Gravity anomaly extraction method, device, equipment and storage medium

Abstract

The present disclosure provides a gravity anomaly extraction method, device, equipment and storage medium, and belongs to the technical field of gravity exploration. The method comprises: performing terrain correction and curving processing on the Bouguer gravity anomaly of a target region to obtain a first gravity anomaly; performing constant-density gravity stripping processing on the first gravity anomaly to obtain a second gravity anomaly; performing variable-density gravity stripping processing on the second gravity anomaly to obtain a third gravity anomaly, wherein the density of the multiple layers of strata between the stratum where the target geological body is located and the surface is variable in the along-layer lateral direction; determining a first gravity regional field of the target region; and extracting the gravity anomaly of the target geological body according to the third gravity anomaly and the first gravity regional field. The variable-density gravity stripping processing on the second gravity anomaly can eliminate the influence of the variable density of the strata in the along-layer lateral direction on the gravity anomaly of the target geological body, thereby improving the accuracy of the extracted target gravity anomaly.

Description

TECHNICAL FIELD

[0001] The present disclosure relates to the technical field of gravity exploration, and in particular, to a method and device for extracting gravity anomaly, equipment and a storage medium. BACKGROUND

[0002] Gravity exploration is an important method in oil and gas exploration, and plays an important role in the study of regional structure, faulted basin, local structural belt, buried hill, rift, and piedmont zone. In gravity exploration, the deviation between the actual observed gravity value and the theoretical normal gravity value caused by the uneven density distribution of underground rock and ore bodies is called gravity anomaly. By qualitatively or quantitatively interpreting the gravity anomaly, the geological body structure and the distribution of rock and ore bodies in the target area can be inferred.

[0003] In related technologies, the method for extracting gravity anomaly includes: performing terrain correction and curvature flattening processing on the Bouguer gravity anomaly of a target area to obtain a first gravity anomaly; performing constant-density gravity stripping processing on the first gravity anomaly to obtain a second gravity anomaly, in which the density of the multiple layers between the stratum where the target geological body is located and the surface is a constant; determining a first gravity regional field of the target area; and determining the difference between the second gravity anomaly and the first gravity regional field as the gravity anomaly of the target geological body.

[0004] In a complex area, the accuracy of the gravity anomaly of the target geological body extracted by the above method is low, and may result in incorrect geological interpretation. SUMMARY

[0005] Embodiments of the present disclosure provide a method and device for extracting gravity anomaly, equipment and a storage medium, which can improve the accuracy of the extracted gravity anomaly of the target geological body. The technical solution is as follows:

[0006] In a first aspect, a method for extracting gravity anomaly is provided, which includes: performing terrain correction and curvature flattening processing on the Bouguer gravity anomaly of a target area to obtain a first gravity anomaly; performing constant-density gravity stripping processing on the first gravity anomaly to obtain a second gravity anomaly, in which the density of the multiple layers between the stratum where the target geological body is located and the surface is a constant; determining a stratum along-layer lateral density distribution model of the target area according to well logging data and electrical exploration data of the target area, in which the density of the multiple layers between the stratum where the target geological body is located and the surface varies in the stratum along-layer lateral direction; performing variable-density gravity stripping processing on the second gravity anomaly according to the stratum along-layer lateral density distribution model to obtain a third gravity anomaly; determining a first gravity regional field of the target area; and extracting the gravity anomaly of the target geological body according to the third gravity anomaly and the first gravity regional field.

[0007] Optionally, the stratum variable density gravity stripping processing on the second gravity anomaly according to the stratum along-layer transverse density distribution model to obtain a third gravity anomaly comprises: calculating a density difference between an upper interface and a lower interface of each stratum according to the stratum along-layer transverse density distribution model; calculating a variable density gravity stripping value of each stratum according to the density difference; and taking a difference value between the second gravity anomaly and the variable density gravity stripping value of the multi-layer stratum as the third gravity anomaly.

[0008] Optionally, the extracting the gravity anomaly of the target geologic body according to the third gravity anomaly and the first gravity regional field comprises: performing humidity gravity correction on the third gravity anomaly to obtain a fourth gravity anomaly; and determining a difference value between the fourth gravity anomaly and the first gravity regional field as the gravity anomaly of the target geologic body.

[0009] Optionally, the performing humidity gravity correction on the third gravity anomaly to obtain a fourth gravity anomaly comprises: determining a water table according to resistivity data of the target region; calculating a humidity gravity correction value according to a density difference between an upper stratum and a lower stratum of the water table; and taking a difference value between the third gravity anomaly and the humidity gravity correction value as the fourth gravity anomaly.

[0010] Optionally, the determining the first gravity regional field of the target region comprises: determining a magnetic force anomaly of the target geologic body; determining a plurality of interpolation cutting radii of the target region; calculating a second gravity regional field corresponding to each interpolation cutting radius; determining a target interpolation cutting radius from the plurality of interpolation cutting radii according to similarity between the second gravity regional field and the magnetic force anomaly, the second gravity regional field corresponding to the target interpolation cutting radius having the maximum similarity with the target magnetic force anomaly; and determining the second gravity regional field corresponding to the target interpolation cutting radius as the first gravity regional field of the target region.

[0011] In a second aspect, the application provides a device for extracting gravity anomaly, which comprises: a terrain correction and flattening processing module, configured to perform terrain correction and flattening processing on Bouguer gravity anomaly of a target area to obtain first gravity anomaly; a constant-density gravity stripping processing module, configured to perform constant-density gravity stripping processing on the first gravity anomaly to obtain second gravity anomaly, wherein in the constant-density gravity stripping processing, the densities of multiple layers between the stratum where a target geological body is located and the surface are constant; a first determination module, configured to determine a stratum along-layer lateral density distribution model of the target area according to well logging data and electrical prospecting data of the target area, wherein in the stratum along-layer lateral density distribution model, the densities of multiple layers between the stratum where the target geological body is located and the surface vary laterally along the layer; a variable-density gravity stripping processing module, configured to perform variable-density gravity stripping processing on the second gravity anomaly according to the stratum along-layer lateral density distribution model to obtain third gravity anomaly; a second determination module, configured to determine a first gravity regional field of the target area; and a gravity anomaly extraction module, configured to extract gravity anomaly of the target geological body according to the third gravity anomaly and the first gravity regional field.

[0012] Optionally, the variable-density gravity stripping processing module is configured to calculate a density difference between an upper interface and a lower interface of each of the strata according to the stratum along-layer lateral density distribution model; calculate a variable-density gravity stripping value of each of the strata according to the density difference; and take a difference between the second gravity anomaly and the variable-density gravity stripping value of the multiple layers as the third gravity anomaly.

[0013] Optionally, the gravity anomaly extraction module is configured to perform humidity gravity correction on the third gravity anomaly to obtain fourth gravity anomaly; and determine a difference between the fourth gravity anomaly and the first gravity regional field as the gravity anomaly of the target geological body.

[0014] Optionally, the gravity anomaly extraction module is configured to determine a water table according to resistivity data of the target area; calculate a humidity gravity correction value according to a density difference between an upper stratum and a lower stratum of the water table; and take a difference between the third gravity anomaly and the humidity gravity correction value as the fourth gravity anomaly.

[0015] Optionally, the second determining module is configured to determine the magnetic anomaly of the target geologic body; determine a plurality of interpolation cutting radii of the target region; calculate a second regional gravity field corresponding to each of the interpolation cutting radii; determine a target interpolation cutting radius from the plurality of interpolation cutting radii according to similarity between the second regional gravity field corresponding to the target interpolation cutting radius and the target magnetic anomaly, the second regional gravity field corresponding to the target interpolation cutting radius having the maximum similarity with the target magnetic anomaly; and determine the second regional gravity field corresponding to the target interpolation cutting radius as the first regional gravity field of the target region.

[0016] In a third aspect, a computer device is provided, including: a processor; a memory for storing processor-executable instructions; and wherein the processor is configured to execute the method of the first aspect.

[0017] In a fourth aspect, a computer readable medium is provided, when instructions in the computer readable medium are executed by a processor of a computer device, the computer device is enabled to execute the method of the first aspect.

[0018] In a fifth aspect, a computer program product is provided, including computer programs / instructions, and wherein the computer programs / instructions, when executed by a processor, implement the method of the first aspect.

[0019] The technical scheme provided by the embodiments of the present disclosure has the following beneficial effects:

[0020] In the embodiments of the present disclosure, the Bouguer gravity anomaly of the target region is terrain-corrected and curved-processed to obtain a first gravity anomaly; the first gravity anomaly is processed by constant-density gravity stripping to obtain a second gravity anomaly, and in the constant-density gravity stripping, the densities of the multiple layers between the stratum where the target geologic body is located and the surface are constant; the stratum along layer lateral density distribution model of the target region is determined according to the well logging data and the electrical exploration data of the target region; the second gravity anomaly is processed by variable-density gravity stripping according to the stratum along layer lateral density distribution model to obtain a third gravity anomaly; and the gravity anomaly of the target geologic body is extracted according to the third gravity anomaly and the first regional gravity field. Since the densities of the multiple layers between the stratum where the target geologic body is located and the surface are variable in the lateral direction in the stratum along layer lateral density distribution model, the second gravity anomaly is processed by variable-density gravity stripping according to the stratum along layer lateral density distribution model, which can eliminate the influence of the variable density in the lateral direction of the stratum on the gravity anomaly of the target geologic body, thereby improving the accuracy of the extracted target gravity anomaly. BRIEF DESCRIPTION OF DRAWINGS

[0021] In order to more clearly illustrate the technical solutions in the embodiments of the present disclosure, the drawings needed to be used in the embodiments description will be briefly introduced. Obviously, the drawings in the following description are only some embodiments of the present disclosure, and other drawings can be obtained by those skilled in the art without creative effort based on these drawings.

[0022] Figure 1 is a flowchart of a gravity anomaly extraction method provided by an embodiment of the present disclosure;

[0023] Figure 2 is a flowchart of another gravity anomaly extraction method provided by an embodiment of the present disclosure;

[0024] Figure 3 is a schematic diagram of a Bouguer gravity anomaly map provided by an embodiment of the present disclosure;

[0025] Figure 4 is a distribution diagram of a target geologic body provided by an embodiment of the present disclosure;

[0026] Figure 5 is a schematic diagram of a gravity anomaly map of a target geologic body provided by an embodiment of the present disclosure;

[0027] Figure 6 is a schematic diagram of another gravity anomaly map of a target geologic body provided by an embodiment of the present disclosure;

[0028] Figure 7 is a structural block diagram of a gravity anomaly extraction device provided by an embodiment of the present disclosure;

[0029] Figure 8 is a structural block diagram of a computer device provided by an embodiment of the present disclosure. DETAILED DESCRIPTION

[0030] In order to make the objects, technical solutions and advantages of the present disclosure clearer, the embodiments of the present disclosure will be further described in detail below with reference to the drawings.

[0031] Figure 1 is a flowchart of a gravity anomaly extraction method provided by an embodiment of the present disclosure, which can be executed by a computer device. Referring to Figure 1 , the method comprises:

[0032] In step 101, the Bouguer gravity anomaly of a target region is terrain-corrected and curved-processed to obtain a first gravity anomaly.

[0033] The target region is a region to be studied.

[0034] The Bouguer gravity anomaly refers to the gravity anomaly obtained by subtracting the normal gravity value from the gravity data of the target area after latitude correction, height correction, constant-density intermediate layer correction and constant-density topographic correction. The gravity data of the target area is collected by a gravity meter or the like on the ground surface of the target area. The normal gravity value is calculated by a gravity formula on a horizontal ellipsoidal surface.

[0035] The topographic correction refers to the correction for eliminating the gravity anomaly caused by the density fluctuation of the ground surface.

[0036] The flattening processing refers to converting the gravity anomaly on the fluctuating topography to the gravity anomaly on the same plane.

[0037] In step 102, the first gravity anomaly is subjected to constant-density gravity stripping processing to obtain a second gravity anomaly. In the constant-density gravity stripping processing, the densities of the multiple layers between the stratum where the target geological body is located and the ground surface are constant.

[0038] The constant-density gravity stripping refers to stripping the constant-density gravity response of the multiple layers between the stratum where the target geological body is located and the ground surface.

[0039] In step 103, the along-stratum lateral density distribution model of the stratum of the target area is determined according to the well logging data and the electrical prospecting data of the target area.

[0040] In the along-stratum lateral density distribution model, the densities of the multiple layers between the stratum where the target geological body is located and the ground surface vary in the along-stratum lateral direction.

[0041] In step 104, the second gravity anomaly is subjected to variable-density gravity stripping processing according to the along-stratum lateral density distribution model to obtain a third gravity anomaly.

[0042] The variable density of the stratum in the lateral direction is mainly caused by the lithology change in the lateral direction of the stratum. The variable-density gravity stripping refers to stripping the variable-density gravity response of the multiple layers between the stratum where the target geological body is located and the ground surface.

[0043] In step 105, the first gravity regional field of the target area is determined.

[0044] The first gravity regional field refers to the gravity anomaly of the target area caused by the Moho interface between the crust and the upper mantle.

[0045] In step 106, the gravity anomaly of the target geological body is extracted according to the third gravity anomaly and the first gravity regional field.

[0046] The gravity anomaly of the target geologic body is used to reflect the influence of the residual mass of deep local geologic structure (or ore body). Since the first gravity regional field is also included in the third gravity anomaly, the first gravity regional field needs to be removed to separate the gravity anomaly of the target geologic body in the third gravity anomaly.

[0047] In the embodiments of the present disclosure, the Bouguer gravity anomaly of the target region is terrain-corrected and curved and flattened to obtain a first gravity anomaly; the first gravity anomaly is subjected to a constant-density gravity stripping processing to obtain a second gravity anomaly, in which the densities of the multiple layers between the stratum where the target geologic body is located and the surface are constants; the stratum along the layer lateral density distribution model of the target region is determined according to the well logging data and the electrical exploration data of the target region; the second gravity anomaly is subjected to a variable-density gravity stripping processing according to the stratum along the layer lateral density distribution model to obtain a third gravity anomaly; and the gravity anomaly of the target geologic body is extracted according to the third gravity anomaly and the first gravity regional field. Since the densities of the multiple layers between the stratum where the target geologic body is located and the surface are variable in the lateral direction in the stratum along the layer lateral density distribution model, the second gravity anomaly is subjected to the variable-density gravity stripping processing according to the stratum along the layer lateral density distribution model, which can eliminate the influence of the variable density in the lateral direction of the stratum on the gravity anomaly of the target geologic body, thereby improving the accuracy of the extracted target gravity anomaly.

[0048] Figure 2 FIG. 2 is a flowchart of another method for extracting a gravity anomaly provided by the embodiments of the present disclosure, which can be executed by a computer device. Referring to FIG. 2, Figure 2 The method includes the following steps.

[0049] In step 201, gravity data of a target region is acquired.

[0050] In some embodiments, the surface of the target region is provided with multiple measuring points, and the multiple measuring points are uniformly spaced. For example, the multiple measuring points are arranged in an array with a spacing of 1 meter. The gravity data of the multiple measuring points of the target region can be acquired by a gravity meter or the like.

[0051] In step 202, a Bouguer gravity anomaly of the target region is obtained according to the gravity data.

[0052] The related content of the Bouguer gravity anomaly is described above in step 101, and the detailed description is omitted here.

[0053] In step 203, the Bouguer gravity anomaly of the target region is terrain-corrected and curved and flattened to obtain a first gravity anomaly.

[0054] For example, step 203 includes the following steps.

[0055] First, terrain correction values of the target region are calculated according to surface density data of the target region.

[0056] The surface density data of the target area refers to the density of the exposed strata at multiple measuring points in the target area as measured in practice.

[0057] The terrain correction value for the target area can be calculated using formula (1), as follows:

[0058]

[0059] In formula (1), Δg represents the terrain correction value of the target area; G represents the gravitational constant, which is generally 6.67 × 10 N·m. 2 / kg2; Δσ represents the density difference between the surface density and the average surface density, where the surface density is the variation and the average surface density is the average value among the surface density data. For example, the average surface density is 2.30 g / cm³. 3 A coordinate system is established with the ground measuring point as the origin and the vertical direction downward as positive. x, y, and z represent the three-dimensional coordinates of the geological body to be calculated between the floating reference surface of the stratum where the surface is located and the surface.

[0060] The second step is to subtract the terrain correction value from the Bouguer gravity anomaly to obtain the terrain-corrected gravity anomaly.

[0061] The third step is to perform curvature-leveling processing on the gravity anomaly after terrain correction to obtain the first gravity anomaly.

[0062] For example, the gravity anomalies of each measuring point in the target area, after terrain correction, can be converted to the elevation level of the highest measuring point. Exemplarily, the method for curvature-to-level conversion can be an iterative method, etc.

[0063] In step 204, the first gravity anomaly is subjected to constant density gravity delamination to obtain the second gravity anomaly.

[0064] In constant-density gravity stripping, the densities of the multiple strata between the target geological body and the surface are all constant. In some embodiments, step 204 includes:

[0065] The first step is to determine the constant density difference between the upper and lower interfaces of each stratum between the strata where the target geological body is located and the surface.

[0066] For example, the average density data of each formation layer is taken as the constant density of each layer. Since the density of each formation layer is constant, the density difference between the upper and lower interfaces of each layer is also constant. The density data of each formation layer can be obtained through density logging.

[0067] The second step is to calculate the constant density gravity stripping value for each stratum based on the constant density difference.

[0068] Exemplarily, the formula (2) is used to perform the three-dimensional gravity forward calculation to obtain the constant-density gravity stripping value of each stratum, and the formula (2) is as follows:

[0069]

[0070] In the formula (2), Δg i represents the constant-density gravity stripping value of the i-th stratum in the multi-layer stratum between the stratum where the target geological body is located and the surface; Δσ i represents the constant-density difference between the upper interface and the lower interface of the i-th stratum; G represents the gravitational constant, and the value is generally 6.67×10 N·m2 / kg2; a coordinate system is established with the ground measuring point as the coordinate origin and the longitudinal downward as positive, and x, y and z represent the three-dimensional coordinates of the geological body to be calculated in the i-th stratum. A coordinate system is established with the ground measuring point as the coordinate origin and the longitudinal downward as positive. The coordinates of the i-th geological body to be calculated are (x, y, z).

[0071] In the third step, the difference between the first gravity anomaly and the constant-density gravity stripping value of the multi-layer stratum is taken as the second gravity anomaly.

[0072] In some examples, the second gravity anomaly is obtained by subtracting the constant-density gravity stripping value of each stratum from the first gravity anomaly. In other examples, the sum of the constant-density gravity stripping values of the multi-layer stratum between the stratum where the target geological body is located and the surface is calculated; the second gravity anomaly is obtained by subtracting the sum of the constant-density gravity stripping values of the multi-layer stratum from the first gravity anomaly. The constant-density gravity stripping value of each stratum is calculated by using the formula (2) in the second step.

[0073] In step 205, the stratum along-layer lateral density distribution model of the target region is determined according to the well logging data and the electrical exploration data of the target region.

[0074] The electrical exploration data includes the resistivity data of the target region. The resistivity distribution model of the target region can be determined according to the resistivity data of the target region. In the resistivity distribution model of the target region, the resistivity of the multi-layer stratum between the stratum where the target geological body is located and the surface changes in the along-layer lateral direction.

[0075] The well logging data includes the density data of the target region. According to the density data and the resistivity distribution model of the target region, the stratum along-layer lateral density distribution model of the target region can be obtained. In the stratum along-layer lateral density distribution model of the target region, the density of the multi-layer stratum between the stratum where the target geological body is located and the surface changes in the along-layer lateral direction.

[0076] In step 206, the second gravity anomaly is subjected to the variable-density gravity stripping processing according to the stratum along-layer lateral density distribution model to obtain the third gravity anomaly.

[0077] In some embodiments, step 206 comprises:

[0078] First, according to the density distribution model of the strata along the layer, the density difference between the upper and lower interfaces of each stratum is calculated.

[0079] Since the density data of each stratum is variable in the lateral direction, the density difference between the upper and lower interfaces of each stratum is also variable.

[0080] Second, according to the density difference, the variable density gravity stripping value of each stratum is calculated.

[0081] For example, formula (3) is used to calculate the three-dimensional gravity forward, and the variable gravity stripping value of each stratum is obtained, formula (3) is as follows:

[0082]

[0083] In formula (3), Δg i ' represents the variable density gravity stripping value of the i-th stratum among the multiple strata between the stratum where the target geological body is located and the surface; Δσ i ' represents the density difference between the upper and lower interfaces of the i-th stratum; G represents the gravitational constant; a coordinate system is established with the ground survey point as the coordinate origin and the vertical downward direction as positive, and x, y, z represent the three-dimensional coordinates of the geological body to be calculated in the i-th stratum.

[0084] Third, the difference between the second gravity anomaly and the variable density gravity stripping value of the multiple strata is taken as the third gravity anomaly.

[0085] In some examples, the third gravity anomaly is obtained by subtracting the variable density gravity stripping value of each stratum from the second gravity anomaly. In other examples, the sum of the variable density gravity stripping values of the multiple strata between the stratum where the target geological body is located and the surface is calculated; the third gravity anomaly is obtained by subtracting the sum of the variable density gravity stripping values of the multiple strata from the second gravity anomaly. The variable density gravity stripping value of each stratum is calculated using formula (3) of the second step.

[0086] Since the density of each stratum in the target area can be variable in the lateral direction, the variable density gravity stripping processing of the second gravity anomaly in step 205 can eliminate the influence of the variable density of the strata along the layer on the gravity anomaly of the target geological body, thereby improving the accuracy of the extracted gravity anomaly of the target geological body.

[0087] In step 207, the third gravity anomaly is subjected to humidity gravity correction to obtain the fourth gravity anomaly.

[0088] In some embodiments, step 207 comprises:

[0089] In a first step, the phreatic surface is determined according to the resistivity data of the target region.

[0090] Phreatic water refers to groundwater within a water-saturated layer, buried above a first stable aquifuge, and having a free water surface. The free surface of the phreatic water is referred to as the phreatic surface. The stratum above the phreatic surface does not contain water medium, the pores are filled with air, the stratum has poor conductivity, and the resistivity data has a relatively high value. The stratum below the phreatic surface contains water medium, the stratum has a certain conductivity, and the resistivity data has a relatively low value. According to the obvious difference in the value of the resistivity data of the target region, the phreatic surface of the target region can be determined. The resistivity data of the target region can be obtained by a relevant technical person through resistivity logging or electrical prospecting method.

[0091] In a second step, the humidity gravity correction value is calculated according to the density difference between the upper stratum and the lower stratum of the phreatic surface.

[0092] In the embodiments of the present disclosure, the humidity gravity correction value is calculated by using formula (3). For related content, refer to the foregoing step 206, and detailed description is omitted here.

[0093] In a third step, the difference between the third gravity anomaly and the humidity gravity correction value is taken as the fourth gravity anomaly.

[0094] The third gravity anomaly is subtracted by the humidity gravity correction value to obtain the fourth gravity anomaly.

[0095] Due to the difference in humidity of the underground stratum, the density of the underground stratum also has a difference, which affects the gravity anomaly of the target geological body. The humidity gravity correction is performed on the third gravity anomaly, which can eliminate the influence of the humidity change of the stratum on the gravity anomaly of the target geological body, thereby improving the accuracy of the extracted gravity anomaly of the target geological body.

[0096] In step 208, the first gravity regional field of the target region is determined.

[0097] In the embodiments of the present disclosure, the interpolation cutting method is used to determine the first gravity regional field of the target region. The basic principle of determining the gravity regional field by using the interpolation cutting method is that a cutting operator repeatedly acts on the field value of the measuring point, and the iterative cutting is performed until the value converges to a stable value, so that the gravity regional field is obtained. In some embodiments, step 207 includes:

[0098] In a first step, the magnetic force anomaly of the target geological body is determined.

[0099] In some embodiments, the method for determining the magnetic anomaly of the target geologic body comprises: obtaining the reduced-to-pole magnetic anomaly of the target region by reducing-to-pole processing the magnetic data of the target region collected by a magnetic instrument or the like at the surface of the target region; obtaining the magnetic regional field by upward continuation of the magnetic data collected at the surface of the target region by selecting a target upward continuation height; and obtaining the magnetic anomaly of the target geologic body by subtracting the magnetic regional field from the reduced-to-pole magnetic anomaly.

[0100] The method for determining the magnetic anomaly of the target geologic body in the embodiments of the present disclosure is not specifically limited, and other methods can also be used to obtain the magnetic anomaly of the target geologic body.

[0101] Secondly, a plurality of interpolation cutting radii of the target region are determined.

[0102] The plurality of interpolation cutting radii are not all the same. For example, the plurality of interpolation cutting radii are determined by a skilled person according to actual needs.

[0103] Thirdly, the second gravity regional field corresponding to each interpolation cutting radius is calculated.

[0104] The gravity data of the plurality of measuring points of the target region obtained in step 201 is subjected to gridding processing, and the gridding gravity data of all grid nodes of the target region can be obtained. For example, the gridding processing of the gravity data means that each grid node is assigned with the gravity data of a measuring point. The position coordinates of each grid node only include the row coordinates and the longitudinal coordinates of the grid node. The position coordinates of each grid node represent the position coordinates of the corresponding measuring point.

[0105] In some examples, the second gravity regional field corresponding to each interpolation cutting radius is calculated by using formula (4) as follows:

[0106] R(i,j)=[1-a(i,j) / 2]*B(i,j)+[a(i,j) / 2]*G(i,j) (4)

[0107] In formula (4), (i,j) represents the row coordinates and the column coordinates of a measuring point in the gridding gravity data; R(i,j) represents the second gravity regional field; a(i,j) represents the weighting coefficient; G(i,j) represents the gravity data of the measuring point (i,j); and B(i,j) represents the average value of the gravity data of the four measuring points around the measuring point (i,j), which is calculated by using formula (5) as follows:

[0108] B(i,j)=0.25*[G(i+r,j)+G(i-r,j)+G(i,j+r)+G(i,j-r)] (5)

[0109] In formula (5), G(i+r, j), G(i-r, j), G(i, j+r) and G(i, j-r) represent gravity data of four measuring points around the measuring point (i, j), and r represents the cutting radius, which is an integer multiple of the distance between the measuring points.

[0110] In a fourth step, the target interpolation cutting radius is determined from the plurality of interpolation cutting radii according to the similarity between the second gravity regional field and the target magnetic anomaly.

[0111] The target interpolation cutting radius is one of the plurality of interpolation cutting radii, and the second gravity regional field corresponding to the target interpolation cutting radius has the maximum similarity with the target magnetic anomaly.

[0112] In some embodiments, a magnetic anomaly map of the target geological body can be generated according to the magnetic anomaly of the target geological body. A second gravity regional field map of each interpolation cutting radius can be generated according to the second gravity regional field corresponding to each interpolation cutting radius. Since the magnetic anomaly of the target geological body can reflect the shape and distribution of the target geological body, and the gravity anomaly of the target geological body can be obtained by subtracting the gravity regional field of the target region from the fourth gravity anomaly, the magnetic anomaly of the target geological body has certain similarity with the gravity regional field of the target region, for example, the trend of the magnetic contour line in the magnetic anomaly map of the target geological body is consistent with the trend of the gravity contour line in the gravity regional field map. Therefore, the similarity between the second gravity regional field and the target magnetic anomaly can be determined by comparing the consistency of the trend of the magnetic contour line in the magnetic anomaly map of the target geological body and the trend of the gravity contour line in the second gravity regional field map. The interpolation cutting radius corresponding to the second gravity regional field with the closest trend of the magnetic contour line in the magnetic anomaly map of the target geological body is taken as the target interpolation cutting radius.

[0113] In a fifth step, the second gravity regional field corresponding to the target interpolation cutting radius is determined as the first gravity regional field of the target region.

[0114] Since the magnetic anomaly of the target geological body can accurately reflect the shape and distribution of the target geological body, the first gravity regional field determined according to the similarity between the second gravity regional field corresponding to the plurality of interpolation cutting radii and the target magnetic anomaly is closer to the actual gravity regional field of the target region, and thus the accuracy of the extracted gravity anomaly of the target geological body can be improved.

[0115] In step 209, the difference between the fourth gravity anomaly and the first gravity regional field is determined as the gravity anomaly of the target geological body.

[0116] The fourth gravity anomaly minus the first gravity regional field gives the gravity anomaly of the target geological body.

[0117] It should be noted that step 206 or step 207 is an optional step. In some embodiments, step 206 can not be performed, and the second gravity anomaly is directly subjected to the humidity gravity correction to obtain a fourth gravity anomaly; and the difference between the fourth gravity anomaly and the first gravity regional field is determined as the gravity anomaly of the target geological body. In some other embodiments, step 207 can not be performed, and the difference between the third gravity anomaly and the first gravity regional field is determined as the gravity anomaly of the target geological body.

[0118] In addition, the execution order of step 207 is not limited in the embodiments of the present disclosure, and step 207 can be performed first, and then step 206 is performed.

[0119] In order to verify the effect of the gravity anomaly extraction method provided in the embodiments of the present disclosure, the shape and distribution characteristics of the target geological body in the target region can be analyzed according to the drilling data in advance in the embodiments of the present disclosure. Then, the drilling data analysis result of the target region is compared with the gravity anomaly map of the target geological body obtained by using the gravity anomaly extraction method provided by the related art and the gravity anomaly map of the target geological body obtained by using the gravity anomaly extraction method provided in the embodiments of the present disclosure, to verify the effect of the gravity anomaly extraction method in the embodiments of the present disclosure.

[0120] Figure 3 is a distribution sketch of a target geological body provided in the embodiments of the present disclosure, as shown in Figure 3 According to the drilling data of the target region, it is analyzed that there are two small-area target geological bodies in the deep layer of the target region (the region shown by reference numeral 1 in the figure).

[0121] Figure 4 is a schematic sketch of a Bouguer gravity anomaly map provided in the embodiments of the present disclosure, as shown in Figure 4 The region shown by reference numeral 2 in the figure represents the corresponding Bouguer gravity anomaly of the deep target geological body. It can be known by comparison that, Figure 4 the region 2 in Figure 3 is inconsistent with the region 1 in

[0122] Figure 5 is a schematic sketch of a gravity anomaly map of a target geological body provided in the embodiments of the present disclosure, which is obtained by using the gravity anomaly extraction method in the related art. As shown in Figure 5 The region shown by reference numeral 3 in the figure represents the gravity anomaly of the deep target geological body of the target region. The area of the region 3 is large, and is greatly different from the shape and distribution of the target geological body in Figure 3 , and there is a false and wrong distribution.

[0123] Figure 6is another gravity anomaly map of a target geologic body provided by an embodiment of the present disclosure, which is obtained by the method for extracting a gravity anomaly in the embodiment of the present disclosure. As shown in Figure 6 , the area shown by reference numeral 4 in the figure represents the gravity anomaly of the deep target geologic body of the target area. Figure 6 The area 4 in Figure 3 is basically consistent with the shape and distribution of the target geologic body in Figure 3 , and is closer to the actual distribution of the deep target geologic body. Therefore, the method in the embodiment of the present disclosure is better than the related art.

[0124] In the embodiment of the present disclosure, the Bouguer gravity anomaly of the target area is subjected to terrain correction and curvature flattening processing to obtain a first gravity anomaly; the first gravity anomaly is subjected to constant-density gravity stripping to obtain a second gravity anomaly; the second gravity anomaly is subjected to variable-density gravity stripping according to a stratum rock layer lateral density distribution model to obtain a third gravity anomaly; the third gravity anomaly is subjected to humidity gravity correction to obtain a fourth gravity anomaly; and the difference between the fourth gravity anomaly and the gravity regional field of the target area is taken as the gravity anomaly of the target geologic body. The variable-density gravity stripping of the second gravity anomaly can eliminate the influence of the variable density in the lateral direction of the stratum on the gravity anomaly of the target geologic body; the humidity gravity correction of the third gravity anomaly can eliminate the influence of the humidity change of the stratum on the gravity anomaly of the target geologic body, thereby improving the accuracy of the extracted gravity anomaly of the target geologic body.

[0125] It should be noted that for a complex area, for example, an area with large terrain undulations, fast surface lithology changes (complex surface), an area with steep stratum dip angle and developed tectonic faults (complex underground structure), seismic exploration is difficult, and it is difficult to obtain three-dimensional seismic velocity converted three-dimensional density data. Therefore, the conventional three-dimensional density gravity stripping technique is difficult to apply to the extraction of the gravity anomaly of the complex area. The method for extracting a gravity anomaly provided in the embodiment of the present disclosure can realize variable-density gravity stripping according to limited well logging data and electrical exploration data of the complex area. Therefore, the method for extracting a gravity anomaly provided in the embodiment of the present disclosure is applicable to the extraction of the gravity anomaly of the complex area.

[0126] Optionally, the method for extracting a gravity anomaly provided in the embodiment of the present disclosure can also be applicable to a non-complex area.

[0127] Figure 7 is a structural block diagram of a device 700 for extracting a gravity anomaly provided by an embodiment of the present disclosure. As shown in Figure 7 , the device includes a terrain correction and curvature flattening processing module 701, a constant-density gravity stripping processing module 702, a first determination module 703, a variable-density gravity stripping processing module 704, a second determination module 705, and a gravity anomaly extraction module 706.

[0128] The terrain correction and flattening module 701 is configured to perform terrain correction and flattening processing on the Bouguer gravity anomaly of the target region to obtain a first gravity anomaly. The constant-density gravity stripping processing module 702 is configured to perform constant-density gravity stripping processing on the first gravity anomaly to obtain a second gravity anomaly. In the constant-density gravity stripping processing, the densities of the multiple layers between the stratum where the target geological body is located and the surface are constant. The first determination module 703 is configured to determine a stratum along layer lateral density distribution model of the target region according to well logging data and electrical prospecting data of the target region. In the stratum along layer lateral density distribution model, the densities of the multiple layers between the stratum where the target geological body is located and the surface vary laterally along the stratum. The variable-density gravity stripping processing module 704 is configured to perform variable-density gravity stripping processing on the second gravity anomaly according to the stratum along layer lateral density distribution model to obtain a third gravity anomaly. The second determination module 705 is configured to determine a first gravity regional field of the target region. The gravity anomaly extraction module 706 is configured to extract a gravity anomaly of the target geological body according to the third gravity anomaly and the first gravity regional field.

[0129] Optionally, the variable-density gravity stripping processing module 704 is configured to calculate a density difference between an upper interface and a lower interface of each of the strata according to the stratum along layer lateral density distribution model, calculate a variable-density gravity stripping value of each of the strata according to the density difference, and take a difference between the second gravity anomaly and the variable-density gravity stripping value of the multiple layers as the third gravity anomaly.

[0130] Optionally, the gravity anomaly extraction module 706 is configured to perform humidity gravity correction on the third gravity anomaly to obtain a fourth gravity anomaly, and determine a difference between the fourth gravity anomaly and the first gravity regional field as the gravity anomaly of the target geological body.

[0131] Optionally, the gravity anomaly extraction module 706 is configured to determine a water table according to resistivity data of the target region, calculate a humidity gravity correction value according to a density difference between an upper stratum and a lower stratum of the water table, and take a difference between the third gravity anomaly and the humidity gravity correction value as the fourth gravity anomaly.

[0132] Optionally, the second determination module 705 is configured to determine the magnetic anomaly of the target geologic body; determine a plurality of interpolation cut radii of the target region; calculate a second regional gravity field corresponding to each interpolation cut radius; determine a target interpolation cut radius from the plurality of interpolation cut radii according to the similarity between the second regional gravity field and the magnetic anomaly, the second regional gravity field corresponding to the target interpolation cut radius having the maximum similarity with the target magnetic anomaly; and determine the second regional gravity field corresponding to the target interpolation cut radius as the first regional gravity field of the target region.

[0133] It should be noted that the gravity anomaly extraction device 700 provided by the above embodiments is only used as an example for dividing the above functions, and in actual applications, the above functions can be completed by different functional modules according to needs, that is, the internal structure of the device is divided into different functional modules to complete all or part of the above described functions. In addition, the gravity anomaly extraction device 700 and the gravity anomaly extraction method provided by the above embodiments belong to the same concept, and the specific implementation process is described in detail in the method embodiments, which will not be repeated here.

[0134] Figure 8 is a structural block diagram of a computer device provided by the embodiments of the present disclosure. As shown in Figure 8 the computer device 800 includes a processor 801 and a memory 802.

[0135] The processor 801 can include one or more processing cores, such as an 8-core processor, an 8-core processor, etc. The processor 801 can be implemented in at least one of the hardware forms of a DSP (Digital Signal Processing), a FPGA (Field-Programmable Gate Array), and a PLA (Programmable Logic Array). The processor 801 can also include a main processor and a coprocessor, the main processor being a processor for processing data in an awake state, also known as a CPU (Central Processing Unit), and the coprocessor being a low-power processor for processing data in a standby state. In some embodiments, the processor 801 can be integrated with a GPU (Graphics Processing Unit), which is responsible for rendering and drawing the content required to be displayed by the display screen. In some embodiments, the processor 801 can also include an AI (Artificial Intelligence) processor, which is used to process machine learning-related computing operations.

[0136] The memory 802 can include one or more computer-readable media, which can be non-transitory. The memory 802 can also include high-speed random access memory and nonvolatile, computer-readable media such as one or more magnetic disk storage devices, optical storage devices, flash memory devices, etc. In some embodiments, the non-transitory computer-readable media of the memory 802 is used for storing at least one instruction for being executed by the processor 801 to implement the method for extracting gravity anomaly provided in the embodiments of the present disclosure.

[0137] Those skilled in the art can understand that, Figure 8 The structure shown in the figure does not constitute a limitation on the computer device 800, and can include more or fewer components than shown, or combine certain components, or adopt a different arrangement of components.

[0138] The embodiments of the present disclosure also provide a non-transitory computer-readable medium, when the instructions in the medium are executed by the processor of the computer device 800, the computer device 800 can execute the method for extracting gravity anomaly provided in the embodiments of the present disclosure.

[0139] A computer program product includes computer programs / instructions, which, when executed by a processor, implement the method for extracting gravity anomaly provided in the embodiments of the present disclosure.

[0140] The above is only an optional embodiment of the present disclosure, and does not limit the present disclosure. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present disclosure shall be included in the protection scope of the present disclosure.

Claims

1. A method for extracting gravity anomalies, characterized in that, The method includes: The Bouguer gravity anomaly in the target area is corrected for topography and flattened to obtain the first gravity anomaly; The first gravity anomaly is subjected to constant density gravity stripping treatment to obtain the second gravity anomaly. In the constant density gravity stripping treatment, the density of the multiple strata between the strata where the target geological body is located and the surface is constant. Based on well logging data and electrical exploration data of the target area, a lateral density distribution model of the strata along the strata in the target area is determined. In the lateral density distribution model of the strata along the strata, the density of the multiple strata between the strata where the target geological body is located and the surface varies in the lateral direction along the strata. Based on the lateral density distribution model along the strata, the second gravity anomaly is subjected to variable density gravity stripping to obtain the third gravity anomaly. Determine the first gravity field of the target region; The water table is determined based on the resistivity data of the target area; The humidity gravity correction value is calculated based on the density difference between the upper and lower strata of the water table. The difference between the third gravity anomaly and the humidity gravity correction value is taken as the fourth gravity anomaly; The difference between the fourth gravity anomaly and the first gravity region field is determined as the gravity anomaly of the target geological body.

2. The method according to claim 1, characterized in that, The process of performing stratigraphic variable density gravity stripping processing on the second gravity anomaly based on the stratigraphic lateral density distribution model to obtain the third gravity anomaly includes: Based on the lateral density distribution model along the strata, the density difference between the upper and lower interfaces of each stratum is calculated. Based on the density difference, the variable density gravity stripping value for each of the strata is calculated; The difference between the second gravity anomaly and the variable density gravity stripping value of the multi-layered strata is taken as the third gravity anomaly.

3. The method according to any one of claims 1 to 2, characterized in that, The determination of the first gravity region field of the target region includes: Identify the magnetic anomaly of the target geological body; Determine multiple interpolation cut radii for the target region; Calculate the second gravity region field corresponding to each interpolation cutting radius; Based on the similarity between the second gravity region field and the magnetic anomaly, a target interpolation cutting radius is determined from the plurality of interpolation cutting radii, wherein the second gravity region field corresponding to the target interpolation cutting radius has the greatest similarity to the magnetic anomaly; The second gravity region field corresponding to the target interpolation cutting radius is determined as the first gravity region field of the target region.

4. A device for extracting gravity anomalies, characterized in that, The device includes: The terrain correction and curvature leveling module is used to perform terrain correction and curvature leveling on the Bouguer gravity anomaly in the target area to obtain the first gravity anomaly. A constant density gravity stripping processing module is used to perform constant density gravity stripping processing on the first gravity anomaly to obtain a second gravity anomaly. In the constant density gravity stripping processing, the density of the multiple strata between the strata where the target geological body is located and the surface is constant. The first determining module is used to determine the lateral density distribution model of the strata along the layers in the target area based on the well logging data and electrical exploration data of the target area. In the lateral density distribution model of the strata along the layers, the density of the multiple strata between the strata where the target geological body is located and the surface varies laterally along the layers. The variable density gravity stripping module is used to perform variable density gravity stripping on the second gravity anomaly according to the lateral density distribution model along the strata to obtain the third gravity anomaly. The second determining module is used to determine the first gravity region field of the target region; The gravity anomaly extraction module is used to determine the water table based on the resistivity data of the target area; calculate the humidity gravity correction value based on the density difference between the upper and lower strata of the water table; take the difference between the third gravity anomaly and the humidity gravity correction value as the fourth gravity anomaly; and determine the difference between the fourth gravity anomaly and the first gravity area field as the gravity anomaly of the target geological body.

5. The apparatus according to claim 4, characterized in that, The variable density gravity stripping module is used to calculate the density difference between the upper and lower interfaces of each stratum according to the lateral density distribution model along the stratum; calculate the variable density gravity stripping value of each stratum according to the density difference; and take the difference between the second gravity anomaly and the variable density gravity stripping value of the multi-layer strata as the third gravity anomaly.

6. A computer device, characterized in that, include: processor; Memory used to store processor-executable instructions; The processor is configured to perform the method as described in any one of claims 1 to 3.

7. A computer-readable medium, characterized in that, When the instructions in the computer-readable medium are executed by the processor of a computer device, the computer device is enabled to perform the method as described in any one of claims 1 to 3.

8. A computer program product comprising a computer program / instructions, characterized in that, When the computer program / instructions are executed by the processor, they implement the method described in any one of claims 1 to 3.

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