CN113188976B - Method and system for determining anisotropic permeability of sandwich-shaped shale - Google Patents

Abstract

The invention provides a method and system for determining the anisotropic permeability of interlayered shale. First, shale matrix parameters and interlayer parameters are determined based on shale cores; secondly, a molecular dynamics model is constructed based on the average pore radius of the shale matrix; The molecular dynamics model simulates the flow of shale oil in the nanopores of the shale matrix to determine the permeability of the shale matrix; then, the permeability of the sandwiched bar is determined based on the average pore radius of the sandwiched bar and the sandwiched bar porosity; finally, based on the shale matrix The permeability of interlayers, the permeability of interlayers, the proportion of shale matrix and the proportion of interlayers determine the horizontal and vertical permeability. Based on the combination of the pore structure of the shale core and the molecular dynamics model, the present invention uses the molecular dynamics model to simulate the flow of shale oil in the nanopores of the shale matrix, so that the horizontal and vertical directions of the interlayer shale can be accurately calculated. It solves the problem that the existing technology cannot achieve accurate measurement of the anisotropic permeability of interlayer shale.

Description

A method and system for determining anisotropic permeability of interlayer shale

technical field

The invention relates to the technical field of oil and gas field development, in particular to a method and system for determining the anisotropic permeability of interlayered shale.

Background technique

Shale oil is an important unconventional energy source, and crude oil mainly exists in shale pores in adsorbed and free states. The reservoir types of shale oil include matrix type, fracture type and interlayer type. Because interlayer shale contains carbonate rock or sandstone strips (also called interlayers) with high porosity and permeability, the actual production process is relatively high, which is the focus of shale oil development. However, under the influence of bedding, the interlayered shale has obvious anisotropy characteristics, that is, the rock permeability in parallel bedding and vertical bedding directions (that is, the permeability in the horizontal direction and the permeability in the vertical direction) are different. Accurate determination of shale anisotropic permeability is of great significance for shale reservoir evaluation, hydraulic fracturing design and production performance prediction.

At present, the measurement of anisotropic permeability of interlayer shale has the following problems:

On the one hand, since the shale is very brittle, the presence of microfractures or bedding will make the interlayered shale easy to crack along the fracture plane, so it is difficult to obtain a complete core column. At the same time, the core needs to be washed with oil before permeability measurement, which can easily cause core damage. However, the measurement of rock permeability often requires a whole core for experiments, and an incomplete core will make it difficult to measure the permeability of interlayer shale.

On the other hand, due to the large difference in shale permeability parallel to the bedding and perpendicular to the bedding direction, the results may differ by several orders of magnitude, so the conventional permeability testing method will bring large errors.

Patent CN206431021U relates to a simulation test device for shale permeability, which can measure the effective gas permeability under different pressure conditions, but this device can only test the permeability in the parallel bedding direction, but cannot test the permeability in the vertical bedding direction. Rate. Patent CN106769790A relates to a shale permeability testing device and method based on liquid pressure pulses under the action of ultrasonic waves. It mainly measures the permeability by observing the difference of the pulse decay curve of the standard brine passing through the core to be tested. However, shale is easy to swell in contact with water, resulting in changes in permeability, and accurate permeability values cannot be obtained. Patent CN109100278A relates to a method for calculating apparent permeability considering the distribution characteristics of shale pore size. The apparent permeability of shale reservoir scale is obtained by superimposing the distribution frequencies of capillaries with different diameters. However, this method only considers the migration mechanism of shale gas, and is not suitable for measuring the rock permeability of shale oil reservoirs, nor can it reflect the anisotropic characteristics of interlayered shale.

SUMMARY OF THE INVENTION

The purpose of the present invention is to provide a method and system for determining the anisotropic permeability of interlayer shale, so as to solve the problem that the anisotropic permeability of interlayer shale cannot be accurately measured.

In order to achieve the above object, the present invention provides a method for determining the anisotropic permeability of interlayer shale, the method comprising:

S1: Obtain interlayered shale cores;

S2: Determine shale matrix parameters and sandwich parameters based on the shale core; the shale matrix parameters include the proportion h ₁ of the shale matrix, the average pore radius r ₁ of the shale matrix, and the shale matrix porosity Φ ₁ ; The parameters of the clip include the proportion h ₂ of the clip, the average pore radius r ₂ of the clip and the porosity of the clip Φ ₂ ;

S3: Build a molecular dynamics model based on the average pore radius r ₁ of the shale matrix;

S4: using the molecular dynamics model to simulate the flow of shale oil in the nanopores of the shale matrix to determine the permeability of the shale matrix;

S5: Determine the permeability of the clip based on the average pore radius r ₂ of the clip and the clip porosity Φ ₂ ;

S6: Determine the horizontal permeability and vertical permeability of the interlayered shale based _on the permeability of the shale matrix, the permeability of the interlayers, the proportion _h1 of the shale matrix and the proportion h2 of the interlayers.

Optionally, the determining of shale matrix parameters and clamping parameters based on the shale core specifically includes:

S21: Determine the average pore radius r ₁ of the shale matrix and the porosity Φ ₁ of the shale matrix through the nitrogen adsorption experiment;

S22: Determine the average pore radius r ₂ of the clip and the porosity of the clip Φ ₂ through the high-pressure mercury intrusion experiment;

S23: photographing the cross section of the shale core to obtain a rock sample image perpendicular to the bedding direction;

S24: using image analysis software to analyze the rock sample image to obtain the proportion h ₁ of the shale matrix and the proportion h ₂ of the clip.

Optionally, the construction of a molecular dynamics model based on the average pore radius r ₁ of the shale matrix specifically includes:

S31: Obtaining the mineral composition of the shale matrix by the mineral X-ray whole-rock analysis method;

S32: Obtain on-site shale oil components through hydrocarbon component analysis experiments;

S33: Construct a molecular dynamics model according to the mineral composition of the shale matrix, the composition of the on-site shale oil, and the average pore radius r ₁ of the shale matrix.

Optionally, the use of the molecular dynamics model to simulate the flow of shale oil in the nanopores of the shale matrix to determine the permeability of the shale matrix specifically includes:

S41: using the molecular dynamics model to simulate the flow of shale oil in the nanopores of the shale matrix to obtain a velocity profile;

S42: Fitting the velocity profile to obtain boundary conditions for shale oil flow; the boundary conditions include positive slip, no slip or negative slip;

S43: Determine the permeability of the shale matrix based on the boundary conditions, the average pore radius _{r1 of} the shale matrix, and the shale matrix porosity Φ1.

Optionally, the permeability of the clip is determined based on the average pore radius r ₂ of the clip and the porosity of the clip Φ ₂ , and the specific formula is:

where k ₂ is the permeability of the clip.

Optionally, the horizontal permeability and vertical permeability of the interlayered shale are determined based _on the permeability of the shale matrix, the permeability of the interlayers, the proportion _h1 of the shale matrix, and the proportion h2 of the interlayers. The formula is:

Among them, k′ is the horizontal permeability of interlayered shale, _k ″ is the vertical permeability of interlayered shale, _h1 is the proportion of shale matrix, h2 is the proportion of interlayers, and _k1 is the proportion of shale matrix Permeability, k ₂ is the permeability of the clip.

The present invention also provides a system for determining the anisotropic permeability of interlayer shale, the system comprising:

An acquisition module for acquiring interlayer shale cores;

A parameter determination module for determining shale matrix parameters and clamping parameters based on the shale core; the shale matrix parameters include the proportion h ₁ of the shale matrix, the average pore radius r ₁ of the shale matrix, and the shale matrix Porosity Φ ₁ ; the parameters of the clip include the proportion h ₂ of the clip, the average pore radius r ₂ of the clip, and the porosity of the clip Φ ₂ ;

Molecular dynamics model building module, used to build a molecular dynamics model based on the average pore radius r ₁ of the shale matrix;

The shale matrix permeability determination module is used to simulate the flow of shale oil in the nanopores of the shale matrix by using the molecular dynamics model to determine the permeability of the shale matrix;

The module for determining the permeability of the clip, which is used to determine the permeability of the clip based on the average pore radius r ₂ of the clip and the porosity of the clip Φ ₂ ;

The anisotropic permeability determination module is used to determine the horizontal permeability and vertical permeability of interlayered shale based _on the permeability of the shale matrix, the permeability of the interlayer, the proportion of shale matrix _h1 and the proportion of interlayers h2. penetration.

Optionally, the parameter determination module specifically includes:

The shale matrix parameter determination unit is used to determine the average pore radius r ₁ of the shale matrix and the shale matrix porosity Φ ₁ through the nitrogen adsorption experiment;

A clip parameter determination unit, used to determine the clip average pore radius r ₂ and clip porosity Φ ₂ through high-pressure mercury intrusion experiments;

a rock sample image acquisition unit, used for photographing the section of the shale core to obtain a rock sample image perpendicular to the bedding direction;

The image analysis unit is used for analyzing the rock sample image by using image analysis software to obtain the proportion h ₁ of the shale matrix and the proportion h ₂ of the clip.

Optionally, the molecular dynamics model building module specifically includes:

The shale matrix mineral composition determination unit is used to obtain the shale matrix mineral composition through the mineral X-ray whole-rock analysis method;

The shale oil composition acquisition unit is used to obtain the on-site shale oil composition through the hydrocarbon composition analysis experiment;

The molecular dynamics model building unit is used for building a molecular dynamics model according to the mineral composition of the shale matrix, the composition of the field shale oil and the average pore radius r ₁ of the shale matrix.

Optionally, the shale matrix permeability determination module specifically includes:

a simulation unit for simulating the flow of shale oil in the nanopores of the shale matrix by using the molecular dynamics model to obtain a velocity profile;

a boundary condition determination unit, used for fitting the velocity profile to obtain boundary conditions of shale oil flow; the boundary conditions include positive slip, no slip or negative slip;

A shale matrix permeability determination unit for determining the permeability of the shale matrix based on the boundary conditions, the average pore radius r ₁ of the shale matrix, and the shale matrix porosity Φ ₁ .

According to the specific embodiments provided by the present invention, the present invention discloses the following technical effects:

Based on the combination of the pore structure of the shale core and the molecular dynamics model, the present invention uses the molecular dynamics model to simulate the flow of shale oil in the nanopores of the shale matrix, so that the horizontal and vertical directions of the interlayered shale can be accurately calculated. It solves the problem that the existing technology cannot realize the accurate measurement of the anisotropic permeability of interlayer shale. In addition, this technology breaks through the defects that standard core columns are required for conventional permeability experimental tests, but shale is fragile and core columns are difficult to obtain. The patent of the present invention only needs to be able to clearly distinguish the core fragments or fragments of the shale matrix and the interlayer, so the practicability is stronger.

Description of drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the accompanying drawings required in the embodiments will be briefly introduced below. Obviously, the drawings in the following description are only some of the present invention. In the embodiments, for those of ordinary skill in the art, other drawings can also be obtained according to these drawings without creative labor.

1 is a flowchart of a method for determining the anisotropic permeability of interlayered shale according to an embodiment of the present invention;

2 is a structural diagram of a system for determining the anisotropic permeability of interlayered shale according to the second embodiment of the present invention;

Fig. 3 is the pore size distribution diagram of the experiment of nitrogen adsorption and high pressure mercury intrusion of interlayer shale according to the third embodiment of the present invention;

4 is a schematic diagram of the construction of an abstract model of interlayer shale according to Embodiment 3 of the present invention;

5 is a schematic diagram of a molecular simulation model of shale kerogen slits, calcite slits and shale oil in Example 3 of the present invention;

6 is a schematic diagram of the velocity and boundary conditions of the flow of shale oil in the pores of the shale matrix according to the third embodiment of the present invention;

FIG. 7 is a schematic diagram of the horizontal and vertical permeability of the sandwiched shale according to the third embodiment of the present invention.

Detailed ways

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, but not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

The purpose of the present invention is to provide a method and system for determining the anisotropic permeability of interlayer shale, so as to solve the problem that the anisotropic permeability of interlayer shale cannot be accurately measured.

In order to make the above objects, features and advantages of the present invention more clearly understood, the present invention will be described in further detail below with reference to the accompanying drawings and specific embodiments.

Example 1

As shown in Figure 1, the present invention provides a method for determining the anisotropic permeability of interlayer shale, the method comprising:

S1: Obtain interlayered shale cores.

S2: Determine shale matrix parameters and sandwich parameters based on the shale core; the shale matrix parameters include the proportion h ₁ of the shale matrix, the average pore radius r ₁ of the shale matrix, and the shale matrix porosity Φ ₁ ; The parameters of the clip include the proportion h ₂ of the clip, the average pore radius r ₂ of the clip and the porosity of the clip Φ ₂ . The shale core includes a pore structure of a shale matrix and a pore structure of sandwich bars. The proportions mentioned above are the proportions of the thickness.

S3: Build a molecular dynamics model based on the average pore radius r ₁ of the shale matrix.

S4: Using the molecular dynamics model to simulate the flow of shale oil in the nanopores of the shale matrix to determine the permeability of the shale matrix.

S5: Determine the permeability of the clip based on the average pore radius r ₂ of the clip and the clip porosity Φ ₂ .

S6: Determine the horizontal permeability and vertical permeability of the interlayered shale based _on the permeability of the shale matrix, the permeability of the interlayers, the proportion _h1 of the shale matrix and the proportion h2 of the interlayers.

Each step is discussed in detail below:

S1: Obtain interlayered shale cores. The interlayered shale core selected in the present invention may not necessarily be a core column, but may also be a core block, as long as the shale matrix and the interlayer can be clearly distinguished.

Normal measurement of permeability generally requires standard cylindrical cores. For interlayer shale, it is very difficult to obtain core columns because of its brittleness. Therefore, the present patent does not require a complete core column, but only needs to be able to determine the ratio of shale matrix and interlayer through the shale core.

S2: Determine shale matrix parameters and clamping parameters based on the shale core, specifically including:

S21: Determine the average pore radius r ₁ of the shale matrix and the porosity Φ ₁ of the shale matrix through a nitrogen adsorption experiment.

S22: Determine the average pore radius r ₂ of the clip and the porosity Φ ₂ of the clip through a high-pressure mercury intrusion experiment.

S23: Photograph the cross section of the shale core to obtain a rock sample image perpendicular to the bedding direction.

S24: using image analysis software to analyze the rock sample image to obtain the proportion h ₁ of the shale matrix and the proportion h ₂ of the clip.

S3: Build a molecular dynamics model based on the average pore radius r ₁ of the shale matrix, including:

S31: Obtaining the mineral composition of the shale matrix by the mineral X-ray whole-rock analysis method.

S32: Obtain the on-site shale oil composition through a hydrocarbon composition analysis experiment.

S33: Construct a molecular dynamics model according to the mineral composition of the shale matrix, the composition of the on-site shale oil, and the average pore radius r ₁ of the shale matrix.

S4: Use the molecular dynamics model to simulate the flow of shale oil in the nanopores of the shale matrix, and determine the permeability of the shale matrix, specifically including:

S41: Using the molecular dynamics model to simulate the flow of shale oil in the nanopores of the shale matrix to obtain a velocity profile.

S42: Fitting the velocity profile to obtain boundary conditions for shale oil flow; the boundary conditions include positive slip, no slip or negative slip.

S43: Determine the permeability of the shale matrix based on the boundary conditions, the average pore radius r ₁ of the shale matrix, and the shale matrix porosity Φ ₁ , specifically including:

计算第一渗透率；其中，Ls_i为第i种矿物孔隙内的滑移长度，k′₁为第一渗透率，m<n。Assuming that there are n kinds of minerals in the shale matrix, and the boundary condition of shale oil flowing in the pores of m kinds of minerals is positive slip or no slip, according to

Calculate the first permeability; where Ls _i is the slip length in the pores of the i-th mineral, k′ ₁ is the first permeability, and m<n.

计算第二渗透率；其中，k″₁为第二渗透率，δ_i为第i种矿物孔隙内的边界层厚度。When the boundary of shale oil flowing in the pores of nm minerals is negative slip, according to

Calculate the second permeability; wherein, k″ ₁ is the second permeability, and δ _i is the thickness of the boundary layer in the pores of the i-th mineral.

The permeability of the shale matrix is calculated according to k ₁ =k′ ₁ +k″ ₁ .

S5: Determine the permeability of the clip based on the average pore radius r ₂ of the clip and the clip porosity Φ _2. The specific formula is:

Among them, k ₂ is the permeability of the clip, Φ ₂ is the porosity of the clip, and r ₂ is the average pore radius of the clip.

S6: Determine the horizontal and vertical permeability of interlayered shale based on the permeability of shale matrix, the permeability of interlayers, the proportion of shale matrix _h1 and the proportion of interlayers h2. The specific _formula is:

Among them, k′ is the horizontal permeability of interlayered shale, _k ″ is the vertical permeability of interlayered shale, _h1 is the proportion of shale matrix, h2 is the proportion of interlayers, and _k1 is the proportion of shale matrix Permeability, k ₂ is the permeability of the clip.

Embodiment 2

As shown in Figure 2, the present invention also discloses a system for determining the anisotropic permeability of interlayer shale, the system comprising:

The acquisition module 201 is used to acquire the interlayer shale core.

A parameter determination module 202, configured to determine shale matrix parameters and clamping parameters based on the shale core; the shale matrix parameters include the proportion h ₁ of the shale matrix, the average pore radius r ₁ of the shale matrix, and the shale matrix The matrix porosity Φ ₁ ; the parameters of the strip include the proportion h ₂ of the strip, the average pore radius r ₂ of the strip, and the porosity of the strip Φ ₂ .

The molecular dynamics model building module 203 is used for building a molecular dynamics model based on the average pore radius r ₁ of the shale matrix.

The shale matrix permeability determination module 204 is configured to use the molecular dynamics model to simulate the flow of shale oil in the nanopores of the shale matrix to determine the permeability of the shale matrix.

The sandwich bar permeability determination module 205 is used to determine the permeability of the sandwich bar based on the sandwich bar average pore radius r ₂ and the sandwich bar porosity Φ ₂ .

The anisotropic permeability determination module 206 is used to determine the horizontal permeability of the interlayer shale based _on the permeability of the shale matrix, the permeability of the interlayer, the proportion _h1 of the shale matrix and the proportion h2 of the interlayer. vertical permeability.

As an optional implementation manner, the parameter determination module 202 of the present invention specifically includes:

The shale matrix parameter determination unit is used to determine the average pore radius r ₁ of the shale matrix and the shale matrix porosity Φ ₁ through the nitrogen adsorption experiment.

The unit for determining the parameters of the clip bars is used to determine the average pore radius r ₂ of the clip bars and the porosity Φ ₂ of the clip bars through the high-pressure mercury intrusion experiment.

The rock sample image acquisition unit is used for photographing the section of the shale core to obtain a rock sample image perpendicular to the bedding direction.

The image analysis unit is used for analyzing the rock sample image by using image analysis software to obtain the proportion h ₁ of the shale matrix and the proportion h ₂ of the clip.

As an optional embodiment, the molecular dynamics model building module 203 of the present invention specifically includes:

The shale matrix mineral composition determination unit is used to obtain the shale matrix mineral composition through the mineral X-ray whole-rock analysis method.

The shale oil component acquisition unit is used to obtain on-site shale oil components through hydrocarbon component analysis experiments.

The molecular dynamics model building unit is used for building a molecular dynamics model according to the mineral composition of the shale matrix, the composition of the field shale oil and the average pore radius r ₁ of the shale matrix.

As an optional embodiment, the shale matrix permeability determination module 204 of the present invention specifically includes:

A simulation unit for simulating the flow of shale oil in the nanopores of the shale matrix by using the molecular dynamics model to obtain a velocity profile.

The boundary condition determination unit is used for fitting the velocity profile to obtain the boundary condition of shale oil flow; the boundary condition includes positive slip, no slip or negative slip.

A shale matrix permeability determination unit for determining the permeability of the shale matrix based on the boundary conditions, the average pore radius r ₁ of the shale matrix, and the shale matrix porosity Φ ₁ .

Embodiment 3

Specific examples:

S1: First select on-site interlayered shale cores.

S21: The pore structure of the shale matrix is measured by the nitrogen adsorption experiment, and the average pore radius r ₁ of the shale matrix is 6.42×10 ^-3 μm, and the porosity of the shale matrix Φ ₁ is 3.69%; the pore structure of the shale matrix is shown in the figure (a) in 3.

S22: The pore structure of the clip is measured by the high-pressure mercury intrusion experiment, and the average pore radius r ₂ of the clip is 5.57 μm and the porosity of the clip Φ ₂ is 5.63%; the pore structure of the clip is shown in (b) in Figure 3. Show.

S23: Photograph the cross section of the interlayered shale core perpendicular to the shale bedding direction to obtain a rock sample image perpendicular to the bedding direction.

S24: Import the rock sample image into ImageJ, and use the Analyze module in ImageJ to measure the thickness of the shale matrix h ₁ =2.095cm and the thickness of the clip h ₂ =0.405cm, and the ratio of clip to shale matrix is 0.405 : 2.095 (normalized to 0.162: 0.838) for the abstract model of interlayered shale, as shown in Figure 4.

S31-S33: Obtain shale matrix mineral components by X-ray diffraction whole-rock mineral analysis method: kerogen, calcite, quartz, plagioclase, gypsum, dolomite, pyrite and clay minerals; shale in this example The matrix model takes kerogen slits and calcite slits as examples. The kerogen slits are shown in Fig. 5(a), and the calcite slits are shown in Fig. 5(b). The molecular dynamics model of shale oil adopts a multi-component model. In this example, in order to simplify the calculation, a mixture of methane, n-octane and bitumen is used, as shown in (c) in Figure 5, which respectively represent the Light components, intermediate components and heavy components.

模拟以1fs为时间步长，整个过程将持续30ns以达到流动速度剖面的平衡，最后20ns的模拟用于统计分析。流体流动的速度剖面采用微元法计算得到。S41: Molecular simulation adopts LAMMPS simulator, simulation conditions are T=353K, P=30MPa, the wall surface is fixed during the simulation process, and a force parallel to the wall surface (x direction) is applied to each alkane atom

The simulation takes 1 fs as time step, the whole process will last 30 ns to reach the equilibrium of the flow velocity profile, and the last 20 ns of the simulation is used for statistical analysis. The velocity profile of the fluid flow is calculated using the microelement method.

S42: Fit the velocity profile using the Poiseuille equation with negative slip. The fitting formula is:

where v is the flow velocity of the fluid at position z, m/s; n is the number density of alkane atoms in the slit, 1/m ³ ; F is the applied driving force, N; z is the position from the center of the pore, m ; w is the width of the slit, m; δ _i is the thickness of the boundary layer of the i-th mineral, m; η is the effective viscosity of the fluid, Pa·s. Finally, the boundary layer thickness of shale oil flow is obtained: kerogen pore δ ₁ =0.85nm, calcite pore δ ₂ =0.13nm, as shown in (a) and (b) in FIG. 6 , respectively. From Figure 6(a) and (b), it can be found that the shale oil has negative slip when flowing in the kerogen and calcite slits, so the Poiseuille equation with negative slip is used to fit the velocity profile.

S43: The permeability equation of the shale matrix is as follows:

where k ₁ is the permeability of the shale matrix; Φ ₁ is the porosity of the shale matrix; r ₁ is the average pore radius of the shale matrix; δ ₁ is the thickness of the boundary layer of kerogen; δ ₂ is the boundary of calcite layer thickness.

S5: According to the average pore radius r ₂ of the clip and the porosity of the clip Φ ₂ to determine the permeability of the clip, the specific formula is:

In the formula: k ₂ is the permeability of the clip; Φ ₂ is the porosity of the clip; r ₂ is the average pore radius of the clip.

S6: Based on the permeability of the shale matrix and the interlayer, according to the proportion of the interlayer and the proportion of the shale matrix, the permeability in the horizontal direction and the vertical direction of the interlayered shale are constructed.

As shown in (a) of Figure 7, the specific formula of the permeability in the horizontal direction of the interlayer shale is:

As shown in Fig. 7(b), the specific formula for the permeability of the interlayered shale in the vertical direction is:

where k′ is the horizontal permeability of interlayered shale, _k ″ is the vertical permeability of interlayered shale, _h1 is the proportion of shale matrix, and h2 is the proportion of interlayers.

The various embodiments in this specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments, and the same and similar parts between the various embodiments can be referred to each other. For the system disclosed in the embodiment, since it corresponds to the method disclosed in the embodiment, the description is relatively simple, and the relevant part can be referred to the description of the method.

In this paper, specific examples are used to illustrate the principles and implementations of the present invention. The descriptions of the above embodiments are only used to help understand the methods and core ideas of the present invention; meanwhile, for those skilled in the art, according to the present invention There will be changes in the specific implementation and application scope. In conclusion, the contents of this specification should not be construed as limiting the present invention.

Claims (9)

1. A method for determining anisotropic permeability of laminated shale, the method comprising:

s1: obtaining an interlayer shale core;

s2: determining shale matrix parameters and holding strip parameters based on the shale core; the shale matrix parameters comprise the proportion h of the shale matrix ₁ Page, pageAverage pore radius r of rock matrix ₁ And shale matrix porosity Φ ₁ (ii) a The holding strip parameters comprise the proportion h of the holding strip ₂ Average void radius r of holding strip ₂ And the porosity of the holding strip phi ₂ ；

S3: based on the average pore radius r of the shale matrix ₁ Constructing a molecular dynamics model;

s4: simulating the flow of shale oil in the nanopores of the shale matrix by using the molecular dynamics model, and determining the permeability of the shale matrix;

s5: based on mean pore radius r of the clamping strip ₂ And the porosity of the holding strip phi ₂ Determining the permeability of the holding strip;

s6: based on the permeability of the shale matrix, the permeability of the holding strip and the proportion h of the shale matrix ₁ And the ratio h of the clamping strip ₂ Determining the horizontal permeability and the vertical permeability of the sandwich-shaped shale, wherein the specific formula is as follows:

wherein k 'is the horizontal permeability of the laminated shale, k' is the vertical permeability of the laminated shale, h ₁ Is the proportion of shale matrix, h ₂ Is the ratio of holding strips, k ₁ Permeability, k, of shale matrix ₂ Permeability of the gib.

2. The method for determining the anisotropic permeability of the laminated shale according to claim 1, wherein the determining of the shale matrix parameters and the holding strip parameters based on the shale core specifically comprises:

s21: determination of average pore radius r of shale matrix by nitrogen adsorption experiment ₁ And shale matrix porosity Φ ₁ ；

S22: average void radius r of holding strip is determined by high-pressure mercury injection experiment ₂ And holding strip porosity Φ ₂ ；

S23: photographing the cross section of the shale core to obtain a rock sample image vertical to the bedding direction;

s24: analyzing the rock sample image by adopting image analysis software to obtain the proportion h of the shale matrix ₁ And the ratio h of the clamping strip ₂ 。

3. The method for determining the anisotropic permeability of laminated shale according to claim 1, wherein the shale matrix based average pore radius r ₁ Constructing a molecular dynamics model, which specifically comprises the following steps:

s31: obtaining shale matrix mineral components by a mineral X-ray whole rock analysis method;

s32: obtaining on-site shale oil components through a hydrocarbon component analysis experiment;

s33: according to shale matrix mineral composition, the in-situ shale oil composition and shale matrix average pore radius r ₁ And (5) constructing a molecular dynamics model.

4. The method for determining the anisotropic permeability of the laminated shale according to claim 1, wherein the simulating the flow of shale oil in the nanopores of the shale matrix by using the molecular dynamics model to determine the permeability of the shale matrix specifically comprises:

s41: simulating the flow of shale oil in the nanopores of the shale matrix by using the molecular dynamics model to obtain a velocity profile;

s42: fitting a speed profile to obtain boundary conditions of shale oil flow; the boundary condition comprises positive slip, no slip or negative slip;

s43: based on the boundary condition, the average pore radius r of the shale matrix ₁ And shale matrix porosity Φ ₁ And determining the permeability of the shale matrix.

5. The method for determining anisotropic permeability of laminated shale according to claim 1, wherein the average void radius r is based on a strip-holding average ₂ And the porosity of the holding strip phi ₂ Determining the permeability of the holding strip, wherein the specific formula is as follows:

wherein k is ₂ Permeability of the gib.

6. A system for determining anisotropic permeability of interbed shale, the system comprising:

the acquisition module is used for acquiring the sandwich-shaped shale core;

a parameter determination module for determining shale matrix parameters and holding strip parameters based on the shale core; the shale matrix parameters comprise the proportion h of the shale matrix ₁ Average pore radius r of shale matrix ₁ And shale matrix porosity Φ ₁ (ii) a The holding strip parameters comprise the proportion h of the holding strip ₂ Average void radius r of holding strip ₂ And the porosity of the holding strip phi ₂ ；

A molecular dynamics model construction module for constructing a model based on the average pore radius r of the shale matrix ₁ Constructing a molecular dynamics model;

the shale matrix permeability determining module is used for simulating the flow of shale oil in the nanopores of the shale matrix by using the molecular dynamics model and determining the permeability of the shale matrix;

a batten permeability determination module for determining average pore radius r based on battens ₂ And the porosity of the holding strip phi ₂ Determining the permeability of the holding strip;

an anisotropic permeability determination module for determining permeability of shale matrix, permeability of the holding strip, and a proportion h of the shale matrix ₁ And the ratio h of the clamping strip ₂ Determining the horizontal permeability and the vertical permeability of the sandwich-shaped shale, wherein the specific formula is as follows:

wherein k 'is the horizontal permeability of the laminated shale, k' is the vertical permeability of the laminated shale, h ₁ Is the proportion of shale matrix, h ₂ Is the ratio of holding strip, k ₁ Permeability, k, of shale matrix ₂ Permeability of the gib.

7. The system for determining anisotropic permeability of laminated shale according to claim 6, wherein the parameter determination module specifically comprises:

a shale matrix parameter determination unit for determining the average pore radius r of the shale matrix through a nitrogen adsorption experiment ₁ And shale matrix porosity Φ ₁ ；

A clamping strip parameter determination unit for determining average pore radius r of the clamping strip through a high-pressure mercury intrusion experiment ₂ And the porosity of the holding strip phi ₂ ；

The rock sample image acquisition unit is used for photographing the cross section of the shale core to obtain a rock sample image vertical to the bedding direction;

the image analysis unit is used for analyzing the rock sample image by adopting image analysis software to obtain the proportion h of the shale matrix ₁ And the ratio h of the clamping strip ₂ 。

8. The system for determining anisotropic permeability of laminated shale according to claim 6, wherein the molecular dynamics model building module specifically comprises:

the shale matrix mineral composition determining unit is used for obtaining shale matrix mineral compositions through a mineral X-ray whole rock analysis method;

the shale oil component acquisition unit is used for acquiring on-site shale oil components through a hydrocarbon component analysis experiment;

a molecular dynamics model construction unit for constructing a model based on the mineral composition of the shale matrix, the in-situ shale oil composition and the average pore radius r of the shale matrix ₁ And (5) constructing a molecular dynamics model.

9. The system for determining anisotropic permeability of laminated shale according to claim 6, wherein the shale matrix permeability determination module specifically comprises:

the simulation unit is used for simulating the flow of shale oil in the shale matrix nanopores by using the molecular dynamics model to obtain a velocity profile;

the boundary condition determining unit is used for fitting the velocity profile to obtain a boundary condition of shale oil flow; the boundary condition comprises positive slip, no slip or negative slip;

a shale matrix permeability determination unit for determining a shale matrix average pore radius r based on the boundary condition ₁ And shale matrix porosity Φ ₁ And determining the permeability of the shale matrix.

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