Method and device for determining paleotransformation band of normal fault

Abstract

The invention relates to the technical field of oil-gas exploration and development, and discloses a normal fault ancient transformation zone determination method and device, and the method comprises the steps: calculating the data of fault displacement along the fault trend based on the burial depth of the upper and lower walls of a target fault; determining the distribution positions of a plurality of measurement points based on the fault displacement plane change trend; drawing a fault displacement and extension distance curve according to the fault displacement data of each measurement point at different layers, and identifying an extreme point of the curve; and identifying the target fault ancient transformation band according to the extreme point of the curve. According to the method, the position, the type and the evolution process of the ancient transformation zone are quantitatively recognized based on normal fault growth process recovery for the first time, and a solution is provided for determining the ancient transformation zone of the steep slope zone of the broken basin. The normal fault ancient transformation zone identification method has the advantages of being high in operability and accurate and reliable in prediction result, and provides a basis for exploration and deployment of structure-lithologic oil and gas reservoirs and stratum-lithologic oil and gas reservoirs of abrupt slope zones of fault basins.

Description

Technical Field

[0001] The present invention relates to the technical field of oil and gas exploration and development, and in particular to a method and device for determining a normal fault paleotransformation zone. Background Art

[0002] Fault basins are an important type of oil and gas basins. The Cenozoic continental fault basins in eastern my country are rich in oil and gas resources. Since the 1960s, after nearly 60 years of large-scale oil and gas exploration, geological theories and understandings such as continental oil generation theory, compound oil and gas accumulation in fault basins, "full depression oil-bearing" and "trough oil accumulation" in oil-rich sags have gradually been formed, which have guided and promoted oil and gas exploration in continental fault basins and made important contributions to ensuring our energy security. With the continuous advancement of exploration, the scale of structural closures has been reduced, and the exploration objects need to be transformed into more concealed stratigraphic-lithological oil and gas reservoirs. The steep slope zone of the fault basin is close to the hydrocarbon generation and expulsion center, and various types of favorable sand bodies are developed. It is a key exploration area for structural-lithological and stratigraphic-lithological oil and gas reservoirs. In recent years, breakthroughs have been made in the exploration of lithological oil and gas reservoirs in steep slope zones such as Dongying Sag, Zhanhua Sag, Dongpu Sag, and Huanghekou Sag in the Bohai Bay Basin. Exploration practice shows that predicting the location and spatial distribution of favorable sand bodies adjacent to source rock formations is the key to ensuring the success of lithologic oil and gas reservoir exploration. Sand bodies are brought into the lake basin by rivers, and the latter always flow along the structural highs to the structural lows at the basin margin. The transformation zone (including slope break zone and conversion zone) developed between the head and tail faults of the steep slope belt is usually a local structural low and the entrance of the river into the lake basin. Therefore, from the perspective of structural analysis, the key to finding favorable sand bodies lies in determining the location, characteristics and evolution process of the transformation zone.

[0003] Since the segmented growth process of normal faults is universal (Cartwright et al., Geological Society of London Special Publications, 1996; Morley, AAPG Bulletin, 1999), a large normal fault is usually composed of multiple smaller normal faults. The growth process of normal faults is usually divided into three evolutionary stages: independent growth stage, fault juxtaposition stage, and fault linkage stage (Dou Lirong, Petroleum Exploration and Development, 2000; Dou Lirong & TURNER J, Acta Petrolei Sinica, 2000), also known as isolated growth stage, soft connection stage, and hard connection stage (Fu Xiaofei, et al., Journal of China University of Mining and Technology, 2015; Wang Haixue, et al., Progress in Geophysics, 2019). In the independent growth stage, the normal fault throw has an obvious linear relationship with the extension length, while in the fault juxtaposition stage, the actual fault throw is less than the theoretical fault throw corresponding to the extension length. In the fault linkage stage, the fault throw and extension length show a linear relationship again. For a complete normal fault that is currently in the linkage stage (i.e., the fault appears as a complete and continuous normal fault in the current plane and cross-section diagrams), how to identify the paleotransformation zones developed in its independent growth stage and the fault juxtaposition stage is a key issue that needs to be solved urgently.

[0004] The prior art related to the present invention is a transformation zone analysis technology established based on the head and tail faults that are currently in the isolated growth stage. Transformation zones are a hot topic in basin tectonic research. Dahlstrom first used the term transformation zone to describe the structural characteristics of discontinuous and partially overlapping sections between thrust-fold belts, and believed that transformation zones can maintain the conservation of shortening between overlapping sections of thrust faults, or can gradually and regularly change the shortening. Morley continued to use the concept of transformation zones. He believed that for extensional areas, structural zones that transfer tensile strains also exist. In a regional sense, the transformation zone in the rift can be defined as an accommodative deformation structural system that maintains regional tensile strain conservation or gradual changes. However, the difference between the two is that the former applies the transmission zone to thrust fault zones under the background of compression, while the latter extends it to extensional structures. Domestic scholars, represented by Professor Chen Fajing and Professor Qi Jiafu, have conducted in-depth research on the transformation zone of extensional basins and established a variety of division schemes and analysis techniques, including:

[0005] Technical solution 1: Take the transformation zone as the largest term, and further clarify and define the connotation of the transmission zone, accommodation zone, and transformation zone. The classification basis: First, according to the connection mode between normal faults, the transformation zone is divided into the transmission zone, accommodation zone, and transformation zone; according to the overlap degree of the head and tail normal faults, the transmission zone is further divided into overlapping type and parallel type, and according to the dip relationship of the faults, it is divided into opposite type, back type, and same type; according to the attitude relationship of the head and tail normal faults of the accommodation zone, it is further divided into broken line type, collinear type, and approach type (Chen Fajing, et al., Modern Geology, 2011; Chen Zhaonian et al., Modern Geology, 2005).

[0006] Technical solution 2: According to the relationship between the dips of the head and tail faults, they are divided into the same-direction-inclined type, the anti-inclined type and the opposite-inclined type; according to the overlap, contact mode and arrangement mode of the head and tail faults, they are divided into buffer type, relay type, growth and decline type, transfer type and reduction type, a total of 15 types (Qi Jiafu, Marine Oil and Gas Geology, 2007).

[0007] The existing technical schemes 1 and 2 provide static theoretical models and analysis techniques for the analysis of transformation zones between the head and tail normal faults, which are suitable for the analysis of the style, position and type of transformation zones between normal faults that are currently in the isolated growth stage (or independent growth stage). However, there is a lack of analysis on the identification and characterization of ancient transformation zones of normal faults that are currently in the chain stage of development, and there is a lack of practical guiding significance for the exploration of structural-lithological oil and gas reservoirs and lithological-stratigraphic oil and gas reservoirs in the ancient transformation zones of the steep slope zones of rift basins / depression basins. Summary of the invention

[0008] The present invention aims to solve at least one of the technical problems in the above-mentioned technology to a certain extent. To this end, the first aspect of the present invention proposes a method for determining a normal fault paleotransformation zone, comprising:

[0009] The data of fault throw along the fault direction is calculated based on the buried depth of the upper and lower walls of the target fault;

[0010] Determine the distribution positions of several measuring points based on the variation trend of the fault throw plane;

[0011] According to the fault throw data of each measuring point at different layers, a fault throw and extension distance curve is drawn, and the extreme value points of the curve are identified;

[0012] The target fault paleotransformation zone is identified according to the extreme points of the curve.

[0013] Preferably, the maximum point of the fault throw and extension distance curve represents the maximum fault throw position of the segmented fault, and the minimum point represents the growth point of the segmented fault.

[0014] Preferably, the target fault paleotransformation zone is identified based on the extreme points of the curve, including: when it is determined that the number of growth points of the segmented fault is less than 2, the target fault is determined to be an independent growth fault and no paleotransformation zone is developed.

[0015] Preferably, the target fault paleotransformation zone is identified according to the extreme points of the curve, and further includes: when it is determined that the number of growth points of the segmented fault is not less than 2, determining that the target fault is formed by hard-connecting multiple segmented faults to develop a paleotransformation zone.

[0016] Preferably, identifying the target fault paleotransformation zone according to the extreme points of the curve further includes:

[0017] The target fault is divided into N-1 segments, and the fault growth process is restored layer by layer using the segment maximum fault distance subtraction method, and the location, type and evolution stage of the paleotransformation zone development are determined according to the arrangement of the adjacent head and tail segment faults;

[0018] Wherein, N represents the number of growth points of the segmented fault.

[0019] The second aspect of the present invention provides a normal fault paleotransformation zone determination system, comprising:

[0020] A data calculation module is used to calculate the data of fault throw along the fault direction based on the buried depth of the upper and lower walls of the target fault;

[0021] A measuring point determination module is used to determine the distribution positions of several measuring points based on the variation trend of the fault distance plane;

[0022] A curve drawing module is used to draw a fault throw and extension distance curve according to the fault throw data of each measuring point at different layers, and identify the extreme value points of the curve;

[0023] The fault identification module is used to identify the target fault paleotransformation zone according to the extreme points of the curve.

[0024] Preferably, the maximum point of the fault throw and extension distance curve represents the maximum fault throw position of the segmented fault, and the minimum point represents the growth point of the segmented fault;

[0025] The method performed by the fault identification module includes:

[0026] When it is determined that the number of growth points of the segmented fault is less than 2, the target fault is determined to be an independent growth fault and no paleotransformation zone is developed.

[0027] Preferably, the method performed by the fault identification module further includes:

[0028] When it is determined that the number of growth points of the segmented fault is not less than 2, it is determined that the target fault is formed by hard-connecting a plurality of segmented faults, and a paleotransformation zone is developed.

[0029] Preferably, the method performed by the fault identification module further includes:

[0030] The target fault is divided into N-1 segments, and the fault growth process is restored layer by layer using the segment maximum fault distance subtraction method, and the location, type and evolution stage of the paleotransformation zone development are determined according to the arrangement of the adjacent head and tail segment faults;

[0031] Wherein, N represents the number of growth points of the segmented fault.

[0032] A third aspect of the present invention provides a computer-readable storage medium, in which a computer program or instructions are stored; when the computer program or instructions are executed by a processor, they are at least used to implement the above method.

[0033] Compared with the prior art, the present invention has the following beneficial effects:

[0034] The present invention proposes for the first time a solution for identifying paleotransformation zones of normal faults. The segmented growth process of normal faults is universal. Large-scale normal faults are usually formed by multiple adjacent head and tail faults through soft connections and hard connections. Therefore, a transformation zone must exist during a certain growth period of the fault. As the fault continues to grow, the transformation zone will be destroyed, making it impossible to identify and confirm these paleotransformation zones at the current stage. The present invention proposes for the first time to quantitatively identify the location, type and evolution process of paleotransformation zones based on the restoration of the normal fault growth process, providing a solution for determining paleotransformation zones in steep slope zones of rift basins. The method for identifying paleotransformation zones of normal faults of the present invention is highly operational, and the prediction results are accurate and reliable, providing a basis for the exploration and deployment of structural-lithologic oil and gas reservoirs and stratigraphic-lithologic oil and gas reservoirs in steep slope zones of rift basins.

[0035] Other features and advantages of the present invention will be described in the following description, and partly become apparent from the description, or understood by practicing the present invention. The purpose and other advantages of the present invention can be realized and obtained by the structures particularly pointed out in the written description and the accompanying drawings.

[0036] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] The accompanying drawings are used to provide a further understanding of the present invention and constitute a part of the specification. Together with the embodiments of the present invention, they are used to explain the present invention and do not constitute a limitation of the present invention. In the accompanying drawings:

[0038] Figure 1A schematic diagram of a method for determining a normal fault paleotransformation zone according to an embodiment;

[0039] Figure 2 A schematic diagram of a variation trend of the fault distance plane provided in an embodiment;

[0040] Figure 3 A schematic diagram of a fault throw and extension distance curve provided in an embodiment;

[0041] Figure 4 A schematic diagram of the relationship between the fault extension length and the total fault distance given in the embodiment;

[0042] Figure 5 A schematic diagram of a fault growth process mode provided for an embodiment;

[0043] Figure 6 A schematic diagram of the location and type of paleotransformation zones given for an embodiment;

[0044] Figure 7 A schematic diagram of a normal fault paleotransformation zone determination system provided for an embodiment;

[0045] Figure 8 A schematic diagram of a computer-readable storage medium. DETAILED DESCRIPTION

[0046] The preferred embodiments of the present invention are described below in conjunction with the accompanying drawings. The preferred embodiments described herein are only used to illustrate and explain the present invention and are not used to limit the present invention.

[0047] Figure 1 The method for determining a normal fault paleotransformation zone provided by the present invention comprises:

[0048] S101. Calculating data on the fault offset along the fault strike based on the buried depth of the upper and lower walls of the target fault;

[0049] S102. Determine the distribution positions of several measuring points based on the variation trend of the fault distance plane;

[0050] S103. Draw a fault throw and extension distance curve according to the fault throw data of each measuring point at different layers, and identify the extreme value points of the curve;

[0051] S104. Identify the target fault paleotransformation zone according to the extreme points of the curve.

[0052] In some embodiments of the present invention, the maximum point of the fault throw and extension distance curve represents the maximum fault throw position of the segmented fault, and the minimum point represents the growth point of the segmented fault.

[0053] In some embodiments of the present invention, the target fault paleotransformation zone is identified according to the extreme points of the curve, including: when it is determined that the number of growth points of the segmented fault is less than 2, the target fault is determined to be an independent growth fault and no paleotransformation zone is developed; when it is determined that the number of growth points of the segmented fault is not less than 2, the target fault is determined to be a plurality of segmented faults spliced ​​together by hard connection and a paleotransformation zone is developed. In some embodiments of the present invention, the target fault paleotransformation zone is identified according to the extreme points of the curve, and also includes: dividing the target fault into N-1 segments, using the segment maximum fault distance subtraction method to restore the fault growth process layer by layer, and determining the location, type and evolution stage of the paleotransformation zone development according to the arrangement of adjacent head and tail segmented faults; wherein N represents the number of growth points of the segmented fault.

[0054] Using the method of the present invention, the Sufyan Sag (a typical continental fault depression) in the southern Jiangsu steep slope zone was used as an example to identify the normal fault paleotransformation zone. The process includes:

[0055] Step 1: According to the burial depth of the two plates of the Sunan steep slope zone sag-control fault-Sunan (FS) fault, the fault throws at the top of the basement, the top of the AG3 segment, the top of the AG2 segment, the top of the AG1 segment, and the top of the Bentiu Formation were calculated, and the fault throw plane change trend (the fault throw plane change trend is shown in Figure 2) was used to calculate the fault throw plane change trend. Figure 2 As shown, the horizontal and vertical axes represent the location range of the study area; the gray represents the depth gradient; the numbers are the locations of the measurement points, and the locations of the measurement points and their fault distances at the top of the base (see Table 1 for details), the top of the AG3 segment, the top of the AG2 segment, and the top of the AG1 segment (see Table 2 for details) are determined.

[0056] Table 1

[0057]

[0058]

[0059] Table 2

[0060]

[0061]

[0062] Step 2: Based on the current fault throw and extension distance curves of each measuring point at the top of the basement, the top of AG3, the top of AG2, the top of AG1 and the top of the Bentiu Formation (such as Figure 3 The maximum and minimum points of the curve are identified. The maximum point of the fault throw corresponds to the maximum fault throw position of the segmented fault, while the minimum point of the fault throw represents the growth point of the segmented fault.

[0063] Step 3: After dividing the Sunan Fault into two segmented faults according to the location and number of growth points of the Sunan Fault, the maximum fault distance subtraction method of the segmented faults is used to restore the growth stages of the Sunan Fault at the end of the deposition of the AG1 segment, the end of the deposition of the AG2 segment, the end of the deposition of the AG3 segment, and the end of the deposition of the AG4 segment layer by layer (e.g. Figure 4 shown).

[0064] Step 4: Based on the results of the fault growth process recovery, establish the Su Nan fault growth process model (such as Figure 5 As shown in the figure), determine the location and type of paleotransformation zones (such as Figure 6 (shown)

[0065] The growth evolution of the FS fault can be divided into three stages. Take the growth process of the fault at the top of the basement as an example: at the end of the deposition of the AG5-AG2 segments, the fault appeared as two independent faults, FS-1 and FS2, at the top of the basement. The two faults continued to grow toward each other but were not connected, and were in an isolated growth stage. During the deposition of the AG1 segment, the FS-1 and FS2 faults were linked at the top of the basement and completed the evolution from the soft connection stage to the hard connection stage. During the deposition of the Bentiu Formation and later strata, the fault appeared as a complete fault linked to the east and west at the top of the basement and was active as a whole ( Figure 5 ).

[0066] A transformation zone is developed between the two isolated faults. The transformation zone is located 37.8 to 45.3 km east of the western end of the FS fault and has been continuously developed during the deposition of the AG5 to AG1 segments. The breakpoint burial depth curve of the Sunan Fault (FS) at the top of the basement and the top of the AG3 to AG1 segments shows that the FS-1 fault in the western section of the fault has the same dip as the FS-2 fault in the eastern section, both of which are north-dipping. The arrangement is right-order right-lateral. Therefore, it can be seen that the type of the transformation zone is the same direction type ( Figure 5 &6).

[0067] During the deposition of AG5 to AG2, the fault-distance curves of the FS fault at the top of the basement, the top of the AG3 segment, and the top of the AG2 segment all showed two isolated segments in the west and the east, indicating that during this depositional stage, the FS-1 segment and the FS-2 segment were in an isolated growth stage. The types of the transformation zone at the top of the basement, the top of the AG3 segment, and the top of the AG2 segment were all unidirectional buffer transformation zones or conversion slopes, with a slope dipping northwest ( Figure 6 ).

[0068] like Figure 7As shown, based on the same technical concept, the present invention also provides a normal fault paleotransformation zone determination system, including: a data calculation module 201, used to calculate the data of the fault displacement along the fault direction based on the buried depth of the upper and lower plates of the target fault; a measuring point determination module 202, used to determine the distribution positions of several measuring points based on the plane change trend of the fault displacement; a curve drawing module 203, used to draw the fault displacement and extension distance curve according to the fault displacement data of each measuring point at different layers, and identify the extreme points of the curve; a fault identification module 204, used to identify the target fault paleotransformation zone according to the extreme points of the curve. Figure 8 As shown, the present invention also provides a computer-readable storage medium 1100, in which a computer program or instruction is stored; when the computer program or instruction is executed by a processor, it is at least used to implement the above-mentioned method for determining the normal fault paleotransformation zone.

[0069] Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include these modifications and variations.

Claims

1. A method for determining a normal fault paleotransformation zone, characterized in that: include: The data of fault throw along the fault direction is calculated based on the buried depth of the upper and lower walls of the target fault; Determine the distribution positions of several measuring points based on the variation trend of the fault throw plane; According to the fault throw data of each measuring point at different layers, a fault throw and extension distance curve is drawn, and the extreme value points of the curve are identified; The target fault paleotransformation zone is identified according to the extreme points of the curve.

2. The method for determining a normal fault paleotransformation zone according to claim 1, characterized in that: The maximum point of the fault throw and extension distance curve represents the maximum fault throw position of the segmented fault, and the minimum point represents the growth point of the segmented fault.

3. The method for determining a normal fault paleotransformation zone according to claim 2, characterized in that: The target fault paleotransformation zone is identified according to the extreme points of the curve, including: when it is determined that the number of growth points of the segmented fault is less than 2, the target fault is determined to be an independent growth fault and no paleotransformation zone is developed.

4. The method for determining a normal fault paleotransformation zone according to claim 2, characterized in that: The target fault paleotransformation zone is identified according to the extreme points of the curve, and also includes: when it is determined that the number of growth points of the segmented fault is not less than 2, determining that the target fault is formed by hard-connecting multiple segmented faults to develop a paleotransformation zone.

5. The method for determining a normal fault paleotransformation zone according to claim 2, characterized in that: The target fault paleotransformation zone is identified according to the extreme value points of the curve, and further includes: The target fault is divided into N-1 segments, and the fault growth process is restored layer by layer using the segment maximum fault distance subtraction method, and the location, type and evolution stage of the paleotransformation zone development are determined according to the arrangement of the adjacent head and tail segment faults; Wherein, N represents the number of growth points of the segmented fault.

6. A normal fault paleotransformation zone determination system, characterized in that: include: A data calculation module is used to calculate the data of fault throw along the fault direction based on the buried depth of the upper and lower walls of the target fault; A measuring point determination module is used to determine the distribution positions of several measuring points based on the variation trend of the fault distance plane; A curve drawing module is used to draw a fault throw and extension distance curve according to the fault throw data of each measuring point at different layers, and identify the extreme value points of the curve; The fault identification module is used to identify the target fault paleotransformation zone according to the extreme points of the curve.

7. The normal fault paleotransformation zone determination system according to claim 6, characterized in that: The maximum point of the fault throw and extension distance curve represents the maximum fault throw position of the segmented fault, and the minimum point represents the growth point of the segmented fault; The method performed by the fault identification module includes: When it is determined that the number of growth points of the segmented fault is less than 2, the target fault is determined to be an independent growth fault and no paleotransformation zone is developed.

8. The normal fault paleotransformation zone determination system according to claim 7, characterized in that: The method performed by the fault identification module further includes: When it is determined that the number of growth points of the segmented fault is not less than 2, it is determined that the target fault is formed by hard-connecting a plurality of segmented faults, and a paleotransformation zone is developed.

9. The normal fault paleotransformation zone determination system according to claim 7, characterized in that: The method performed by the fault identification module further includes: The target fault is divided into N-1 segments, and the fault growth process is restored layer by layer using the segment maximum fault distance subtraction method, and the location, type and evolution stage of the paleotransformation zone development are determined according to the arrangement of the adjacent head and tail segment faults; Wherein, N represents the number of growth points of the segmented fault.

10. A computer-readable storage medium, characterized in that: The computer-readable storage medium stores a computer program or instructions; when the computer program or instructions are executed by the processor, they are at least used to implement the method according to any one of claims 1 to 5.

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