Method and device for obtaining fracture permeability of unconventional reservoirs

Abstract

The present application relates to the technical field of oil exploration and development, and particularly relates to a method and device for obtaining fracture permeability of unconventional reservoirs, which comprises: establishing a relationship between T2 relaxation time of fluid in a core sample fracture and specific surface of a rock sample; obtaining target fracture width of intersecting tabular fractures according to the relationship between T2 relaxation time of fluid in the core sample fracture and the specific surface of the rock sample; and obtaining permeability of the intersecting tabular fractures according to the target fracture width. The method can quantitatively identify fracture width in a tight reservoir and further obtain fracture permeability, thus contributing to unconventional reservoir evaluation.

Description

Technical Field

[0001] This invention relates to the field of petroleum exploration and development technology, and in particular to a method and apparatus for obtaining fracture permeability in unconventional reservoirs. Background Technology

[0002] Because tight reservoirs have very poor porosity and permeability, studying fracture development within them is particularly important. Since fracture permeability depends on fracture width, determining this parameter is crucial for understanding the physical properties of unconventional reservoirs. However, there is currently no specific method for quantitatively identifying fracture width in tight reservoirs, which directly affects the acquisition of fracture permeability in unconventional reservoirs, and consequently, their evaluation. Summary of the Invention

[0003] The purpose of this invention is to provide a method and apparatus for obtaining fracture permeability in unconventional reservoirs, in order to solve the above-mentioned technical problems.

[0004] To achieve the above objectives, the present invention provides a method for obtaining fracture permeability in unconventional reservoirs, comprising:

[0005] Establish the relationship between the T2 relaxation time of fluid in the fracture of the core sample and the specific surface area of ​​the rock sample;

[0006] The target fracture width of the intersecting plate-like fracture is obtained based on the relationship between the T2 relaxation time of the fluid in the fracture of the core sample and the specific surface area of ​​the rock sample.

[0007] The permeability of intersecting plate-like fractures is obtained based on the target fracture width.

[0008] The present invention also provides an apparatus for obtaining the fracture permeability of unconventional reservoirs, comprising:

[0009] Establish a unit to establish the relationship between the T2 relaxation time of the fluid in the fracture of the core sample and the specific surface area of ​​the rock sample;

[0010] The width acquisition unit is used to obtain the target fracture width of the intersecting plate fracture based on the relationship between the T2 relaxation time of the fluid in the fracture of the core sample and the specific surface area of ​​the rock sample.

[0011] The permeability acquisition unit is used to obtain the permeability of intersecting plate-like fractures based on the target fracture width.

[0012] The present invention also provides an electronic device, comprising: a processor coupled to a memory;

[0013] The processor is configured to read and execute a computer program stored in the memory to implement the method described in any of the preceding embodiments.

[0014] The present invention also provides a computer-readable storage medium storing a program or instructions that, when executed by a processor, implement the method as described in any of the preceding claims.

[0015] The technical effects and advantages of this invention are as follows:

[0016] This invention protects a method for obtaining fracture permeability in unconventional reservoirs. The method includes: establishing the relationship between the T2 relaxation time of the fluid in the fracture of a core sample and the specific surface area of ​​the rock sample; obtaining the target fracture width of intersecting plate fractures based on the relationship between the T2 relaxation time of the fluid in the fracture of the core sample and the specific surface area of ​​the rock sample; and obtaining the permeability of the intersecting plate fractures based on the target fracture width. This method can quantitatively identify fracture widths in tight reservoirs and thus obtain fracture permeability, contributing to the evaluation of unconventional reservoirs.

[0017] Other features and advantages of the invention will be set forth in the description which follows, and will be apparent in part from the description, or may be learned by practicing the invention. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0019] Figure 1 A flowchart illustrating a method for obtaining fracture permeability in unconventional reservoirs;

[0020] Figure 2 Model of intersecting plate-like fractures in rocks;

[0021] Figure 3 A three-dimensional view of the overlapping area of ​​intersecting plate-shaped seams;

[0022] Figure 4 This is a top view of the overlapping area of ​​the intersecting plate-like seams;

[0023] Figure 5 This is a diagram of an electronic device. Detailed Implementation

[0024] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0025] It should be noted that the structures, proportions, sizes, etc., illustrated in the accompanying drawings are merely for illustrative purposes to aid those skilled in the art and to facilitate understanding and reading. They are not intended to limit the scope of the invention and therefore have no substantial technical significance. Any modifications to the structure, changes in proportions, or adjustments to size, without affecting the effectiveness and purpose of the invention, should still fall within the scope of the technical content disclosed herein. Furthermore, the terms "upper," "lower," "left," "right," "middle," and "one" used in this specification are merely for clarity and not intended to limit the scope of the invention. Changes or adjustments to their relative relationships, without substantially altering the technical content, should also be considered within the scope of the invention.

[0026] To address the shortcomings of existing technologies, this invention discloses a method for obtaining fracture permeability in unconventional reservoirs, such as... Figure 1 As shown, it includes:

[0027] 1. Establish the relationship between the T2 relaxation time of the fluid in the fracture of the core sample and the specific surface area of ​​the rock sample. Since this step is existing technology, it will not be described in detail here. For details, please refer to the article No. 1000-4556(2008)02-0273-08 in the Journal of Spectroscopy, which discusses the method of converting pore radius distribution from nuclear magnetic resonance T2 spectrum.

[0028] The formula relating the T2 relaxation time of the fluid in the fracture of the core sample to the specific surface area of ​​the rock sample is as follows:

[0029]

[0030] In the formula, T 2S ρ is the relaxation time of the rock particle surface. s S is the relaxation rate; S / V is the specific surface area of ​​the rock.

[0031] 2. Based on the relationship between the T2 relaxation time of the fluid in the core sample fracture and the specific surface area of ​​the rock sample, the target fracture aperture of the intersecting plate fracture is obtained.

[0032] 2.1 Obtaining the specific surface area of ​​the rock includes: establishing a model of intersecting plate-like fractures in the rock; obtaining the surface area and volume of all fractures based on the model of intersecting plate-like fractures; the ratio of the surface area and volume of all fractures is the specific surface area of ​​the rock.

[0033] In this context, the rock specific surface area is the surface area of ​​the crack divided by the volume of the crack.

[0034] The rock intersecting plate-like fracture model is as follows: An ideal rock unit is modeled as a cube, with numerous intersecting plate-like fractures. The fractures are assumed to be plate-like, smooth, and without any filling material. Figures 2-4 As shown in the diagram. Suppose there are n parallel plate-shaped seams of equal width in the X direction and m parallel plate-shaped seams of equal width in the Y direction. When these seams intersect, there will be m·n overlapping intersection areas.

[0035] Surface area and volume of cracks in different directions:

[0036] X direction:

[0037] S1=(h f *L m2 *2+W f1 *L m2 *2+W f1 *h f *2)*n

[0038] V1=(h f *L m2 *W f1 )*n

[0039] In the formula, S1 is the surface area of ​​the crack corresponding to the X direction; h f L represents the height of the intersecting plate-like fracture model of the rock phase in the Z direction. m2 W represents the width of the intersecting plate-like fracture model in the Y direction. f1 denoted as , where is the width of the crack in the X direction; n is the number of cracks in the X direction; and V1 is the volume of the crack corresponding to the X direction.

[0040] Y direction:

[0041] S2=(h f *L m1 *2+W f2 *L m1 *2+W f2 *h f *2)*m

[0042] V2=(W f2 *L m1 *h f )*m

[0043] In the formula, S2 is the crack surface area corresponding to the Y direction; h f L represents the height of the intersecting plate-like fracture model of the rock phase in the Z direction. m1 W represents the length of the intersecting plate-like fracture model in the X direction. f2 V1 is the width of the crack in the Y direction; m is the number of cracks in the Y direction; V2 is the crack volume in the corresponding Y direction.

[0044] Overlapping crack surface area:

[0045]

[0046] In the formula, S3 is the surface area of ​​the overlapping cracks in the X and Y directions; θ is the angle between the cracks; a is the length of the crack in the overlapping area in the Y direction; and b is the length of the crack in the overlapping area in the X direction.

[0047] Overlapping crack volume:

[0048]

[0049] Surface area of ​​all cracks in the XY direction:

[0050] S = S1 + S2 - S3 = [(h f *L m2 *2+W f1 *L m2 *2+W f1 *h f *2)*n+

[0051]

[0052] Volume of all cracks in the XY direction:

[0053]

[0054] Rock specific surface area:

[0055]

[0056] 2.2 Substituting the rock specific surface area formula into The relationship between the T2 relaxation time of the fluid in the fracture of the core sample and the fracture width was obtained:

[0057]

[0058] Assume W f2 =k*W f1 Substituting this equation into equation 2.2, we obtain the following quadratic equation in one variable, where W... f1 As the independent variable:

[0059]

[0060] Among them, coefficient coefficient Coefficient C = 2ρ s *h f *(n*L m2 +m*L m1 ).

[0061] The root value, i.e., the target crack width, is obtained based on coefficients A, B, and C.

[0062]

[0063] 3. Obtain the permeability of intersecting plate-like fractures based on the target crack width.

[0064] Specifically, the Hagen-Poiseiulle equation is:

[0065]

[0066] Darcy's Law is:

[0067]

[0068] Solving these two equations yields the formula for fracture permeability:

[0069]

[0070] For a plunger-shaped core, the end face area of ​​the fracture is:

[0071] A = h f w f

[0072] Substituting the formula for the fracture end face area into the formula for fracture permeability, and simplifying, we obtain the final formula for fracture permeability:

[0073]

[0074] In the formula, q is the seepage flow rate; h f W represents the height of the intersecting plate-like fracture model in the Z direction. f For W f1 The value represents the width of the crack in the X direction; Δp is the displacement pressure difference; μ is the gas viscosity; L is the target crack length; K is the target crack permeability; and A is the target crack end face area.

[0075] Finally, the target crack width W is obtained in section 2.2. f1 Substituting these values ​​into the final fracture permeability formula, we obtain the formula for the permeability of intersecting plate-like fractures:

[0076]

[0077] The present invention also provides an apparatus for obtaining the permeability of unconventional reservoir fractures, comprising: a setup unit for establishing the relationship between the T2 relaxation time of the fluid in the fracture of a core sample and the specific surface area of ​​the rock sample; a width acquisition unit for obtaining the target fracture width of intersecting plate fractures based on the established relationship between the T2 relaxation time of the fluid in the fracture of the core sample and the specific surface area of ​​the rock sample; and a permeability acquisition unit for obtaining the permeability of intersecting plate fractures based on the target fracture width.

[0078] Since the protection provided by this device is similar to that provided by the method described above, it will not be described in detail here. Please refer to the discussion section of the method described above for more information.

[0079] The present invention also provides a device, such as Figure 5 As shown, the electronic device includes: at least one processor, at least one communication interface, at least one memory, and at least one communication bus; optionally, the communication interface can be an interface of a communication module, such as the interface of a GSM module; the processor may be a CPU, an Application Specific Integrated Circuit (ASIC), or one or more integrated circuits configured to implement embodiments of the present invention. The memory may include high-speed RAM memory, and may also include non-volatile memory, such as at least one disk storage device. The memory stores a program, and the processor calls the program stored in the memory to execute the methods provided in the above embodiments of this application.

[0080] Corresponding to the methods described above in this application, this application also provides a computer storage medium. The computer storage medium stores a computer program, which is executed by a processor to perform the methods provided in the above embodiments of this application.

[0081] Finally, it should be noted that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for obtaining fracture permeability in unconventional reservoirs, characterized in that, include: Establish the relationship between the T2 relaxation time of fluid in the fracture of the core sample and the specific surface area of ​​the rock sample; The target fracture width of the intersecting plate-like fracture is obtained based on the relationship between the T2 relaxation time of the fluid in the fracture of the core sample and the specific surface area of ​​the rock sample. The permeability of intersecting plate-like fractures is obtained based on the target fracture width.

2. The method according to claim 1, characterized in that, The relationship between the T2 relaxation time of the fluid in the fracture of the core sample and the specific surface area of ​​the rock sample is shown in the following equation: In the formula, T 2S ρ is the relaxation time of the rock particle surface. s S is the relaxation rate; S / V is the specific surface area of ​​the rock.

3. The method according to claim 2, characterized in that, Obtain the specific surface area of ​​the rock sample, including: Establish a model of intersecting plate-like fractures in rock facies; Based on the rock intersecting plate fracture model, obtain the surface area and volume of all fractures; The ratio of the surface area of ​​all fractures to the volume of all fractures is the specific surface area of ​​the rock sample. In the rock intersecting plate-like fracture model, there are n parallel plate-like fractures of equal width in the X direction of the rock, and m parallel plate-like fractures of equal width in the Y direction. The plate-like fractures in these two directions intersect, and the included angle between the fractures in the two directions ranges from 0 to 180 degrees.

4. The method according to claim 3, characterized in that, Obtain the surface area of ​​all cracks, including: Obtain the surface area of ​​the cracks in the rock along the X direction, the surface area of ​​the cracks along the Y direction, and the surface area of ​​the overlapping cracks in the X and Y directions. The surface areas of all cracks are obtained based on the crack surface areas corresponding to the X direction, the crack surface areas corresponding to the Y direction, and the overlapping crack surface areas in the X and Y directions.

5. The method according to claim 4, characterized in that, The surface area of ​​the crack in the X direction is obtained by the following formula: S1=(h f *L m2 *2+W f1 *L m2 *2+W f1 *h f *2)*n In the formula, S1 is the surface area of ​​the crack corresponding to the X direction; h f L represents the height of the intersecting plate-like fracture model of the rock phase in the Z direction. m2 W represents the width of the intersecting plate-like fracture model in the Y direction. f1 denoted as , where is the width of the crack in the X direction; and is the number of cracks in the X direction.

6. The method according to claim 5, characterized in that, The crack surface area in the Y direction is obtained using the following formula: S2=(h f *L m1 *2+W f2 *L m1 *2+W f2 *h f *2)*m In the formula, S2 is the crack surface area corresponding to the Y direction; h f L represents the height of the intersecting plate-like fracture model of the rock phase in the Z direction. m1 W represents the length of the intersecting plate-like fracture model in the X direction. f2 is the width of the crack in the Y direction; m is the number of cracks in the Y direction.

7. The method according to claim 6, characterized in that, The surface area of ​​the overlapping cracks in the X and Y directions is obtained by the following formula: In the formula, S3 is the surface area of ​​the overlapping cracks in the X and Y directions; θ is the angle between the cracks; a is the length of the crack in the overlapping area in the Y direction; and b is the length of the crack in the overlapping area in the X direction.

8. The method according to claim 7, characterized in that, The surface area of ​​all cracks is obtained using the following formula: In the formula, S represents the total surface area of ​​all cracks.

9. The method according to claim 8, characterized in that, Obtain all crack volumes, including: Obtain the fracture volume in the rock along the X direction, the fracture volume in the Y direction, and the overlapping fracture volume in the X and Y directions; All crack volumes are obtained based on the crack volume corresponding to the X direction, the crack volume corresponding to the Y direction, and the overlapping crack volumes in the X and Y directions.

10. The method according to claim 9, characterized in that, The crack volume in the X direction is obtained using the following formula: V1=(h f *L m2 *W f1 )*n In the formula, V1 is the crack volume corresponding to the X direction.

11. The method according to claim 10, characterized in that, The crack volume in the Y direction is obtained using the following formula: V2=(W f2 *L m1 *h f )*m In the formula, V2 is the crack volume corresponding to the Y direction.

12. The method according to claim 11, characterized in that, The volume of the overlapping cracks in the X and Y directions is obtained by the following formula: In the formula, V3 is the overlapping crack volume in the X and Y directions.

13. The method according to claim 12, characterized in that, All crack volumes were obtained using the following formula: In the formula, V represents the total volume of all cracks.

14. The method according to claim 13, characterized in that, The specific surface area of ​​a rock sample is obtained using the following formula: In the formula, The specific surface area of ​​the rock sample.

15. The method according to claim 14, characterized in that, Substituting the specific surface area formula of the rock sample The relationship between the T2 relaxation time of the fluid in the fracture of the core sample and the fracture width was obtained:

16. The method according to claim 15, characterized in that, Obtaining the target crack width of intersecting plate-like cracks includes: Obtain the relationship between the crack widths in the X and Y directions; Substituting the relationship between the crack widths in the X and Y directions into the relationship between the T2 relaxation time of the fluid in the core sample crack and the crack width, we obtain an equation with the target crack width as the independent variable. Solve the equation with the target crack width as the independent variable to obtain the target crack width.

17. The method according to claim 16, characterized in that, The formula relating the crack widths in the X and Y directions is as follows: W f2 =k*W f1 The equation with the target crack width as the independent variable is shown below: The formula for the target crack width is as follows:

18. The method according to claim 17, characterized in that, Obtaining the permeability of intersecting plate-like seams includes: Based on the Hagen-Poiseiulle equation, Darcy's law equation, and the end face area of ​​the target fracture, the relationship between the permeability and the fracture width of the intersecting plate-like fracture is obtained. Substitute the formula for the target crack width into the relationship between the permeability of the intersecting plate-like crack and the crack width to obtain the permeability of the intersecting plate-like crack.

19. The method according to claim 18, characterized in that, The Hagen-Poiseiulle equation is: Darcy's Law is: The end face area of ​​the target crack is: A=h f w f The relationship between the permeability of intersecting plate-like fractures and the fracture aperture is as follows: In the formula, q is the seepage flow rate; h f W represents the height of the intersecting plate-like fracture model in the Z direction. f For W f1 The value represents the width of the crack in the X direction; Δp is the displacement pressure difference; μ is the gas viscosity; L is the target crack length; K is the target crack permeability; and A is the target crack end face area.

20. The method according to claim 19, characterized in that, The formula for the permeability of intersecting plate-like joints is shown below:

21. An apparatus for obtaining fracture permeability in unconventional reservoirs, characterized in that, include: Establish a unit to establish the relationship between the T2 relaxation time of the fluid in the fracture of the core sample and the specific surface area of ​​the rock sample; The width acquisition unit is used to obtain the target fracture width of the intersecting plate fracture based on the relationship between the T2 relaxation time of the fluid in the fracture of the core sample and the specific surface area of ​​the rock sample. The permeability acquisition unit is used to obtain the permeability of intersecting plate-like fractures based on the target fracture width.

22. An electronic device, characterized in that, include: Processor, the processor being coupled to memory; The processor is configured to read and execute a computer program stored in the memory to implement the method as described in any one of claims 1-20.

23. A computer-readable storage medium storing a program or instructions, characterized in that, When the program or instructions are executed by the processor, they implement the method as described in any one of claims 1-20.

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