Method and system for judging formation of crack at anticline of rock stratum extrusion structure

Abstract

The invention discloses a method and system for judging formation of cracks at the anticline position of a rock stratum extrusion structure, and the method comprises the steps: calculating the critical curvature of a rock stratum from an extrusion state to a fracture state according to the rock mechanical parameters of a to-be-evaluated rock stratum; and the curvature of each point on the anticline of the rock stratum to be evaluated is obtained, and the initial formation of the current extrusion anticline structure crack is judged by using the critical curvature according to the curvature. The method can quantitatively evaluate whether the anticline top crack forms the initial crack or not.

Description

Technical Field

[0001] The present invention relates to the technical field of reservoir geomechanics, and particularly to a method and system for judging the formation of fractures at the anticline of a rock formation extrusion structure. Background Art

[0002] The deep sandstones and carbonate rocks in the Tarim Basin of China are lithologically dense, belonging to extra-low porosity and extra-low permeability. The improvement of reservoir physical properties is closely related to the degree of fracture development. Structural anticlines are the main development sites of fractures in deep sandstones and carbonate rocks and are the key exploration targets. Under the action of neutral surface folding, the closer the anticline is, the greater the curvature of the bent rock formation, and the more developed the fractures are.

[0003] The prior art mainly uses seismic curvature attributes to qualitatively judge the degree of fracture development, without considering rock physical parameters, lacking the constraints of rock mechanics and kinematics, and the prediction effect of structural fractures cannot meet the actual needs. Therefore, whether a more effective quantitative calculation method for structural fractures can be proposed is of great significance for the exploration of deep sandstones and carbonate rocks.

[0004] In the Chinese patent "A Method and Device for Predicting the Main Fracture Formation Period Based on Rock Mechanical Properties" (patent number: CN202210348920) in the existing patent literature, a scheme for establishing a two-dimensional in-situ stress profile in different tectonic periods based on reservoir rock mechanical parameters is proposed. This scheme is based on finite element numerical simulation to predict the fracture distribution density, and takes the maximum value of the fracture distribution density as the main geological period of fracture formation. This scheme regards rock mechanical parameters as static parameters, does not consider that the rock mechanical properties will change before and after fracture formation, and many parameters involved in finite element simulation, such as paleo-stress, boundary conditions, etc., are difficult to obtain in actual work. This scheme is more suitable for theoretical analysis, and the predicted fractures are difficult to be combined with on-site work.

[0005] In the Chinese patent "A Method for Quantitative Prediction of Fractures Based on Seismic Attributes" (patent number: CN201611177648) in the existing patent literature, a technical scheme for calculating a fracture prediction attribute body by combining a curvature attribute body and a corrected coherence attribute body based on post-stack seismic data commonly used in actual work is proposed. This scheme does not consider the mechanical mechanism of fracture formation. Both the curvature attribute and the coherence attribute belong to qualitative predictions, and the obtained current curvature cannot simply represent the curvature in the paleo-geological period.

[0006] In summary, the prior art needs to provide a quantitative evaluation scheme that takes into account the mechanical change characteristics of rock fracture formation. Summary of the Invention

[0007] The object of the present invention is to provide an evaluation scheme that takes into account the mechanical change characteristics of rock formation fractures, so as to quantitatively evaluate whether initial fractures are formed at the anticline top of the strata extrusion structure.

[0008] To solve the above technical problems, an embodiment of the present invention provides a method for judging the formation of fractures at the anticline of a strata extrusion structure, including: calculating the critical curvature of the strata from the extrusion state to the fracture state according to the rock mechanical parameters of the strata to be evaluated; obtaining the curvature of each point on the anticline of the strata to be evaluated, and judging the initial formation of fractures in the current extrusion anticline structure according to the curvature and using the critical curvature.

[0009] Preferably, in the step of judging the initial formation of fractures in the current extrusion anticline structure according to the real-time curvature and using the critical curvature, it includes: when the curvature of one or more position points on the anticline top of the strata to be evaluated exceeds the critical curvature, it is determined that initial fractures are formed at the current position point.

[0010] Preferably, when the curvature of each position point on the anticline top of the strata to be evaluated does not exceed the critical curvature, it is determined that no fractures are formed at the top of the current strata.

[0011] Preferably, in the step of calculating the critical curvature of the strata to be evaluated from the extrusion state to the fracture state, it includes: calculating the critical curvature according to the rock mechanical parameters of the strata to be evaluated and using Hooke's law fracture criterion.

[0012] Preferably, according to the strata thickness of the strata to be evaluated, as well as the tensile strength and Young's modulus of the anticline top of the strata, the critical curvature is calculated using the rock fracture critical curvature formula, where the rock fracture critical curvature formula is calculated using the following expression:

[0013]

[0014] where k0 represents the critical curvature, δ represents the tensile strength, E represents the Young's modulus, and h represents the strata thickness.

[0015] On the other hand, an embodiment of the present invention provides a computer-readable storage medium, which contains a series of instructions for executing the above method steps.

[0016] In addition, an embodiment of the present invention further provides a system for determining the formation of fractures at the anticline of a rock formation extrusion structure, including: a critical curvature calculation module configured to calculate the critical curvature of the rock formation from the extrusion state to the fracture state according to the rock mechanics parameters of the rock formation to be evaluated; an initial fracture formation determination module configured to obtain the curvatures of each point on the anticline of the rock formation to be evaluated and, based on the curvatures, use the critical curvature to determine the initial formation of fractures in the current extrusion anticline structure.

[0017] Preferably, the initial fracture formation determination module is further configured to determine that an initial fracture is formed at the current position point when the curvature of one or more position points on the top of the anticline of the rock formation to be evaluated exceeds the critical curvature.

[0018] Preferably, the initial fracture formation determination module is further configured to determine that no fracture is formed at the top of the current rock formation when the curvatures of all position points on the top of the anticline of the rock formation to be evaluated do not exceed the critical curvature.

[0019] Preferably, the critical curvature calculation module is further configured to calculate the critical curvature according to the rock mechanics parameters of the rock formation to be evaluated by using the Hooke's law fracture criterion.

[0020] Compared with the prior art, one or more of the above embodiments may have the following advantages or beneficial effects:

[0021] The present invention proposes a method and a system for determining the formation of fractures at the anticline of a rock formation extrusion structure. By analyzing the curvature changes of the rock formation in different deformation stages and the magnitude relationship with the critical curvature, the critical conditions suitable for the initial formation of tensile fractures at the top of the deep carbonate rock anticline are formulated, so as to judge whether the tensile fractures at the top of the anticline are formed and the geological period of formation in a quantitative evaluation manner, which meets the requirements of the site and has wide engineering application value and scientific research value in the exploration field of carbonate rock scale reservoirs.

[0022] Other features and advantages of the present invention will be described in the following specification, and, in part, will be obvious from the specification, or will be understood by implementing the present invention. The objectives and other advantages of the present invention can be achieved and obtained by the structures specifically pointed out in the specification, the claims, and the drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] The drawings are used to provide a further understanding of the present invention and constitute a part of the specification. They are used together with the embodiments of the present invention to explain the present invention and do not constitute a limitation to the present invention. In the drawings:

[0024] Figure 1 It is a schematic diagram of the steps of the method for determining the formation of fractures at the anticline of a rock formation extrusion structure according to an embodiment of the present application.

[0025] Figure 2 It is a schematic diagram of the derivation principle of the rock fracture critical curvature formula in the method for judging the formation of fractures at the anticline of the rock formation extrusion structure in the embodiment of the present application.

[0026] Figure 3 It is a block diagram of the modules of the system for judging the formation of fractures at the anticline of the rock formation extrusion structure in the embodiment of the present application. Specific Embodiments

[0027] The following will combine the accompanying drawings and embodiments to detail the implementation manners of the present invention, so as to fully understand how the present invention applies technical means to solve technical problems and the implementation process of achieving technical effects and implement accordingly. It should be noted that as long as there is no conflict, each embodiment in the present invention and each feature in each embodiment can be combined with each other, and the formed technical solutions are all within the protection scope of the present invention.

[0028] In addition, the steps shown in the flowchart of the accompanying drawings can be executed in a computer system such as a set of computer-executable instructions. And although the logical order is shown in the flowchart, in some cases, the steps shown or described can be executed in a different order than here.

[0029] The terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments. Unless the context clearly indicates otherwise, the singular forms "a" and "an" used herein are also intended to include the plural. It should also be understood that the terms "comprises" and / or "comprising" used herein specify the presence of the stated features, integers, steps, operations, units and / or components, and do not exclude the presence or addition of one or more other features, integers, steps, operations, units, components and / or their combinations.

[0030] To solve the technical problems in the above background art, the embodiments of the present application propose a method and a system for judging the formation of fractures at the anticline of the rock formation extrusion structure. This method and system consider the control effect of the rock mechanical properties and curvature changes during the formation of the anticline on the formation of fractures. Simplify the problems in the prior art into the initial formation conditions of fractures, which can avoid the changes in rock mechanical parameters; comprehensively give the critical curvature of the initial formation of fractures at the top of the anticline by rock mechanics and structural analysis methods to judge whether fractures are formed, so as to quantitatively evaluate whether initial fractures are formed at the top of deep sandstone and carbonate anticlines, filling the quantitative judgment of the formation of fractures at the top of the anticline caused by the squeezing and bending deformation of the rock, and can be effectively used to judge whether fractures can be formed at the top of the extrusion structure anticline, which is beneficial to field practical applications.

[0031] Example 1

[0032] Figure 1 This is a schematic diagram of the steps of the method for judging the formation of fractures at the anticline of a rock formation extrusion structure in an embodiment of the present application. The following will refer to Figure 1 Figure 1 to illustrate the specific step process of the method for judging the formation of fractures at the anticline of a rock formation extrusion structure (also referred to as the "fracture formation judgment method") described in the embodiments of the present invention.

[0033] Step S110 calculates the critical curvature at which the rock formation changes from the extrusion state to the fracture state according to the rock mechanical parameters of the rock formation to be evaluated. It should be noted that in the embodiments of the present invention, the rock formation to be evaluated is a tight sandstone or carbonate rock scale reservoir.

[0034] In step S110, according to the rock mechanical parameters of the rock formation to be evaluated, the critical curvature at which the current rock formation to be evaluated changes from the extrusion state to the fracture state is calculated.

[0035] For the anticline of the rock formation formed by extrusion, the condition for generating fractures is that only when a certain thickness of the rock formation bends to a certain curvature, the rock above the neutral plane is in a tensile state, and the tensile stress increases with the increase of the bending degree. When it exceeds the tensile strength of the rock formation, tensile fractures are formed.

[0036] Therefore, in the embodiments of the present invention, it is necessary to calculate the critical curvature corresponding to the initial fracture formation of the rock formation.

[0037] In one embodiment, according to the rock mechanical parameters of the rock formation to be evaluated, the critical curvature is calculated using Hooke's law fracture criterion.

[0038] In a specific embodiment, according to the thickness of the rock formation to be evaluated, as well as the tensile strength and Young's modulus at the top of the anticline of the rock formation, the critical curvature is calculated using the critical curvature formula for rock fracture.

[0039] Figure 2 This is a schematic diagram of the derivation principle of the critical curvature formula for rock fracture in the method for judging the formation of fractures at the anticline of a rock formation extrusion structure in an embodiment of the present application. As Figure 2 shown, assume that the length of the rock formation to be studied is L and the thickness of the rock formation is h. When an isopachous rock formation with a length of L and a thickness of h is in pure bending, as the rock formation bends, the top surface length of the current rock formation becomes L + ΔL. Then, the curvature k of the rock formation is k = 1 / R, where R represents the radius of curvature corresponding to the top surface of the rock formation with an arc length of L + ΔL. Among them, θ represents the central angle corresponding to the top surface of the rock formation with an arc length of L + ΔL.

[0040] From Figure 2 it can be known that:

[0041]

[0042] That is:

[0043]

[0044] Due to the Hooke's law rupture criterion, there is:

[0045] δ = Eε (3)

[0046] Furthermore, it is obtained that:

[0047]

[0048] Substitute the current expression (4) into expression (2), and it is obtained that:

[0049]

[0050] Furthermore, the critical curvature formula for rock fracture is obtained and expressed by the following expression:

[0051]

[0052] Among them, k0 represents the critical curvature, δ represents the tensile strength, E represents the modulus of pattern, h represents the thickness of the rock formation. ε represents the elongation or compression.

[0053] In this way, after calculating the critical curvature of the current rock formation to be evaluated, it enters step S120.

[0054] Step S120 obtains the curvatures of each position point on the anticline of the extrusion structure of the rock formation to be evaluated, and based on the curvatures of each position point, uses the critical curvature calculated in step S110 to judge the initial formation state of the cracks in the current extrusion anticline structure.

[0055] In step S120, in the first embodiment, when the curvature of one or more position points on the top of the anticline of the extrusion structure of the rock formation to be evaluated exceeds the critical curvature, it is determined that an initial crack is formed at the current position point.

[0056] At this time, not only can it be judged that an initial crack has been formed in the current rock formation (i.e., the initial stage of crack formation), but also the position where the initial crack is formed can be marked (i.e., the formation position of the early crack).

[0057] In step S120, in the second embodiment, when the curvatures of each position point on the top of the anticline of the extrusion structure of the rock formation to be evaluated do not exceed the critical curvature, it is determined that no crack is formed at the top of the current rock formation.

[0058] That is to say, if the curvatures of all position points on the top of the anticline of the extrusion structure of the current rock formation do not exceed the critical curvature, it is determined that no initial crack has appeared at the top of the current rock formation anticline, that is, no early crack has been formed.

[0059] Specifically, if the curvature value at each position point on the current rock formation anticline is greater than the critical curvature, the rock formation will rupture to form fractures; otherwise, it will not.

[0060] Therefore, based on Hooke's law fracture criterion and rock mechanics parameters, the present invention derives an algorithm for the critical curvature of rock fracture, thereby completing the judgment of the initial formation of fractures in the compressive anticline structure.

[0061] Example 2

[0062] Based on the above method for judging fracture formation, an embodiment of the present invention also provides a computer-readable storage medium, on which a computer program is stored. Executing the computer program runs a method for judging the formation of fractures at the anticline of the rock formation extrusion structure. The computer program can run computer instructions, and the computer instructions include computer program code, which can be in the form of source code, object code, executable file or some intermediate form, etc.

[0063] The computer-readable storage medium may include: any entity or device capable of carrying computer program code, recording medium, USB flash drive, mobile hard disk, magnetic disk, optical disc, computer memory, read-only memory (ROM, Read-Only Memory), random access memory (RAM, Random Access Memory), electrical carrier signal, telecommunication signal, and software distribution medium, etc.

[0064] It should be noted that the content included in the computer-readable storage medium can be appropriately increased or decreased according to the requirements of legislation and patent practice in the jurisdiction. For example, in some jurisdictions, it is appropriately increased or decreased according to the requirements of legislation and patent practice. For example, in some jurisdictions, it is appropriately increased or decreased according to the requirements of legislation and patent practice. For example, in some jurisdictions according to patent practice, the computer-readable storage medium does not include electrical carrier signals and telecommunication signals.

[0065] Example 3

[0066] Based on the above method for judging fracture formation, an embodiment of the present invention also provides a system for judging the formation of fractures at the anticline of the rock formation extrusion structure (also referred to as "fracture formation judgment system"). This fracture formation judgment system is used to implement the above method for judging fracture formation.

[0067] Figure 3 It is a block diagram of the module of the system for judging the formation of fractures at the anticline of the rock formation extrusion structure according to the embodiment of the present application. As Figure 3 shown, the fracture formation judgment system described in the embodiment of the present invention includes: a critical curvature calculation module 31 and an initial fracture formation judgment module 32.

[0068] Specifically, the critical curvature calculation module 31 is implemented according to the method described in step S110 above, and is configured to calculate the critical curvature of the rock formation from the extrusion state to the fracture state based on the rock mechanics parameters of the rock formation to be evaluated; the initial fracture formation judgment module 32 is implemented according to the method described in step S120 above, and is configured to obtain the curvature of each point on the anticline of the rock formation to be evaluated, and use the critical curvature to judge the initial formation of the current extrusion anticline structure fracture according to the curvature.

[0069] In one embodiment, the critical curvature calculation module 31 is further configured to calculate the critical curvature based on the rock mechanics parameters of the rock formation to be evaluated by using the Hooke's law fracture criterion.

[0070] In one embodiment, the initial fracture formation judgment module 32 is further configured to determine that an initial fracture is formed at the current position point when the curvature of one or more position points on the top of the anticline of the rock formation to be evaluated exceeds the critical curvature.

[0071] In one embodiment, the initial fracture formation judgment module 32 is further configured to determine that no fracture is formed at the top of the current rock formation when the curvature of each position point on the top of the anticline of the rock formation to be evaluated does not exceed the critical curvature.

[0072] The present invention discloses a method and a system for judging the formation of fractures at the anticline of the rock formation extrusion structure. By analyzing the curvature change of the rock formation in different deformation stages and the magnitude relationship with the critical curvature, the critical conditions suitable for the initial formation of tensile fractures at the top of the deep carbonate rock anticline are formulated, so as to judge whether the tensile fractures at the top of the anticline are formed and the geological period of formation in a quantitative evaluation manner, which meets the on-site requirements and has wide engineering application value and scientific research value in the exploration field of carbonate rock scale reservoirs.

[0073] The above is only a preferred specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention should be covered by the protection scope of the present invention. Therefore, the protection scope of the present invention should be subject to the protection scope of the claims.

[0074] In the description of the present invention, unless otherwise specified, "a plurality of" means two or more; the orientation or positional relationship indicated by terms such as "upper", "lower", "left", "right", "inner", "outer", "front end", "rear end", "head", "tail", etc. is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be construed as a limitation on the present invention. In addition, terms such as "first", "second", "third", etc. are only used for descriptive purposes and cannot be construed as indicating or implying relative importance.

[0075] In the description of the present invention, it should be noted that, unless otherwise clearly defined and limited, the terms "connected" and "coupled" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0076] It should be understood that the embodiments disclosed in the present invention are not limited to the specific structures, processing steps or materials disclosed herein, but should extend to equivalent alternatives of these features understood by those of ordinary skill in the relevant art. It should also be understood that the terms used herein are only for the purpose of describing specific embodiments and do not imply limitation.

[0077] The "one embodiment" or "embodiment" mentioned in the specification means that the specific features, structures or characteristics described in connection with the embodiment are included in at least one embodiment of the present invention. Therefore, the phrases "one embodiment" or "embodiment" that appear throughout the specification do not necessarily all refer to the same embodiment.

[0078] Although the disclosed embodiments of the present invention are as above, the content described above is only an embodiment adopted for the convenience of understanding the present invention and is not used to limit the present invention. Any person skilled in the technical field to which the present invention pertains can make any modifications and changes in the form of implementation and details without departing from the spirit and scope disclosed by the present invention. However, the scope of patent protection of the present invention shall still be subject to the scope defined by the appended claims.

Claims

1. A method for judging the formation of fractures at the anticline of a rock formation extrusion structure, characterized in that, Comprising: Calculating the critical curvature at which the rock formation changes from the extrusion state to the fracture state according to the rock mechanical parameters of the rock formation to be evaluated; Obtaining the curvature of each point on the anticline of the rock formation to be evaluated, and judging the initial formation of the current compressional anticline structural fracture according to the curvature and using the critical curvature.

2. The method according to claim 1, wherein In the step of judging the initial formation of the current compressional anticline structural fracture according to the real-time curvature and using the critical curvature, it includes: When the curvature of one or more position points on the top of the anticline of the rock formation to be evaluated exceeds the critical curvature, it is determined that an initial fracture is formed at the current position point.

3. The method according to claim 2, wherein: When the curvature of each position point on the top of the anticline of the rock formation to be evaluated does not exceed the critical curvature, it is determined that no fracture is formed at the top of the current rock formation.

4. The method according to any one of claims 1 to 3, characterized in that In the step of calculating the critical curvature at which the rock formation to be evaluated changes from the extrusion state to the fracture state, it includes: Calculating the critical curvature according to the rock mechanical parameters of the rock formation to be evaluated by using the Hooke's law fracture criterion.

5. The method according to any one of claims 1 to 4, wherein: Calculating the critical curvature according to the thickness of the rock formation to be evaluated, the tensile strength and Young's modulus at the top of the anticline of the rock formation by using the critical curvature formula for rock fracture, wherein the critical curvature formula for rock fracture is calculated by using the following expression: Wherein, k0 represents the critical curvature, δ represents the tensile strength, E represents Young's modulus, and h represents the thickness of the rock formation.

6. A computer-readable storage medium, characterized in that, It includes a series of instructions for executing the method steps according to any one of claims 1 to 5.

7. A system for determining the formation of fractures at the anticline of a rock formation extrusion structure, characterized in that, Comprising: A critical curvature calculation module configured to calculate the critical curvature at which the rock formation changes from the extrusion state to the fracture state according to the rock mechanical parameters of the rock formation to be evaluated; An initial fracture formation judgment module configured to obtain the curvature of each point on the anticline of the rock formation to be evaluated, and judge the initial formation of the current compressional anticline structural fracture according to the curvature and using the critical curvature.

8. The system according to claim 7, wherein: The initial fracture formation judgment module is further configured to, when the curvature of one or more position points on the top of the anticline of the rock formation to be evaluated exceeds the critical curvature, determine that an initial fracture is formed at the current position point.

9. The system according to claim 8, wherein: The initial fracture formation judgment module is further configured to, when the curvature of each position point on the top of the anticline of the rock formation to be evaluated does not exceed the critical curvature, determine that no fracture is formed at the top of the current rock formation.

10. The system according to any one of claims 7 to 9, wherein: The critical curvature calculation module is further configured to calculate the critical curvature according to the rock mechanical parameters of the rock formation to be evaluated by using the Hooke's law fracture criterion.

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