A method for identifying a strong-tectonic extrusion zone clastic rock tensional-shearing fracture and related device

Abstract

A method for identifying a tensile-shear fracture in a strong-tectonic extrusion zone clastic rock and related device, comprising: collecting geological data of a well drilling a target layer at a turning end position of an extrusion anticline in a same tectonic belt; determining a homogenized fracture opening degree in a single lithologic layer and a difference between a horizontal maximum principal stress and a vertical stress of the single lithologic layer based on the geological data, drawing an intersection graph, and determining a potential position of tensile-shear fracture development on the intersection graph; verifying the potential position of tensile-shear fracture development on the intersection graph through a tensile-shear fracture identified on a single well core; and determining an identification standard of the tensile-shear fracture based on the verification. The present application calculates in-situ ground stress and the difference between the horizontal maximum principal stress and the vertical stress by using logging data, and identifies the tensile-shear fracture of a well section lacking coring data in a strong-tectonic extrusion zone based on core data verification and the relationship between the normalized fracture opening degree and the corresponding ground stress difference, thereby providing a basis for the prediction and evaluation of the tensile-shear fracture in a similar area.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of oil and gas exploration and development, and particularly relates to a method for identifying clastic rock tensile-shear fractures in a strong tectonic extrusion area and a related device. BACKGROUND

[0002] Oil and gas resources are all stored in reservoirs, and the filtration capacity of the reservoirs has a significant impact on oil and gas exploration and development. In China, the potential of clastic rock oil and gas resources is huge. Among the many control factors of deep clastic rock effective reservoirs, tectonic fractures are the key control factors for the scale development of deep low-porosity and low-permeability reservoirs and the enrichment of oil and gas in strong tectonic extrusion areas. They are not only important reservoir spaces, but also the seepage channels of various formation fluids, especially dissolution fluids and hydrocarbon fluids. Tectonic fractures, especially fractures with a large underground opening degree, can greatly improve the filtration capacity of low-permeability and tight reservoirs. The opening degree of a fracture is closely related to the mechanical properties of the fracture. Generally, the opening degree of a tensile fracture is the largest, the opening degree of a tensile-shear fracture is the second, and the opening degree of a shear fracture is the smallest. In a strong tectonic extrusion area, tensile fractures rarely develop. Therefore, how to identify tensile-shear fractures with a large opening degree is of great significance for the prediction of high-permeability reservoirs.

[0003] At present, the main method for identifying tensile-shear fractures in sandstone reservoirs is to visually and intuitively judge the appearance of the fractures on outcrops or drilling cores. However, the above methods have certain problems:

[0004] (1) Outcrops are located on the ground and are mostly located at the edge of a basin. Oil and gas reservoirs are buried several kilometers underground and are mostly located in the interior of a basin. Although outcrops can directly identify tensile-shear fractures, they cannot solve the problem of identifying fractures in underground reservoirs.

[0005] (2) The method for identifying tensile-shear fractures based on core observation can play a good role in positions where drilling cores are taken, but the layer sections where drilling cores are taken are few, especially for deep clastic rock reservoirs, the cost of drilling cores is high, and this method is not applicable to most layer sections without cores. SUMMARY

[0006] The purpose of the present application is to provide a method for identifying tensile-shear fractures in clastic rock in a strong tectonic extrusion area and a related device to solve the problem of identifying fractures in underground reservoirs.

[0007] To achieve the above purpose, the present application adopts the following technical solutions:

[0008] In a first aspect, the present application provides a method for identifying tensile-shear fractures in clastic rock in a strong tectonic extrusion area, comprising:

[0009] Collecting geological data of a well that drills a target layer at a position of a hinge of a compressional anticline in a same tectonic belt;

[0010] Based on the geological data, the homogenized fracture opening degree in a single lithologic layer and the difference between the horizontal maximum principal stress and the vertical stress of the single lithologic layer are determined, a crossplot is drawn, and the potential position of the tensile-shear fracture development is determined on the crossplot;

[0011] The potential position of the tensile-shear fracture development determined on the crossplot is verified by the tensile-shear fracture identified on the single well core;

[0012] On the basis of the verification, the identification criterion of the tensile-shear fracture is determined.

[0013] Optionally, the geological data includes core logging data, imaging logging data and interpretation results, conventional logging data and interpretation results, core photos and description results.

[0014] Optionally, the number and name of the well with imaging logging and drilling coring are determined according to the geological data, and it is ensured that at least one well has both imaging logging and drilling coring and the tensile-shear fracture can be identified on the well core.

[0015] Optionally, the crossplot is drawn, and the potential position of the tensile-shear fracture development is determined on the crossplot:

[0016] The homogenized fracture opening degree in a single lithologic layer is determined, and then the difference between the horizontal maximum principal stress and the vertical stress of the corresponding single lithologic layer is determined, and a crossplot is drawn according to them, and the area with larger fracture opening degree and the vertical stress close to or greater than the horizontal maximum principal stress on the crossplot is determined as the potential position of the tensile-shear fracture development.

[0017] Optionally, the potential position of the tensile-shear fracture development determined on the crossplot is verified:

[0018] If the identification results of the logging data and the core data are consistent, it is considered that the logging identification result is reliable.

[0019] Optionally, if they are not consistent, the logging identification scheme is adjusted, the identification is performed again, and the logging identification result is compared with the identification result of the core data to determine whether the logging identification result is reliable.

[0020] Optionally, the identification criterion of the tensile-shear fracture is determined:

[0021] The top boundary of the homogenized opening degree envelope of the shear fracture is determined according to the crossplot, and the discrimination value of the homogenized fracture opening degree is determined accordingly; then the discrimination value of the difference between the horizontal maximum principal stress and the vertical stress is determined according to the right boundary of the tensile-shear fracture with larger opening degree, and the identification criterion of the tensile-shear fracture in the strong tectonic extrusion area of the clastic rock is established according to the relationship between the homogenized fracture opening degree in a single lithologic layer and the difference between the horizontal maximum principal stress and the vertical stress.

[0022] In a second aspect, the present invention provides a system for identifying tension-shear fractures in clastic rocks in a strong tectonic compression zone, comprising:

[0023] A data acquisition module is used to collect geological data of wells that encounter target layers at the turning point of the compression anticline within the same structural belt;

[0024] A mapping module is used to determine the homogenized fracture opening within a single lithology layer and the difference between the horizontal maximum principal stress and the vertical stress within a single lithology layer based on geological data, draw a crossplot, and identify the potential locations for the development of tension-shear fractures on the crossplot;

[0025] Verification module, used to verify the potential locations of tensile shear fracture development identified on the cross-plot using tensile shear fractures identified on single well cores;

[0026] The output module is used to determine the identification criteria of tension-shear cracks based on the verification.

[0027] In a third aspect, the present invention provides a computer device comprising a memory, a processor, and a computer program stored in the memory and executable on the processor. When the processor executes the computer program, the processor implements the steps of a method for identifying tensile shear fractures in clastic rocks in a strong tectonic compression zone.

[0028] In a fourth aspect, the present invention provides a computer-readable storage medium storing a computer program, which, when executed by a processor, implements the steps of a method for identifying tensile shear fractures in clastic rocks in a strong tectonic compression zone.

[0029] Compared with the prior art, the present invention has the following technical effects:

[0030] In response to the technical problems existing in the above-mentioned method for identifying tension-shear fractures in the absence of core data, the present invention proposes a method for identifying tension-shear fractures in sandstone reservoirs in strong tectonic compression areas based on logging data. This method is an indirect geological discrimination method. On the one hand, the fracture aperture is obtained based on the interpretation results of electrical imaging logging data, and the normalized fracture aperture of a single well is calculated. On the other hand, the in-situ ground stress is calculated using the logging data and the difference between the horizontal maximum principal stress and the vertical stress is calculated. On the basis of verification with core data, the relationship between the normalized fracture aperture and the corresponding ground stress difference is used to identify tension-shear fractures in well sections in strong tectonic compression areas where core data is lacking, providing a basis for the prediction and evaluation of tension-shear fractures in similar areas. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 Flow chart of the method for identifying tension-shear fractures in clastic rocks in a strong tectonic compression zone provided by an embodiment of the present invention

[0032] Figure 2The cross-plot, verification plot, and identification plot of the homogenized crack opening and ground stress difference provided by the embodiments of the present invention are shown. DETAILED DESCRIPTION

[0033] The present invention will be further described below with reference to the accompanying drawings:

[0034] See also Figures 1 to 2 In response to the technical problems existing in the above-mentioned method for identifying tension-shear fractures in the absence of core data, the present invention proposes a method for identifying tension-shear fractures in sandstone reservoirs in strong tectonic compression areas based on logging data. This method is an indirect geological discrimination method. On the one hand, the fracture aperture is obtained based on the interpretation results of electrical imaging logging data, and the normalized fracture aperture of a single well is calculated; on the other hand, the in-situ ground stress is calculated using the logging data and the difference between the horizontal maximum principal stress and the vertical stress is calculated. On the basis of verification with core data, the relationship between the normalized fracture aperture and the corresponding ground stress difference is used to identify tension-shear fractures in the well sections in the strong tectonic compression area where there is a lack of core data.

[0035] Example 1:

[0036] A method for identifying tension-shear fractures in clastic rocks in a strong tectonic compression zone comprises:

[0037] Collect geological data of wells that encounter the target layer at the turning point of the compression anticline within the same structural belt;

[0038] Based on geological data, determine the homogenized fracture opening within a single lithologic layer and the difference between the maximum horizontal principal stress and the vertical stress within the single lithologic layer, draw a crossplot, and identify potential locations for the development of tension-shear fractures on the crossplot;

[0039] The potential locations of tensile shear fractures identified on the cross-plot are verified by the tensile shear fractures identified on the single well cores.

[0040] Based on the verification, the identification criteria for tension-shear cracks are determined.

[0041] Example 2:

[0042] The specific plan is as follows:

[0043] (1) Select wells with complete data on the target layer drilled near the turning point of the compression anticline in the same structural belt with similar tectonic stress fields in the study area, and collect as much geological data as possible related to this plan, including core and lithologic logging data, imaging logging data and interpretation results, conventional logging data and interpretation results, core photos and description results, etc. Determine the number and names of wells with imaging logging and drilling coring (Table 1). It is necessary to ensure that there is at least one well with both imaging logging and drilling coring and that tension-shear fractures can be identified in the core of this well so that the identification results can be verified.

[0044] (2) Obtain the weighted arithmetic mean fracture aperture of each open fracture from the results of electrical imaging logging interpretation. Then, extract the lithology and thickness data of the single lithology layer with developed fractures from the lithologic logging data. Calculate the average fracture aperture within the single lithology layer based on the number of fractures developed in the single lithology layer and the corresponding fracture aperture. Normalize the fracture aperture of each well by dividing the average fracture aperture of the single lithology layer in the target layer of the well by the average fracture aperture of the target layer of the well, thereby obtaining the normalized fracture aperture within the single lithology layer of the target layer of the well (dimension is 1, Table 2). Then, obtain the average vertical stress, average horizontal maximum principal stress and average horizontal minimum principal stress within the single lithology layer from the results of the in-situ stress interpretation of the logging data. Subtract the vertical stress from the horizontal maximum principal stress to obtain the difference between the two in-situ stresses within the same lithology layer (unit: MPa, Table 2). When a tensile stress field develops in the formation, the difference is less than or equal to zero. The difference between the horizontal maximum principal stress and the vertical stress is used as the abscissa, and the normalized fracture aperture of the corresponding lithologic layer is used as the ordinate to draw the corresponding cross-plot ( Figure 2 ). On the cross-plot, determine the area where the crack opening is large and the vertical stress is close to or greater than the horizontal maximum principal stress, that is, the potential location for the development of tension-shear cracks.

[0045] Table 1 Statistics of drilling geological data in the study area

[0046]

[0047] (3) According to the tensile shear fractures identified on the cross-plot, find the corresponding core data. Carefully observe the morphology of the fractures on the corresponding core and determine the nature of the fractures. If the result of the core data identification is also a tensile shear fracture, the logging identification result is considered reliable; if the two are inconsistent, the logging identification scheme needs to be adjusted. The verification results of this embodiment show that the tensile shear fractures identified on the cross-plot are reliable, because the fractures identified on the corresponding core are also tensile shear fractures ( Figure 2 ): Unlike shear fractures, whose walls are smooth and straight, they are slightly rough and uneven, with small amounts of authigenic minerals often filling low areas of the surrounding rock. Consequently, shear deformation and tensile deformation are observed along the fracture surface and in the direction normal to the fracture surface, respectively.

[0048] Table 2 Comprehensive data of single lithologic layer, fracture opening and ground stress

[0049]

[0050]

[0051]

[0052] (4) Based on the core data verification, the identification criteria of the tensile-shear fractures in the target layer of the study area are determined. First, the judgment limit of the fracture opening is determined. According to the intersection diagram ( Figure 2 ) It is determined that the top boundary of the shear crack homogenization opening envelope is approximately 1.5. Figure 2 The difference between the maximum horizontal principal stress and the vertical stress at the right boundary of a tensile shear fracture with a large aperture is approximately 5 MPa. Therefore, when the in-situ stress difference within a single lithologic layer is less than 5 MPa and the normalized fracture aperture is greater than 1.5, the tectonic fracture developed within that lithologic layer is a tensile shear fracture. Combined with the above analysis, based on the relationship between the normalized fracture aperture and the difference between the maximum horizontal principal stress and the vertical stress within a single lithologic layer, a standard for identifying tensile shear fractures in clastic rocks in strong tectonic compression zones can be established (Table 3), providing a basis for the prediction and evaluation of tensile shear fractures in similar areas.

[0053] Table 3 Identification criteria for tensile shear fractures in the target layer of the study area based on the relationship between the homogenized fracture aperture and the ground stress difference

[0054] Homogenized fracture opening within a single lithologic layer Difference between horizontal maximum principal stress and vertical stress / MPa Crack properties ＞1.5 ≤5 Tension shear cracks ＞1.5 ＞5 Shear cracks ＜1.5 ≤5 Shear cracks ＜1.5 ＞5 Shear cracks

[0055] In another embodiment of the present invention, a system for identifying tensile shear fractures in clastic rocks in a strong tectonic compression zone is provided, which can be used to implement the above-mentioned method for identifying tensile shear fractures in clastic rocks in a strong tectonic compression zone. Specifically, the system includes:

[0056] A data acquisition module is used to collect geological data of wells that encounter target layers at the turning point of the compression anticline within the same structural belt;

[0057] A mapping module is used to determine the homogenized fracture opening within a single lithology layer and the difference between the horizontal maximum principal stress and the vertical stress within a single lithology layer based on geological data, draw a crossplot, and identify the potential locations for the development of tension-shear fractures on the crossplot;

[0058] Verification module, used to verify the potential locations of tensile shear fracture development identified on the cross-plot using tensile shear fractures identified on single well cores;

[0059] The output module is used to determine the identification criteria of tension-shear cracks based on the verification.

[0060] The module division in the embodiments of the present invention is illustrative and represents only one logical functional division. In actual implementation, other division methods may be used. Furthermore, the functional modules in various embodiments of the present invention may be integrated into a single processor, exist physically as separate modules, or two or more modules may be integrated into a single module. The integrated modules may be implemented in either hardware or software functional modules.

[0061] In another embodiment of the present application, a computer device is provided, which comprises a processor and a memory, the memory is configured to store a computer program, the computer program comprises program instructions, and the processor is configured to execute the program instructions stored in the computer storage medium. The processor can be a central processing unit (CPU), and can also be other general-purpose processors, digital signal processors (DSP), application specific integrated circuits (ASIC), field-programmable gate arrays (FPGA) or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc., which are the computing core and control core of the terminal, and are suitable for implementing one or more instructions, and are particularly suitable for loading and executing one or more instructions in the computer storage medium to implement a corresponding method process or a corresponding function; the processor in the embodiments of the present application can be used for the operation of the strong tectonic extrusion zone clastic rock tensile-shear fracture identification method.

[0062] In another embodiment of the present application, the present application further provides a storage medium, specifically a computer readable storage medium (Memory), which is a memory device in the computer device, and is configured to store programs and data. It can be understood that the computer readable storage medium herein can include the built-in storage medium in the computer device, and of course can also include the expansion storage medium supported by the computer device. The computer readable storage medium provides a storage space, and the storage space stores the operating system of the terminal. In addition, one or more instructions suitable for being loaded and executed by the processor are also stored in the storage space, and the instructions can be one or more computer programs (including program codes). It should be noted that the computer readable storage medium herein can be a high-speed RAM memory, or a non-volatile memory such as at least one disk memory. One or more instructions stored in the computer readable storage medium can be loaded and executed by the processor to implement the corresponding steps of the strong tectonic extrusion zone clastic rock tensile-shear fracture identification method in the above embodiments.

[0063] It will be understood by those skilled in the art that embodiments of the present invention may be provided as methods, systems, or computer program products. Thus, the present invention may take the form of an entirely hardware embodiment, an entirely software embodiment, or an embodiment combining software and hardware. Furthermore, the present invention may take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to magnetic disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0064] The present invention is described with reference to flowcharts and / or block diagrams of methods, devices (systems), and computer program products according to embodiments of the present invention. It should be understood that each process and / or block in the flowcharts and / or block diagrams, as well as combinations of processes and / or blocks in the flowcharts and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to produce a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the flowcharts and / or block diagrams. Figure 1 a process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0065] These computer program instructions may also be stored in a computer readable memory that can direct a computer or other programmable data processing device to work in a specific manner, so that the instructions stored in the computer readable memory produce an article of manufacture comprising an instruction device, which implements the process Figure 1 a process or multiple processes and / or boxes Figure 1 The function specified in one or more boxes.

[0066] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operational steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing the instructions executed on the computer or other programmable device for implementing the process. Figure 1 a process or multiple processes and / or boxes Figure 1 A step that specifies a function in one or more boxes.

[0067] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to the above embodiments, ordinary technicians in the field should understand that the specific implementation methods of the present invention can still be modified or replaced by equivalents. Any modification or equivalent replacement that does not depart from the spirit and scope of the present invention should be covered by the scope of protection of the claims of the present invention.

Claims

1. A method for identifying tension-shear fractures in clastic rocks in strong tectonic compression zones, characterized by: include: Collect geological data of wells that encounter the target layer at the turning point of the compression anticline within the same structural belt; Based on geological data, determine the homogenized fracture opening within a single lithologic layer and the difference between the maximum horizontal principal stress and the vertical stress within the single lithologic layer, draw a crossplot, and identify potential locations for the development of tension-shear fractures on the crossplot; The potential locations of tensile shear fractures identified on the cross-plot are verified by the tensile shear fractures identified on the single well cores. Based on the verification, the identification criteria of tension-shear cracks are determined; Draw an intersection diagram and determine the potential location of tension-shear crack development on the intersection diagram: Determine the homogenized fracture opening within a single lithologic layer, then determine the difference between the horizontal maximum principal stress and the vertical stress of the corresponding single lithologic layer. Draw a crossplot based on these differences, and identify areas on the crossplot where the fracture opening is large and the vertical stress is close to or greater than the horizontal maximum principal stress, i.e., potential locations for the development of tension-shear fractures. Identification criteria for tensile shear cracks: The top boundary of the homogenized shear fracture opening envelope is determined based on the crossplot, and the discrimination value of the homogenized fracture opening is determined accordingly. The discrimination value of the difference between the horizontal maximum principal stress and the vertical stress is then determined based on the right boundary of the tensile-shear fracture with a larger opening. Based on the relationship between the homogenized fracture opening and the difference between the horizontal maximum principal stress and the vertical stress within a single lithologic layer, an identification standard for tensile-shear fractures in clastic rocks in strong tectonic compression zones is established.

2. The method for identifying tensile shear fractures in clastic rocks in a strong tectonic compression zone according to claim 1, characterized in that: Geological data include core logging data, imaging logging data and interpretation results, conventional logging data and interpretation results, core photos and description results.

3. The method for identifying tensile shear fractures in clastic rocks in a strong tectonic compression zone according to claim 2, characterized in that: Based on the geological data, the number and names of the wells with imaging logging and drilling coring were determined to ensure that there was at least one well with both imaging logging and drilling coring and that tension-shear fractures could be identified on the core of the well.

4. The method for identifying tension-shear fractures in clastic rocks in a strong tectonic compression zone according to claim 1, characterized in that: Verify the potential locations of tensile-shear crack development determined on the intersection diagram: If the identification results of the well logging data are consistent with those of the core data, the well logging identification results are considered reliable.

5. The method for identifying tensile shear fractures in clastic rocks in a strong tectonic compression zone according to claim 4, characterized in that: If the two are inconsistent, adjust the well logging identification plan, re-identify, and then compare the identification results with the core data to determine whether the well logging identification results are reliable.

6. A system for identifying tension-shear fractures in clastic rocks in strong tectonic compression zones, characterized by: include: A data acquisition module is used to collect geological data of wells that encounter target layers at the turning point of the compression anticline within the same structural belt; A mapping module is used to determine the homogenized fracture opening within a single lithology layer and the difference between the horizontal maximum principal stress and the vertical stress within a single lithology layer based on geological data, draw a crossplot, and identify the potential locations for the development of tension-shear fractures on the crossplot; Verification module, used to verify the potential locations of tensile shear fracture development identified on the cross-plot using tensile shear fractures identified on single well cores; An output module is used to determine the identification criteria of tension-shear cracks based on the verification; Draw an intersection diagram and determine the potential location of tension-shear crack development on the intersection diagram: Determine the homogenized fracture opening within a single lithologic layer, then determine the difference between the horizontal maximum principal stress and the vertical stress of the corresponding single lithologic layer. Draw a crossplot based on these differences, and identify areas on the crossplot where the fracture opening is large and the vertical stress is close to or greater than the horizontal maximum principal stress, i.e., potential locations for the development of tension-shear fractures. Identification criteria for tensile shear cracks: The top boundary of the homogenized shear fracture opening envelope is determined based on the crossplot, and the discrimination value of the homogenized fracture opening is determined accordingly. The discrimination value of the difference between the horizontal maximum principal stress and the vertical stress is then determined based on the right boundary of the tensile-shear fracture with a larger opening. Based on the relationship between the homogenized fracture opening and the difference between the horizontal maximum principal stress and the vertical stress within a single lithologic layer, an identification standard for tensile-shear fractures in clastic rocks in strong tectonic compression zones is established.

7. A computer device comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein: When the processor executes the computer program, the steps of the method for identifying tensile shear fractures in clastic rocks in a strong tectonic compression zone as described in any one of claims 1 to 5 are implemented.

8. A computer-readable storage medium storing a computer program, characterized in that: When the computer program is executed by a processor, the steps of the method for identifying tension-shear fractures in clastic rocks in a strong tectonic compression zone as described in any one of claims 1 to 5 are implemented.

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