Strong structure extrusion area clastic rock tension-shear crack identification method and related device

Abstract

The invention discloses a method for identifying clastic rock tension-shear cracks in a strong tectonic extrusion area and a related device. The method comprises the following steps: acquiring geological data of a well of a drilled target stratum at an extrusion anticline turning end position in the same tectonic zone; based on the geological data, determining the opening degree of the homogenized fracture in the single lithologic layer and the difference value between the horizontal maximum principal stress and the vertical stress of the single lithologic layer, drawing a cross plot, and determining the potential development position of the tension-shear fracture on the cross plot; verifying the potential position for determining the development of the tension-shear fracture on the cross plot through the identified tension-shear fracture on the single well core; and on the basis of verification, determining an identification standard of the tension shear crack. According to the method, the in-situ crustal stress and the difference value between the horizontal maximum principal stress and the vertical stress are calculated by using the logging data, and on the basis of core data verification, the tension-shear fracture of the well section lacking the coring data in the strong structure extrusion area is identified by using the relationship between the normalized fracture opening and the corresponding crustal stress difference. And a basis is provided for prediction and evaluation of tension-shear cracks in similar regions.

Description

Technical Field

[0001] The invention belongs to the technical field of oil and gas exploration and development, and in particular relates to a method for identifying tension-shear fractures of clastic rocks in a strong structural compression zone and a related device. Background Art

[0002] Oil and gas resources are all stored in reservoirs, and the permeability of reservoirs has a significant impact on oil and gas exploration and development. In my country, clastic oil and gas resources have great potential. Among the many controlling factors of deep clastic effective reservoirs, structural fractures are the key controlling factors for the large-scale development and oil and gas enrichment of deep low-porosity and low-permeability reservoirs in strong structural compression areas. It is not only an important storage space, but also a seepage channel for various formation fluids, especially dissolution fluids and hydrocarbon fluids. Structural fractures, especially those with relatively large underground opening, can greatly improve the permeability of low-permeability-tight reservoirs. The opening of the fracture is closely related to the mechanical properties of the fracture. Generally, the opening of tension fractures is the largest, followed by tension-shear fractures, and the smallest is (compression) shear fractures. In strong structural compression areas, tension fractures are rarely developed. Therefore, how to identify tension-shear fractures with large opening 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 make an intuitive judgment based on the morphology of fractures on field outcrops or drilling cores. However, the above methods all have certain problems:

[0004] (1) Field outcrops are located on the surface, and are mostly located at the edge of the basin. Oil and gas reservoirs are buried several thousand meters underground, and most of them are located inside the basin. Although field outcrops can directly identify tension-shear fractures, they cannot solve the problem of fracture identification in underground reservoirs.

[0005] (2) The method of identifying tension-shear fractures based on core observation can play a good role in locations where cores are drilled and sampled. However, the number of layers where cores are drilled and sampled is small, especially in deep clastic reservoirs. The cost of drilling and sampling is very high. For most layers where cores are not drilled, this method is not applicable. Summary of the invention

[0006] The purpose of the present invention is to provide a method and related device for identifying tension-shear fractures of clastic rocks in a strong structural compression zone, so as to solve the problem of fracture identification in underground reservoirs.

[0007] To achieve the above object, the present invention adopts the following technical solutions:

[0008] In a first aspect, the present invention provides a method for identifying tension-shear fractures in clastic rocks in a strong tectonic compression zone, comprising:

[0009] Collect geological data of wells that encounter the target layer at the turning point of the compression anticline in the same structural belt;

[0010] Based on geological data, determine the homogenized fracture opening within a single lithology layer and the difference between the horizontal maximum principal stress and the vertical stress of a single lithology layer, draw a cross-plot, and determine the potential location of the development of tension-shear fractures on the cross-plot;

[0011] The potential locations of tensile shear fractures identified on the cross-plot are verified by the tensile shear fractures identified on the core of a single well.

[0012] Based on the verification, the identification criteria of tension-shear cracks are 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 names of wells with imaging logging and drilling coring are determined based on geological data to ensure that there is at least one well with both imaging logging and drilling coring and that tension-shear fractures can be identified on the core of the well.

[0015] Optionally, draw a cross-plot and identify potential locations for the development of tension-shear fractures on the cross-plot:

[0016] Determine the homogenized fracture opening within a single lithology layer, and then determine the difference between the horizontal maximum principal stress and the vertical stress of the corresponding single lithology layer. Draw a cross-plot based on them, and determine the area with a large fracture opening and a vertical stress close to or greater than the horizontal maximum principal stress on the cross-plot, that is, the potential location for the development of tension-shear fractures.

[0017] Optionally, verify the potential locations of tensile shear fracture development identified on the cross plot:

[0018] 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.

[0019] Optionally, if the two are inconsistent, the well logging identification scheme is adjusted, the identification is performed again, and then compared with the identification result of the core data to determine whether the well logging identification result is reliable.

[0020] Optionally, determine the identification criteria for tension-shear cracks:

[0021] The top boundary of the homogenized opening envelope of the shear fracture is determined according to the intersection diagram, and the discrimination value of the homogenized fracture opening 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 tension-shear fracture with a larger opening, and the identification standard of the tension-shear fracture of clastic rocks in strong tectonic compression areas is established according to the relationship between the homogenized fracture opening and the difference between the horizontal maximum principal stress and the vertical stress in a single lithology layer.

[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 end of the compression anticline in the same structural belt;

[0024] A drawing 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 of a single lithology layer based on geological data, draw a cross-plot, and determine the potential location of the development of tension-shear fractures on the cross-plot;

[0025] A verification module is used to verify the potential locations of the development of tension-shear fractures determined on the cross-plot through the tension-shear fractures identified on the core of a single well;

[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, wherein when the processor executes the computer program, steps of a method for identifying tension-shear fractures of clastic rocks in a strong tectonic compression zone are implemented.

[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 tension-shear fractures of clastic rocks in a strong tectonic compression zone.

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

[0030] In view of the technical problems existing in the above-mentioned tension-shear fracture identification method under the condition of lack of core data, the present invention proposes a tension-shear fracture identification method for sandstone reservoirs in strong tectonic compression areas based on logging data. The method is an indirect geological discrimination method. On the one hand, the fracture aperture is obtained according to the interpretation results of the electrical imaging logging data, and the normalized fracture aperture of a single well is calculated; on the other hand, the in-situ geostress is calculated using the logging data and the difference between the maximum horizontal principal stress and the vertical stress is calculated. On the basis of core data verification, the relationship between the normalized fracture aperture and the corresponding geostress difference is used to identify the tension-shear fractures of the well sections in the strong tectonic compression areas where the coring data is lacking, thereby 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 present invention provides a cross-plot of the homogenized fracture opening and the ground stress difference, a verification plot and an identification plot. DETAILED DESCRIPTION

[0033] The present invention is further described below in conjunction with the accompanying drawings:

[0034] See also Figure 1 to Figure 2 In view of the technical problems existing in the above-mentioned tension-shear fracture identification method under the condition of lack 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. The method is an indirect geological discrimination method. On the one hand, the fracture aperture is obtained according to 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 geostress is calculated using the logging data and the difference between the maximum horizontal principal stress and the vertical stress is calculated. On the basis of core data verification, the relationship between the normalized fracture aperture and the corresponding geostress difference is used to identify the tension-shear fractures in the well section in the strong tectonic compression area where the core data is lacking.

[0035] Embodiment 1:

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

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

[0038] Based on geological data, determine the homogenized fracture opening within a single lithology layer and the difference between the horizontal maximum principal stress and the vertical stress of a single lithology layer, draw a cross-plot, and determine the potential location of the development of tension-shear fractures on the cross-plot;

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

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

[0041] Embodiment 2:

[0042] The specific plan is as follows:

[0043] (1) Select wells with complete data on the target layer near the turning point of the compression anticline in the same structural belt with similar tectonic stress field in the study area, and collect as much geological data as possible related to this plan, including core and lithology 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 on the core of the well in order to verify the identification results.

[0044] (2) Obtain the weighted arithmetic mean fracture aperture of each open fracture from the interpretation results of electrical imaging logging, and then extract the lithology and thickness data of the single lithology layer with developed fractures from the lithology logging data. Calculate the average fracture aperture in the single lithology layer according to the number of fractures developed in the single lithology layer and the corresponding fracture aperture. The fracture aperture of each well is normalized, that is, the average fracture aperture of the single lithology layer in the target layer of the well is divided by the average fracture aperture of the target layer of the well, so as to obtain the normalized fracture aperture in the single lithology layer of the target layer of the well (dimension is 1, Table 2). Then, the average vertical stress, the average horizontal maximum principal stress and the average horizontal minimum principal stress in the single lithology layer are obtained from the interpretation results of the geostress of the logging data. The difference between the two geostresses in the same lithology layer is obtained by subtracting the vertical stress from the horizontal maximum principal stress (unit: MPa, Table 2). When the tensile stress field develops in the formation, the difference is less than or equal to zero. The corresponding cross-plot is drawn with the difference between the horizontal maximum principal stress and the vertical stress as the abscissa and the normalized fracture aperture of the corresponding lithology layer as the ordinate ( 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 ): Their fracture walls are not smooth and straight like shear fractures, but slightly rough and uneven, and a small amount of authigenic minerals are often filled in the low-lying positions of the surrounding rock. Therefore, shear deformation and tensile deformation are observed along the fracture surface and in the normal direction of the fracture surface, respectively.

[0048] Table 2 Comprehensive data of single lithology 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 cross-plot ( Figure 2 ) determines 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 the tensile shear crack with a larger opening is about 5MPa. Therefore, when the difference in ground stress within a single lithology layer is less than 5MPa and the homogenized opening of the crack is greater than 1.5, the tectonic crack developed in the lithology layer is a tensile shear crack. Combined with the above analysis, the identification standard of tensile shear cracks in clastic rocks in strong tectonic compression areas can be established based on the relationship between the homogenized crack opening and the difference between the maximum horizontal principal stress and the vertical stress within a single lithology layer (Table 3), providing a basis for the prediction and evaluation of tensile shear cracks in similar areas.

[0053] Table 3 Identification criteria of 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 lithology layer The difference between the maximum horizontal principal stress and the vertical stress / MPa Crack properties ＞1.5 ≤5 Tension shear crack ＞1.5 ＞5 Shear crack ＜1.5 ≤5 Shear crack ＜1.5 ＞5 Shear crack

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

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

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

[0058] A verification module is used to verify the potential locations of the development of tension-shear fractures determined on the cross-plot through the tension-shear fractures identified on the core of a single well;

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

[0060] The division of modules in the embodiments of the present invention is schematic and is only a logical function division. There may be other division methods in actual implementation. In addition, each functional module in each embodiment of the present invention may be integrated into one processor, or may exist physically separately, or two or more modules may be integrated into one module. The above-mentioned integrated modules may be implemented in the form of hardware or in the form of software functional modules.

[0061] In another embodiment of the present invention, a computer device is provided, the computer device including a processor and a memory, the memory is used to store a computer program, the computer program includes program instructions, and the processor is used to execute the program instructions stored in the computer storage medium. The processor may be a central processing unit (CPU), or other general-purpose processors, digital signal processors (DSP), application-specific integrated circuits (ASIC), field-programmable gate arrays (FPGA) or other programmable logic devices, discrete gates or transistor logic devices, discrete hardware components, etc. It is the computing core and control core of the terminal, which is suitable for implementing one or more instructions, and is specifically suitable for loading and executing one or more instructions in the computer storage medium to implement the corresponding method flow or corresponding function; the processor described in the embodiment of the present invention can be used for the operation of a method for identifying tension-shear fractures in clastic rocks in a strong structural compression zone.

[0062] In another embodiment of the present invention, the present invention also provides a storage medium, specifically a computer-readable storage medium (Memory), which is a memory device in a computer device for storing programs and data. It is understandable that the computer-readable storage medium here can include both the built-in storage medium in the computer device and the extended storage medium supported by the computer device. The computer-readable storage medium provides a storage space, which 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 these instructions can be one or more computer programs (including program codes). It should be noted that the computer-readable storage medium here can be a high-speed RAM memory or a non-volatile memory, such as at least one disk memory. The processor can load and execute one or more instructions stored in the computer-readable storage medium to implement the corresponding steps of the above-mentioned embodiment regarding a method for identifying shear fractures in clastic rocks in a strong structural compression zone.

[0063] Those skilled in the art will appreciate that embodiments of the present invention may be provided as methods, systems, or computer program products. Therefore, the present invention may take the form of a complete hardware embodiment, a complete software embodiment, or an embodiment combining software and hardware. Moreover, 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 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 flowchart and / or block diagram, as well as the combination of processes and / or blocks in the flowchart and / or block diagram, 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 flowchart and / or block diagram. 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 capable of directing a computer or other programmable data processing device to operate in a specific manner, so that the instructions stored in the computer readable memory produce an article of manufacture including an instruction device, which implements the process Figure 1 A process or multiple processes and / or boxes Figure 1 A 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 operating steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing instructions for implementing the process. Figure 1 A process or multiple processes and / or boxes Figure 1 The steps for the functions specified 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 rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, ordinary technicians in the relevant 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 within 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 areas, characterized in that: include: Collect geological data of wells that encounter the target layer at the turning point of the compression anticline in the same structural belt; Based on geological data, determine the homogenized fracture opening within a single lithology layer and the difference between the horizontal maximum principal stress and the vertical stress of a single lithology layer, draw a cross-plot, and determine the potential location of the development of tension-shear fractures on the cross-plot; The potential locations of tensile shear fractures identified on the cross-plot are verified by the tensile shear fractures identified on the core of a single well. Based on the verification, the identification criteria of tension-shear cracks are determined.

2. The method for identifying tension-shear fractures in clastic rocks in strong tectonic compression zones according to claim 1 is characterized in that: The 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 tension-shear fractures in clastic rocks in a strong tectonic compression zone according to claim 2 is characterized in that: The number and names of wells with imaging logging and drilling coring are determined based on geological data to ensure that there is at least one well with both imaging logging and drilling coring and that tension-shear fractures can be identified on the core of the well.

4. The method for identifying tension-shear fractures in clastic rocks in strong tectonic compression zones according to claim 1, characterized in that: 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 lithology layer, and then determine the difference between the horizontal maximum principal stress and the vertical stress of the corresponding single lithology layer. Draw a cross-plot based on them, and determine the area with a large fracture opening and a vertical stress close to or greater than the horizontal maximum principal stress on the cross-plot, that is, the potential location for the development of tension-shear fractures.

5. The method for identifying tension-shear fractures in clastic rocks in strong tectonic compression zones according to claim 1, characterized in that: Verify the potential locations of tension-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.

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

7. The method for identifying tension-shear fractures in clastic rocks in strong tectonic compression zones according to claim 1, characterized in that: Identification criteria for determining tension-shear cracks: The top boundary of the homogenized opening envelope of the shear fracture is determined according to the intersection diagram, and the discrimination value of the homogenized fracture opening 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 tension-shear fracture with a larger opening, and the identification standard of the tension-shear fracture of clastic rocks in strong tectonic compression areas is established according to the relationship between the homogenized fracture opening and the difference between the horizontal maximum principal stress and the vertical stress in a single lithology layer.

8. A system for identifying tension-shear fractures in clastic rocks in strong structural compression areas, characterized in that: include: A data acquisition module is used to collect geological data of wells that encounter target layers at the turning end of the compression anticline in the same structural belt; A drawing module is used to determine the homogenized fracture opening within a single lithology layer and the difference between the maximum horizontal principal stress and the vertical stress of a single lithology layer based on geological data, draw a cross-plot, and determine the potential location of the development of tension-shear fractures on the cross-plot; A verification module is used to verify the potential locations of the development of tension-shear fractures determined on the cross-plot through the tension-shear fractures identified on the core of a single well; The output module is used to determine the identification criteria of tension-shear cracks based on the verification.

9. A computer device comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that: When the processor executes the computer program, 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 7 are implemented.

10. A computer-readable storage medium storing a computer program, characterized in that: When the computer program is executed by a processor, the steps of a method for identifying tension-shear fractures in clastic rocks in a strong tectonic compression zone as described in any one of claims 1 to 7 are implemented.

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