A method for spatial evolution of extensional basin compression strike-slip fault

Abstract

The present application relates to a kind of tension basin extrusion strike-slip fault spatial evolution method, belong to oil and gas field exploration and development, mineral evaluation prediction technical field.It includes the following steps: by prestack, poststack processing of seismic data, using the discontinuity of seismic data properties, using coherence algorithm contrast target point (x, y, z) and with (x, y, z) as center, all data points in the spatial range of seismic bin length radius contrast, similarity is obtained;Inheritance type fault period is distinguished, and the standard for distinguishing is that the point of each change of strike is taken as the distinguishing point;For different period, make fault attribute slice, form fault plane pattern diagram, implement strike-slip fault plane distribution characteristics, judge strike-slip fault relative displacement direction;By implementing associated structure generation period.The problem of fine identification of zone level strike-slip fault is solved, and the identification accuracy of strike-slip fracture zone fault is higher.

Description

TECHNICAL FIELD

[0001] The present application relates to a kind of tension basin extrusion type strike-slip fault spatial evolution method, belong to oil and gas field exploration and development, mineral evaluation prediction technical field. BACKGROUND

[0002] No.2 and No.3 strike-slip faults in Fulongquan fault depression of Songliao Basin are two large strike-slip fault zones connecting Fulongquan inverted structural belt and Dalaoye inverted structural belt, with a length of nearly 30 km. According to years of exploration and development, oil and gas shows are found in both inverted structural belts, especially in Fulongquan inverted structural belt with higher structural position, and multiple layers are developed profitably. With exploration outsourcing, oil and gas discoveries are obtained in the south of strike-slip fault zone, but the differences between wells are obvious, and the understanding of oil and gas accumulation rules is unclear. The main reason is that the stress and formation mechanism of strike-slip fault are unclear, and thus the control of oil and gas reservoir is unclear. At the same time, the strike of strike-slip fault intersects with the strike of other extensional faults in the work area, with an angle greater than 60°, resulting in extremely complex faults and strong multi-solution.

[0003] Seismic coherent data volume is an important means and effective tool for solving fault identification, and is well applied in important stages of oil and gas field exploration and development. However, the basic principle of coherent data volume is calculated according to the difference of strata on both sides of the fault. Therefore, it is difficult to identify strike-slip faults and faults with small throw.

[0004] At the same time, strike-slip faults in extensional basins are often low-order adjustment faults, and the period of strike-slip stress is shorter than that of extensional stress, and the stress influence is smaller, which leads to difficulty in analyzing the formation mechanism of strike-slip faults and the direction of relative displacement of both sides of strike-slip faults. Due to the single formation period of strike-slip faults in extensional basins and the variety of stress release modes, there are great differences in spatial patterns of faults in different layers and different positions of strike-slip faults, leading to great difficulty in fine understanding of strike-slip faults.

[0005] At present, there are relatively few research methods for stress analysis of strike-slip faults, and most of the published documents use basin-level large regional tectonic stress field to judge the stress source of strike-slip, but for specific study area, the recognition of strike-slip fault form is mainly stayed, and the fine description of formation mechanism is lacked. Therefore, we propose a kind of tension basin extrusion type strike-slip fault spatial evolution method to finely understand the fault form change caused by strike-slip stress in different layers, and finely understand the formation mechanism of strike-slip fault. SUMMARY

[0006] To solve the above problems existing in the prior art, the present application discloses a kind of tension basin extrusion type strike-slip fault spatial evolution method, which is used to determine the stress release mode of extrusion type strike-slip fault in tension basin, and then analyze the formation mechanism of strike-slip fault.

[0007] The technical scheme adopted by the present application is a method for spatial evolution of a pull-apart basin extrusion strike-slip fault, comprising the following steps:

[0008] Step 1: Fine highlighting of the strike-slip fault is performed through pre-stack and post-stack processing of seismic data to ensure the fine identification accuracy of the fault.

[0009] Step 2: The similarity is calculated by comparing the target point (x, y, z) with all data points in the spatial range centered at (x, y, z) and having a seismic bin length as the radius using the coherence algorithm based on the discontinuity attribute of the seismic data; the similarity is 0 when the fault exists and is 100 when the fault does not exist; the similarity comparison method is used to further highlight the fault to prepare for the fault evolution.

[0010] Step 3: The spatial closure of the fault is ensured through the interpretation of the seismic discontinuity attribute cross section and longitudinal section to determine the position and shape of the fault and to distinguish the period of the inherited fault, with the change point of each strike direction as the distinguishing point.

[0011] Step 4: The fault attribute slices are made for different periods to form a fault plane pattern map to determine the strike-slip fault plane distribution characteristics; usually, the change of the fault period corresponds to the stress conversion period, the stress is greatly weakened, the end of the fault is rotated, the end of the strike-slip fault is dispersed into multiple faults, with the further enhancement of the rotation force, the end of the strike-slip fault is disconnected and dispersed into multiple shorter strike-slip faults to form a goose line strike-slip fault structure; the left end of the strike-slip fault is dispersed upward or the right end is dispersed downward, which is a clockwise rotation, and the relative displacement direction of the fault is parallel to the right strike-slip fault; otherwise, it is a counterclockwise rotation, and the relative displacement direction of the fault is parallel to the left strike-slip fault; when the strike-slip fault forms a goose line structure, the relative displacement direction of the strike-slip fault is determined according to whether the strata between the strike-slip faults are extrusion uplift or stretching subsidence.

[0012] Step 5: The stress analysis is carried out using the stress Mohr circle, and the relative displacement direction of the strike-slip fault reflects the regional comprehensive stress direction, which can be decomposed into two perpendicular components C and E, wherein the C component direction is opposite to the extrusion stress direction, which is the direction of the maximum principal stress of the region; the E component direction is opposite, which is the direction of the tensile stress; in the tensile basin, the extrusion type strata associated structure produced by the parallel C component is particularly obvious, and the formation period of the strike-slip fault zone can be determined by determining the period when the associated structure is produced.

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

[0014] Further, the pre-stack depth migration processing in step 1 is specifically: first, the travel time of seismic wave propagation in the ground is calculated according to the seismic data and the velocity model, then the time seismic data is converted into depth domain data according to the relationship between the travel time and the velocity, and finally the image of the underground structure is obtained through the imaging algorithm.

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

[0016]

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

[0018] Further, the post-stack is processed by using blue filtering in step 1, the seismic data is filtered in the time-space domain to enhance the fault imaging ability of the seismic signal; the three-dimensional Fourier transform is used The seismic data is converted into the frequency domain; wherein F(u, v, w) represents a 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 space variables, the high frequency of the seismic data is filtered through band-pass filtering, and the fault imaging quality is improved.

[0019] Further, in step 3, for the extensional basin, as the strike-slip fault extends from deep to shallow and from the center to the wings, the structural stress of each period of the strike-slip fault is weakened, resulting in stress difference at different positions of the strike-slip fault, rotation of the strike-slip fault, and different strikes of the faults of different periods.

[0020] The application discloses a method for spatial evolution of extensional basin compression type strike-slip fault, which has the beneficial effects that: the method solves the problem of fine identification of zone level strike-slip fault, can provide a geological model for fine dissection of a netted fault group and faults, and compared with the existing analysis method of strike-slip fault, the method is more specific in research range, has higher identification precision of the strike-slip fault, and is more reliable and more implemented in fine description of fault lithologic traps. BRIEF DESCRIPTION OF DRAWINGS

[0021] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the accompanying drawings required by the embodiments or prior art description will be briefly introduced. Obviously, the accompanying drawings in the following description are some embodiments of the present application, and other drawings can be obtained by a person of ordinary skill in the art without any creative labor.

[0022] Figure 1 A flowchart of the present application;

[0023] Figure 2 A fault evolution pattern diagram of the strike-slip fault zone in the Fulongquan sag in the embodiment of the present application;

[0024] Figure 3 A feathered fault classification pattern diagram in the embodiment of the present application;

[0025] Figure 4 A stress Mohr circle diagram in the strike-slip movement period of the Fulongquan sag in the embodiment of the present application;

[0026] Figure 5 A parallel C-component seismic profile diagram in the embodiment of the present application;

[0027] Figure 6 A strike-slip fault end fault combination pattern diagram in the embodiment of the present application. Specific implementation method

[0028] In order to make the purpose, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be described clearly and completely in combination with the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are only some of the embodiments of the present application, but not all the embodiments. The description of the at least one exemplary embodiment is actually only illustrative, but not as any limitation on the present application and its application or use. Based on the embodiments in the present application, all other embodiments obtained by a person of ordinary skill in the art without any creative labor are within the scope of protection of the present application.

[0029] In order to further understand the inventive content of the present application, the present application will be further described in combination with the specific implementation manner.

[0030] The logging method used in the following embodiments is a conventional method unless otherwise specified. The present application will be described in detail in combination with the accompanying drawings as follows:

[0031] As shown in the accompanying drawings, Figure 1 The technical solutions adopted by the present application are as follows: a space evolution method of a pull-apart basin compression type strike-slip fault, comprising the following steps:

[0032] Step 1: Through pre-stack and post-stack processing of seismic data, fine highlight of strike-slip faults is ensured to guarantee the fine identification accuracy of faults. Pre-stack depth migration processing is performed in pre-stack, 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 specifically includes: first, the travel time of seismic wave propagation underground is calculated according to seismic data and velocity model, then the time seismic data is converted into depth domain data according to the relationship between travel time and velocity, and finally the image of underground structure is obtained through imaging algorithm. The time seismic data is processed by using wave equation and Huygens principle, and the specific formula is as follows:

[0033]

[0034] 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 function representing the propagation and attenuation of the seismic wave field at the target point (x, y, z); S(x', y', t) is the seismic record, representing the recorded seismic wave signal at the transmitting point (x', y', t); R(x', y', t) is the seismic data resampling function, representing the matching relationship between the target point (x, y, z) and the transmitting point (x', y', t) seismic record; The gradient of the velocity function represents the change of wave velocity in the underground medium.

[0035] Post-stack blue filter processing is adopted to filter the seismic data in time-space domain to enhance the fault imaging capability of seismic signal; three-dimensional Fourier transform The seismic data is converted into frequency domain; where F(u, v, w) represents the function or data in 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 seismic data is filtered by band-pass filtering to improve the fault imaging quality.

[0036] Step 2: Using the discontinuity property of seismic data, the similarity between the target point (x, y, z) and all data points in the spatial range with (x, y, z) as the center and the seismic bin length as the radius is calculated by using the coherence algorithm; when the fault exists, the similarity is 0, and when the fault does not exist, the similarity is 100; through the similarity comparison method, the fault is further highlighted to prepare for the fault evolution.

[0037] Step 3: Through seismic discontinuity attribute cross-section and longitudinal section interpretation, the spatial closure of the fault is ensured, the position and shape of the fault are implemented, and the period of inherited fault is distinguished, and the distinguishing standard is that each time the strike changes is taken as the distinguishing point.

[0038] Step 4: Fault attribute slices are made for different stages to form a fault plane pattern map, and the strike-slip fault plane distribution characteristics are determined. Generally, the change of fault stage corresponds to the stress conversion period, and the stress is greatly weakened. The end of the fault rotates, and the end of the strike-slip fault is dispersed into multiple faults. With the further enhancement of the rotation force, the end of the strike-slip fault is disconnected and dispersed into multiple shorter strike-slip faults, forming a V-shaped strike-slip fault structure. When observed vertically along the strike of the fault, 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 right strike-slip fault. Conversely, it is a counterclockwise rotation, and the relative displacement direction of the fault is parallel to the left strike-slip fault. When the strike-slip fault forms a V-shaped structure, the relative displacement direction of the strike-slip fault is determined according to whether the strata between the strike-slip faults are uplifted or stretched and subsided.

[0039] Step 5: Stress analysis is carried out using the stress Mohr circle. The relative displacement direction of the strike-slip fault reflects the regional comprehensive stress direction, which can be decomposed into two vertical components C and E. The C component direction is relatively compressive stress direction, which is the direction of the maximum principal stress of the region. The E component direction is opposite, which is the direction of the tensile stress. In a tensile basin, the compressive strata associated structure produced by the parallel C component is particularly obvious. By determining the period when the associated structure is produced, the formation period of the strike-slip fault zone can be determined.

[0040] Example 1:

[0041] The Fulongquan sag of Changling fault depression in Songliao Basin is an important gas production area in Jilin Oilfield. The early development around the inversion structure has been realized, but the subsequent evaluation is difficult to be discarded. The main difficulty is to separate from the inversion structure and develop strike-slip faults. The strike of the strike-slip fault is oblique to the tensile fault at a large angle (> 60°), and locally presents a network feature. At the end of the strike-slip fault, the stress is reduced, and the fault rotates, resulting in difficulty in identifying the fault, strong multi-solution, lack of standard for spatial combination of the fault, and further leading to difficulty in identifying the fault-lithology trap.

[0042] In view of the above problems, prestack and poststack processing of seismic data is carried out around the favorable area. Through prestack splicing processing, the time difference and imaging difference between different years of data are eliminated. Then, poststack data blue filter processing is carried out to improve the signal-to-noise ratio of the data and further optimize the fault imaging quality.

[0043] On this basis, the seismic data is processed into a coherence volume, and the seismic signals generated by the difference between the two plates of the fault are used to accurately identify and describe the fault.

[0044] For example Figure 2The fault distribution characteristics of each main period of strike-slip fault are shown; the spatial interpretation of the fault is carried out by using actual seismic data and coherence volume, and the fault evolution is carried out; in Fulongquan sag, the evolution of faults in three periods is carried out, which are fault depression period, fault depression conversion period and depression period; through the coherence slice of each period, the fault mode of each period of strike-slip fault zone is implemented; according to the evolution characteristics of the fault, it is clear that the fault depression period is two northwest-southeast strike-slip faults; 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 feathered faults, and the geosyncline between the feathered faults is according to the classification of the feathered faults, as shown in Figure 3 According to the classification mode diagram, the strike-slip direction of the feathered fault can be effectively distinguished; by judging the arrangement mode of the feathered fault, combined with whether the stratum between the feathered faults is relatively stretched and subsided or extruded and uplifted, the category of the feathered fault can be determined; among them, left row represents left movement, counterclockwise rotation; right row represents right movement, clockwise rotation. It is clear that it is right row right step type; through the evolution characteristics of the fault from the early to the late period, it is determined that the strike-slip fault zone is right-lateral strike-slip.

[0045] As shown in Figures 4-5 , the regional stress direction is parallel to the strike-slip direction, which can be decomposed into two components perpendicular to each other, C and E components, among which the C component direction is opposite, producing thrust faults perpendicular to the C component, and extrusion structures along the C component; combined with the stress Mohr circle analysis, the main stress direction of the strike-slip fault in Fulongquan area is parallel to the strike of the strike-slip fault, which is southeast; along the C component, two opposite extrusion reverse faults are developed, among which the east side is inherited on the early trap-controlling fault, and the Fudong inversion structure is associated; therefore, it can be determined that the strike-slip fault zone and the inversion structure are contemporaneous and homologous, and the formation of the strike-slip fault zone in the late Mingshui Formation is implemented.

[0046] Combined with the above research, as shown in Figure 6 , in the previous research, the left fault combination mode is mainly used in this work area, and through the actual drilling, the fault combination of the key layer series of Denglougu Formation in the fault depression period is modified, and the modified fault combination is more geological; on this basis, a batch of fault-lithology traps with an area of 0.1-2km 2 , a total area of 150km 2 , effectively guide the deployment of well Fu45, and obtain commercial discovery in the strike-slip fault zone.

[0047] Through the above description of the embodiments, those skilled in the art can clearly understand that the embodiments can be implemented by means of software with the necessary universal hardware platforms, the software implements the programming of the related mathematical methods, and the hardware provides the platform and storage. Based on such understanding, the above technical solutions can be embodied in the form of a software product in essence or in the form of a contribution to the related art. The computer software product can be stored in a computer readable storage medium, such as a ROM / RAM, a magnetic disk, an optical disk, etc., and includes a plurality of instructions for causing a computer device (which can be a personal computer, a server, or a network device, etc.) to execute the method described in each embodiment or some parts of the embodiment. Currently, the Geoeast software of PetroChina can implement the prestack and poststack processing, the extraction of discontinuous attributes, and the browsing of seismic data and the interpretation of faults in the present application; the stress analysis currently has no related software support and can be analyzed by manual drawing.

[0048] Finally, it should be noted that: the above embodiments are only used to illustrate the technical solutions of the present application, and not to limit them; although the present application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that: it can still modify the technical solutions recorded in the foregoing embodiments, or make equivalent replacement for part or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present application.

Claims

1. A method for spatial evolution of pull-apart basin extrusion strike-slip fault, comprising the following steps: Step 1: Through pre-stack and post-stack processing of seismic data, fine highlight of strike-slip fault is carried out to ensure the fine identification accuracy of the fault; Step 2: Using the discontinuity attribute of seismic data, the similarity is calculated by comparing the target point (x, y, z) with all data points in the spatial range centered on (x, y, z) with the seismic bin length as the radius; when the fault exists, the similarity is 0, and when the fault does not exist, the similarity is 100; Step 3: Through seismic discontinuity attribute cross section interpretation, the spatial closure of the fault is ensured, the position and shape of the fault are implemented, and the period of the inherited fault is distinguished, and the difference standard is that each time the strike changes is taken as the distinguishing point; Step 4: For different periods, fault attribute slices are made to form a fault plane pattern map, and the strike-slip fault plane distribution characteristics are implemented, and the change of fault period corresponds to the stress conversion period, and the stress is greatly weakened, and the end of the fault is rotated, and the end of the strike-slip fault is dispersed into multiple faults, and with the further enhancement of the rotating force, the end of the strike-slip fault is disconnected and dispersed into multiple shorter strike-slip faults, forming a goose line strike-slip fault structure; observing the strike of the vertical fault, the left end of the strike-slip fault is dispersed upward or the right end is dispersed downward, which is clockwise rotation, and the relative displacement direction of the fault is parallel to the right of the strike-slip fault; otherwise, it is counterclockwise rotation, and the relative displacement direction of the fault is parallel to the left of the strike-slip fault; when the strike-slip fault forms a goose line structure, the relative displacement direction of the strike-slip fault is judged according to whether the stratum between the strike-slip faults is extrusion uplift or stretching subsidence; Step 5: Stress analysis is carried out by using the stress Mohr circle, and the relative displacement direction of the strike-slip fault reflects the regional comprehensive stress direction, which can be decomposed into two vertical components C and E, wherein the direction of the C component is opposite to the extrusion stress direction, which is the direction of the maximum principal stress of the region; the direction of the E component is opposite, which is the direction of the tensile stress; in the tensile basin, the extrusion type stratum associated structure produced by the parallel C component is particularly obvious, and the formation period of the strike-slip fault zone can be determined by implementing the associated structure generation period.

2. The method according to claim 1, wherein, In step 1, the pre-stack depth migration processing is carried out, and the time domain data is converted into depth domain data by using the relationship between travel time and velocity.

3. The method according to claim 2, wherein, In step 1, the pre-stack depth migration processing is as follows: first, the travel time of seismic wave propagation underground is calculated according to the seismic data and the velocity model, then the time seismic data is converted into depth domain data according to the relationship between travel time and velocity, and finally the image of underground structure is obtained by imaging algorithm.

4. The method according to claim 3, wherein, In step 1, the time seismic data is processed by using wave equation and Huygens principle, and 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 a Green function representing the propagation and attenuation of the seismic wavefield generated at the target point (x, y, z); S(x', y', t) is a seismic record, representing the seismic wave signal recorded at the emission point (x', y', t); and R(x', y', t) is a seismic data resampling function, representing the matching relationship between the seismic record at the target point (x, y, z) and the emission point (x', y', t). The gradient of the velocity function represents the change in wave velocity in the subsurface medium.

5. The method of spatial evolution of pull-apart basin compressional strike-slip faults according to claim 1, wherein, In step 1, the blue filter is used for poststack processing, and the seismic data are filtered in the time-space domain; the three-dimensional Fourier transform is used The seismic data are converted to the frequency domain; wherein F(u,v,w) represents a 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 method of spatial evolution of pull-apart basin compressional strike-slip faults according to claim 1, wherein, In step 3, for the tensile basin, with the extension of the strike-slip fault from deep to shallow and from the center to the wings, the structural stress of each period of the strike-slip fault is weakened, resulting in stress difference at different positions of the strike-slip fault, rotation of the strike-slip fault, and different strikes of the faults of different periods.

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