Method for making a fully anisotropic matrix fracture flow model

Abstract

This invention provides a method for constructing a fully anisotropic matrix fracture seepage model. The method includes: Step 1, establishing a Cartesian coordinate system and determining the overall parameters of the seepage model; Step 2, determining the physical properties of the matrix system; Step 3, determining the physical properties of the fracture system and designing the fracture system; Step 4, cutting and bonding the physical model. This method for constructing a fully anisotropic matrix fracture seepage model is also applicable to other research fields related to anisotropic seepage phenomena, and can simulate the complex and fully anisotropic permeability characteristics of actual fractured reservoirs, enabling the study of seepage and development laws in such reservoirs.

Description

Technical Field

[0001] This invention relates to the field of oilfield development technology, and in particular to a method for creating a fully anisotropic matrix fracture seepage model. Background Technology

[0002] Anisotropic reservoirs are reservoirs with directional permeability. They are widely distributed, have great development potential, and occupy an important position in the global and Chinese petroleum industries. Compared with conventional reservoirs, the main challenge in developing anisotropic reservoirs is understanding and adjusting the direction of fluid migration within the formation. The main factor influencing fluid migration direction and determining the flow relationship between injection and production wells is permeability anisotropy. Therefore, targeted research on the seepage mechanism and development laws of anisotropic reservoirs is essential.

[0003] Currently, physical simulation experiments for seepage and development in anisotropic reservoirs remain difficult to conduct, primarily because it is challenging to establish an anisotropic physical model that closely resembles the actual reservoir. Anisotropic reservoirs often develop multiple sets of directional natural fractures. Both the fracture system and the matrix system exhibit varying degrees of anisotropy, and the complex, fully anisotropic coupling between them determines the fluid seepage patterns. Previously, the methods for creating anisotropic seepage media mainly included four types: pre-filled fracture filler compaction, mechanical tension-compression fracture creation, parallel plate stacking fracture formation, and selective bonding of cubic rock blocks. All four methods have certain limitations: they either cannot quantitatively control fracture distribution or can only achieve simple fracture anisotropy, failing to simulate fully anisotropic characteristics.

[0004] Chinese patent application No. 201010190001.9 discloses a method for preparing anisotropic fracture seepage media. This method uses natural geological rock as raw material to process small rock blocks, which are then sequentially connected in a predetermined manner to form a large-scale rock mass. The gaps between the small rock blocks form a three-dimensional fracture system within the large rock mass, and the distribution of fractures within the large rock mass is quantitatively controlled, resulting in a heterogeneous anisotropic fracture seepage media with quantitative fracture distribution. However, this invention only considers the anisotropy of the fracture system and cannot simulate the influence of matrix system anisotropy on fluid seepage.

[0005] Chinese patent application No. 201910236413.2 discloses a method and apparatus for constructing an anisotropic reservoir physical model. The method includes: converting anisotropic reservoir parameters into isotropic reservoir parameters; wherein the isotropic reservoir formation thickness in the isotropic reservoir parameters is greater than the anisotropic reservoir formation thickness in the anisotropic reservoir parameters; and constructing an anisotropic reservoir physical model based on similarity criteria using the isotropic reservoir parameters. This invention also fails to consider the influence of matrix anisotropy on the entire reservoir.

[0006] Chinese patent application CN201010560496.X discloses a method for establishing a predictable physical model for water-driven development of fractured anisotropic reservoirs. This method includes: (a) establishing similarity criteria for simulating the development of fractured reservoirs based on the characteristics of water-driven oil production, utilizing seepage mechanics theory and similarity analysis. These similarity criteria include similarity in shape and space, wellbore geometry, rock properties, oil-water viscosity, gravity-pressure, the ratio of movable oil in the matrix and fractures, the distribution of oil content within the matrix, the temporal similarity of matrix absorption and fracture displacement characteristics, the similarity of absorption intensity distribution, and the temporal process similarity; (b) the implementation of the similarity criteria and the design of model parameters; and (c) establishing a macroscopic physical model of the reservoir that satisfies multiple similarities to comprehensively simulate and predict the seepage characteristics and development process of actual fractured reservoirs. This invention establishes a predictable physical simulation similarity criterion system for fractured anisotropic reservoirs, which is comprehensive in function and easy to implement.

[0007] The above-mentioned existing technologies are all quite different from the present invention and have failed to solve the technical problem we want to solve. Therefore, we have invented a new method for making a completely anisotropic matrix crack seepage model. Summary of the Invention

[0008] The purpose of this invention is to establish a method for creating a fully anisotropic matrix fracture seepage model, which can simulate the complex and fully anisotropic permeability characteristics of actual fractured reservoirs, and can be used to study the seepage and development laws of such reservoirs.

[0009] The objective of this invention can be achieved through the following technical measures: a method for fabricating a fully anisotropic matrix fracture seepage model, the method comprising:

[0010] Step 1: Establish a rectangular coordinate system and determine the overall parameters of the seepage model;

[0011] Step 2: Determine the physical properties of the matrix system;

[0012] Step 3: Determine the physical property parameters of the crack system and design the crack system;

[0013] Step 4: Cut and glue the physical model.

[0014] The objective of this invention can also be achieved through the following technical measures:

[0015] In step 1, a rectangular coordinate system is established with the earth as the reference point. Using the east, north, and up directions as coordinate lines, each corresponding to a unit coordinate vector. The fully anisotropic permeability tensor of the fractured reservoir to be simulated in the geodetic coordinate system is given by equation (1):

[0016]

[0017] In the formula, This is the overall permeability tensor of the matrix fracture seepage model.

[0018] For the matrix fracture seepage model to be constructed, the following conditions must be met:

[0019]

[0020] in, For the permeability tensor of the matrix system in the seepage model; Let be the permeability tensor of the fracture system in the seepage model.

[0021] In step 2, the natural rock used as the raw material for constructing the matrix system for the matrix fracture seepage model is required to have relatively weak heterogeneity. Standard core columns are drilled parallel and perpendicular to the depositional direction of the natural rock, and the horizontal permeability K of the natural rock is measured through core gas permeability experiments. mh and vertical permeability K mv .

[0022] In step 2, with the rock deposition plane γ m Establish a rectangular coordinate system for the reference frame. With sedimentary plane γ m The line of intersection with the horizontal plane is a coordinate line, corresponding to a unit coordinate vector. In plane γ m Internal take and The vertical direction is another coordinate line, corresponding to the unit coordinate vector. Then, take the direction perpendicular to the deposition plane as the third coordinate line, corresponding to the unit coordinate vector. Then the matrix system in γ m The anisotropic permeability tensor in the coordinate system is:

[0023]

[0024] The anisotropy coefficient of the matrix system can be expressed as:

[0025]

[0026] Equation (3) can be simplified to:

[0027]

[0028] Rock sedimentary plane γ m The angle of inclination relative to the ground plane is α.m The azimuth angle is β m Then any tensor By γ m Cartesian coordinate system Transform to Geodetic Rectangular Coordinate System tensor The formula for calculating the tensor at time is (6), where the coordinate transformation coefficients are (7):

[0029]

[0030]

[0031] By combining equations (5) to (7), the anisotropic permeability tensor of the matrix system in the geodetic coordinate system can be calculated:

[0032]

[0033] In step 3, the permeability tensor of the fracture system can be expressed as:

[0034]

[0035] K in the formula fh The equivalent permeability of the fracture system is determined by equation (10):

[0036]

[0037] The model fracture system consists of a single set of parallel fractures in a specified direction, with an equivalent permeability K. fh It can also be expressed as:

[0038]

[0039] Where: n f denoted as crack density and b as crack aperture.

[0040] In step 3, the fracture system of the matrix fracture seepage model to be constructed needs to satisfy the geodetic coordinate system. The permeability tensor can be obtained by simultaneously solving equations (1) to (2) and (8):

[0041]

[0042] By combining equations (10) to (12), the crack density n of the model crack system can be obtained. f The correspondence between the crack aperture b and the crack size b:

[0043]

[0044] A single set of parallel cracks in a crack system at the crack plane γ fA rectangular coordinate system established for the reference object The anisotropic permeability tensor within is given by equation (14):

[0045]

[0046] Right now:

[0047]

[0048] Assuming the crack plane γ of the crack system f Geodetic coordinate system The inclination angle is α f The azimuth angle is β f Combining equations (6) to (7) and (15), we obtain the fracture system in the geodetic coordinate system. The anisotropic permeability tensor below:

[0049]

[0050] Combining equations (12) and (16), we get:

[0051]

[0052] Solving equation system (17) yields the dip angle of the parallel cracks in the crack system:

[0053] When k fxy >0, k fxz >0 and

[0054] When k fxy >0, k fxz <0 and

[0055] When k fxy <0,k fx <0 and

[0056] When k fxy <0,k fx >0 and

[0057] Azimuth angle of the crack system parallel to the crack:

[0058] When k fxy >0, k fxz >0 and

[0059] When k fxy >0, k fxz <0 and

[0060] When kfxy <0,k fxz <0 and

[0061] When k fxy <0,k fxz >0 and

[0062] In step 4, the crack density n of the crack system is artificially given. f The parameters such as the opening, dip angle, and azimuth angle of the parallel crack are obtained by calculating according to equations (13), (18) to (19).

[0063] In step 4, the large-scale cubic rock mass is directionally cut into rock slabs of uniform thickness, ensuring that the dip angle and azimuth angle of the cutting plane are equal to the dip angle and azimuth angle of the designed fracture plane; the spacing between the cutting planes, i.e., the thickness of the rock slab, is equal to the given fracture density n. f The reciprocals are equal.

[0064] The method for creating a fully anisotropic matrix fracture seepage model in this invention is also applicable to other research fields related to anisotropic seepage phenomena. It can simulate the complex fully anisotropic permeability characteristics of actual fractured reservoirs and is used to study the seepage and development laws of such reservoirs.

[0065] The advantages of this invention are at least reflected in the following three aspects: it can quantitatively control the fracture distribution parameters in the seepage model, including direction, density and aperture, and the established physical model is repeatable; it considers the influence of matrix system anisotropy on fluid seepage, and can simulate the complex and completely anisotropic permeability characteristics of actual fractured reservoirs; it uses natural rocks as raw materials, and the seepage medium produced has the properties of natural rocks, which can more realistically express the natural physical properties of the reservoir. Attached Figure Description

[0066] Figure 1 A flowchart of a specific embodiment of the method for creating a fully anisotropic matrix fracture seepage model according to the present invention;

[0067] Figure 2 This is a schematic diagram of a point-bonding method for rock slabs in a specific embodiment of the present invention;

[0068] Figure 3 This is a schematic diagram of a point-bonding method for rock slabs in another specific embodiment of the present invention;

[0069] Figure 4 This is a schematic diagram of a completely anisotropic matrix fracture seepage model in a specific embodiment of the present invention. Detailed Implementation

[0070] To make the above and other objects, features and advantages of the present invention more apparent and understandable, preferred embodiments are described below in detail with reference to the accompanying drawings:

[0071] The following are several specific embodiments of the application of the present invention.

[0072] Example 1

[0073] In a specific embodiment 1 of the present invention, such as Figure 1 As shown, Figure 1 The flowchart illustrates the method for fabricating a fully anisotropic matrix fracture seepage model according to the present invention. This method includes the following steps:

[0074] 101. Determine the overall parameters of the seepage model

[0075] First, establish a rectangular coordinate system with the earth as the reference point. Using the east, north, and up directions as coordinate lines, each corresponding to a unit coordinate vector. The fully anisotropic permeability tensor of the fractured reservoir to be simulated in the geodetic coordinate system is given by equation (1):

[0076]

[0077] In the formula, This is the overall permeability tensor of the matrix fracture seepage model.

[0078] For the matrix fracture seepage model to be constructed, the following conditions must be met:

[0079]

[0080] in, For the permeability tensor of the matrix system in the seepage model; Let be the permeability tensor of the fracture system in the seepage model.

[0081] 102. Determine the physical properties of the matrix system.

[0082] As the raw material for constructing the matrix system of the matrix fracture seepage model, the natural rock is required to have relatively weak heterogeneity. Standard core columns were drilled parallel and perpendicular to the depositional direction of the natural rock, and the horizontal permeability K of the natural rock was measured through core gas permeability experiments. mh and vertical permeability K mv .

[0083] With rock sedimentary plane γ m Establish a rectangular coordinate system for the reference frame. With sedimentary plane γ m The line of intersection with the horizontal plane is a coordinate line, corresponding to a unit coordinate vector. In plane γ m Internal take and The vertical direction is another coordinate line, corresponding to the unit coordinate vector. Then, take the direction perpendicular to the deposition plane as the third coordinate line, corresponding to the unit coordinate vector. Then the matrix system in γ m The anisotropic permeability tensor in the coordinate system is:

[0084]

[0085] The anisotropy coefficient of the matrix system can be expressed as:

[0086]

[0087] Equation (3) can be simplified to:

[0088]

[0089] Rock sedimentary plane γ m The angle of inclination relative to the ground plane is α. m The azimuth angle is β m Then any tensor By γ m Cartesian coordinate system Transform to Geodetic Rectangular Coordinate System tensor The formula for calculating the tensor at time is (7), where the coordinate transformation coefficients are (6):

[0090]

[0091]

[0092] By combining equations (5) to (7), the anisotropic permeability tensor of the matrix system in the geodetic coordinate system can be calculated:

[0093]

[0094] 103. Crack System Design

[0095] The permeability tensor of a fractured system can be expressed as:

[0096]

[0097] K in the formula fh The equivalent permeability of the fracture system is determined by equation (10):

[0098]

[0099] The model fracture system consists of a single set of parallel fractures in a specified direction, with an equivalent permeability K. fh It can also be expressed as:

[0100]

[0101] Where: n f denoted as crack density and b as crack aperture.

[0102] The fracture system of the matrix fracture seepage model to be constructed must satisfy the geodetic coordinate system. The permeability tensor can be obtained by simultaneously solving equations (1) to (2) and (8):

[0103]

[0104] By combining equations (10) to (12), the crack density n of the model crack system can be obtained. f The correspondence between the crack aperture b and the crack size b:

[0105]

[0106] A single set of parallel cracks in a crack system at the crack plane γ f A rectangular coordinate system established for the reference object The anisotropic permeability tensor within is given by equation (14):

[0107]

[0108] Right now:

[0109]

[0110] Assuming the crack plane γ of the crack system f Geodetic coordinate system The inclination angle is α f The azimuth angle is β f Combining equations (6) to (7) and (15), we obtain the fracture system in the geodetic coordinate system. The anisotropic permeability tensor below:

[0111]

[0112] Combining equations (12) and (16), we get:

[0113]

[0114] Solving equation system (17) yields the dip angle of the parallel cracks in the crack system:

[0115] When k fxy >0, k fxz >0 and

[0116] When k fxy >0, k fxz <0 and

[0117] When k fxy <0,k fx <0 and

[0118] When k fxy <0,k fxz >0 and

[0119] Azimuth angle of the crack system parallel to the crack:

[0120] When k fxy >0, k fxz >0 and

[0121] When k fxy >0, k fxz <0 and

[0122] When k fxy <0,k fxz <0 and

[0123] When k fxy <0,k fxz >0 and

[0124] 104. Cutting and bonding of physical models

[0125] The crack density n of the artificially given crack system f The opening, dip angle, azimuth angle and other parameters of the parallel crack are obtained by calculating according to formulas (13), (18) to (19).

[0126] Large-scale cubic rock masses are directionally cut into rock slabs of uniform thickness, ensuring that the dip and azimuth angles of the cutting planes are equal to those of the designed fracture planes; the spacing between the cutting planes, i.e., the thickness of the rock slabs, is determined by the given fracture density n. f The reciprocals are equal.

[0127] Example 2

[0128] In a specific embodiment 2 of the present invention, the method for fabricating a fully anisotropic matrix fracture seepage model of the present invention includes the following steps:

[0129] S1 obtains the fully anisotropic permeability tensor of a certain oil reservoir in the geodetic coordinate system.

[0130] The S2 test was used to prepare the natural rocks of the matrix system. The depositional plane had a dip angle of 15° and an azimuth angle of 44° relative to the earth. The horizontal permeability along the depositional plane was 2.5 × 10⁻⁶. -3 μm 2 The vertical permeability is 1.5 × 10⁻⁶. -3 μm 2 According to equation (8), the anisotropic permeability tensor of the matrix system in the geodetic coordinate system can be calculated as follows:

[0131] S3 obtains the anisotropic permeability tensor of the fracture system through equation (12). If the design crack density is 20 cracks / m, then the crack aperture b is 135μm obtained from equation (13);

[0132] S4 is obtained from equation (11) K fh =4.1×10 -3 μm 2 The corresponding k can be calculated from equation (9). fxy =0.60, k fxz =0.93, k fyz = -0.2, the dip angle α of the parallel crack is calculated from equations (18) and (19). f =72°, azimuth β f =12°;

[0133] S5 cuts the rock slab based on the crack density of 20 cracks / m, crack aperture of 135μm, crack dip angle of 72°, and crack azimuth angle of 12° obtained from the above steps, and then bonds them together to form a completely anisotropic matrix crack seepage model.

[0134] Example 3

[0135] In a specific embodiment 3 of the present invention, the processed and manufactured uniform thickness rock slab is used as... Figures 2-3 The point-bonding method shown uses epoxy resin as the adhesive. A square metal sheet of equal thickness is pre-set at the center of the circular bonding point to ensure that the thickness of the metal sheet is equal to the designed crack opening. Different rock slabs are bonded together to reassemble a large-scale cubic rock mass, i.e., a completely anisotropic matrix fracture seepage model, such as... Figure 4 As shown.

[0136] Finally, it should be noted that the above description is merely 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.

[0137] Except for the technical features described in the specification, all other technologies are known to those skilled in the art.

Claims

1. A method for fabricating a fully anisotropic matrix fracture seepage model, characterized in that, The method for creating this fully anisotropic matrix fracture seepage model includes: Step 1: Establish a rectangular coordinate system and determine the overall parameters of the seepage model; Step 2: Determine the physical properties of the matrix system; Step 3: Determine the physical property parameters of the crack system and design the crack system; The fracture system of the matrix fracture seepage model to be constructed must satisfy the geodetic coordinate system. The permeability tensor can be obtained by the following formula: Crack density in the model crack system and crack opening The correspondence is as follows: A single set of parallel cracks in a crack system at the crack plane A rectangular coordinate system established for the reference object The anisotropic permeability tensor within is: Right now: Assuming the crack plane of the crack system Geodetic coordinate system The inclination angle is azimuth angle is Combining the above equations, we obtain the fracture system in the geodetic coordinate system. The anisotropic permeability tensor below: Therefore, we can conclude that: Solving the above system of equations yields the dip angle of the parallel cracks in the crack system: when , and , ; when , and , ; when , and , ; when , and , ; Azimuth angle of the crack system parallel to the crack: when , and , ; when , and , ; when , and , ; when , and , ; Step 4: Cut and glue the physical model.

2. The method for fabricating a fully anisotropic matrix fracture seepage model according to claim 1, characterized in that, In step 1, a rectangular coordinate system is established with the earth as the reference point. Using the east, north, and up directions as coordinate lines, each corresponding to a unit coordinate vector. The known perfectly anisotropic permeability tensor of the fractured reservoir to be simulated in the geodetic coordinate system can be expressed as: In the formula, This represents the overall permeability tensor of the matrix fracture seepage model; For the matrix fracture seepage model to be constructed, the following conditions must be met: in, For the permeability tensor of the matrix system in the seepage model; Let be the permeability tensor of the fracture system in the seepage model.

3. The method for fabricating a fully anisotropic matrix fracture seepage model according to claim 2, characterized in that, In step 2, the natural rock used as the raw material for constructing the matrix system for the matrix fracture seepage model is required to have relatively weak heterogeneity. Standard core columns are drilled parallel and perpendicular to the depositional direction of the natural rock, and the horizontal permeability of the natural rock is measured through core gas permeability experiments. and vertical permeability .

4. The method for fabricating a fully anisotropic matrix fracture seepage model according to claim 3, characterized in that, In step 2, with the rock deposition plane Establish a rectangular coordinate system for the reference frame. : based on the sedimentary plane The line of intersection with the horizontal plane is a coordinate line, corresponding to a unit coordinate vector. ; in plane Internal take and The vertical direction is another coordinate line, corresponding to the unit coordinate vector. Then, take the direction perpendicular to the deposition plane as the third coordinate line, corresponding to the unit coordinate vector. The matrix system in The anisotropic permeability tensor in the coordinate system is: The anisotropy coefficient of the matrix system can be expressed as: ； Matrix system in The formula for the anisotropic permeability tensor in the coordinate system can be simplified to: Rock sedimentary plane The angle of inclination relative to the ground plane is azimuth angle is Then any tensor Depend on Cartesian coordinate system Transform to Geodetic Rectangular Coordinate System tensor The formula for calculating the tensor at time is: ； The coordinate transformation coefficients are: Combining the above formulas, the anisotropic permeability tensor of the matrix system in the geodetic coordinate system can be calculated: 。 5. The method for fabricating a fully anisotropic matrix fracture seepage model according to claim 4, characterized in that, In step 3, the permeability tensor of the fracture system can be expressed as: In the formula The equivalent permeability of the fracture system is determined by the following formula. The model fracture system consists of a single set of parallel fractures in a specified direction, with an equivalent permeability of It can also be expressed as: In the formula: Crack density, This refers to the crack opening.

6. The method for fabricating a fully anisotropic matrix fracture seepage model according to claim 1, characterized in that, In step 4, the crack density of the crack system is artificially given. Based on the crack density of the model crack system and crack opening The parameters such as the opening, dip angle, and azimuth angle of parallel cracks are obtained by calculating the corresponding formulas, the dip angle formula of parallel cracks in the crack system, and the azimuth angle formula of parallel cracks in the crack system.

7. The method for fabricating a fully anisotropic matrix fracture seepage model according to claim 1, characterized in that, In step 4, the large-scale cubic rock mass is directionally cut into rock slabs of uniform thickness, ensuring that the dip angle and azimuth angle of the cutting plane are equal to the dip angle and azimuth angle of the designed fracture plane; the spacing between the cutting planes, i.e., the thickness of the rock slab, is equal to the given fracture density. The reciprocals are equal.

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