CN115704759A - Lamina-shaped shale stress sensitive mathematical characterization method - Google Patents
Lamina-shaped shale stress sensitive mathematical characterization method Download PDFInfo
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Abstract
The invention provides a striated laminar shale stress sensitive mathematical characterization method, which comprises the following steps: step 1, carrying out permeability test on a striated laminar shale core sample to obtain a shale gas permeability value; step 2, testing the grained lamellar shale core sample to obtain a porosity value; step 3, carrying out a overburden pore infiltration experiment to obtain the pore compression coefficient of the grained lamellar shale; step 4, performing a high-pressure mercury pressing experiment to obtain the maximum pore radius and the average pore radius of the shale and the pore volume corresponding to the bedding joint; and 5, establishing a pressure-sensitive mathematical model of the striated laminar shale to obtain a relation curve of the permeability of the striated laminar shale and the net overlying pressure. The striation-layered shale stress sensitive mathematical characterization method accurately describes the change and the rule of the shale permeability along with the net overlying pressure, has stronger reliability and accuracy, and provides effective technical support for shale oil elasticity development capacity prediction and development scheme formulation.
Description
Technical Field
The invention relates to the technical field of shale oil exploration and development, in particular to a striation laminar shale stress sensitive mathematical characterization method.
Background
The land shale oil reservoir with the depressed economic yang mainly comprises a striated laminar shale interval and a thin interbed interval, wherein due to the existence of the striated layer, the reservoir space spans millimeter, micrometer and nanometer scales, and the permeability is relatively high. Due to the existence of the striation layer, the permeability of the striation layer shale is very sensitive to the change along with the net overlying pressure, meanwhile, the shale development mainly adopts an elastic mining mode as a main mode, and the establishment of the permeability pressure-sensitive characterization method of the striation layer shale plays an important role in the characterization of the permeability of shale oil and the capacity calculation.
Chinese patent application CN201310100202.9 discloses a shale gas permeability tester, which comprises a gas cylinder, a pressure regulating valve, a pneumatic valve I, a pressure sensor I, a pneumatic valve II, a pressure sensor II and an emptying valve which are sequentially connected through a sealing pipeline, and further comprises a manual valve, a model cup, a temperature sensor, a sample cup and a constant temperature device; the method comprises the steps of drilling a rock core into particles with a certain shape, placing the particles in a constant-temperature closed container, adding a certain pressure, recording the change of the pressure along with time in real time, and calculating the permeability of a shale matrix. The test of the shale permeability is not influenced by the crack permeability any more, and the matrix permeability of the shale can be accurately measured. The invention patent can test the permeability of the shale matrix, but cannot characterize the stress sensitivity of the shale permeability.
Chinese patent application CN201510400596.9 discloses a shale reservoir fracturing fracture stress sensitivity testing device and a method using the same, and belongs to the field of shale gas. This shale reservoir fracturing fracture stress sensitivity testing arrangement includes: a shale sample holder for holding a shale sample; the gas kettle and the confining pressure pump are respectively connected with a gas inlet of the shale sample holder; the pressure sensor is arranged between the air inlet of the shale sample holder and the air kettle; the displacement pump is connected with the gas kettle; the gas flowmeter is arranged at the gas outlet of the shale sample holder, the shale reservoir fracturing fracture stress sensitivity testing device and the method for evaluating the stress sensitivity of the shale reservoir fracturing fracture by using the shale reservoir fracturing fracture stress sensitivity testing device solve the problem that the stress sensitivity evaluation of the shale artificial fracture is difficult, and the stress sensitivity evaluation of the artificial fracture formed by fracturing the shale in the actual mining process can be deeply evaluated aiming at the stress sensitivity evaluation of the shale stress sensitivity. The stress sensitivity of the shale reservoir fracturing fracture is tested, but the stress sensitivity of the shale reservoir core cannot be characterized.
Chinese patent application 201810763909.0 discloses a shale apparent permeability calculation method considering stress sensitivity effect, which divides a flow channel of shale gas into an inorganic capillary and an organic capillary, and respectively establishes inorganic pore and organic pore calculation models; considering the difference of flowing mechanisms of shale gas in inorganic substance and organic substance capillary tubes, respectively establishing an apparent permeability calculation model of inorganic substance and organic substance by introducing a fractal theory; and further adopting an area weighting method, and combining the influences of water saturation and stress sensitivity effect on the apparent permeability in the shale exploitation process, establishing an apparent permeability calculation method considering various influence factors. According to the invention, a shale organic pore and inorganic pore permeability calculation model is established, and the heterogeneity of a shale reservoir is not considered.
At present, for the characterization of the streak-layered shale stress sensitivity, the permeability of the streak-layered shale is analyzed to change along with the net overlying pressure, and the shale stress sensitivity characteristic is obtained mainly by analyzing the relationship between the permeability of the shale and the net overlying pressure through a flow experiment. However, for the lamella shale, the lamella shale core is easy to crack from a natural deposition surface in the experimental process, and the practical experimental completion degree of the lamella shale core is poor. The prior art is greatly different from the prior art, the technical problem which is to be solved by the inventor is not solved, and therefore a novel striation laminar shale stress sensitive mathematical characterization method is invented.
Disclosure of Invention
The invention aims to provide a stress-sensitive mathematical characterization method for the striated laminar shale, which accurately describes the change rule of the permeability of the striated laminar shale along with the net overlying pressure and overcomes the defects of the prior art.
The object of the invention can be achieved by the following technical measures: the method for mathematically characterizing the stress sensitivity of the striated laminar shale comprises the following steps:
and 5, establishing a pressure-sensitive mathematical model of the striated laminar shale to obtain a relation curve of the striated laminar shale permeability and the net overlying pressure.
The object of the invention can also be achieved by the following technical measures:
in the step 1, a striated shale columnar rock sample of a certain research block is selected, the length L and the diameter D of the rock sample are obtained by a measurement method, and a striated shale permeability value K is obtained through a steady-state method gas permeability test 0 。
In step 2, the volume V of rock sample particles is obtained by the helium porosimetry g And subtracting the particle volume from the rock sample volume to obtain a rock sample pore volume V p And obtaining the porosity of the lamellar shale.
In step 2, the formula for calculating the porosity of the striated laminar shale is as follows:
in the formula:
is the pore volume of the shale rock sample in cm 3 ；
Porosity of grained lamellar shale,%; d is the diameter, cm, and L is the length, cm.
In step 3, performing overburden pore permeability experiments on the grained lamellar shale core sample by using a CMS300 overburden pore permeability tester, setting a overburden pressure value not more than 40MPa, setting different overburden pressure values and obtaining a permeability value and a porosity value under the overburden pressure value so as to ensure that the shale sample does not crack in the experimental process of the grained lamellar shale core sample, obtaining a relation curve of net overburden pressure and shale permeability and a relation curve of net overburden pressure and shale porosity, and performing exponential fitting on the relation curve of net overburden pressure and shale porosity to obtain a grained lamellar shale porosity compression coefficient.
In the step 4, a high-pressure mercury injection experiment is carried out on the striated laminar shale core sample, the mass m of the rock sample is weighed by using a balance, and the high-pressure mercury injection experiment is carried out to obtain the maximum pore radius R max Average pore radius
Volume of bedding joint pores V 1c 。
In step 5, a shale compression model is established according to the deposition characteristics of the striated laminar shale, the bedding joints in the striated laminar shale are approximately simulated by a flat plate, the shale matrix part is simulated by a capillary tube model, and then the permeability of the bedding joints, the permeability of the shale matrix and the compression coefficient of the bedding joints are as follows:
in the formula, k f The bedding gap permeability value, mD;
the porosity value corresponding to the bedding joint,%; v 1c The pore volume is cm 3 ；V p Is the volume of the pores of the rock sample in cm 3 (ii) a Omega is the width of the bedding seam, mu m; k is a radical of m Is the matrix permeability value, mD, in the shale sample;
the porosity value,%, corresponding to the core matrix; r is the radius of the matrix of the rock core, and is mum; c f The bedding joint compression coefficient is 1/MPa; sigma is effective stress, MPa; c m The compression coefficient of the core matrix is 1/MPa.
In step 5, simultaneous formula 2-5 obtains the characteristic parameter alpha when the bedding joint compression is taken as the main characteristic in the initial stage of elastic development,
in the formula, alpha is a characteristic parameter for representing the compression characteristic of the lamellar shale, and the larger the value of alpha is, the more obvious the compression effect is, and the stronger the stress sensitivity is; wherein lambda is the ratio of the width of the bedding seam to the radius of the pores of the matrix,
phi is core porosity,%; phi p Matrix porosity,%; phi (phi) of f Bedding joint porosity,%; r is the pore radius of the matrix, mu m; rmax is the width of the bedding seam, μm.
In step 5, a striation laminar shale stress sensitivity mathematical model is established, according to the overburden permeability curve, the permeability-net overburden pressure curve is subjected to exponential fitting, and the obtained striation laminar shale stress sensitivity mathematical characterization formula is as follows:
the formula (7) is a stress sensitive mathematical model aiming at the striated laminar shale established by the method; in the formula, k 0 Core initial permeability, mD; alpha is a characteristic parameter for representing the compression characteristic of the lamellar shale; c Φ The core pore compression coefficient is 1/MPa; sigma is effective stress, MPa; lambda is the ratio of the width of the bedding seam to the radius of the matrix pores; phi is core porosity,%; phi (phi) of p Substrate porosity,%; phi f Porosity of the bedding joint,%.
And step 5, verifying the established stress sensitive mathematical model to ensure the accuracy of the mathematical model.
The invention relates to a stress-sensitive mathematical characterization method of striated laminar shale, which aims at a striated laminar shale sample, establishes a mathematical model of the permeability of the striated laminar shale changing along with net overlying pressure through a pore permeability testing technology and a mercury intrusion experiment technology, analyzes the change condition of the permeability of irregular striated laminar shale along with pressure, and verifies the established pressure-sensitive mathematical model through a CMS300 pore infiltration experiment technology. When the method calculates that the permeability of the shale changes along with the net overlying pressure, the method considers the distribution size of the striated layer pores and the pores of the shale matrix based on a high-pressure mercury intrusion experiment technology, establishes a pressure-sensitive mathematical model of the striated layer shale by combining the deposition characteristics of the striated layer shale, accurately describes the change rule of the permeability of the striated layer shale along with the net overlying pressure, and overcomes the defects of the prior art. Compared with the prior art, the invention has the following advantages:
because the method fully considers the pore volume corresponding to the bedding seams of the grained laminated shale and the matrix when calculating the stress sensitivity of the grained laminated shale, combines the overburden pore permeability data and the mercury intrusion data, accurately describes the change and the rule of the shale permeability along with the net overburden pressure, and has stronger reliability and accuracy, the method provides effective technical support for the prediction of shale oil elasticity development capacity and the formulation of a development scheme.
Drawings
FIG. 1 is a flow chart of an embodiment of a striated laminar shale stress-sensitive mathematical characterization method of the present invention;
FIG. 2 is a graph illustrating the change in permeability of shale overburden in accordance with an embodiment of the present invention;
FIG. 3 is a graph illustrating the porosity change of shale overburden in accordance with one embodiment of the present invention;
fig. 4 is a comparison graph of the calculated value and the measured value of the shale mathematical model in an embodiment of the invention.
Detailed Description
It is to be understood that the following detailed description is exemplary and is intended to provide further explanation of the invention as claimed. Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs.
It is noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of exemplary embodiments according to the invention. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, and it should be understood that when the terms "comprises" and/or "comprising" are used in this specification, they specify the presence of the stated features, steps, operations, and/or combinations thereof, unless the context clearly indicates otherwise.
The invention provides a mathematical characterization method for the stress sensitivity of striated laminar shale, which comprises the following steps: selecting a core sample of a striated and laminated shale column sample of a certain research block, and performing permeability test on the striated and laminated shale core by using a steady state method to obtain a shale gas permeability value; then testing the block-grained layer shale sample by a helium hole method to obtain a porosity value; then carrying out a overburden pore permeability experiment on the shale sample by using CMS300 to obtain a permeability and pressure change curve and a porosity and pressure change curve; then, carrying out a high-pressure mercury pressing experiment on the shale sample to obtain the maximum pore radius and the average pore radius of the shale and the pore volume corresponding to the bedding joint; according to the deposition characteristics of the striated laminar shale and the experimental data, a pressure-sensitive mathematical model of the striated laminar shale is established, a relation curve of the permeability of the striated laminar shale and the net overlying pressure is obtained, and verification is carried out according to the experimental data.
The following are several specific examples to which the invention may be applied.
Example 1:
in an embodiment 1 to which the present invention is applied, as shown in fig. 1, the method for stress-sensitive mathematical characterization of the stratiform shale includes the following steps:
101, selecting a banded shale columnar rock sample of a certain research block, obtaining the rock sample degree L =2.534cm and the diameter D =2.502cm by using a measurement method, and obtaining a banded shale permeability value K through a steady-state method gas-measuring permeability experiment 0 ＝0.67mD；
Step 201, obtaining the volume V of rock sample particles by using a helium hole method g ＝12.03cm 3 And subtracting the particle volume from the rock sample volume to obtain a rock sample pore volume V p ＝0.42cm 3 And obtaining the porosity phi =3.37% of the lamellar shale.
In the formula:
is the pore volume, cm, of the shale rock sample 3 ；
The porosity of the layered shale is decimal.
301, performing a overburden porosity experiment on the block streak-layer shale core sample by using a CMS300 overburden porosity tester, setting a overburden pressure value not more than 40MPa, setting different overburden pressure values and obtaining a permeability value and a porosity value under the overburden pressure value so as to ensure that the shale sample does not crack in the experimental process of the streak-layer shale core sample, and obtaining a relation curve (figure 2) of net overburden pressure and shale permeability and a relation curve (figure 3) of the net overburden pressure and the shale porosity;
302, performing exponential fitting on a relation curve of the net overlying pressure and the porosity of the shale to obtain a pore compression coefficient C of the striated laminar shale φ ＝0.006；
Step 401, performing a high-pressure mercury intrusion test on the striated and laminated shale core sample, weighing a rock sample mass m by using a balance, and adding m and V p Inputting the mercury pressure test system to perform a high-pressure mercury pressure experiment to obtain the maximum pore radius R max =0.517 μm, mean pore radius
Volume of bedding joint pores V 1c ＝0.0809cm 3 。
Step 501, establishing a shale compression model according to the deposition characteristics of the striated laminar shale, wherein the bedding joints in the striated laminar shale are approximately simulated by a flat plate, and the shale matrix part is simulated by a capillary tube model, so that the permeability of the bedding joints, the permeability of the shale matrix, the compression coefficient of the bedding joints and the compression coefficient of the shale matrix are as follows:
in the formula, k f The bedding gap permeability value, mD;
the value of the porosity of the bedding cracks is shown; omega is the width of the bedding seam; k is a radical of m Is the matrix permeability value, mD, in the shale sample;
the porosity value corresponding to the core matrix; r is the core matrix radius; c f The compression coefficient of the bedding joint is 1/MPa; sigma is effective stress, MPa; c m The compression coefficient of the core matrix is 1/MPa.
By combining the above formulas, the characteristic parameter alpha can be obtained when the bedding seam compression is taken as the main characteristic in the initial stage of elastic development,
in the formula, alpha is a characteristic parameter for representing the compression characteristic of the lamellar shale, and the larger the value of alpha is, the more obvious the compression effect is, and the stronger the stress sensitivity is; lambda is the ratio of the width of the bedding seam to the radius of the matrix pores,
wherein λ =4.575, # p ＝2.72％，φ f ＝0.65％，α＝30.00。
Step 601, establishing a striation laminar shale stress sensitivity mathematical model, and fitting a permeability-net overlying pressure curve by using an index according to an overlying pressure permeability curve to obtain a striation laminar shale stress sensitivity mathematical representation formula as follows:
the formula (7) is a stress sensitive mathematical model for the striated laminar shale established by the method.
Step 701, obtaining calculation data according to the established striated laminar shale stress sensitivity mathematical model, and verifying the calculation data and the overburden permeability data, wherein the result is shown in fig. 4, which illustrates the accuracy of the striated laminar shale stress sensitivity mathematical model established by the method.
The ground permeability of the striated and laminated shale sample of the embodiment of the invention is 0.67mD, and the established stress sensitive mathematical model is k =0.67e -0.18σ 。
Example 2:
in specific embodiment 2 to which the present invention is applied, the method for mathematically characterizing stress sensitivity of the striated laminar shale comprises the following steps:
step 101, selecting a striated shale columnar rock sample of a certain research block, obtaining the rock sample degree L =2.501cm and the diameter D =2.511cm by using a measurement method, and obtaining a striated shale permeability value K through a steady-state method gas permeability test 0 ＝0.012mD；
Step 201, obtaining the volume V of rock sample particles by using a helium hole method g ＝12.12cm 3 And subtracting the particle volume from the rock sample volume to obtain a rock sample pore volume V p ＝0.26cm 3 And obtaining the porosity phi =2.1% of the lamellar shale.
In the formula:
is the pore volume of the shale rock sample in cm 3 ；
The porosity of the layered shale is decimal.
301, carrying out overburden pore and permeability experiment on the block streak-shaped shale core sample by utilizing a CMS300 overburden pore and permeability tester, setting a overburden pressure value not more than 40MPa, setting different overburden pressure values and obtaining a permeability value and a porosity value under the overburden pressure value to ensure that the shale sample does not crack in the experimental process of the streak-shaped shale core sample, obtaining a relation curve of net overburden pressure and shale porosity, carrying out index fitting on the relation curve of the net overburden pressure and the shale porosity, and obtaining a pore compression coefficient C of the streak-shaped shale φ ＝0.005；
Step 401, performing a high-pressure mercury intrusion test on the striated and laminated shale core sample, weighing a rock sample mass m by using a balance, and adding m and V p Inputting the mercury pressure test system to perform a high-pressure mercury pressure experiment to obtain the maximum pore radius R max =0.432 μm, mean pore radius
Volume of bedding joint pores V 1c ＝0.0557cm 3 。
Step 501, establishing a shale compression model according to the deposition characteristics of the striated laminar shale, wherein the bedding joints in the striated laminar shale are approximately simulated by a flat plate, and the shale matrix part is simulated by a capillary tube model, so that the permeability of the bedding joints, the permeability of the shale matrix, the compression coefficient of the bedding joints and the compression coefficient of the shale matrix are as follows:
in the formula, k f The bedding gap permeability value, mD;
the value of the porosity of the bedding seams is obtained; omega is the width of the bedding seam; k is a radical of m Is the matrix permeability value, mD, in the shale sample;
the porosity value corresponding to the core matrix; r is the core matrix radius; c f The compression coefficient of the bedding joint is 1/MPa; sigma is effective stress, MPa; c m The compression coefficient of the core matrix is 1/MPa.
By combining the above formulas, the characteristic parameter alpha can be obtained when the bedding seam compression is taken as the main characteristic in the initial stage of elastic development,
in the formula, alpha is a characteristic parameter for representing the compression characteristic of the striated laminar shale, and the larger the value of alpha is, the more obvious the compression effect is, and the stronger the stress sensitivity is; lambda is the ratio of the width of the bedding seam to the radius of the matrix pores,
where λ =4.408, φ p ＝1.65％，φ f ＝0.45％，α＝27.5。
Step 601, establishing a striation laminar shale stress sensitivity mathematical model, and fitting a permeability-net overlying pressure curve by using an index according to an overlying pressure permeability curve to obtain a striation laminar shale stress sensitivity mathematical representation formula as follows:
the formula (7) is a stress sensitive mathematical model for the striated laminar shale established by the method.
Step 701, obtaining calculation data according to the established striated laminar shale stress sensitivity mathematical model, and verifying the calculation data and the overburden permeability data, wherein the result is shown in fig. 4, which illustrates the accuracy of the striated laminar shale stress sensitivity mathematical model established by the method.
The ground permeability of the striated and layered shale sample of the embodiment of the invention is 0.012mD, and the established stress sensitive mathematical model is k =0.012e -0.138σ 。
Example 3:
in specific embodiment 3 to which the present invention is applied, the method for mathematically characterizing stress sensitivity of the striated laminar shale comprises the following steps:
step 101, selecting a striated shale columnar rock sample of a certain research block, obtaining the rock sample degree L =2.545cm and the diameter D =2.532cm by using a measurement method, and obtaining a striated shale permeability value K through a steady-state method gas permeability test 0 ＝1.04mD；
Step 201, obtaining the volume V of rock sample particles by using a helium hole method g ＝12.14cm 3 Obtaining the rock sample pore volume V by subtracting the particle volume from the rock sample volume p ＝0.67cm 3 And obtaining the porosity phi =5.24% of the lamellar shale.
In the formula:
is the pore volume of the shale rock sample in cm 3 ；
The porosity of the layered shale is decimal.
301, carrying out overburden pore and permeability experiment on the block striation laminated shale core sample by utilizing a CMS300 overburden pore and permeability tester, setting overburden pressure value not more than 40MPa, setting different overburden pressure values and obtaining permeability value and porosity value under the overburden pressure value to ensure that the shale sample does not crack in the experimental process of the striation laminated shale core sample, and obtaining net overburden pressure and shale porosityThe relationship curve of (1) is subjected to exponential fitting on the relationship curve of the net overlying pressure and the porosity of the shale to obtain the pore compression coefficient C of the striated laminar shale φ ＝0.008；
Step 401, performing a high-pressure mercury intrusion test on the striated and laminated shale core sample, weighing a rock sample mass m by using a balance, and adding m and V p Inputting the mercury pressure test system to perform a high-pressure mercury pressure experiment to obtain the maximum pore radius R max =1.135 μm, mean pore radius
Volume of bedding joint pores V 1c ＝0.143cm 3 。
Step 501, establishing a shale compression model according to the deposition characteristics of the striated laminar shale, wherein the bedding joint in the striated laminar shale is approximately simulated by a flat plate, and the shale matrix part is simulated by a capillary tube model, so that the permeability of the bedding joint, the permeability of the shale matrix, the compression coefficient of the bedding joint and the compression coefficient of the shale matrix are as follows:
in the formula, k f The bedding gap permeability value, mD;
the value of the porosity of the bedding cracks is shown; omega is the width of the bedding seam; k is a radical of formula m Is the matrix permeability value, mD, in the shale sample;
the porosity value corresponding to the core matrix; r is the core matrix radius; c f The compression coefficient of the bedding joint is 1/MPa; sigma is effective stress, MPa; c m The compression coefficient of the core matrix is 1/MPa.
By combining the above formulas, the characteristic parameter alpha can be obtained when the bedding seam compression is taken as the main characteristic in the initial stage of elastic development,
in the formula, alpha is a characteristic parameter for representing the compression characteristic of the striated laminar shale, and the larger the value of alpha is, the more obvious the compression effect is, and the stronger the stress sensitivity is; lambda is the ratio of the width of the lamellar gap to the radius of the matrix pores,
where λ =5.536, φ p ＝4.12％，φ f ＝1.12％，α＝38.9。
Step 601, establishing a striation laminar shale stress sensitivity mathematical model, and fitting a permeability-net overlying pressure curve by using an index according to an overlying pressure permeability curve to obtain a striation laminar shale stress sensitivity mathematical representation formula as follows:
the formula (7) is a stress sensitive mathematical model for the striated laminar shale established by the method.
Step 701, obtaining calculation data according to the established striated laminar shale stress sensitivity mathematical model, and verifying the calculation data and the overburden permeability data, wherein the result is shown in fig. 4, which illustrates the accuracy of the striated laminar shale stress sensitivity mathematical model established by the method.
The ground permeability of the striated and laminar shale sample of one embodiment of the invention is 1.04mD, and the established stress sensitive mathematical model is k =1.04e -0.311σ 。
Finally, it should be noted that: although the present invention has been described in detail with reference to the foregoing embodiments, it will be apparent to those skilled in the art that changes may be made in the embodiments and/or equivalents thereof without departing from the spirit and scope of the invention. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
In addition to the technical features described in the specification, the technology is known to those skilled in the art.
Claims (10)
1. The striated laminar shale stress sensitive mathematical characterization method is characterized by comprising the following steps of:
step 1, carrying out permeability test on a striated laminar shale core sample to obtain a shale gas permeability value;
step 2, testing the grained and layered shale core sample to obtain a porosity value;
step 3, carrying out a overburden pore permeation experiment to obtain the pore compression coefficient of the grained lamellar shale;
step 4, performing a high-pressure mercury pressing experiment to obtain the maximum pore radius and the average pore radius of the shale and the pore volume corresponding to the bedding joint;
and 5, establishing a pressure-sensitive mathematical model of the striated laminar shale to obtain a relation curve of the permeability of the striated laminar shale and the net overlying pressure.
2. The method for stress-sensitive mathematical characterization of stratiform shale as claimed in claim 1, wherein in step 1, a stratiform shale columnar rock sample of a certain research block is selected, the length L and diameter D of the rock sample are obtained by a dimensioning method, and a stratiform shale permeability value K is obtained by a steady-state method gas permeability test 0 。
3. The stratiform shale stress of claim 1The sensitive mathematical characterization method is characterized in that in the step 2, the volume V of rock sample particles is obtained by using a helium hole method g Obtaining the rock sample pore volume V by subtracting the particle volume from the rock sample volume p And obtaining the porosity of the grained laminar shale.
4. The method for stress-sensitive mathematical characterization of stratiform shale according to claim 3, wherein in step 2, the formula for calculating the porosity of stratiform shale is:
in the formula:
is the pore volume of the shale rock sample in cm 3 ；
In% for lamellar shale porosity, D is the diameter, cm, and L is the length, cm.
5. The method for mathematically characterizing stress sensitivity of striated and laminated shale as claimed in claim 1, wherein in step 3, a CMS300 overburden porosity tester is used for overburden porosity and permeability experiments on the striated and laminated shale core sample, wherein in order to ensure that the shale sample does not crack during the experiments, the overburden pressure value is set to be not more than 40MPa, different overburden pressure values are set and permeability values and porosity values under the overburden pressure value are obtained, a relation curve between net overburden pressure and shale permeability and a relation curve between net overburden pressure and shale porosity are obtained, and meanwhile, an exponential fitting is performed on the relation curve between net overburden pressure and shale porosity to obtain the porosity coefficient of the striated and laminated shale.
6. The method for the stress-sensitive mathematical characterization of the stratiform shale according to claim 1, wherein in step 4, the sample of the stratiform shale core is subjected toPerforming high-pressure mercury-pressing experiment, weighing rock sample mass m by using balance, and performing high-pressure mercury-pressing experiment to obtain maximum pore radius R max Average pore radius
Volume of bedding joint pores V lc 。
7. The method for the stress-sensitive mathematical characterization of the stratiform shale according to claim 1, wherein in step 5, a shale compression model is established according to the sedimentary characteristics of the stratiform shale, the bedding cracks in the stratiform shale are approximately simulated by a flat plate, the shale matrix part is simulated by a capillary tube model, and then the permeability of the bedding cracks, the permeability of the shale matrix, the compressibility of the bedding cracks and the compressibility of the shale matrix are as follows:
in the formula, k f The bedding seam permeability value, mD;
the porosity value corresponding to the bedding joint,%; v lc Is the volume cm of the pores of the bedding seams 3 ；V p Is the volume of the pores of the rock sample in cm 3 (ii) a Omega is the width of the bedding seam, mu m; k is a radical of formula m Is shaleMatrix permeability value in sample, mD;
the porosity value,%, corresponding to the core matrix; r is the radius of the matrix of the rock core, and is mum; c f The bedding joint compression coefficient is 1/MPa; sigma is effective stress, MPa; c m The compression coefficient of the core matrix is 1/MPa.
8. The method for the stress-sensitive mathematical characterization of the shale with striations according to claim 7, wherein in step 5, simultaneous equations 2-5 obtain the characteristic parameter α when the bedding crack compression is the main characteristic in the early stage of the development of elasticity,
in the formula, alpha is a characteristic parameter for representing the compression characteristic of the lamellar shale, and the larger the value of alpha is, the more obvious the compression effect is, and the stronger the stress sensitivity is; wherein lambda is the ratio of the width of the bedding seam to the radius of the pores of the matrix,
phi is core porosity,%; phi (phi) of p Matrix porosity,%; phi f Bedding joint porosity,%; r is the pore radius of the matrix, mu m; rmax is the width of the bedding seam, μm.
9. The method for mathematically characterizing the stress sensitivity of the stratiform shale according to claim 8, wherein in step 5, a stratiform shale stress sensitivity mathematical model is established, and a permeability-net overburden pressure curve is exponentially fitted according to the overburden permeability curve to obtain a stratiform shale stress sensitivity mathematical characterization formula as follows:
a formula (7) is a stress sensitive mathematical model aiming at the striated laminar shale, which is established by the method; in the formula, k 0 Core initial permeability, mD; alpha is a characteristic parameter for representing the compression characteristic of the lamellar shale; c Φ The core pore compression coefficient is 1/MPa; sigma is effective stress, MPa; lambda is the ratio of the width of the bedding seam to the radius of the matrix pores; phi is core porosity,%; phi p Matrix porosity,%; phi f Is the porosity of the bedding joint,%.
10. The method for the stress-sensitive mathematical characterization of the stratiform shale according to claim 1, wherein the step 5 further comprises verifying the established stress-sensitive mathematical model to ensure the accuracy of the mathematical model.
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| CN117409408A (en) * | 2023-12-15 | 2024-01-16 | 北京大学 | Layer seam parameter acquisition method, device, equipment and readable storage medium |
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| CN116840124A (en) * | 2023-06-21 | 2023-10-03 | 西南石油大学 | Method for quantitatively representing shale reservoir core hole seam configuration |
| CN116840124B (en) * | 2023-06-21 | 2023-12-22 | 西南石油大学 | Method for quantitatively representing shale reservoir core hole seam configuration |
| CN117409408A (en) * | 2023-12-15 | 2024-01-16 | 北京大学 | Layer seam parameter acquisition method, device, equipment and readable storage medium |
| CN117409408B (en) * | 2023-12-15 | 2024-03-08 | 北京大学 | Layer seam parameter acquisition method, device, equipment and readable storage medium |
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