A method for quickly realizing three-dimensional structure recovery to eliminate structural abnormalities

Abstract

This invention relates to a rapid method for three-dimensional structural restoration by eliminating structural anomalies, belonging to the field of geological structural restoration technology in oil and gas field exploration. The method first establishes a three-dimensional stratigraphic fault model based on the interpreted horizon and interpreted faults of the target segment. Then, according to the seismic network, the model is decomposed into L and XL directions, and structural restoration is performed in both directions respectively. Finally, the restoration results of the two directions are combined to obtain the structural restoration result of the target interface. This method not only preserves the complete information of the stratigraphy but also eliminates structural anomalies, improving the accuracy and reliability of structural restoration.

Description

Technical Field

[0001] This invention relates to the field of geological structure restoration technology in oil and gas field exploration, and in particular to a rapid method for three-dimensional structure restoration that eliminates structural anomalies. Background Technology

[0002] In oil and gas field exploration where the formation conditions and oil-reservoir relationship are controlled by paleogeography, paleogeography plays a crucial role, qualitatively guiding the distribution of oil, gas, and reservoirs. Common quantitative paleogeographic reconstruction methods include the impression method and the residual thickness method. Both methods are derived through interface subtraction and are well-suited for areas with few faults. However, in areas with large-thrust faults, the strata on the hanging wall and footwall of the fault are often interlaced and superimposed. Applying these two methods will create significant structural anomalies near the fault (see Appendix). Figure 2 This seriously affects the reliability of paleogeographic reconstruction results.

[0003] There are currently two main types of solutions to this problem:

[0004] (1) Simple Removal Method: The essential reason for the occurrence of structural anomalies is that faults cause strata to slide along the fault plane, resulting in the intersection and superposition of strata, which in turn leads to anomalies when calculating the thickness of strata in the vertical direction. The simple removal method adopts the approach of "removing first and then interpolating". First, the intersecting and superimposed parts of the strata are removed, the strata are flattened, and then the missing areas are interpolated, thereby avoiding the occurrence of structural anomalies (Cao Zhenmin, 2023; Zhang Pengfei, 2023).

[0005] (2) Balanced profile method: The balanced profile method is a technical method based on geometric principles (conservation of line length, area, and volume) to restore structural deformation to a reasonable undeformed state, thereby eliminating the problem of stratigraphic overlap and superposition caused by tectonics. It is currently the most accurate method for eliminating structural anomalies and has many application examples. The basic application idea of ​​this method is: select one or several typical profiles perpendicular to the structural trend; convert the profiles into two-dimensional models; perform structural restoration on the models and flatten the strata; finally, use the obtained balanced profiles as the regional structural restoration results, or interpolate the three-dimensional paleogeomorphological results of the region through several such balanced profiles (Bao Hanyong, 2024; Han Yunjie, 2022; Fu Dongyang, 2020).

[0006] It is not difficult to see the technical problems of the above two methods: (1) Although the simple excision method is easy to implement, it removes the strata near the fault, and the subsequent interpolation results will inevitably differ from the original landform. Especially in areas with small dip angles and large fault displacements, the structural restoration results have large errors, which is not conducive to detailed paleogeographic depiction; (2) The balanced profile method solves the structural anomaly problem from a geometric perspective, but this method has a large amount of computation and a complex calculation process, which limits the application of this technology. At present, most examples of this method are applied to one or several typical two-dimensional profiles. Although some foreign commercial software has achieved three-dimensional structural restoration, it also has the problems of complex calculation process and long calculation time, and lacks a fast implementation method for three-dimensional structural restoration. Summary of the Invention

[0007] To address the aforementioned technical problems, this invention aims to develop a rapid method for 3D structural reconstruction by eliminating structural anomalies, based on the concept of balanced profile technology. This method simplifies the 3D structural problem and achieves rapid reconstruction of 3D structures while ensuring the accuracy of paleogeographic reconstruction. The method first establishes a 3D stratigraphic fault model based on the interpreted horizons and interpreted faults of the target segment. Then, it decomposes the model into L and XL directions according to the seismic network, and performs structural reconstruction in both directions separately. Finally, it combines the reconstruction results from both directions to obtain the structural reconstruction (paleogeographic reconstruction) result of the target interface.

[0008] The specific technical solution is as follows:

[0009] S1, input the seismic horizons and faults that have been interpreted in the time or depth domains;

[0010] S2. Based on the seismic horizons and faults, a three-dimensional stratigraphic fault model is established. During the modeling process: ① the seismic horizons are moderately smoothed; ② some minor faults are removed, and only faults with large horizontal displacements are retained; ③ the interpretation of the horizons near the fault plane is checked and appropriate adjustments are made to ensure that the horizons are in contact with the fault plane and that there are no missing or excessive faults.

[0011] S3 decomposes the established fracture model into L and XL directions, transforming the three-dimensional model into a series of two-dimensional cross-sectional models composed of layers and cross sections in these two directions.

[0012] S3, perform structural restoration in the L direction, and select the first two-dimensional profile model according to the line number order;

[0013] S4, determine the location and number of cross sections in the profile, and count the dip direction of the cross sections. The direction with the most dip direction is used as the structural recovery calculation direction for the profile.

[0014] S5. Project the target interface onto the overlying strata along the calculation direction. The projection process follows the following: ① The target strata and its projection point must be on the same side of the section. ② Prioritize vertical projection and record the projection distance so that the target interface and the overlying strata correspond in the vertical direction. ③ If there is no corresponding vertical projection point, perform oblique projection along the dip direction of the adjacent section and record the projection angle and distance at the projection point.

[0015] S6, flatten the overlying strata. While flattening the strata near the fault, the hanging wall of the fault is moved horizontally so that the hanging wall of the fault comes into contact with the footwall of the fault, and there is no situation where the strata are missing or exceeded.

[0016] S7. Based on the projection angle and projection distance recorded during the projection process, the structural restoration result of the profile is obtained by back-projecting the target interface of the flattened overlying strata.

[0017] S8. Following the line number sequence, perform the steps S4-S7 above on all two-dimensional sections in the L direction to obtain the structural restoration result in the L direction.

[0018] S9. For the XL direction, repeat the recovery process in the L direction (S3-S8) to obtain the structural recovery result in the XL direction;

[0019] S10: By combining the structural reconstruction calculation results of the target interface in the L and XL directions, the three-dimensional structural reconstruction result of the target interface is obtained.

[0020] Compared with the prior art, the present invention can achieve the following positive technical effects:

[0021] 1) Compared with the simple excision method, the present invention does not excise the strata near the fault during the structural restoration process, thus preserving the complete information of the strata and eliminating structural anomalies. This significantly improves the accuracy and reliability of structural restoration (paleomorphological restoration).

[0022] 2) Compared with the equilibrium profile method, this invention decomposes the three-dimensional construction problem into two-dimensional problems in two directions, making it easier to implement. It also uses the projection method to simplify the construction restoration process. While ensuring the reliability of the restoration results, it realizes the rapid realization of three-dimensional construction restoration, solving the problem that the equilibrium profile method can only be applied in two dimensions or that the process is complicated in three dimensions.

[0023] 3) A rapid method for 3D structural restoration that can effectively eliminate structural anomalies is provided. This method follows geometric principles and has a reliable theoretical basis in the process of structural restoration. At the same time, it simplifies complex 3D problems and improves the computational efficiency of the method. It is conducive to the development and large-scale application of technologies in the fields of structural restoration and paleogeographic characterization. Attached Figure Description

[0024] Figure 1 These are schematic diagrams and flowcharts of the present invention;

[0025] Figure 2 These are simplified diagrams of common fault patterns and their flattened results. Figure 2 'a' represents a simple pattern of a normal fault. Figure 2 c represents the corresponding flattening result. Figure 2 b represents a simplified representation of a reverse fault. Figure 2 d represents the corresponding flattening result;

[0026] Figure 3 Seismic network map of the study area as an example;

[0027] Figure 4 This is a three-dimensional stratigraphic fracture model diagram constructed during the implementation process of the example;

[0028] Figure 5 The following is an example illustrating the restoration effect of a two-dimensional cross-section during implementation, and a comparison with a simple flattening. Figure 5 'a' represents a two-dimensional cross-sectional model. Figure 5 b represents the simple flattening result of this model. Figure 5 c represents the result obtained by applying the method of this invention to the model. Figure 5 d is Figure 5 c. Display after removing the cross-section;

[0029] Figure 6 This is a simplified schematic diagram of the method of the present invention when projecting onto the target interface;

[0030] Figure 7 The final target stratum is shown in the restored paleogeographic plan as an example. Detailed Implementation

[0031] Example 1

[0032] A fast method for 3D structure recovery that eliminates structural anomalies, comprising the following steps:

[0033] Step 1, Input the seismic horizon in the depth domain and fracture Where num is the stratigraphic level and fracture number, It's the line number in the L direction. It's the track number for the XL direction. It is depth;

[0034] Step 2: Adjust the input stratigraphy and fractures appropriately to establish a three-dimensional stratigraphic fracture model. , Data points Is the type a stratigraphic level or a fault?

[0035] Step 2-1: Perform appropriate smoothing of the seismic horizon.

[0036] Step 2-2: Remove some minor fractures, retaining only faults with large horizontal displacements.

[0037] Steps 2-3: Check the interpretation of the strata near the cross-section and make appropriate adjustments to ensure that the strata are in contact with the cross-section and that there are no missing or excessive strata.

[0038] Step 3: Decompose the established 3D model into a series of 2D cross-sectional models consisting of layers and sections along the L and XL directions. First, perform cross-sectional processing along the L direction, resulting in the following cross-section. Num refers to the section number. This represents the stratigraphic level in the cross-section, fully represented as follows: num refers to the floor number. This represents the cross-section in the profile, fully represented as... ;

[0039] Step 4: Perform structural restoration along the L direction, selecting the first two-dimensional profile model according to the line number order;

[0040] Step 5: Determine the location and number of cross sections in the selected profile, and count the dip direction of the cross sections. The direction with the most dip directions will be used as the structural restoration calculation direction for the profile.

[0041] Step 6: Project the target layer onto the overlying strata along the calculation direction. The projected overlying strata are represented as follows: , The distance refers to the vertical projection. These refer to the angle and distance of the oblique projection, respectively. The projection process follows three principles: ① The target layer and its projection point must be on the same side of the cross section; ② Vertical projection is given priority, and the projection distance is recorded; ③ If there is no corresponding vertical projection point, oblique projection is performed along the dip direction of the adjacent cross section, and the projection angle and distance are recorded at the projection point.

[0042] Step 7: Level the overlying strata. During the leveling process, while leveling the strata near the fault, the hanging wall of the fault is moved horizontally so that the hanging wall of the fault comes into contact with the footwall of the fault, and there is no situation where the strata are missing or exceeded.

[0043] Step 8: Based on the projection information recorded during the projection process, back-project the target layer based on the flattened overlying strata to obtain the structural reconstruction result of the target layer of the profile. The result also records the current coordinates of the destination layer. And ancient coordinates, ;

[0044] Step 9: Following the line number sequence, perform steps 5 to 8 on the two-dimensional cross-section along the L direction sequentially to obtain the structural reconstruction result along the L direction. , These are the ancient coordinates recovered along the L direction;

[0045] Step 10: Repeat the restoration process in the L direction for the cross-section in the XL direction, performing steps 4 to 9 to obtain the structural restoration result in the XL direction. , These are ancient coordinates recovered along the XL direction;

[0046] Step 11: Combine the structural reconstruction calculation results of the target interface in the L and XL directions to obtain the final reconstruction result. ,in

[0047] , , .

[0048] Example 2

[0049] Figures 3 to 7 This is an example of a rapid method for 3D structural reconstruction based on 3D seismic data of a certain study area, wherein: Figure 3 For the seismic network of this study area, Figure 4 This is a three-dimensional stratigraphic fault model established based on data from this study area. Figure 5 The following is an example of the restoration effect of the present invention and a comparison with the effect of simple flattening, using a cross-section along the L direction as an example. Figure 6 This is a diagram illustrating the projection method during the restoration process. Figure 7 The target stratum in the embodiment is shown in the restored paleogeographic plan (the height values ​​in the plan only represent relative height, with lower values ​​representing higher elevations). Figure 5 and Figure 7 It can be seen that the present invention effectively eliminates structural anomalies and provides a fast and accurate method for three-dimensional structural recovery.

[0050] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A specific step of a three-dimensional structure recovery quick implementation method for eliminating structural anomalies, comprising: Step 1, input seismic horizon in depth domain and fault where num is horizon, fault number, is line number in L direction, is trace number in XL direction, is depth; Step 2, adjust the input horizon and fault appropriately, build a 3D horizon-fault model , point is horizon or fault, Step 2-1, moderately smoothing the seismic horizon, Step 2-2, removing part of the micro-faults and only keeping the faults with large horizontal displacement, Step 2-3, checking the interpretation of the horizon near the fault surface and making appropriate adjustment so that the horizon is in contact with the fault surface without missing or exceeding, Step 3, the established three-dimensional model is decomposed into a series of two-dimensional section models composed of layer position and section in L direction and XL direction, section processing in L direction is performed first, the section is , Num indicates section number, , indicates layer position in the section, and is completely indicated as , num indicates layer position number, , indicates section in the section, and is completely indicated as ; Step 4, conducting structure recovery in L direction, and selecting the first two-dimensional profile model according to the order of line number, Step 5, determining the position and number of the fault surface in the selected profile, and counting the dip direction of the fault surface, and taking the direction with more dip as the structure recovery calculation direction of the profile, Step 6, project the destination layer to the overlying layer in the calculation direction, and the projected overlying layer is represented as , denotes the distance of the vertical projection, denote the angle and distance of the oblique projection, respectively, and the projection process follows 3 principles: ① the destination layer and its projection point must be on the same side of the section, ② the vertical projection is performed preferentially, and the projection distance is recorded, ③ when there is no corresponding vertical projection point, the oblique projection is performed along the dip direction of the adjacent section, and the projection angle and distance are recorded at the projection point; Step 7, flattening the overlying strata, and in the flattening process, the strata near the fault surface are flattened while the hanging wall of the fault is horizontally moved so that the hanging wall of the fault is in contact with the footwall of the fault without missing or exceeding the strata. Step 8, based on the projection information recorded in the projection process, the destination stratum is deprojected from the flattened overlying stratum, thereby obtaining the structure recovery result of the destination stratum of the profile The result records the present coordinates of the destination stratum, and the paleo-coordinates, ; Step 9, sequentially perform the steps of Step 5 to Step 8 described above on the two-dimensional profile in the L direction according to the order of the lines to obtain the structure recovery result in the L direction , is the paleo-coordinate recovered along the L direction; Step 10, repeat the recovery process of L direction for the profile along XL direction, perform the processing of step 4 to step 9 to obtain the recovery result of structure along XL direction , is the paleo-coordinate recovered along XL direction; Step 11, the integrated purpose interface recovers the configuration in the L direction and the XL direction to obtain the final recovery result wherein ， ， 。

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