CN113188976B - Method and system for determining anisotropic permeability of sandwich-shaped shale - Google Patents
Method and system for determining anisotropic permeability of sandwich-shaped shale Download PDFInfo
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Abstract
The invention provides a method and a system for determining anisotropic permeability of sandwich-shaped shale, which are characterized by firstly determining shale matrix parameters and holding strip parameters based on a shale core; secondly, constructing a molecular dynamics model based on the average pore radius of the shale matrix; simulating the flow of shale oil in the nanopores of the shale matrix by using a molecular dynamics model, and determining the permeability of the shale matrix; then determining the permeability of the holding strip based on the average pore radius of the holding strip and the porosity of the holding strip; and finally, determining the horizontal permeability and the vertical permeability based on the permeability of the shale matrix, the permeability of the holding strips, the proportion of the shale matrix and the proportion of the holding strips. According to the invention, based on the combination of the pore structure of the shale core and the molecular dynamics model, the flow of shale oil in the shale matrix nanopores is simulated by using the molecular dynamics model, so that the permeability of the laminated shale in the horizontal direction and the vertical direction can be accurately calculated, and the problem that the prior art cannot realize accurate measurement of the anisotropic permeability of the laminated shale is solved.
Description
Technical Field
The invention relates to the technical field of oil and gas field development, in particular to a method and a system for determining anisotropic permeability of sandwich-shaped shale.
Background
Shale oil is an important unconventional energy source, and crude oil exists in shale pores mainly in an adsorbed state and a free state. Reservoir types of shale oil include three types, matrix type, fracture type, and sandwich type. Because the laminated shale contains carbonate or sandstone strips (also called as holding strips) with higher porosity and permeability, the yield is higher in the actual production process, and the method is the key point of shale oil development. However, under the influence of bedding, the laminated shale has a distinct anisotropic characteristic that parallel bedding and vertical bedding rock permeabilities (i.e., horizontal permeability and vertical permeability) are different. The method for accurately measuring the anisotropic permeability of the shale has important significance on shale reservoir evaluation, hydraulic fracturing design and production dynamic prediction.
The prior measurement of the anisotropic permeability of the laminated shale has the following problems:
on the one hand, a complete core string is difficult to obtain because the shale is brittle, the presence of microcracks or bedding can make the laminated shale prone to fracture along the fracture faces. Meanwhile, before permeability measurement, oil washing needs to be carried out on the rock core, and the process is very easy to cause damage to the rock core. The permeability of rock is measured by using a whole core, and the permeability of the laminated shale is difficult to measure due to the incomplete core.
On the other hand, the permeability of shale in the directions parallel to the bedding and perpendicular to the bedding direction is different greatly, and the result may be different by several orders of magnitude, so that the conventional permeability testing method brings great error.
Patent CN206431021U relates to a shale permeability simulation test device, which can measure the effective permeability of gas under different pressure conditions, but this device can only test the permeability in the parallel bedding direction, but cannot test the permeability in the perpendicular bedding direction. Patent CN106769790A relates to a shale permeability testing device and method based on liquid pressure pulse under the action of ultrasonic waves, and mainly aims to measure the permeability by observing the difference of pulse attenuation curves of standard brine passing through a rock core to be tested. However, shale is easily swellable in water, resulting in permeability changes and failure to obtain accurate permeability values. Patent CN109100278A relates to an apparent permeability calculation method considering shale pore size distribution characteristics, and the apparent permeability of shale reservoir scale is obtained by calculating the distribution frequency superposition of capillaries with different pipe diameters. However, the method only considers the migration mechanism of shale gas, is not suitable for measuring the rock permeability of a shale oil reservoir, and cannot reflect the anisotropic characteristic of the laminated shale.
Disclosure of Invention
The invention aims to provide a method and a system for determining the anisotropic permeability of laminated shale, which solve the problem that the anisotropic permeability of laminated shale cannot be accurately measured.
In order to achieve the above object, the present invention provides a method for determining anisotropic permeability of laminated shale, wherein the method comprises:
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 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 ；
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 holding strip porosity Φ 2 Determining the permeability of the holding strip;
s6: permeability based on shale matrix, permeability of the holding stripShale matrix proportion h 1 And the ratio h of the clamping strip 2 And determining the horizontal permeability and the vertical permeability of the laminated shale.
Optionally, the determining shale matrix parameters and holding strip parameters based on the shale core specifically includes:
s21: determination of average pore radius r of shale matrix by nitrogen adsorption experiment 1 And shale matrix porosity Φ 1 ；
S22: determining average pore radius r of holding strip by high-pressure mercury-pressing experiment 2 And the porosity of the holding strip phi 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 。
Optionally, 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.
Optionally, 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 includes:
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 matrixPorosity phi 1 And determining the permeability of the shale matrix.
Optionally, the average pore radius r based on the holding strip 2 And holding strip porosity Φ 2 Determining the permeability of the holding strip, wherein the specific formula is as follows:
wherein k is 2 Permeability of the gib.
Optionally, the permeability based on shale matrix, permeability of the holding strip, and proportion h of 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.
The invention also provides a system for determining anisotropic permeability of laminated shale, 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 And determining the horizontal permeability and the vertical permeability of the laminated shale.
Optionally, the parameter determining module specifically includes:
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 。
Optionally, the molecular dynamics model building module specifically includes:
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;
molecular kinetic modelA model building unit for building a model from a shale matrix mineral constituent, the in-situ shale oil constituent and a shale matrix average pore radius r 1 And (5) constructing a molecular dynamics model.
Optionally, the shale matrix permeability determining module specifically includes:
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.
According to the specific embodiment provided by the invention, the invention discloses the following technical effects:
according to the invention, based on the combination of the pore structure of the shale core and the molecular dynamics model, the flow of shale oil in the shale matrix nanopores is simulated by using the molecular dynamics model, so that the permeability of the laminated shale in the horizontal direction and the vertical direction can be accurately calculated, and the problem that the prior art cannot realize accurate measurement of the anisotropic permeability of the laminated shale is solved. In addition, the technology breaks through the defects that the conventional permeability experiment test needs a standard core column, but the shale is fragile, and the core column is difficult to obtain. The invention only needs to clearly distinguish the shale matrix and the core fragments or fragments of the holding strip, so the practicability is stronger.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings needed to be used in the embodiments will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings without inventive exercise.
FIG. 1 is a flow chart of a method for determining anisotropic permeability of laminated shale according to an embodiment of the present invention;
FIG. 2 is a structural diagram of a system for determining anisotropic permeability of a second interbedded shale according to an embodiment of the present invention;
FIG. 3 is a pore size distribution diagram of a three-sandwich shale nitrogen adsorption and high-pressure mercury intrusion experiment according to an embodiment of the invention;
FIG. 4 is a schematic diagram of the three-sandwich shale abstract model construction according to the embodiment of the invention;
FIG. 5 is a schematic view of a molecular simulation model of a three-shale kerogen slit, a calcite slit, and shale oil according to an embodiment of the present invention;
FIG. 6 is a schematic representation of the velocity of flow of shale oil through the pores of a shale matrix and boundary conditions according to an embodiment of the present invention;
FIG. 7 is a schematic illustration of horizontal and vertical permeability of tri-interbedded shale in accordance with an embodiment of the present invention.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be obtained by a person skilled in the art without making any creative effort based on the embodiments in the present invention, belong to the protection scope of the present invention.
The invention aims to provide a method and a system for determining the anisotropic permeability of laminated shale, which solve the problem that the anisotropic permeability of laminated shale cannot be accurately measured.
In order to make the aforementioned objects, features and advantages of the present invention comprehensible, embodiments accompanied with figures are described in further detail below.
Example one
As shown in fig. 1, the present invention provides a method for determining anisotropic permeability of laminated shale, comprising:
s1: and obtaining the sandwich-shaped 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 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 of holding strip r 2 And the porosity of the holding strip phi 2 . The shale core comprises a pore structure of a shale matrix and a pore structure of a holding strip. The proportion of the thickness is the proportion of the thickness.
S3: based on the average pore radius r of the shale matrix 1 And (5) constructing a molecular dynamics model.
S4: and 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 The permeability of the gib is determined.
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 And determining the horizontal permeability and the vertical permeability of the laminated shale.
The individual steps are discussed in detail below:
s1: and obtaining the sandwich-shaped shale core. The selected sandwich shale core is not necessarily a core column, but also can be a core block as long as shale matrix and holding strips can be clearly distinguished.
A standard cylindrical core is typically required for proper permeability measurements. For laminated shales, it is very difficult to obtain a core string because it is brittle. Therefore, the method does not need a complete core column, and only needs to be capable of determining the proportion of the shale matrix and the holding strip through the shale core.
S2: determining shale matrix parameters and holding strip parameters based on the shale core, which specifically comprises the following steps:
s21: determination of average pore radius r of shale matrix by nitrogen adsorption experiment 1 And shale matrix porosity Φ 1 。
S22: passing heightAverage pore radius r of holding strip determined by mercury intrusion test 2 And the porosity of the holding strip phi 2 。
S23: and taking a picture of 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 。
S3: based on the average pore radius r of the shale matrix 1 Constructing a molecular dynamics model, which specifically comprises the following steps:
s31: obtaining the shale matrix mineral components by a mineral X-ray whole rock analysis method.
S32: the on-site shale oil composition is obtained through a hydrocarbon composition analysis experiment.
S33: according to the shale matrix mineral composition, the on-site shale oil composition and the shale matrix average pore radius r 1 And (5) constructing a molecular dynamics model.
S4: the molecular dynamics model is utilized to simulate the flow of shale oil in the nanopores of the shale matrix, and the permeability of the shale matrix is determined, and the method specifically comprises the following steps:
s41: and (3) 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 the velocity profile to obtain boundary conditions of shale oil flow; the boundary conditions include 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 Determining the permeability of the shale matrix, which specifically comprises the following steps:
assuming that there are n kinds of minerals in the shale matrix, the boundary condition of shale oil flowing in the pores of the m kinds of minerals is positive slip or no slip according to
Calculating a first permeability; wherein Ls is i Is slip length, k 'in the pore space of the ith mineral' 1 Is the first permeability, m<n。
When the boundary of the shale oil flowing in the n-m mineral pores is in negative slip, the method is based on
Calculating a second permeability; wherein, k ″) 1 Is the second permeability, δ i Is the thickness of the boundary layer in the pores of the ith mineral.
According to k 1 ＝k′ 1 +k″ 1 And calculating 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, wherein the specific formula is as follows:
wherein k is 2 Permeability of the holding strip,. phi 2 Is the porosity of the holding strip, r 2 Is the average void radius of the gib.
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.
Example two
As shown in fig. 2, the present invention also discloses a system for determining anisotropic permeability of laminated shale, the system comprising:
the obtaining module 201 is configured to obtain a sandwich-shaped shale core.
A parameter determination module 202 configured to determine 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 of holding strip r 2 And holding strip porosity Φ 2 。
A molecular dynamics model construction module 203 for constructing a model based on the average pore radius r of the shale matrix 1 And (5) constructing a molecular dynamics model.
The shale matrix permeability determination module 204 is configured to simulate the flow of shale oil in the nanopores of the shale matrix by using the molecular dynamics model, and determine the permeability of the shale matrix.
A sliver permeability determination module 205 for determining a permeability based on the average void radius r of the sliver 2 And the porosity of the holding strip phi 2 The permeability of the gib is determined.
An anisotropic permeability determination module 206 for determining a permeability of the shale matrix based on the permeability of the shale matrix, the permeability of the battens, and a proportion h of the shale matrix 1 And the ratio h of the clamping strip 2 And determining the horizontal permeability and the vertical permeability of the laminated shale.
As an optional implementation manner, the parameter determining module 202 of the present invention specifically includes:
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 。
And 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 。
As an optional embodiment, the molecular dynamics model building module 203 of the present invention specifically includes:
the shale matrix mineral composition determining unit is used for obtaining the shale matrix mineral composition through a mineral X-ray whole rock analysis method.
The shale oil composition acquisition unit is used for acquiring the on-site shale oil composition through a hydrocarbon composition 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.
As an optional implementation manner, the shale matrix permeability determining module 204 specifically includes:
and the simulation unit is used for simulating the flow of the shale oil in the nanopores of the shale matrix 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 conditions include 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.
EXAMPLE III
Specific examples are:
s1: firstly, selecting an on-site laminated shale core.
S21: measuring the pore structure of the shale matrix through a nitrogen adsorption experiment to obtain the average pore radius r of the shale matrix 1 Is 6.42 multiplied by 10 -3 μ m, shale matrix porosity Φ 1 3.69%; the pore structure of the shale matrix is shown in fig. 3 (a).
S22: by pressing mercury under high pressureThe pore structure of the holding strip is measured in an experiment to obtain the average pore radius r of the holding strip 2 5.57 μm and a clip porosity of phi 2 5.63 percent; the pore structure of the clip strip is shown in fig. 3 (b).
S23: and taking a picture of the cross section of the sandwich shale core in the direction vertical to the bedding direction of the shale to obtain a rock sample image in the direction vertical to the bedding direction.
S24: importing the rock sample picture into ImageJ, and respectively measuring the thickness h of the shale matrix by utilizing an Analyze module in the ImageJ 1 2.095cm and thickness h of the clamping strip 2 A sandwich shale abstract model with a 0.405:2.095 (normalized to 0.162:0.838) ratio of the battens to shale matrix was obtained as shown in fig. 4.
S31-S33: obtaining shale matrix mineral components by an X-ray diffraction whole rock mineral analysis method: kerogen, calcite, quartz, plagioclase, gypsum, dolomite, pyrite, and clay minerals; the shale matrix model in the present embodiment is exemplified by a kerogen slit as shown in fig. 5 (a) and a calcite slit as shown in fig. 5 (b). The molecular dynamics model of shale oil uses a multi-component model, and this example uses a mixture of methane, n-octane, and bitumen for the sake of simplifying the calculation, as shown in fig. 5 (c), which represents the light component, the intermediate component, and the heavy component, respectively, in shale oil.
S41: the molecular simulation adopts a LAMMPS simulator, the simulation conditions are T353K and P30 MPa, the wall surface is fixed in the simulation process, and an acting force parallel to the wall surface (in the x direction) is applied to each alkane atom
The simulation was done in 1fs time steps and the entire process would last 30ns to reach the equilibrium of the flow velocity profile, and the last 20ns simulation was used for statistical analysis. The velocity profile of the fluid flow is calculated by a infinitesimal method.
S42: and fitting the velocity profile by adopting a Poiseup equation containing negative slip. The fitting formula is:
wherein v is the flow velocity of the fluid at position z, m/s; n is the density of the number of atoms of alkane in the slit, 1/m 3 (ii) a F is the applied driving force, N; z is the position from the center of the aperture, m; w is the width of the slit, m; delta i Is the boundary layer thickness of the ith mineral, m; η is the effective viscosity of the fluid, Pa · s. Finally obtaining the thickness of the boundary layer of shale oil flow: kerogen pore delta 1 0.85nm, calcite pore delta 2 0.13nm, as shown in fig. 6(a) and (b), respectively. From fig. 6(a) and (b), it can be found that shale oil flows in both kerogen and calcite slits with negative slip, and therefore the velocity profile is fitted using the poisson equation containing negative slip.
S43: the permeability equation for shale matrices is as follows:
in the formula: k is a radical of 1 Permeability of the shale matrix; phi 1 Porosity of the shale matrix; r is a radical of hydrogen 1 Is the average pore radius of the shale matrix; delta 1 Is the boundary layer thickness of kerogen; delta 2 Is the boundary layer thickness of calcite.
S5: according to mean pore radius r of the holding strip 2 And the porosity of the holding strip phi 2 Determining the permeability of the holding strip, wherein the specific formula is as follows:
in the formula: k is a radical of 2 Permeability of the clip; phi 2 Porosity of the holding strip; r is 2 Is the average pore radius of the gib.
S6: and (3) integrating the permeability of the shale matrix and the holding strips, and constructing the permeability of the holding-strip-shaped shale in the horizontal direction and the permeability of the holding-strip-shaped shale in the vertical direction according to the proportion of the holding strips and the proportion of the shale matrix.
As shown in fig. 7 (a), the specific formula of the permeability of the laminated shale in the horizontal direction is as follows:
as shown in fig. 7 (b), the specific formula of the permeability of the sandwiched shale in the vertical direction is:
in the formula: 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 proportion of the holding strip.
The embodiments in the present description are described in a progressive manner, each embodiment focuses on differences from other embodiments, and the same and similar parts among the embodiments are referred to each other. For the system disclosed by the embodiment, the description is relatively simple because the system corresponds to the method disclosed by the embodiment, and the relevant points can be referred to the method part for description.
The principle and the embodiment of the present invention are explained by applying specific examples, and the above description of the embodiments is only used to help understanding the method and the core idea of the present invention; meanwhile, for a person skilled in the art, according to the idea of the present invention, the specific embodiments and the application range may be changed. In view of the foregoing, the description is not to be taken in a limiting sense.
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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