Spatial evolution method for extrusion type strike-slip fault of tension basin

Abstract

The invention relates to a tension basin extrusion type strike-slip fault spatial evolution method, and belongs to the technical field of oil and gas field exploration and development and mineral evaluation and prediction. Comprising the following steps of: through seismic data pre-stack and post-stack processing, comparing a target point (x, y, z) with all data points in a spatial range which takes (x, y, z) as a center and takes the length of a seismic surface element as a radius by using a coherence algorithm according to seismic data discontinuity attributes, and calculating similarity; inherited fault periods are distinguished, and the distinguishing standard is that points with the trend changed each time serve as distinguishing points; fault attribute slices are made for different periods, a fault plane mode pattern is formed, strike-slip fault plane distribution characteristics are implemented, and the relative displacement direction of the strike-slip fault is judged; the generation period is constructed by implementing the accompanying. The problem of fine identification of the zone-level strike-slip fault is solved, and the identification precision of the strike-slip fault zone fault is higher.

Description

Technical Field

[0001] The invention relates to a method for spatial evolution of compressional strike-slip faults in a tension basin, and belongs to the technical field of oil and gas field exploration and development, and mineral evaluation and prediction. Background Art

[0002] The No. 2 and No. 3 strike-slip faults in the Fulongquan Depression of the Songliao Basin are two large strike-slip fault zones connecting the Fulongquan inversion tectonic zone and the Dalaoye inversion tectonic zone, with a length of nearly 30 km. According to years of exploration and development, oil and gas shows have been found in both inversion tectonic zones, especially in the Fulongquan inversion tectonic zone with a higher structural position, where multiple layers have been effectively mobilized and developed. With the outward exploration, oil and gas discoveries have been made in the southern part of the strike-slip fault zone, but the differences between wells are obvious, and the law of oil and gas accumulation is not clearly understood. The main reason is that the stress and formation mechanism of the strike-slip fault are not clearly understood, and the control effect on the oil and gas reservoir is unclear. At the same time, the strike-slip fault strike intersects with the strike of other tensile faults in the work area, with an angle greater than 60°, making the fault extremely complex and highly multi-solution.

[0003] Seismic coherent data is an important means and effective tool for fault identification, and is well applied in the important stage of oil and gas field exploration and development. However, the basic principle of coherent data is calculated based on the difference between the two sides of the fault. Therefore, it is difficult to identify strike-slip faults and faults with small fault distance.

[0004] At the same time, strike-slip faults in extensional basins are often low-order accommodative faults. Compared with tensile stress, compressive stress exists for a shorter period of time and has less stress impact, which makes it difficult to analyze the formation mechanism of strike-slip faults and the relative displacement direction of the two plates of strike-slip faults unclear. Since strike-slip faults in extensional basins have a single formation period and diverse stress release modes, there are large differences in the spatial patterns of faults in different strata and locations of strike-slip faults, which makes it difficult to have a detailed understanding of strike-slip faults.

[0005] At present, there are relatively few research methods for stress analysis of strike-slip faults. Most of the publicly published literature uses the basin-level large-area tectonic stress field to comprehensively judge the stress source of strike-slip. However, for the specific study area, the understanding of the strike-slip faults mostly stays at the level of morphology, lacking a detailed description of the formation mechanism. For this reason, we propose a spatial evolution method for compressional strike-slip faults in tensional basins to finely understand the changes in fault morphology caused by strike-slip stress in different strata, and at the same time, finely understand the formation mechanism of strike-slip faults. Summary of the invention

[0006] In order to solve the above problems existing in the prior art, the present invention discloses a spatial evolution method of compressional strike-slip faults in tensional basins, which determines the stress release mode of compressional strike-slip faults in tensional basins and further completes the analysis of the formation mechanism of strike-slip faults.

[0007] The technical solution adopted by the present invention is: a method for spatial evolution of compressional strike-slip faults in a tensional basin, comprising the following steps:

[0008] Step 1: Through pre-stack and post-stack processing of seismic data, the strike-slip faults are finely highlighted to ensure the fine identification accuracy of the faults.

[0009] Step 2: Using the discontinuity attribute of seismic data, a coherent algorithm is used to compare the target point (x, y, z) with all data points in the spatial range centered at (x, y, z) and with the seismic bin length as the radius to obtain the similarity. When a fault exists, the similarity is 0, and when a fault does not exist, the similarity is 100. Through the similarity comparison method, the fault is further highlighted to prepare for the evolution of the fault.

[0010] Step 3: Through the interpretation of the horizontal and vertical sections of the seismic discontinuity attributes, the spatial closure of the fault is ensured, the location and morphology of the fault are determined, and the inherited fault stages are distinguished. The distinction criterion is the point where the direction changes each time as the distinguishing point.

[0011] Step 4: Make fault attribute slices for different periods to form a fault plane pattern diagram and implement the plane distribution characteristics of the strike-slip fault. Usually, the change of fault period corresponds to the stress conversion period, the stress is greatly reduced, the end of the fault rotates, and the end of the strike-slip fault will disperse into multiple faults. As the rotation force further increases, the end of the strike-slip fault will break and disperse into multiple shorter strike-slip faults, forming an en-echelon strike-slip fault structure; observed vertically from the fault direction, the left end of the strike-slip fault disperses upward or the right end disperses downward, which is a clockwise rotation, and the relative displacement direction of the fault is parallel to the strike-slip fault to the right; otherwise, it is a counterclockwise rotation, and the relative displacement direction of the fault is parallel to the strike-slip fault to the left; when the strike-slip fault forms an en-echelon structure, the relative displacement direction of the strike-slip fault is determined based on whether the strata between the strike-slip faults are compression uplift or tension settlement.

[0012] Step 5: Use the stress Mohr circle to conduct stress analysis. The relative displacement direction of the strike-slip fault reflects the direction of the regional comprehensive stress, which can be decomposed into two perpendicular components, C and E. The direction of the C component is the direction of the compressive stress, which is the direction of the regional maximum principal stress; the direction of the E component is opposite, which is the direction of the tensile stress. In the tensional basin, the compressive stratigraphic associated structure produced by the parallel C component is particularly obvious. By confirming the period of the associated structure, the formation period of the strike-slip fault zone can be clearly determined.

[0013] Furthermore, in the step 1, pre-stack depth migration processing is performed before stacking, and the time domain data is converted into depth domain data by using the relationship between travel time and velocity.

[0014] Furthermore, the pre-stack depth migration processing in step 1 is specifically as follows: first, the travel time of seismic waves propagating underground needs to be calculated based on the seismic data and the velocity model, and then the time seismic data is converted into depth domain data based on the relationship between the travel time and the velocity, and finally an image of the underground structure is obtained through an imaging algorithm.

[0015] Furthermore, the time seismic data in step 1 is processed using the wave equation and Huygens principle, and the specific formula is as follows:

[0016]

[0017] Where I(x, y, z) is the imaging result at the target point (x, y, z); G(x, y, z, x', y', t) is the Green's function representing the propagation and attenuation of the seismic wave field generated at the target point (x, y, z); S(x', y', t) is the seismic record, representing the seismic wave signal recorded at the launch point (x', y', t); R(x', y', t) is the seismic data resampling function, representing the matching relationship between the seismic records at the target point (x, y, z) and the launch point (x', y', t); The gradient of the velocity function represents the variation of wave velocity in the subsurface medium.

[0018] Furthermore, in step 1, blue filtering is used after stacking to filter the seismic data in the time-space domain to enhance the fault imaging capability of the seismic signal; and three-dimensional Fourier transform is used to obtain the seismic data. Convert seismic data to the frequency domain; where F(u, v, w) represents the function or data in the three-dimensional frequency domain, f(x, y, z) is the seismic data at the target point (x, y, z), u, v, w represent frequency variables, x, y, z represent spatial variables, and the high frequency of the seismic data is filtered through bandpass filtering to improve the quality of fault imaging.

[0019] Furthermore, in the step 3, for the tensional basin, as the strike-slip fault extends from deep to shallow and from the center to the two wings, the tectonic stress of each period of the strike-slip fault weakens, resulting in stress differences at different positions of the strike-slip fault, rotation of the strike-slip fault, and different fault directions at different periods.

[0020] The present invention discloses a method for the spatial evolution of compressional strike-slip faults in a tensional basin, which has the following beneficial effects: it solves the problem of fine identification of zone-level strike-slip faults and can provide a geological model for the fine dissection of network fault groups and faults; compared with the existing analysis methods for strike-slip faults, firstly, it is more specific in the research scope, and thus the identification accuracy of faults in strike-slip fault zones is higher, so the fine description of fault lithology traps is more reliable and more practical. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0022] Figure 1 is a flow chart of the present invention;

[0023] Figure 2 This is a fault evolution model diagram of the strike-slip fault zone of the Fulongquan depression in the embodiment of the present invention;

[0024] Figure 3 This is a classification pattern diagram of feather faults in an embodiment of the present invention;

[0025] Figure 4 A schematic diagram of the stress Mohr circle during the strike-slip movement of the Fulongquan depression in an embodiment of the present invention;

[0026] Figure 5 A schematic diagram of a parallel C component seismic profile in an embodiment of the present invention;

[0027] Figure 6 Schematic diagram of the fault combination mode at the end of a strike-slip fault in an embodiment of the present invention.

[0028] Specific implementation methods

[0029] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. The following description of at least one exemplary embodiment is actually only illustrative and is by no means intended to limit the present invention and its application or use. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0030] In order to further understand the content of the present invention, the present invention is further described below in conjunction with specific implementation methods.

[0031] The well logging methods used in the following embodiments are conventional methods unless otherwise specified. The present invention is described in detail with reference to the accompanying drawings as follows:

[0032] like Figure 1 As shown, the technical solution adopted by the present invention is: a method for spatial evolution of compressional strike-slip faults in a tensional basin, comprising the following steps:

[0033] Step 1: Through pre-stack and post-stack processing of seismic data, the strike-slip faults are finely highlighted to ensure the fine identification accuracy of the faults. Pre-stack depth migration processing is performed before stacking, and the time domain data is converted into depth domain data by using the relationship between travel time and velocity. The pre-stack depth migration processing is specifically as follows: first, the travel time of seismic waves propagating underground needs to be calculated based on the seismic data and velocity model, and then the time seismic data is converted into depth domain data based on the relationship between travel time and velocity, and finally the image of the underground structure is obtained through the imaging algorithm. The time seismic data is processed using the wave equation and Huygens principle. The specific formula is as follows:

[0034]

[0035] Where I(x, y, z) is the imaging result at the target point (x, y, z); G(x, y, z, x', y', t) is the Green's function representing the propagation and attenuation of the seismic wave field generated at the target point (x, y, z); S(x', y', t) is the seismic record, representing the seismic wave signal recorded at the launch point (x', y', t); R(x', y', t) is the seismic data resampling function, representing the matching relationship between the seismic records at the target point (x, y, z) and the launch point (x', y', t); The gradient of the velocity function represents the variation of wave velocity in the subsurface medium.

[0036] Blue filtering is used after stacking to filter the seismic data in the time-space domain to enhance the fault imaging capability of seismic signals; three-dimensional Fourier transform is used to Convert seismic data to the frequency domain; where F(u, v, w) represents the function or data in the three-dimensional frequency domain, f(x, y, z) is the seismic data at the target point (x, y, z), u, v, w represent frequency variables, x, y, z represent spatial variables, and the high frequency of the seismic data is filtered through bandpass filtering to improve the quality of fault imaging.

[0037] Step 2: Using the discontinuity attribute of seismic data, a coherent algorithm is used to compare the target point (x, y, z) with all data points in the spatial range centered at (x, y, z) and with the seismic bin length as the radius to obtain the similarity. When a fault exists, the similarity is 0, and when a fault does not exist, the similarity is 100. Through the similarity comparison method, the fault is further highlighted to prepare for the evolution of the fault.

[0038] Step 3: Through the interpretation of the horizontal and vertical sections of the seismic discontinuity attributes, the spatial closure of the fault is ensured, the location and morphology of the fault are determined, and the inherited fault stages are distinguished. The distinction criterion is the point where the direction changes each time as the distinguishing point.

[0039] Step 4: Make fault attribute slices for different periods to form a fault plane pattern diagram and implement the plane distribution characteristics of the strike-slip fault. Usually, the change of fault period corresponds to the stress conversion period, the stress is greatly reduced, the end of the fault rotates, and the end of the strike-slip fault will disperse into multiple faults. As the rotation force further increases, the end of the strike-slip fault will break and disperse into multiple shorter strike-slip faults, forming an en-echelon strike-slip fault structure; observed vertically from the fault direction, the left end of the strike-slip fault disperses upward or the right end disperses downward, which is a clockwise rotation, and the relative displacement direction of the fault is parallel to the strike-slip fault to the right; otherwise, it is a counterclockwise rotation, and the relative displacement direction of the fault is parallel to the strike-slip fault to the left; when the strike-slip fault forms an en-echelon structure, the relative displacement direction of the strike-slip fault is determined based on whether the strata between the strike-slip faults are compression uplift or tension settlement.

[0040] Step 5: Use the stress Mohr circle to conduct stress analysis. The relative displacement direction of the strike-slip fault reflects the direction of the regional comprehensive stress, which can be decomposed into two perpendicular components, C and E. The direction of the C component is the direction of the compressive stress, which is the direction of the regional maximum principal stress; the direction of the E component is opposite, which is the direction of the tensile stress. In the tensional basin, the compressive stratigraphic associated structure produced by the parallel C component is particularly obvious. By confirming the period of the associated structure, the formation period of the strike-slip fault zone can be clearly determined.

[0041] Embodiment 1:

[0042] The Fulongquan trough in the Changling fault depression of the Songliao Basin is an important gas-producing area in the Jilin Oilfield. In the early stage, the inversion structure belt has been developed and utilized effectively, but the subsequent evaluation and deregulation are facing difficulties. The main difficulty is that the strike-slip fault is separated from the inversion structure, and the strike of the fault is oblique to the tension fault at a large angle (>60°), and the fault has a network feature in some parts. In addition, at the end of the strike-slip fault, the stress is reduced and the fault rotates, which makes it difficult to identify the fault and has strong multiple solutions. There is a lack of standards for the spatial combination of faults, which leads to the failure of fault-lithology closure.

[0043] In response to the above problems, pre-stack and post-stack processing of seismic data was carried out around favorable areas; the time differences and imaging differences between data from different years were eliminated through pre-stack concatenation processing; then blue filtering processing was performed on post-stack data to improve the data signal-to-noise ratio and further optimize the fault imaging quality.

[0044] On this basis, coherence bodies are produced for the seismic data, and the faults are accurately identified and characterized by utilizing the incorrelation of seismic signals caused by the stratigraphic differences on both sides of the fault.

[0045] like Figure 2As shown in the figure, it reflects the fault distribution characteristics of each major period of strike-slip faults; using actual seismic data and coherence bodies, the spatial interpretation of faults is carried out, and fault evolution is carried out; in the Fulongquan trough, the evolution of faults in three periods is focused on, namely, the fault depression period, the fault-depression conversion period, and the depression period; through the coherent slices of each period, the fault mode of the strike-slip fault zone in each period is implemented; according to the evolutionary characteristics of the fault, it is clear that there are two northwest-southeast strike-slip faults in the fault depression period; in the fault-depression conversion period, the end of the strike-slip fault rotates, and the whole rotates clockwise to the south, reflecting the right-lateral strike-slip characteristics; in the depression period, the end of the strike-slip fault is further split into feather faults, and there are grabens between the feather faults. According to the classification of feather faults, such as Figure 3 As shown in the figure, according to the classification pattern diagram, the strike-slip direction of the feather fault can be effectively distinguished; by judging the arrangement of the feather faults and combining whether the strata between the feather faults are relatively stretched and subsided or compressed and uplifted, the type of the feather fault can be determined; the left row represents movement to the left and rotates counterclockwise; the right row represents movement to the right and rotates clockwise. It is clearly right-step type; through the evolution characteristics of the fault from early to late stage, the strike-slip fault zone is determined to be right-lateral strike-slip.

[0046] like Figure 4-5 As shown in the figure, it represents the regional stress direction parallel to the strike-slip direction, which can be decomposed into two mutually perpendicular components, C and E components. The C component is opposite in direction, resulting in a thrust fault perpendicular to the C component, and compressional structures will be associated along the C component; combined with the stress Moore circle analysis, the main stress direction of the strike-slip fault in the Fulongquan area is parallel to the strike-slip fault trend, which is southeast; two relative compressional reverse faults are developed along the C component, of which the eastern side is inherited on the early controlling fault, accompanied by the Fudong inversion structure; therefore, it can be clearly stated that the strike-slip fault zone and the inversion structure are coeval and co-sourced, confirming that the strike-slip fault zone was formed at the end of the Mingshui Formation.

[0047] Combining the above studies, Figure 6 As shown in the figure, in previous studies, the fault combination on the left was the main method in this work area. Through actual drilling, the fault combination of the Denglouku Formation in the fault depression period of the key gas-bearing strata was revised. After the revision, the fault combination was more geologically regular. On this basis, a number of fault-lithologic traps were implemented, with a single area of ​​0.1-2km 2 , total area 150km 2 , which effectively guided the deployment of the Fu-45 well and made commercial discoveries in the strike-slip fault zone.

[0048] 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, the software implements the programming of related mathematical methods, and the hardware provides a platform and storage. Based on this understanding, the above technical solution can be essentially or the part that contributes to the relevant technology can be embodied in the form of a software product, and the computer software product can be stored in a computer-readable storage medium, such as ROM / RAM, a disk, an optical disk, etc., including a number of instructions for 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 some parts of the embodiment. Now, PetroChina's Geoeast software can implement the pre-stack and post-stack processing, discontinuity attribute extraction, and browsing of seismic data and interpretation of faults in the present invention; stress analysis currently has no relevant software support, and can be analyzed by manual drawing.

[0049] 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 replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for spatial evolution of compressional strike-slip faults in a tensional basin, comprising the following steps: Step 1: Through pre-stack and post-stack processing of seismic data, the strike-slip faults are finely highlighted to ensure the fine identification accuracy of the faults; Step 2: Using the discontinuity attribute of seismic data, a coherence algorithm is used to compare the target point (x, y, z) with all data points in the spatial range with (x, y, z) as the center and the seismic bin length as the radius to obtain the similarity; when the fault exists, the similarity is 0, and when the fault does not exist, the similarity is 100; Step 3: Through the interpretation of the horizontal and vertical sections of the seismic discontinuity attributes, the spatial closure of the fault is ensured, the location and morphology of the fault are determined, and the inherited fault stages are distinguished. The distinction standard is the point where the strike direction changes each time as the distinguishing point; Step 4: Produce fault attribute slices for different periods to form a fault plane pattern diagram and implement the plane distribution characteristics of the strike-slip fault. The change of fault period corresponds to the stress conversion period. The stress is greatly weakened, and the end of the fault rotates. The end of the strike-slip fault will be dispersed into multiple faults. As the rotation force is further enhanced, the end of the strike-slip fault will break and disperse into multiple shorter strike-slip faults, forming an en-echelon strike-slip fault structure. Observe the vertical fault direction. The left end of the strike-slip fault disperses upward or the right end disperses downward. It is a clockwise rotation, and the relative displacement direction of the fault is parallel to the strike-slip fault to the right; otherwise, it is a counterclockwise rotation, and the relative displacement direction of the fault is parallel to the strike-slip fault to the left. When the strike-slip fault forms an en-echelon structure, the relative displacement direction of the strike-slip fault is determined according to whether the strata between the strike-slip faults are compression uplift or tensile settlement. Step 5: Use the stress Mohr circle to conduct stress analysis. The relative displacement direction of the strike-slip fault reflects the direction of the regional comprehensive stress, which can be decomposed into two perpendicular components, C and E. The direction of the C component is the direction of the compressive stress, which is the direction of the regional maximum principal stress; the direction of the E component is opposite, which is the direction of the tensile stress. In the tensional basin, the compressive stratigraphic associated structure produced by the parallel C component is particularly obvious. By confirming the period of the associated structure, the formation period of the strike-slip fault zone can be clearly determined.

2. The spatial evolution method of compressional strike-slip faults in a tensional basin according to claim 1, characterized in that: In step 1, pre-stack depth migration processing is performed before stacking, and the time domain data is converted into depth domain data by using the relationship between travel time and velocity.

3. The spatial evolution method of compressional strike-slip faults in a tensional basin according to claim 2, characterized in that: The prestack depth migration processing in step 1 is as follows: first, the travel time of seismic waves propagating underground needs to be calculated based on the seismic data and velocity model, and then the time seismic data is converted into depth domain data based on the relationship between travel time and velocity, and finally the image of the underground structure is obtained through the imaging algorithm.

4. The spatial evolution method of compressional strike-slip faults in a tensional basin according to claim 3, characterized in that: In step 1, the time seismic data is processed using the wave equation and Huygens principle. The specific formula is as follows: Where I(x, y, z) is the imaging result at the target point (x, y, z); G(x, y, z, x', y', t) is the Green's function representing the propagation and attenuation of the seismic wave field generated at the target point (x, y, z); S(x', y', t) is the seismic record, representing the seismic wave signal recorded at the launch point (x', y', t); R(x', y', t) is the seismic data resampling function, representing the matching relationship between the seismic records at the target point (x, y, z) and the launch point (x', y', t); The gradient of the velocity function represents the variation of wave velocity in the subsurface medium.

5. The spatial evolution method of compressional strike-slip faults in a tensional basin according to claim 1, characterized in that: In step 1, blue filtering is used after stacking to filter the seismic data in the time-space domain; three-dimensional Fourier transform is used Convert seismic data to the frequency domain; where F(u, v, w) represents the function or data in the three-dimensional frequency domain, f(x, y, z) is the seismic data at the target point (x, y, z), u, v, w represent frequency variables, and x, y, z represent spatial variables.

6. The spatial evolution method of compressional strike-slip faults in a tensional basin according to claim 1, characterized in that: In step 3, for the extensional basin, as the strike-slip fault extends from deep to shallow and from the center to the two wings, the tectonic stress of each stage of the strike-slip fault weakens, resulting in stress differences at different positions of the strike-slip fault, rotation of the strike-slip fault, and different fault directions at different stages.

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