Time-depth conversion method and device for hidden structure of low-exploration-degree foreland thrust zone

Abstract

The invention provides a time-depth conversion method and device for a hidden structure of a low-exploration-degree foreland thrust zone, and belongs to the technical field of geological exploration. The method comprises the steps of obtaining speed change characteristics of a research area; establishing a geologic structure model by using the seismic interpretation horizon and fault data of the time domain; converting the geologic structure model into an interval velocity model through an interval control breaking block velocity assignment method; establishing virtual well control points in the research area, and extracting an interval velocity curve at each virtual well control point from the interval velocity model; converting the interval velocity curve at the virtual well control point into an average velocity curve; constructing a three-dimensional average velocity body by using a layer control breaking block virtual well control point spatial interpolation method; and performing time-depth conversion on the target layer. The variable-speed mapping is performed based on the time-depth conversion method realized by the invention, and through the obtained depth domain structure map, the identification of the hidden structure of the low-exploration-degree foreland thrust zone can be realized, and reliable depth data is provided for fine description of entrapment.

Description

Technical Field

[0001] The present invention belongs to the technical field of geological exploration, and in particular relates to a time-depth conversion method and device for concealed structures in a foreland thrust belt with a low degree of exploration. Background Art

[0002] Foreland basins are widely distributed around the world. 52% of the relevant oil and gas reserves discovered in the past decade are in foreland basins. Currently, 182 large oil and gas fields have been discovered in 21 foreland basins in the world, revealing the huge exploration potential of foreland basins. For example, the Zagros foreland thrust belt and the Kuqa foreland thrust belt are rich in oil and gas resources and are hot areas for oil and gas exploration.

[0003] As foreland basin exploration continues to advance, the targets it faces are becoming increasingly complex, with exploration gradually shifting towards foreland thrust belts, characterized by multi-stage thrusts and more complex structures. Foreland thrust belts are characterized by dramatic surface topography, complex subsurface structures, large variations in lithology and thickness, dramatic lateral velocity variations, and strong heterogeneity. These characteristics result in low seismic imaging accuracy, making reconstruction of the underlying structures difficult, and severely hindering the identification of traps within foreland thrust belts. Velocity modeling and structural reconstruction are pressing challenges in exploration in this area.

[0004] For the structural identification and reconstruction of the foreland basin thrust belt, different methods are adopted according to the different exploration levels of the region. For areas with medium or higher exploration levels with relatively new seismic data, a method of enhancing the seismic imaging accuracy of pre-stack seismic data can be used to achieve a detailed description of the structure, that is, pre-stack depth migration processing is performed through detailed velocity modeling to confirm the structural characteristics. For areas with low exploration levels, there are usually only a few or no wells in the area, the quality of seismic data is relatively poor, the seismic data is collected at an old age, and it is difficult to improve the imaging quality through migration imaging due to the influence of the basic acquisition parameters, and thus it is difficult to achieve detailed confirmation of the structure. Therefore, for the exploration of complex structural areas with low exploration levels, a feasible method to achieve detailed confirmation of the structure is to perform detailed time-depth conversion based on post-stack seismic data.

[0005] For the time-depth conversion of seismic data, the commonly used methods are mainly the following: 1). Velocity fitting method, that is, the time-depth relationship obtained through well synthetic recording or the time-depth fitting formula (time-depth fitting formula) established by using time-depth data, and the time-depth fitting formula is used for time-depth conversion. For example, a public document entitled "Segmented Optimization Fitting of Time-Depth Conversion Relationship of Deep Strata in the East China Sea" applies this method to the time-depth conversion of the strata in a certain study area in the deep East China Sea, which significantly improves the accuracy of time-depth conversion of deep strata. However, this method is only suitable for relatively flat structures and with a relatively high velocity lateral change ratio. Smaller areas; 2). VSP data time-depth conversion method, that is, using vertical seismic profile VSP velocity to perform time-depth conversion. This method has high velocity conversion accuracy for well points and is suitable for relatively flat structures. When the structure has certain undulations, the conversion error is large; 3). Multi-well intra-differential velocity field time-depth conversion method, that is, through the time-depth curves of the wells drilled in the study area, spatial interpolation is performed under the constraints of the seismic interpretation layer grid to obtain the multi-well intra-differential velocity field and then perform time-depth conversion. This method is suitable for situations where the wells are relatively evenly distributed and the structure is simple in the study area. It is suitable for the longitudinal direction of the well points. The conversion accuracy is high, but the lateral conversion accuracy is greatly affected by the planar distribution of the well points; 4). The time-depth conversion method of the seismic wave velocity field uses the stacked velocity spectrum and the interpreted horizon to reconstruct the average velocity body, that is, the stacked velocity is converted into the root mean square velocity through the dip correction, and then converted into the layer velocity by the Dix formula. The new average velocity body is then directly obtained from the layer velocity for time-depth conversion. This method is suitable for situations where the structural fluctuation is not large and the velocity spectrum quality is good. However, when the structural fluctuation is large and the velocity changes rapidly laterally, the conversion error of this method is large; 5). Well seismic approx. The time-depth conversion method uses the interpretation of the horizons and faults in the study area as geological constraints, and uses the stacking velocity and drilling velocity obtained from seismic processing to establish a velocity model under the constraints of the geological framework to perform time-depth conversion. For example, Zhang Lu et al. applied the well-seismic constraint method to perform time-depth conversion on the top surface of the third section of the Zhuhai Formation in the Wenchang 10-X structural belt, achieving a high conversion accuracy. This method is suitable for situations where the lateral velocity changes are not drastic, the velocity spectrum quality is good, and there are a certain number of drilled wells. However, when the lateral velocity changes drastically in the study area and there are few drilling data, this method has a certain conversion error.

[0006] In general, existing time-to-depth conversion methods are mainly targeted at study areas with a certain degree of exploration and mild lateral velocity variations. Using a certain number of wells or relatively high-quality velocity spectrum data within the study area, time-to-depth conversion is performed through time-to-depth fitting, inter-well velocity interpolation, velocity spectrum interpolation, or well-seismic constrained velocity modeling. However, for complex tectonic areas such as foreland basin thrust belts with drastic lateral velocity variations and low exploration levels, velocity spectrum data are unavailable due to low quality and few wells are drilled. Currently, there is no time-to-depth conversion method suitable for such areas. Therefore, there is an urgent need to find a high-precision time-to-depth conversion and variable velocity mapping method suitable for complex tectonic areas with low exploration levels to achieve a detailed description of structural features. Summary of the Invention

[0007] For complex structural areas such as foreland basin thrust belts, which are subject to drastic lateral velocity variations, low exploration level, no available velocity spectrum data, and few drilling wells, the present invention proposes a time-depth conversion method and device for hidden structures in low-exploration foreland thrust belts to overcome the technical problems of large time-depth conversion errors and difficulty in implementing structural refinement when existing time-depth conversion methods are applied to the aforementioned complex structural areas.

[0008] To achieve the above-mentioned object, a first aspect of an embodiment of the present invention provides a method for time-depth conversion of buried structures in a low-exploration foreland thrust belt, the method comprising:

[0009] The velocity variation characteristics of the study area were obtained through comprehensive analysis of geological data;

[0010] Based on the velocity variation characteristics, a geological structure model in the time domain is established using the seismic interpretation layer and fault data in the time domain;

[0011] Under the constraints of the geological structure model, the layer velocity of each fault block is calculated layer by layer, and the geological structure model is converted into a layer velocity model;

[0012] Establish virtual well control points in the study area and extract interval velocity curves at each virtual well control point from the interval velocity model;

[0013] Converting the interval velocity curve at the virtual well control point into an average velocity curve;

[0014] The average velocity curve of the virtual well control point is interpolated independently in different fault blocks under the layer control, and the average velocity of each layer in the geological structure model is calculated in turn to construct a three-dimensional average velocity body;

[0015] The three-dimensional average velocity body is used to perform time-depth conversion on the seismic data and seismic interpretation horizons of the target layer in the study area.

[0016] Optionally, the velocity variation characteristics of the study area obtained through comprehensive analysis of geological data specifically include:

[0017] According to the location of the basin tectonic belt in the study area, the tectonic background and tectonic deformation characteristics of the study area are determined;

[0018] Determining the stratigraphic distribution characteristics of the study area, the sedimentary background of the target layer, and the number of major stratigraphic layers based on a comprehensive analysis of the first acquired data, wherein the first acquired data includes well logging and core data;

[0019] The velocity variation characteristics of the study area are determined based on the tectonic background, tectonic deformation characteristics, stratigraphic distribution characteristics, sedimentary background of the target layer and the number of main strata.

[0020] Optionally, the method of establishing a geological structure model in the time domain based on velocity variation characteristics and utilizing seismic interpretation horizon and fault data in the time domain specifically includes:

[0021] Acquire 3D time-migrated seismic data;

[0022] Using synthetic records of wells drilled in the study area, time-depth calibration was performed on each set of strata in the study area to obtain the time-depth relationship of the drilled wells;

[0023] Guided by the geological characteristics of the study area, the seismic reflection events corresponding to the calibrated layer interfaces are used to track and interpret the seismic horizons and faults, and the seismic interpretation horizon and fault data of the study area are obtained;

[0024] Each seismic interpretation layer in the study area and the corresponding fault data of each layer are modeled in turn to obtain a geological structure model in the time domain.

[0025] Optionally, the layered calculation of the interval velocity of each fault block under the constraints of the geological structure model to convert the geological structure model into an interval velocity model specifically includes:

[0026] Perform low-pass filtering on the acquired acoustic velocity logging curve to obtain a low-frequency velocity curve;

[0027] Under the constraints of the geological structure model, the velocity assignment of the layer-controlled fault blocks is performed to obtain the velocity value of each layer segment, thereby realizing the conversion of the geological structure model to the layer velocity model;

[0028] The specific value assignment of the stratum-controlled fault block velocity is:

[0029] Under the control of the formation, for a certain fault block in a certain layer segment, at the selected drilled position, the velocity curve segment corresponding to the layer segment in the low-frequency velocity curve is obtained according to the established time-depth relationship. The velocity curve segment is proportionally assigned to the fault block in the layer segment, and so on, completing the velocity assignment of each fault block in each layer segment.

[0030] Optionally, under the control of the formation, for a certain fault block in a certain layer segment, at a selected drilled position, a velocity curve segment corresponding to the layer segment in the low-frequency velocity curve is obtained according to the established time-depth relationship, and the velocity curve segment is proportionally assigned to the fault block in the layer segment, and so on, to complete the velocity assignment of each fault block in each layer segment, specifically including:

[0031] Under the control of the formation, for L i’ L of the layer i’ -F j’ For a fault block, at the selected drilled well location, the velocity curve segment corresponding to the layer segment in the low-frequency velocity curve is obtained according to the established time-depth relationship;

[0032] Read L i’ The temporal thickness H0 between the top and bottom of the interval;

[0033] Read L i’ -F j’ The time thickness H of the CDP numbered n' at the fault block n’ ;

[0034] Starting from the top surface of the layer, the velocity values ​​of each sampling point in the layer are assigned one by one to each sampling point of the CDP numbered n';

[0035] Each sampling point in the interval is a longitudinal velocity sampling point at the selected drilled well position, and the sampling interval of each sampling point is m milliseconds;

[0036] The sampling interval of each sampling point of CDP numbered n' is H n’ *m / H0 milliseconds;

[0037] By analogy, for L i’ -F j’ Each CDP at the fault block is assigned a velocity value, thus completing the L i’ -F j’ Assignment of interval velocity to fault blocks;

[0038] In this way, the velocity assignment of each layer segment and each fault block is completed, thereby converting the geological structure model into a layer velocity model.

[0039] Optionally, establishing virtual well control points in the study area and extracting interval velocity curves at each virtual well control point from the interval velocity model specifically includes:

[0040] According to the plane distribution range of the geological structure model and the bin size of the seismic data, a series of virtual well control points are set in the study area according to the preset grid interval;

[0041] For each virtual well control point, find the CDP corresponding to the virtual well control point from the interval velocity model, and then read the velocity values ​​of each sampling point of the interval velocity model at the CDP in sequence. The sampling points are from the first sampling point at the top of the interval velocity model to the last sampling point at the bottom of the interval velocity model, and the sampling interval between the sampling points is an integer multiple of the seismic sampling interval;

[0042] All the read velocity values ​​are connected to form a curve, which is the interval velocity curve in the time domain at the control point of the virtual well.

[0043] Optionally, converting the interval velocity curve at the virtual well control point into an average velocity curve specifically includes:

[0044] Based on the conversion formula between the interval velocity curve and the average velocity curve, the interval velocity curve at the virtual well control point is converted into the average velocity curve;

[0045] The conversion formula is expressed as:

[0046]

[0047] Among them, Vi_well[k] is the velocity value corresponding to the kth sampling point in the interval velocity curve Vi_well at the virtual well control point, time[k] is the time value corresponding to the kth sampling point in the interval velocity curve Vi_well at the virtual well control point, time[k-1] is the time value corresponding to the k-1th sampling point in the interval velocity curve Vi_well at the virtual well control point, and time[j] is the time value corresponding to the jth sampling point in the interval velocity curve Vi_well at the virtual well control point; Va_well[j] is the average velocity value corresponding to the jth sampling point in the converted average velocity curve Va_well, Num is the total number of sampling points of the interval velocity curve at the virtual well control point, and Num = (Base-Top) / f+1, Base-Top is the time thickness from the top to the bottom of the interval velocity model, and f is the sampling interval between sampling points.

[0048] Optionally, the average velocity curve of the virtual well control point is independently interpolated for different fault blocks under segment control, and the average velocity of each segment in the geological structure model is calculated in sequence to construct a three-dimensional average velocity body, specifically including:

[0049] Under the control of the layer segment, for each fault block of each layer segment, the average velocity curves of all virtual well control points in the fault block are interpolated using the Kriging interpolation method to obtain the average velocity of the fault block. After the Kriging interpolation is completed for all fault blocks in the layer segment, the average velocity of the layer segment is obtained.

[0050] After the average velocities of all layers in the geological structure model are calculated in sequence, a three-dimensional average velocity body of the geological structure model is constructed.

[0051] A second aspect of an embodiment of the present invention provides a time-depth conversion device for buried structures in a low-exploration foreland thrust belt, the device comprising:

[0052] The geological feature acquisition module is used to obtain the velocity change characteristics of the study area through comprehensive analysis of geological data;

[0053] The geological structure model building module is used to build a geological structure model in the time domain based on velocity change characteristics and using seismic interpretation layer and fault data in the time domain;

[0054] The layer velocity model construction module is used to calculate the layer velocity of each fault block under the constraints of the geological structure model and convert the geological structure model into a layer velocity model;

[0055] The interval velocity curve extraction module is used to establish virtual well control points in the study area and extract the interval velocity curve at each virtual well control point from the interval velocity model;

[0056] An average velocity curve generating module is used to convert the interval velocity curve at the virtual well control point into an average velocity curve;

[0057] The 3D average velocity volume construction module is used to independently interpolate the average velocity curve of the virtual well control point in different fault blocks under the layer control, calculate the average velocity of each layer in the geological structure model in turn, and construct the 3D average velocity volume;

[0058] The time-depth conversion module is used to perform time-depth conversion on the seismic data and seismic interpretation horizons of the target layer in the study area using the three-dimensional average velocity body.

[0059] Optionally, the device further comprises a construction map module connected to the time-depth conversion module, and the construction map module is used to generate a depth domain construction map of the target layer.

[0060] A third aspect of an embodiment of the present invention provides a device comprising a memory, a processor, and a computer program stored on the memory and executable on the processor, wherein when the processor executes the program, the method for time-depth conversion of hidden structures in a low-exploration foreland thrust belt as described in the first aspect of an embodiment of the present invention is implemented.

[0061] A fourth aspect of an embodiment of the present invention provides a storage medium having a computer program stored thereon, which, when executed by a processor, implements the time-depth conversion method for hidden structures in a low-exploration foreland thrust belt as described in the first aspect of an embodiment of the present invention.

[0062] The above technical solution is based on the geological structure analysis of complex tectonic areas such as foreland basin thrust belts, and uses seismic interpretation of horizons and fault data to establish a detailed geological structure model. Then, with the geological structure model as a constraint, the geological structure model is converted into a layer velocity model by assigning layer-controlled fault block velocities. To overcome the problem of a small number of drilled wells, after generating the layer velocity model, virtual well control points are established in the study area, and layer velocity curves at the virtual well control points are extracted from the layer velocity model. To achieve time-depth conversion, the layer velocity curves at the virtual well control points are converted into average velocity curves, and then layer-controlled fault block spatial interpolation is performed to obtain a three-dimensional average velocity body. Finally, the three-dimensional average velocity body is used to perform time-depth conversion of the target layer. The depth domain data body after time-depth conversion is used to map the depth domain structure of the target layer.

[0063] The beneficial effects of the present invention are as follows:

[0064] 1) The geological consistency of the velocity model (3D average velocity volume) was improved through the use of stratum-controlled fault block velocity assignment and interpolation techniques, enabling a detailed characterization of the structural characteristics of the underlying target layer in the low-exploration foreland thrust belt. This provides reliable depth data for comprehensive geological studies such as detailed trap description and exploration deployment, and provides technical support for exploration in low-exploration complex structural areas. It effectively solves the problem of difficulty in characterizing the true seismic reflection characteristics of the underlying target layer due to the drastic lateral velocity changes caused by the rapid thickening of the strata within the thrust nappe belt.

[0065] 2) It has the characteristics of strong feasibility, high credibility, and high time-depth conversion efficiency. It has positive significance for promoting the exploration of complex tectonic areas such as foreland basin thrust belts, and for expanding and promoting the exploration of related fields of foreland basin thrust belts with low exploration degree. BRIEF DESCRIPTION OF THE DRAWINGS

[0066] The accompanying drawings are used to provide a further understanding of the embodiments of the present invention and constitute a part of the specification. Together with the following detailed description, they are used to explain the embodiments of the present invention, but do not constitute a limitation of the embodiments of the present invention. In the accompanying drawings:

[0067] Figure 1 A schematic flow chart of a method for time-depth conversion of buried structures in a low-exploration foreland thrust belt provided by an embodiment of the present invention;

[0068] Figure 2 This is a schematic diagram of a seismic interpretation profile;

[0069] Figure 3 This is a cross-section diagram of the geological structure model;

[0070] Figure 4 It is a cross-section diagram of the layer velocity model;

[0071] Figure 5 It is a cross-sectional diagram of a three-dimensional average velocity body;

[0072] Figure 6 Comparison of seismic profiles in the time domain and depth domain of the target layer. In the figure, part (a) is the seismic profile in the time domain of the target layer, and part (b) is the seismic profile in the depth domain of the target layer;

[0073] Figure 7 Comparison of the structural diagrams of the target layer in the time domain and depth domain. In the figure, part (a) is the structural diagram of the target layer in the time domain, and part (b) is the structural diagram of the target layer in the depth domain. DETAILED DESCRIPTION

[0074] The following describes the specific implementation of the embodiment of the present invention in detail with reference to the accompanying drawings. It should be understood that the specific implementation described herein is only used to illustrate and explain the embodiment of the present invention and is not used to limit the embodiment of the present invention.

[0075] Method Example

[0076] like Figures 1 to 7 As shown, this embodiment provides a time-depth conversion method for hidden structures in a low-exploration foreland thrust belt, which is used for time-depth conversion of the target layer in the study area. The study area is located in a complex structural area such as a foreland basin thrust belt, and the exploration level of the area is low, there is no available velocity spectrum data, and the number of drilled wells is small.

[0077] like Figure 1 As shown, the time-depth conversion method provided in this embodiment includes steps S100 to S700, which are specifically as follows:

[0078] S100. Obtain velocity variation characteristics of the study area through comprehensive analysis of geological data, providing a basis for the subsequent creation of geological structure models.

[0079] For example, in one embodiment, the specific implementation process of S100 includes:

[0080] S101. Determine the tectonic setting and tectonic deformation characteristics of the study area based on the location of the basin tectonic belt;

[0081] S102. Determine the stratigraphic distribution characteristics of the study area, the sedimentary background of the target layer, and the number of major stratigraphic layers based on a comprehensive analysis of the first acquired data, wherein the first acquired data includes well logging and core data;

[0082] S103. Determine the velocity variation characteristics of the study area based on the tectonic background, tectonic deformation characteristics, stratigraphic distribution characteristics, sedimentary background of the target layer, and the number of major stratigraphic layers. The velocity variation characteristics of the study area provide a basis for the subsequent establishment of a geological structure model.

[0083] S200. Based on the velocity variation characteristics, a geological structure model in the time domain is established using the seismic interpretation layer and fault data in the time domain.

[0084] For example, in one embodiment, the specific implementation process of S200 is as follows:

[0085] S201. Acquire 3D time-migrated seismic data;

[0086] S202. Using synthetic logs from wells drilled in the study area, perform time-depth calibration on each set of strata in the study area to obtain a time-depth relationship for the wells drilled;

[0087] S203. Based on the geological characteristics of the study area, seismic horizons and faults are tracked and interpreted for the seismic reflection events corresponding to the calibrated layer interfaces to obtain seismic interpretation horizon and fault data for the study area;

[0088] S204. Model each seismic interpretation layer in the study area and the fault data corresponding to each layer in turn to obtain a geological structure model in the time domain.

[0089] As can be seen, synthetic records of wells drilled in the study area can be synthesized using acoustic wave and density curve data from the wells. The time-depth calibration process for each set of strata in the study area can be performed using the calibration process described in conventional embodiments, for example, establishing a one-to-one correspondence between each geological layer in the depth domain and the seismic reflection events in the time domain.

[0090] In addition, in S204, the geological structure model is constructed using the seismic interpretation layer and the fault data corresponding to each layer. The geological structure model construction method in the common embodiment can be used. The following is a preferred construction method, which specifically includes:

[0091] S2041. Clarify the primary and secondary relationships of each fault, defining major faults and secondary faults, with secondary faults being interrupted by major faults;

[0092] S2042. Based on six different stratigraphic contact patterns, namely, stratigraphic erosion, stratigraphic overlap, stratigraphic truncation, parallel top, parallel bottom, and parallel top and bottom, clarify the contact relationships of the various strata in the study area.

[0093] S2043. Set the vertical time range of the geological structure model to be constructed, and use the seismic profile interpretation model as a guide. Set the contact relationship of each stratum and the primary and secondary relationship of the faults in a bottom-up order, and complete the modeling of each seismic interpretation layer and the fault data corresponding to each layer in the study area in turn. After the modeling is completed, the geological structure model in the time domain is obtained.

[0094] S300. Under the constraints of the geological structure model, the interlayer velocity of each fault block is calculated layer by layer, and the geological structure model is converted into an interlayer velocity model. Under the constraints of the geological structure model, the interlayer velocity of each fault block is calculated layer by layer. This process is a layer-controlled fault block velocity assignment method constructed in this embodiment.

[0095] For example, in one embodiment, the specific implementation process of S300 is as follows:

[0096] S301. Low-pass filtering the acquired acoustic velocity logging curve to obtain a low-frequency velocity curve;

[0097] S302. Under the constraints of the geological structure model, perform layer-controlled fault block velocity assignment to obtain velocity values ​​for each layer segment, thereby achieving conversion from the geological structure model to the layer velocity model;

[0098] Specifically, the stratum-controlled fault-block velocity assignment is as follows: Under the control of the stratum, for a fault block in a certain layer segment, at a selected drilled well location, based on the established time-depth relationship, a velocity curve segment corresponding to the layer segment is obtained from the low-frequency velocity curve. This velocity curve segment is proportionally assigned to the fault block in the layer segment, and so on, completing the velocity assignment for each fault block in each layer segment. It is apparent that the selected drilled well location can be the drilled well closest to the fault block.

[0099] For example, in one embodiment, the specific implementation process of S302 is as follows:

[0100] S3021. Under the control of the formation, for L i’ L of the layer i’ -F j’ Fault block, at the selected drilled location, obtain the velocity curve segment Vel-L corresponding to the layer segment in the low-frequency velocity curve according to the established time-depth relationship i’ ;

[0101] S3022. Read L i’ The temporal thickness H0 between the top and bottom of the interval;

[0102] S3023. Read L i’ -F' j’ The time thickness H at the CDP numbered n' on the fault block n’ ;

[0103] S3024. Starting from the top surface of the layer segment, assign the velocity values ​​of each sampling point in the layer segment to each sampling point at the CDP numbered n' in a one-to-one correspondence; wherein the velocity values ​​of each sampling point in the layer segment are extracted from the velocity curve segment Vel-L of the layer segment. i’Each sampling point in this interval is a longitudinal velocity sampling point at the selected drilling position, and the sampling interval of each sampling point is m milliseconds; the sampling interval of each sampling point of the CDP numbered n' is H n’ *m / H0 milliseconds;

[0104] S3025. Similarly, for L i’ -F j’ Each CDP at the fault block is assigned a velocity value, thus completing the L i’ -F j’ The interval velocity of the fault block is assigned, and similarly, the velocity assignment of all fault blocks in all layers is completed, thereby realizing the conversion from the geological structure model to the interval velocity model.

[0105] To facilitate understanding of the specific implementation process of the above S302, an example is given below:

[0106] Taking a certain layer segment L6 as an example, under the control of the formation, for a certain fault block L6-F1 in the L6 layer segment, at the selected drilled position, according to the established time-depth relationship, the velocity curve segment Vel-L6 of the low-frequency velocity curve corresponding to the layer segment is obtained, the time thickness value between the top and bottom of the L6 layer segment is read and recorded as H0, the time thickness value of the CDP numbered 1 (CDP-1) at the fault block L6-F1 is read and recorded as H1, and then the interval velocity of the drilled L6 layer segment is stretched to CDP-1 according to the same proportion, that is, the velocity assignment at CDP-1 is completed, and the velocity value at CDP-1 is recorded as Vel-L6-F1.

[0107] The principle of proportional stretching is as follows:

[0108] Assume that the longitudinal velocity sampling interval of the selected drilled well is m milliseconds, and the sampling interval at CDP-1 in fault block L6-F1 is determined to be H1*m / H0. Then, starting from the first sampling point located on the top surface of the L6 layer segment and ending at the last sampling point located on the bottom surface of the L6 layer segment, the velocity value of each sampling point is assigned one-to-one to each sampling point at CDP-1 of fault block L6-F1. That is, the velocity value of the sampling point at CDP-1 to be assigned every H1*m / H0 milliseconds is equal to the velocity value of the sampling point every m milliseconds at the drilled well, achieving proportional stretching of the sampling interval. The number of sampling points at CDP-1 in fault block L6-F1 is the same as the number of sampling points in the drilled L6 layer segment, completing the velocity assignment at CDP-1 of fault block L6-F1.

[0109] For each CDP at fault block L6-F1 within the L6 segment, velocity assignment is performed according to the same proportional stretching principle described above, resulting in the interlayer velocity value of fault block L6-F1 within the L6 segment. Velocity assignment is then performed for the remaining fault blocks within the L6 segment using the same principle, obtaining the interlayer velocity value for each fault block within the L6 segment. Similarly, velocity assignment is performed for the remaining segments in the geological structure model based on the same principle, obtaining the interlayer velocity value for each segment in the geological structure model. Velocity assignment for the layer-controlled fault blocks is then implemented, converting the geological structure model into an interlayer velocity model.

[0110] S400. Establish virtual well control points in the study area, and extract interval velocity curves at each virtual well control point from the interval velocity model.

[0111] For example, in one embodiment, the specific implementation process of S400 is as follows:

[0112] S401. According to the plane distribution range of the geological structure model and the bin size of the seismic data, a series of virtual well control points are set in the study area according to the preset grid interval;

[0113] S402. For each virtual well control point, find the CDP corresponding to the virtual well control point in the interval velocity model. Then, sequentially read the velocity values ​​of each sampling point of the interval velocity model at the CDP. The sampling points are sequentially from the first sampling point at the top of the interval velocity model to the last sampling point at the bottom of the interval velocity model. The sampling intervals between the sampling points are integer multiples of the seismic sampling interval.

[0114] S403. Connect all the read velocity values ​​into a curve, which is the interval velocity curve in the time domain at the control point of the virtual well.

[0115] S500. Convert the interval velocity curve at the virtual well control point into an average velocity curve. Specifically, to achieve the conversion from the interval velocity curve to the average velocity curve, the conversion method in the common embodiment can be used.

[0116] For example, in one embodiment, the following method for converting layer velocity to average velocity is adopted, which specifically includes the following implementation steps:

[0117] S501. Based on the conversion formula between the interval velocity curve and the average velocity curve, the interval velocity curve at the virtual well control point is converted into the average velocity curve;

[0118] The conversion formula is:

[0119]

[0120] In Formula 1, Vi_well[k] is the velocity value corresponding to the kth sampling point in the interval velocity curve Vi_well at the virtual well control point, time[k] is the time value corresponding to the kth sampling point in the interval velocity curve Vi_well at the virtual well control point, time[k-1] is the time value corresponding to the k-1th sampling point in the interval velocity curve Vi_well at the virtual well control point, time[j] is the time value corresponding to the jth sampling point in the interval velocity curve Vi_well at the virtual well control point, Va_well[j] is the average velocity value corresponding to the jth sampling point in the converted average velocity curve Va_well, Num is the total number of sampling points of the interval velocity curve at the virtual well control point, ANum = (Base-Top) / f+1 (Formula 2), in Formula 2, Base-Top is the time thickness from the top to the bottom of the interval velocity model, and f represents the sampling interval between sampling points.

[0121] The conversion of interval velocity curves to average velocity curves of all virtual well control points in the study area is completed in sequence, that is, the extraction of average velocity curves of all virtual well control points is realized.

[0122] S600. Perform independent interpolation of different fault blocks under layer segment control on the average velocity curve of the virtual well control point, calculate the average velocity of each layer segment in the geological structure model in sequence, and construct a three-dimensional average velocity body.

[0123] For example, the spatial interpolation may adopt the Kriging interpolation method. Based on the Kriging interpolation method, a specific implementation process of S600 is as follows:

[0124] S601. Under the control of the layer segment, for each fault block in each layer segment, use the Kriging interpolation method to interpolate the average velocity curves of all virtual well control points in the fault block to obtain the average velocity of the fault block. After completing the Kriging interpolation for all fault blocks in the layer segment, the average velocity of the layer segment is obtained.

[0125] S602. After sequentially calculating the average velocities of all layers in the geological structure model, construct a three-dimensional average velocity volume of the geological structure model.

[0126] Among them, in S601, under the control of the layer segment, the Kriging interpolation method is used to perform spatially independent interpolation on each block of each layer segment. This is a layer-controlled fault block Kriging interpolation method. This interpolation method can better characterize the lateral drastic change characteristics of the velocity in the study area.

[0127] The following content uses the Kriging interpolation process of the average velocity curve of n virtual well control points in a fault block L6-F1 in a certain layer segment L6 in the geological structure model as an example to illustrate the principle process of the above-mentioned layer-controlled fault block Kriging interpolation method.

[0128] First, the number n of virtual well control points located in the fault block is determined according to the range of the fault block. Let the function V(x) be the average velocity value of a CDP sampling point in the geological structure model. The average velocity value of the n virtual well control points in the fault block can be regarded as the average velocity value of V(x) at n sampling points x1, x2, x3, ..., x n The observation values ​​on are denoted as V(x1), V(x2), V(x3),…, V(x n ), the average velocity value at a CDP sampling point x0 in the fault block is recorded as V(x0), then the average velocity value V(x0) of the CDP point can be obtained by weighting the average velocity values ​​of n known virtual well control points in the fault block, that is:

[0129]

[0130] In Equation 3, λ i is the weight coefficient to be determined. According to the principle of the Kriging interpolation method, when the function V(x) satisfies the assumption of second-order stationarity, and based on the principle of unbiased estimator and minimum estimated variance, the weight coefficient is calculated by constructing the Lagrange condition extreme value. The following set of equations can be used to solve the n weight coefficient values ​​of the best, linear and unbiased estimate:

[0131]

[0132] In formula 4, γ(x i ,x j" ) is x i with x j" The variation function value between them, μ is the Lagrange constant when the variance is minimized, among which the variation function of Kriging interpolation, that is, the semivariance when measuring the degree of spatial correlation between points, is calculated as follows:

[0133]

[0134] In formula 5, h is x i with x j" The distance between them, N(h) is the number of paired sample points with a distance of h.

[0135] S700. Using the three-dimensional average velocity volume, perform time-depth conversion on the seismic data of the target layer in the study area and the seismic interpretation layer. Specifically, the method for performing time-depth conversion based on the three-dimensional average velocity volume can adopt the method process in the common embodiment.

[0136] For example, taking the H8 layer as an example, let the time domain layer value of the H8 layer segment at a certain CDP in the geological structure model be time_B, and the corresponding average velocity value of the H8 layer segment at the CDP in the three-dimensional average velocity body be V a _B, then the depth domain layer value Depth_B of the H8 layer at the CDP can be calculated by formula 6:

[0137] Using the same method, Equation 6 is used to calculate the H8 layer at each CDP in the 3D geological body, thus obtaining the depth domain layer of the H8 layer, thus realizing the conversion of the H8 layer from the time domain to the depth domain. Using the same method, the time-depth conversion of other layers in the study area can be realized.

[0138] For the time domain 3D seismic data volume seismic_time, taking a certain CDP trace as an example, the i′′ sampling point of the CDP trace has two attributes: one is its time value, recorded as seismic_time(i′′), and the other is its seismic reflection amplitude value, recorded as Amplitude_time(i′′). The average velocity value of the 3D average velocity volume corresponding to this sampling point is V a (i″′), using Equations 7 and 8, it can be converted from the time domain to the depth domain, and the depth value seismic_depth(i″′) and the amplitude value Amplitude_depth(i″′) of the i′′th sampling point of the CDP channel are obtained. The same conversion is performed on each sampling point of the CDP channel to realize the conversion of the CDP channel from the time domain to the depth domain:

[0139]

[0140] Amplitude_depth(i″′)=Amplitude_time(i″′) (Equation 8).

[0141] Generally, the time-depth conversion method for concealed structures in low-exploration foreland thrust belts implemented in this embodiment further includes the following steps:

[0142] S800. Generate a depth domain structural map of the target layer, thereby completing variable speed mapping of the target layer.

[0143] Combine Figures 2 to 7 As shown, the specific application examples of the above embodiment in the selected study area are as follows:

[0144] A1. According to the location of the basin tectonic belt in the selected study area, determine the tectonic background and tectonic deformation characteristics of the study area. Figure 2As shown in the figure, the selected study area is located between the Oman Mountains and the Oman Basin in terms of structure. The tectonic background is the thrust belt of the Oman Mountains foreland basin. The structure is complex and affected by the orogenic movement. The structural deformation is mainly thrust-napped, showing an imbricate thrust structure. Based on the well logging and core data of the selected study area, the stratigraphic distribution characteristics of the study area, the sedimentary background of the target layer and the number of major strata were determined. Among them, Figure 3 As shown in the figure, the research area selected by the institute can be divided into T sets of strata from top to bottom, with the value of T being 15. The main target layer is the 9th set of strata, which is a set of carbonate rock deposits. The lithology is mainly limestone and mudstone. The sedimentation of this set of strata is relatively stable, and the thickness of the strata does not change much in the horizontal direction. After determining the tectonic background, tectonic deformation characteristics, stratigraphic distribution characteristics, sedimentary background of the target layer and the number of major strata, based on this, the velocity change characteristics of the selected study area can be learned, which can be described as: the velocity difference within the same set of strata is not large, and the velocity change between different sets of strata is obvious. The target layer, the 9th set of strata and the strata below it, have relatively flat structures, and the velocity difference within the same set of strata is not large. The 5th set of strata and the strata above it gradually and steadily rise eastward, and the velocity change within the same set of strata is not large. The 6th, 7th and 8th sets of strata have drastic lateral velocity changes due to the thrust-nappe structure formed by the orogenic movement and the lateral differences in lithology and thickness. The western part is mainly limestone and mudstone with relatively low velocity, while the eastern part is mainly thrust-napped ophiolite and mudstone with higher velocity.

[0145] A2. First, obtain 3D time-migrated seismic data. Second, use the acoustic wave and density curve data of M wells drilled in the selected study area to create synthetic records. Establish a one-to-one correspondence between the interfaces of each layer in the T-set formation and the seismic reflection phase axis, complete the time-depth calibration, and obtain the time-depth relationship of the M wells drilled. Specifically, M is set to 3, such as Figure 2 As shown in the figure, a one-to-one correspondence between 13 (T-2) layered interfaces and seismic reflection events was established through synthetic records, and the time-depth relationship of the M wells drilled was obtained. Furthermore, guided by the geological characteristics learned from A1 and combined with the calibration results of the drilled wells, the seismic layers and faults corresponding to the seismic reflection events corresponding to the calibrated T-2 layered interfaces were tracked and interpreted to obtain the seismic interpretation layer and fault data of the selected study area. Finally, each seismic interpretation layer and the corresponding fault data of each layer were modeled in turn to obtain a geological structure model in the time domain. Specifically, as shown in the figure, Figure 2As shown, F1 is the main fault, which develops along the mudstone detachment layer, and F2, F3, F4, F5 and F6 developed above it are secondary faults, which gradually disappear in the detachment layer during the thrust and thrust process, that is, they are cut off by the main fault F1. According to the six different stratum contact modes of stratum erosion, stratum overlap, stratum erosion, parallel bottom, parallel top and parallel top and bottom, the contact relationship of each layer in the study area is clarified. In this application example, H1, H8, H7 and H5 are parallel bottom contact models, H2, H3, H9, H10, H11 and H12 are parallel top and bottom contact modes, and H4, H6 and H13 are parallel top contact modes. When setting the longitudinal time range of the geological structure model, the top time of the model is set to 0 milliseconds, and the bottom time Base is set to 4300 milliseconds. As shown in the figure, Figure 3 As shown, Figure 3 This is a cross section of the established time domain geological structure model. The model consists of 15 sets of strata, L1 to L15 from top to bottom.

[0146] A3. Within the constraints of the geological structure model, the interval velocity of each fault block is calculated layer by layer, converting the geological structure model into an interval velocity model. When assigning velocity values ​​to each fault block, the drilled well location closest to the fault block is selected. Figure 4 Shown is a cross-section of the interlayer velocity model constructed in this application example.

[0147] A4. Establish virtual well control points in the study area and extract the layer velocity curve at each virtual well control point from the layer velocity model. The geological structure model obtained in step A2 is 24 kilometers long from east to west and 15 kilometers wide from north to south. The pixel size of the seismic data is 15m×15m. First, according to the plane distribution range of the geological structure model and the pixel size of the seismic data, R virtual well control points are set in the study area with an interval of D meters. In this application example, D takes the value of 150 and R takes the value of 16000. Secondly, based on the layer velocity model, extract the layer velocity curve at each virtual well control point. Taking one of the virtual well control points well as an example, the sampling interval of the vertical upper layer velocity curve is set. The value is f, where f is an integer multiple of the seismic sampling interval Δt. In this application example, Δt = 1 and f is 4. The CDP corresponding to the virtual well control point well is found in the interval velocity model. Starting from the first sampling point at the top of the interval velocity model, with f as the sampling interval, the velocity value at each sampling point in the velocity model at the CDP is read in sequence, all the way to the bottom of the interval velocity model. Then all the read values ​​are connected into a line to obtain the interval velocity curve Vi_well at the virtual well control point well. This curve is the interval velocity curve in the time domain. Referring to the interval velocity curve extraction principle of the virtual well control point well, the interval velocity curve of each virtual well control point is obtained in sequence, that is, the interval velocity curve extraction of all virtual well control points is realized.

[0148] A5. Based on Equation 1, convert the interval velocity curve at the virtual well control point into an average velocity curve. In this application example, Top is set to 0, Base is set to 4300, and f is set to 4.

[0149] A6. The average velocity curve of the virtual well control point is independently interpolated for different fault blocks under layer control. The average velocity of each layer in the geological structure model is calculated in sequence to construct a three-dimensional average velocity volume. Figure 5 Shown is a cross-sectional view of the three-dimensional average velocity body obtained in this application example.

[0150] A7. Use the three-dimensional average velocity volume to perform time-to-depth conversion on the seismic data and seismic interpretation horizons of the target layer in the study area.

[0151] By comparing the seismic profiles in the time domain with the seismic profiles in the depth domain, and comparing the structural maps in the time domain with the structural maps in the depth domain, the reliability of the above time-depth conversion is verified. Figure 6 As shown, based on the seismic reflection of the target layer, its characteristics in the time domain seismic profile and the depth domain seismic profile are compared. The comparative analysis shows that due to the influence of the rapid thickening of mudstone in the thrust nappe belt, which leads to the drastic change in the lateral velocity of the formation, the seismic reflection phase axis of the target layer has an obvious pull-down feature in the time domain seismic profile. After time-depth conversion, the seismic profile in the depth domain can more clearly explain the structural characteristics of the target layer, which illustrates the reliability of the time-depth conversion method provided by this embodiment. Figure 7 As shown, the characteristics of the time domain structural map and the depth domain structural map of the target layer are compared. The comparative analysis shows that the time-depth conversion weakens the influence of the lateral drastic change of the formation velocity caused by the rapid thickening of the mudstone in the thrust belt on the seismic reflection of the underlying target layer. The structural closure characteristics of the target layer that are difficult to identify on the time domain structural map are presented after the time-depth conversion. It can be seen that the depth domain structural map can clearly depict the structural closure characteristics of the target layer, thereby verifying the reliability of the time-depth conversion method provided by this embodiment.

[0152] Device embodiment

[0153] This embodiment provides a time-depth conversion device for concealed structures in a low-exploration foreland thrust belt, comprising a geological feature acquisition module, a geological structure model construction module, a layer velocity model construction module, a layer velocity curve extraction module, an average velocity curve generation module, a three-dimensional average velocity body construction module, and a time-depth conversion module, which are connected in sequence.

[0154] The geological feature acquisition module is used to obtain the velocity change characteristics of the study area through comprehensive analysis of geological data.

[0155] The geological structure model building module is used to build a geological structure model in the time domain based on velocity change characteristics and using seismic interpretation layer and fault data in the time domain.

[0156] The layer velocity model construction module is used to calculate the layer velocity of each fault block under the constraints of the geological structure model and convert the geological structure model into a layer velocity model.

[0157] The interval velocity curve extraction module is used to establish virtual well control points in the study area and extract the interval velocity curves at each virtual well control point from the interval velocity model.

[0158] The average velocity curve generation module is used to convert the interval velocity curve at the virtual well control point into an average velocity curve.

[0159] The 3D average velocity volume construction module is used to independently interpolate the average velocity curve of the virtual well control point in different fault blocks under the layer control, calculate the average velocity of each layer in the geological structure model in turn, and construct a 3D average velocity volume.

[0160] The time-depth conversion module is used to perform time-depth conversion on the seismic data and seismic interpretation horizons of the target layer in the study area using the three-dimensional average velocity body.

[0161] Optionally, the device further includes a mapping module connected to the time-to-depth conversion module, and the mapping module is used to generate a depth domain structural map of the target layer.

[0162] Optionally, the geological feature acquisition module obtains the velocity variation characteristics of the study area through comprehensive analysis of geological data. The specific process is as follows:

[0163] According to the location of the basin tectonic belt in the study area, the tectonic background and tectonic deformation characteristics of the study area are determined;

[0164] Based on a comprehensive analysis of the first acquired data, the stratigraphic distribution characteristics of the study area, the sedimentary background of the target layer, and the number of major stratigraphic layers are determined. The first acquired data includes well logging and core data.

[0165] The velocity variation characteristics of the study area are determined based on the tectonic background, tectonic deformation characteristics, stratigraphic distribution characteristics, sedimentary background of the target layer and the number of main strata.

[0166] Optionally, the geological structure model building module uses the velocity variation characteristics and the time-domain seismic interpretation horizon and fault data to build a time-domain geological structure model. The specific process is as follows:

[0167] Acquire 3D time-migrated seismic data;

[0168] Using synthetic records of wells drilled in the study area, time-depth calibration was performed on each set of strata in the study area to obtain the time-depth relationship of the drilled wells;

[0169] Guided by the geological characteristics of the study area, the seismic reflection events corresponding to the calibrated layer interfaces are used to track and interpret the seismic horizons and faults, and the seismic interpretation horizon and fault data of the study area are obtained;

[0170] Each seismic interpretation layer in the study area and the corresponding fault data of each layer are modeled in turn to obtain a geological structure model in the time domain.

[0171] Optionally, the layer velocity model construction module calculates the layer velocity of each fault block under the constraints of the geological structure model and converts the geological structure model into a layer velocity model. The specific process is as follows:

[0172] Perform low-pass filtering on the acquired acoustic velocity logging curve to obtain a low-frequency velocity curve;

[0173] Under the constraints of the geological structure model, the velocity assignment of the layer-controlled fault blocks is performed to obtain the velocity value of each layer segment, thereby realizing the conversion of the geological structure model to the layer velocity model;

[0174] The specific velocity assignment of the stratum-controlled fault blocks is:

[0175] Under the control of the formation, for a certain fault block in a certain layer segment, at the selected drilled position, the velocity curve segment corresponding to the layer segment in the low-frequency velocity curve is obtained according to the established time-depth relationship. The velocity curve segment is proportionally assigned to the fault block in the layer segment, and so on, completing the velocity assignment of each fault block in each layer segment.

[0176] Optionally, under the control of the formation, for a certain fault block in a certain layer segment, at a selected drilled well position, a velocity curve segment corresponding to the layer segment in the low-frequency velocity curve is obtained according to the established time-depth relationship, and the velocity curve segment is proportionally assigned to the fault block in the layer segment. Similarly, the velocity assignment of each fault block in each layer segment is completed. The specific process is as follows:

[0177] Under the control of the formation, for L i’ L of the layer i’ -F j’ For a fault block, at the selected drilled well location, the velocity curve segment corresponding to the layer segment in the low-frequency velocity curve is obtained according to the established time-depth relationship;

[0178] Read L i’ The temporal thickness H0 between the top and bottom of the interval;

[0179] Read L i’ -F j’ The time thickness H of the CDP numbered n' at the fault block n’ ;

[0180] Starting from the top surface of the layer, the velocity values ​​of each sampling point in the layer are assigned one by one to each sampling point of the CDP numbered n';

[0181] Each sampling point in the interval is a longitudinal velocity sampling point at the selected drilled well position, and the sampling interval of each sampling point is m milliseconds;

[0182] The sampling interval of each sampling point of CDP numbered n' is H n’ *m / H0 milliseconds;

[0183] By analogy, for L i’ -F j’ Each CDP at the fault block is assigned a velocity value, thus completing the L i’ -F j’ Assignment of interval velocity to fault blocks;

[0184] In this way, the velocity assignment of each layer segment and each fault block is completed, thereby converting the geological structure model into a layer velocity model.

[0185] Optionally, the interval velocity curve extraction module establishes virtual well control points in the study area and extracts interval velocity curves at each virtual well control point from the interval velocity model. The specific process is as follows:

[0186] According to the plane distribution range of the geological structure model and the bin size of the seismic data, a series of virtual well control points are set in the study area according to the preset grid interval;

[0187] For each virtual well control point, find the CDP corresponding to the virtual well control point from the interval velocity model, and then read the velocity values ​​of each sampling point of the interval velocity model at the CDP in sequence. The sampling points are from the first sampling point at the top of the interval velocity model to the last sampling point at the bottom of the interval velocity model, and the sampling interval between the sampling points is an integer multiple of the seismic sampling interval;

[0188] All the read velocity values ​​are connected to form a curve, which is the interval velocity curve in the time domain at the control point of the virtual well.

[0189] Optionally, the average velocity curve generation module converts the interval velocity curve at the virtual well control point into an average velocity curve. The specific process is as follows:

[0190] Based on the conversion formula between the interval velocity curve and the average velocity curve, the interval velocity curve at the virtual well control point is converted into the average velocity curve;

[0191] The conversion formula is:

[0192]

[0193] Among them, Vi_well[k] is the velocity value corresponding to the kth sampling point in the interval velocity curve Vi_well at the virtual well control point, time[k] is the time value corresponding to the kth sampling point in the interval velocity curve Vi_well at the virtual well control point, time[k-1] is the time value corresponding to the k-1th sampling point in the interval velocity curve Vi_well at the virtual well control point, and time[j] is the time value corresponding to the jth sampling point in the interval velocity curve Vi_well at the virtual well control point; Va_well[j] is the average velocity value corresponding to the jth sampling point in the converted average velocity curve Va_well, Num is the total number of sampling points of the interval velocity curve at the virtual well control point, and Num = (Base-Top) / f+1, Base-Top is the time thickness from the top to the bottom of the interval velocity model, and f is the sampling interval between sampling points.

[0194] Optionally, the 3D average velocity volume construction module performs independent interpolation of different fault blocks under layer control on the average velocity curve of the virtual well control point, sequentially calculates the average velocity of each layer in the geological structure model, and constructs a 3D average velocity volume. The specific process is as follows:

[0195] Under the control of the layer segment, for each fault block of each layer segment, the average velocity curves of all virtual well control points in the fault block are interpolated using the Kriging interpolation method to obtain the average velocity of the fault block. After the Kriging interpolation is completed for all fault blocks in the layer segment, the average velocity of the layer segment is obtained.

[0196] After the average velocities of all layers in the geological structure model are calculated in sequence, a three-dimensional average velocity body of the geological structure model is constructed.

[0197] The device embodiments described above are merely illustrative. The units described as separate components may or may not be physically separate, and the components shown as units may or may not be physical units, i.e., they may be located in one location or distributed across multiple network units. Some or all of the modules may be selected based on actual needs to achieve the objectives of the present embodiment. Persons of ordinary skill in the art will be able to understand and implement the present invention without inventive effort.

[0198] On the other hand, an embodiment of the present invention further provides an electronic device, comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor implements the time-to-depth conversion method as described in the method embodiment of the present invention when executing the computer program.

[0199] On the other hand, an embodiment of the present invention further provides a storage medium having a computer program stored thereon, which implements the time-to-depth conversion method as described in the method embodiment of the present invention when the computer program is executed by a processor.

[0200] Through the description of the above embodiments, those skilled in the art can clearly understand that each embodiment can be implemented by means of software plus a necessary general hardware platform, or of course, by hardware. Based on this understanding, the essence of the above technical solution or the part that contributes to the existing technology can be embodied in the form of a software product. The computer software product can be stored in a computer-readable storage medium, such as ROM / RAM, a magnetic disk, an optical disk, etc., and includes a number of instructions for enabling a computer device (which can be a personal computer, a server, or a network device, etc.) to execute the methods described in each embodiment or certain parts of the embodiments.

[0201] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the various embodiments of the present invention.

Claims

1. A method for time-depth conversion of buried structures in low-exploration foreland thrust belts, characterized by: The method comprises: The velocity variation characteristics of the study area were obtained through comprehensive analysis of geological data; Based on the velocity variation characteristics, a geological structure model in the time domain is established using the seismic interpretation layer and fault data in the time domain; Under the constraints of the geological structure model, the layer velocity of each fault block is calculated layer by layer, and the geological structure model is converted into a layer velocity model; Establish virtual well control points in the study area and extract interval velocity curves at each virtual well control point from the interval velocity model; Converting the interval velocity curve at the virtual well control point into an average velocity curve; The average velocity curve of the virtual well control point is interpolated independently in different fault blocks under the layer control, and the average velocity of each layer in the geological structure model is calculated in turn to construct a three-dimensional average velocity body; The three-dimensional average velocity body is used to perform time-depth conversion on the seismic data and seismic interpretation horizons of the target layer in the study area.

2. The method for time-depth conversion of buried structures in low-exploration foreland thrust belts according to claim 1, characterized in that: The velocity variation characteristics of the study area obtained through comprehensive analysis of geological data specifically include: According to the location of the basin tectonic belt in the study area, the tectonic background and tectonic deformation characteristics of the study area are determined; Determining the stratigraphic distribution characteristics of the study area, the sedimentary background of the target layer, and the number of major stratigraphic layers based on a comprehensive analysis of the first acquired data, wherein the first acquired data includes well logging and core data; The velocity variation characteristics of the study area are determined based on the tectonic background, tectonic deformation characteristics, stratigraphic distribution characteristics, sedimentary background of the target layer and the number of main strata.

3. The method for time-depth conversion of buried structures in low-exploration foreland thrust belts according to claim 1, characterized in that: The method of establishing a geological structure model in the time domain based on velocity variation characteristics and utilizing seismic interpretation horizon and fault data in the time domain specifically includes: Acquire 3D time-migrated seismic data; Using synthetic records of wells drilled in the study area, time-depth calibration was performed on each set of strata in the study area to obtain the time-depth relationship of the drilled wells; Guided by the geological characteristics of the study area, the seismic reflection events corresponding to the calibrated layer interfaces are used to track and interpret the seismic horizons and faults, and the seismic interpretation horizon and fault data of the study area are obtained; Each seismic interpretation layer in the study area and the corresponding fault data of each layer are modeled in turn to obtain a geological structure model in the time domain.

4. The method for time-depth conversion of buried structures in low-exploration foreland thrust belts according to claim 1, characterized in that: The layer velocity of each fault block is calculated layer by layer under the constraints of the geological structure model, and the geological structure model is converted into a layer velocity model, which specifically includes: Perform low-pass filtering on the acquired acoustic velocity logging curve to obtain a low-frequency velocity curve; Under the constraints of the geological structure model, the velocity assignment of the layer-controlled fault blocks is performed to obtain the velocity value of each layer segment, thereby realizing the conversion of the geological structure model to the layer velocity model; The specific value assignment of the stratum-controlled fault block velocity is: Under the control of the formation, for a certain fault block in a certain layer segment, at the selected drilled position, the velocity curve segment corresponding to the layer segment in the low-frequency velocity curve is obtained according to the established time-depth relationship. The velocity curve segment is proportionally assigned to the fault block in the layer segment, and so on, completing the velocity assignment of each fault block in each layer segment.

5. The method for time-depth conversion of buried structures in low-exploration foreland thrust belts according to claim 4, characterized in that: Under the control of the formation, for a certain fault block in a certain layer segment, at a selected drilled well position, a velocity curve segment corresponding to the layer segment in the low-frequency velocity curve is obtained according to the established time-depth relationship, and the velocity curve segment is proportionally assigned to the fault block in the layer segment. Similarly, the velocity assignment of each fault block in each layer segment is completed, specifically including: Under the control of the formation, for L i’ L of the layer i’ -F j’ For a fault block, at the selected drilled well location, the velocity curve segment corresponding to the layer segment in the low-frequency velocity curve is obtained according to the established time-depth relationship; Read L i’ The temporal thickness H0 between the top and bottom of the interval; Read L i’ -F j’ The time thickness H of the CDP numbered n' at the fault block n’ ; Starting from the top surface of the layer, the velocity values ​​of each sampling point in the layer are assigned one by one to each sampling point of the CDP numbered n'; Each sampling point in the interval is a longitudinal velocity sampling point at the selected drilled well position, and the sampling interval of each sampling point is m milliseconds; The sampling interval of each sampling point of CDP numbered n' is H n’ *m / H0 milliseconds; By analogy, for L i’ -F j’ Each CDP at the fault block is assigned a velocity value, thus completing the L i’ -F j’ Assignment of interval velocity to fault blocks; In this way, the velocity assignment of each layer segment and each fault block is completed, thereby converting the geological structure model into a layer velocity model.

6. The method for time-depth conversion of buried structures in low-exploration foreland thrust belts according to claim 1, characterized in that: The step of establishing virtual well control points in the study area and extracting interval velocity curves at each virtual well control point from the interval velocity model specifically includes: According to the plane distribution range of the geological structure model and the bin size of the seismic data, a series of virtual well control points are set in the study area according to the preset grid interval; For each virtual well control point, find the CDP corresponding to the virtual well control point from the interval velocity model, and then read the velocity values ​​of each sampling point of the interval velocity model at the CDP in sequence. The sampling points are from the first sampling point at the top of the interval velocity model to the last sampling point at the bottom of the interval velocity model, and the sampling interval between the sampling points is an integer multiple of the seismic sampling interval; All the read velocity values ​​are connected to form a curve, which is the interval velocity curve in the time domain at the control point of the virtual well.

7. The method for time-depth conversion of buried structures in low-exploration foreland thrust belts according to claim 6, characterized in that: The converting of the interval velocity curve at the virtual well control point into the average velocity curve specifically includes: Based on the conversion formula between the interval velocity curve and the average velocity curve, the interval velocity curve at the virtual well control point is converted into the average velocity curve; The conversion formula is expressed as: Among them, Vi_well[k] is the velocity value corresponding to the kth sampling point in the interval velocity curve Vi_well at the virtual well control point, time[k] is the time value corresponding to the kth sampling point in the interval velocity curve Vi_well at the virtual well control point, time[k-1] is the time value corresponding to the k-1th sampling point in the interval velocity curve Vi_well at the virtual well control point, and time[j] is the time value corresponding to the jth sampling point in the interval velocity curve Vi_well at the virtual well control point; Va_well[j] is the average velocity value corresponding to the jth sampling point in the converted average velocity curve Va_well, Num is the total number of sampling points of the interval velocity curve at the virtual well control point, and Num = (Base-Top) / f+1, Base-Top is the time thickness from the top to the bottom of the interval velocity model, and f is the sampling interval between sampling points.

8. The method for time-depth conversion of buried structures in low-exploration foreland thrust belts according to claim 1, characterized in that: The average velocity curve of the virtual well control point is independently interpolated in different fault blocks under the layer control, and the average velocity of each layer in the geological structure model is calculated in sequence to construct a three-dimensional average velocity body, specifically including: Under the control of the layer segment, for each fault block of each layer segment, the average velocity curves of all virtual well control points in the fault block are interpolated using the Kriging interpolation method to obtain the average velocity of the fault block. After the Kriging interpolation is completed for all fault blocks in the layer segment, the average velocity of the layer segment is obtained. After the average velocities of all layers in the geological structure model are calculated in sequence, a three-dimensional average velocity body of the geological structure model is constructed.

9. A time-depth conversion device for concealed structures in a low-exploration foreland thrust belt, characterized in that: The device comprises: The geological feature acquisition module is used to obtain the velocity change characteristics of the study area through comprehensive analysis of geological data; The geological structure model building module is used to build a geological structure model in the time domain based on velocity change characteristics and using seismic interpretation layer and fault data in the time domain; The layer velocity model construction module is used to calculate the layer velocity of each fault block under the constraints of the geological structure model and convert the geological structure model into a layer velocity model; The interval velocity curve extraction module is used to establish virtual well control points in the study area and extract the interval velocity curve at each virtual well control point from the interval velocity model; An average velocity curve generating module is used to convert the interval velocity curve at the virtual well control point into an average velocity curve; The 3D average velocity volume construction module is used to independently interpolate the average velocity curve of the virtual well control point in different fault blocks under the layer control, calculate the average velocity of each layer in the geological structure model in turn, and construct the 3D average velocity volume; The time-depth conversion module is used to perform time-depth conversion on the seismic data and seismic interpretation horizons of the target layer in the study area using the three-dimensional average velocity body.

10. The device for time-depth conversion of buried structures in low-exploration foreland thrust belts according to claim 9, characterized in that: The device further comprises a construction map module connected to the time-depth conversion module, and the construction map module is used to generate a depth domain construction map of the target layer.

11. A device comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein: When the processor executes the program, the method for time-depth conversion of buried structures in a low-exploration foreland thrust belt according to any one of claims 1 to 8 is implemented.

12. A storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by a processor, the method for time-depth conversion of buried structures in a low-exploration foreland thrust belt according to any one of claims 1 to 8 is implemented.

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