horizontal axis Y (m) Structural parts XJ-1 18714440 3551170 syncline area XJ-2 18712900 3550390 syncline area XJ-3 18721245 3549710 syncline area XJ-4 18712240 3557625 syncline area XJ-5 18714655 3558935 syncline area XJ-6 18716890 3560160 syncline area XJ-7 18719605 3555260 syncline area XJ-8 18721050 3556055 syncline area

[0092] Table 8 Actual amplitudes of each control point in the syncline area within the large-amplitude structural zone

[0093]

[0094] Then, a cross section passing through each control point in the large-amplitude syncline area and perpendicular to the target fold structure is intercepted in the seismic grid data to obtain a fold profile containing fold lines, middle lines, and sensitive trend lines based on the large-amplitude syncline area; the fold line passing through the control point XJ-4 and its corresponding middle line, as well as the sensitive trend lines based on the large-amplitude syncline area are shown in Figure 2. Figure 7 As shown;

[0095] Then, according to the depth data of each control point in the large-amplitude syncline area in the target fold layer and each sensitive trend line in the large-amplitude syncline area, the amplitude calculation value of each control point calculated based on each sensitive trend line is obtained. The amplitude calculation value of control point j when it is on a certain sensitive trend line is equal to MN, where M is the depth of control point j and N is the depth of the position point with the same geodetic coordinates as control point j in a certain sensitive trend line. The amplitude calculation value of each control point calculated based on each sensitive trend line in the large-amplitude syncline area is shown in Table 9. The actual amplitude of each control point is different from the amplitude calculation value of each control point calculated based on each sensitive trend line in the large-amplitude syncline area. Figure 8 As shown;

[0096] Table 9 Calculated amplitude values ​​of each control point calculated based on the sensitive trend lines in the large-amplitude syncline area

[0097]

[0098] From Table 8-9 and Figure 8 It can be seen that the amplitude calculated based on the sensitive trend line with a sampling interval of 200m is significantly smaller than the actual amplitudes of control points XJ-3, XJ-4, XJ-7, and XJ-8. The amplitude calculated based on the sensitive trend line with a sampling interval of 400m is significantly larger than the actual amplitudes of control points XJ-3, XJ-4, XJ-5, and XJ-6. However, the amplitude calculated based on the sensitive trend line with a sampling interval of 300m has relatively small deviations from the actual amplitudes of each control point. Therefore, the sensitive trend line with a sampling interval of 300m can be used as the optimal trend line of the syncline zone within the large-amplitude structural zone of the target fold layer, and the amplitude calculated based on the sensitive trend line with a sampling interval of 300m can be used as the amplitude of each position in the syncline zone within the large-amplitude structural zone of the target fold layer.

[0099] In order to further improve the calculation accuracy, the amplitude calculation value of each control point calculated based on the sensitive trend line when the sampling interval is 300m and the actual amplitude of each control point are intersected and analyzed. In the intersection analysis, the actual amplitude of each control point is used as the vertical coordinate, and the amplitude calculation value of each control point calculated based on the sensitive trend line when the sampling interval is 300m is used as the horizontal coordinate. The intersection diagram obtained by the intersection analysis is shown in the figure below: Figure 9 As shown, a linear fit is then performed based on the intersection diagram to obtain the corresponding relationship between the amplitude correction value and the amplitude calculation value. The linear relationship obtained by fitting is: A0i( J3 )=0.8956×Ai( J3 )-6.46, among which Ai( J3 ) is the amplitude calculation value of each control point calculated based on the sensitive trend line when the sampling interval is 300m, A0i( J3) is the amplitude correction value; then, based on the amplitude calculation value of each control point calculated based on the sensitive trend line when the sampling interval is 300m, according to the fitted linear relationship, the amplitude correction value of each position in the syncline area within the target fold horizon with a large amplitude is calculated, and the calculated amplitude correction value of each position is used as the amplitude of each position in the syncline area within the target fold horizon with a large amplitude;

[0100] In this embodiment, there are a total of 290,870 grid data points in the high-precision seismic interpretation grid data for the syncline region within the target fold horizon's large-amplitude structural zone. The amplitude calculation values ​​corresponding to the 290,870 grid data points, calculated based on the sensitive trend line when the sampling interval is 300 m, are corrected using the above-mentioned linear relationship to obtain an amplitude correction value for each grid data point. The calculated amplitude correction value is used as the amplitude of each position in the syncline region within the target fold horizon's large-amplitude structural zone. After aggregation, an amplitude data volume of the syncline region within the target fold horizon's large-amplitude structural zone (i.e., a collection of the amplitudes of each position in the syncline region within the target fold horizon's large-amplitude structural zone) is obtained.

[0101] (6) In this embodiment, since the sensitive trend line in the small-amplitude anticline area is the same as the sensitive trend line in the small-amplitude syncline area, the small-amplitude anticline area and the small-amplitude syncline area can be taken as a whole (i.e., the small-amplitude structural area) to determine the amplitude of each position in the small-amplitude structural area;

[0102] A number of data points are selected as control points from the anticline area and the syncline area in the small-amplitude structural area of ​​the target fold. The number of data points selected from the anticline area in the small-amplitude structural area is not less than 4, and the number of data points selected from the syncline area in the small-amplitude structural area is not less than 4. In this embodiment, there are 11 control points selected. The names of the control points in the small-amplitude structural area, their horizontal and vertical coordinates, and the areas in which they are located are shown in Table 10. Then, according to the method in step (2), the actual amplitude of each control point in the small-amplitude structural area is determined. The actual amplitude of each control point in the small-amplitude structural area is shown in Table 11.

[0103] Table 10 Names, horizontal and vertical coordinates and areas of each control point in the small-amplitude structural area

[0104] Control point name Y-axis X(m) Horizontal axis Y (m) Structural locations within small-amplitude structural zones Dfdbx-1 18703980 3565450 syncline area Dfdbx-2 18704020 3567355 syncline area Dfdbx-3 18701435 3562310 syncline area Dfdbx-4 18701450 3566970 syncline area Dfdbx-5 18703100 3561650 syncline area Dfdbx-6 18700815 3566565 anticline area Dfdbx-7 18702270 3566370 anticline area Dfdbx-8 18704510 3565600 anticline area Dfdbx-9 18703200 3564250 anticline area Dfdbx-10 18700920 3565210 anticline area Dfdbx-11 18702240 3562560 anticline area

[0105] Table 11 Actual amplitudes of each control point in the small-amplitude structural area

[0106]

[0107] Then, a cross section passing through each control point in the small-amplitude structural area and perpendicular to the target fold structure is intercepted in the seismic grid data to obtain a fold profile containing fold lines, middle lines, and sensitive trend lines based on the small-amplitude structural area; the fold lines, middle lines, and sensitive trend lines based on the small-amplitude structural area passing through the control point Dfdbx-5 are as follows: Figure 10 As shown;

[0108] Then, according to the depth of each control point in the target fold layer and each sensitive trend line in the small-amplitude structural area, the amplitude calculation value of each control point calculated based on each sensitive trend line in the small-amplitude structural area is obtained. The amplitude calculation value of the control point k calculated based on a certain sensitive trend line in the small-amplitude structural area is equal to ST, where S is the depth of the control point k and T is the depth of the position point with the same geodetic coordinates as the control point k in a certain sensitive trend line. The amplitude calculation value of each control point calculated based on each sensitive trend line in the small-amplitude structural area is shown in Table 12. The actual amplitude of each control point is different from the amplitude calculation value of each control point calculated based on each sensitive trend line in the small-amplitude structural area. Figure 11 As shown;

[0109] Table 12 Amplitude calculation values ​​of each control point calculated based on each sensitive trend line in the small amplitude structural area

[0110]

[0111] From Table 11-12 and Figure 11 It can be seen that the amplitude calculated based on the sensitive trend line when the sampling interval is 300m is significantly smaller than the actual amplitude of the control points Dfdbx-1, Dfdbx-2, Dfdbx-3, Dfdbx-5, and Dfdbx-10. The amplitude calculated based on the sensitive trend line when the sampling interval is 400m is significantly smaller than the actual amplitude of the control points Dfdbx-1, Dfdbx-2, Dfdbx-3, and Dfdbx-4, and is significantly smaller than the actual amplitude of the control points Dfdbx- 6 is obviously too large, while the amplitude calculated based on the sensitive trend line when the sampling interval is 200m is relatively small compared with the actual amplitude of each control point. Therefore, the sensitive trend line when the sampling interval is 200m can be used as the optimal trend line of the anticline and syncline areas in the small-amplitude structural area of ​​the target fold layer, and the amplitude calculated based on the sensitive trend line when the sampling interval is 200m can be used as the amplitude of each position in the anticline and syncline areas in the small-amplitude structural area of ​​the target fold layer.

[0112] In order to further improve the calculation accuracy, the amplitude calculation value obtained based on the sensitive trend line when the sampling interval is 200m and the actual amplitude of each control point are intersected and analyzed. During the intersection analysis, the actual amplitude of each control point is used as the vertical coordinate, and the amplitude calculation value obtained based on the sensitive trend line when the sampling interval is 200m is used as the horizontal coordinate. The intersection diagram obtained by the intersection analysis is shown in the figure below: Figure 12 As shown, a linear fit is then performed based on the intersection diagram to obtain the corresponding relationship between the amplitude calculation value and the amplitude correction value. The linear relationship obtained by fitting is: A0i( J2 )=1.0961×Ai( J2 )-0.01, where Ai( J2 ) is the amplitude calculation value of each control point calculated based on the sensitive trend line when the sampling interval is 200m, A0i( J2 ) is the amplitude correction value; then, based on the amplitude calculation value of each control point calculated based on the sensitive trend line when the sampling interval is 200m, according to the fitted linear relationship, the amplitude correction value of each position in the anticline area and syncline area within the small-amplitude structural area of ​​the target fold horizon is calculated, and the calculated amplitude correction value is used as the amplitude of each position in the anticline area and syncline area within the small-amplitude structural area of ​​the target fold horizon;

[0113] In this embodiment, there are a total of 279,730 grid data points in the high-precision seismic interpretation grid data for the anticline and syncline areas within the small-amplitude structural zone of the target fold horizon. The amplitude calculation values ​​corresponding to the 279,730 grid data points calculated based on the sensitive trend line when the sampling interval is 200 m are corrected using the above-mentioned linear relationship to obtain an amplitude correction value for each grid data point. The calculated amplitude correction value is used as the amplitude of each position in the anticline and syncline areas within the small-amplitude structural zone of the target fold horizon. After aggregation, an amplitude data volume of the anticline and syncline areas within the small-amplitude structural zone of the target fold horizon is obtained (i.e., a collection of amplitude data at different positions in the anticline and syncline areas within the small-amplitude structural zone of the target fold horizon).

[0114] (7) Finally, the amplitude data volume of the anticline area in the large-amplitude structural area of ​​the target fold horizon obtained in step (4), the amplitude data volume of the syncline area in the large-amplitude structural area of ​​the target fold horizon obtained in step (5), and the amplitude data volume of the anticline area and syncline area in the small-amplitude structural area of ​​the target fold horizon obtained in step (6) are combined and summarized to obtain the amplitude data volume of the target fold horizon (i.e., the collection of amplitude data at different positions in the target fold horizon). Then, based on the amplitude data volume of the target fold horizon, a fold structure map that can reflect the distribution of anticlines, synclines, fold inflection points and the degree of fold bending is compiled. The result is as follows: Figure 13 As shown. Figure 13It can be seen that the zero line of the fold point wave amplitude on the fold structure map represents the distribution of the inflection points between the fold anticline and syncline. The area with the fold point wave amplitude > 0 represents the anticline development area, and the area with the fold point wave amplitude < 0 represents the syncline development area. The size of the fold point wave amplitude represents the degree of folding, and the change in the size of the fold point wave amplitude contour line spacing can represent the curvature change of the target fold layer and the development of fractures.

[0115] Experimental example

[0116] In order to verify the accuracy of the method for determining the fold amplitude of the present invention, six experimental points (Table 13) were selected in a certain block of a certain basin in the embodiment. None of the six experimental points were used in the embodiment. Among the six experimental points, three were located in the syncline area and three were located in the anticline area. The actual amplitude of each experimental point was then calculated, and the amplitude of each experimental point was calculated again using the method of the embodiment. The results showed that for the three experimental points located in the syncline area, the error between the calculated amplitude value and the actual amplitude value was no more than 10%, and for the three experimental points located in the anticline area, the error between the calculated amplitude value and the actual amplitude value was no more than 10%.

[0117] Table 13 Error statistics between the calculated amplitude and the actual amplitude at the six experimental points in the study area of ​​the embodiment

[0118]

Claims

1. A method for determining wrinkle amplitude, characterized in that: The following steps are involved: S1, selecting a standard well point from the target well points based on the screening criteria of having the largest number of anticline and syncline segments and the largest anticline-syncline depth difference in the fold line passing through the target well point; the target well point is a well point that has been drilled into the target fold layer; the anticline-syncline depth difference is equal to the difference between the maximum value of the depths at the arc tips of all syncline segments in the fold line and the minimum value of the depths at the arc tips of all anticline segments in the fold line; S2, obtaining the intermediate trend lines corresponding to the standard well points under different sampling parameters, and then screening out sensitive trend lines from all the intermediate trend lines based on the ability to distinguish anticlines and synclines in the target fold layer and being close to the intermediate line as the preferred criteria; the intermediate trend lines are determined by method A or method B, wherein method A comprises the following steps: selecting sampling points on the fold line passing through the standard well point using different sampling parameters, and then performing line fitting on the sampling points under each sampling parameter, where the fitted line is the intermediate trend line corresponding to the standard well point under each sampling parameter; and method B comprises the following steps: selecting sampling points in the target fold layer using different sampling parameters, and then performing surface fitting on the sampling points under each sampling parameter, where the fitted surface is the intermediate trend surface corresponding to the standard well point under each sampling parameter, and the line connecting the position points on the intermediate trend surface under a certain sampling parameter that have the same geodetic coordinates as the data points in the fold line passing through the standard well point is the intermediate trend line corresponding to the standard well point under that sampling parameter; S3, based on the selection criterion of the amplitude calculated based on each sensitive trend line being closest to the actual amplitude, the optimal trend line of different segments in each target area is selected from the sensitive trend lines, and the amplitude calculated based on the optimal trend line or its corrected value is used as the amplitude of the target fold layer.

2. The method for determining the wrinkle amplitude according to claim 1, wherein: In step S2, screening out sensitive trend lines from all intermediate trend lines means screening out sensitive trend lines of the anticline region and the syncline region in the target fold layer from all intermediate trend lines.

3. The method for determining wrinkle amplitude according to claim 2, wherein: In step S2, the principle for determining the sensitive trend line is as follows: when the amplitude calculation values ​​of each arc tip position in the anticline section of the target fold horizon calculated based on a certain intermediate trend line are all greater than half of the actual amplitude, then the intermediate trend line is determined as the sensitive trend line of the anticline area in the target fold horizon; when the amplitude calculation values ​​of each arc tip position in the syncline section of the target fold horizon calculated based on a certain intermediate trend line are all less than half of the actual amplitude, then the intermediate trend line is determined as the sensitive trend line of the syncline area in the target fold horizon.

4. The method for determining the wrinkle amplitude according to any one of claims 1 to 3, characterized in that: In step S2, the sampling parameter is the sampling interval.

5. The method for determining the wrinkle amplitude according to any one of claims 1 to 3, characterized in that: In step S2, performing line fitting on the sampling points under each sampling parameter means performing line fitting according to the position coordinates of the sampling points under each sampling parameter; performing surface fitting on the sampling points under each sampling parameter means performing surface fitting according to the position coordinates of the sampling points under each sampling parameter; the position coordinates include depth coordinates.

6. The method for determining wrinkle amplitude according to claim 1, wherein: In step S3, the target area includes anticline areas within the large-amplitude structural area, syncline areas within the large-amplitude structural area, anticline areas within the small-amplitude structural area, and syncline areas within the small-amplitude structural area; the large-amplitude structural area refers to anticline segments and syncline segments in the fold line passing through the standard well point whose half-wavelength is greater than the target value, and the small-amplitude structural area refers to anticline segments and syncline segments in the fold line passing through the standard well point whose half-wavelength is not greater than the target value; the target value satisfies the following conditions: when the half-wavelength is greater than the target value, the difference between the maximum value of the actual amplitude at the arc tip position in the syncline segment in the fold line passing through the standard well point and the minimum value of the actual amplitude at the arc tip position in the anticline segment in the fold line passing through the standard well point is not less than 170m, and when the half-wavelength is not greater than the target value, the difference between the maximum value of the actual amplitude at the arc tip position in the syncline segment in the fold line passing through the standard well point and the minimum value of the actual amplitude at the arc tip position in the anticline segment in the fold line passing through the standard well point is less than 170m.

7. The method for determining wrinkle amplitude according to claim 1, wherein: In step S3, the method for selecting the optimal trend line of different segments in each target area includes the following steps: selecting a number of target position points from each target area, and then comparing the calculated amplitude value of the target position point with the actual amplitude, and selecting the optimal trend line of different segments in each target area from the sensitive trend line based on the closest selection criterion between the calculated amplitude value and the actual amplitude; the number of target position points is not less than 4.

8. The method for determining the wrinkle amplitude according to any one of claims 1, 6-7, characterized in that: In step S3, the amplitude calculation value is equal to EF, where E is the depth of a certain position and F is the depth of a position in the sensitive trend line that has the same geodetic coordinates as the certain position.

9. The method for determining the wrinkle amplitude according to any one of claims 1, 6-7, characterized in that: The amplitude of a certain position in a certain segment within a certain target area is equal to XY, where X is the depth of the certain position and Y is the depth of the position on the optimal trend line of the certain segment within the certain target area that has the same geodetic coordinates as the certain position.

10. The method for determining the wrinkle amplitude according to any one of claims 1, 6-7, characterized in that: In step S3, when the maximum value of the difference between the amplitude calculation value calculated based on the optimal trend line and the actual amplitude of all target position points in a certain segment within a certain target area is greater than 20m, the correction value of the amplitude calculation value calculated based on the optimal trend line is used as the amplitude of each position in a certain segment within the certain target area; the correction value of the amplitude calculation value is determined by the following method: first determine the correspondence between the amplitude correction value of all target position points in a certain segment within the certain target area and the amplitude calculation value calculated based on the optimal trend line, and then calculate the amplitude correction value of a certain position according to the amplitude calculation value of a certain position in the certain segment within the certain target area calculated based on the optimal trend line, and use the calculated amplitude correction value as the correction value of the amplitude calculation value, and the amplitude correction value of the target position point is the actual amplitude of the target position point.

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