CN111175214A - Method for representing full size of pore diameter of unconventional tight reservoir - Google Patents
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- 239000011148 porous material Substances 0.000 title claims abstract description 149
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- 229910052753 mercury Inorganic materials 0.000 claims abstract description 102
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- 238000012360 testing method Methods 0.000 claims abstract description 67
- 238000009826 distribution Methods 0.000 claims abstract description 56
- 238000001179 sorption measurement Methods 0.000 claims abstract description 44
- 229910052757 nitrogen Inorganic materials 0.000 claims abstract description 37
- 239000011435 rock Substances 0.000 claims abstract description 19
- 239000007788 liquid Substances 0.000 claims abstract description 13
- 238000001035 drying Methods 0.000 claims abstract description 11
- 239000011159 matrix material Substances 0.000 claims description 36
- 239000003245 coal Substances 0.000 claims description 32
- 238000012512 characterization method Methods 0.000 claims description 21
- 239000007789 gas Substances 0.000 claims description 16
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- 238000006467 substitution reaction Methods 0.000 claims description 3
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- 238000007906 compression Methods 0.000 abstract description 3
- 238000011160 research Methods 0.000 description 7
- 238000003825 pressing Methods 0.000 description 6
- CURLTUGMZLYLDI-UHFFFAOYSA-N Carbon dioxide Chemical compound O=C=O CURLTUGMZLYLDI-UHFFFAOYSA-N 0.000 description 4
- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical compound C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 description 4
- 238000005481 NMR spectroscopy Methods 0.000 description 3
- 238000002474 experimental method Methods 0.000 description 3
- 229910002092 carbon dioxide Inorganic materials 0.000 description 2
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- 239000003345 natural gas Substances 0.000 description 2
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 description 1
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- 238000005065 mining Methods 0.000 description 1
- 230000035699 permeability Effects 0.000 description 1
- 239000003208 petroleum Substances 0.000 description 1
- 238000002459 porosimetry Methods 0.000 description 1
- 239000003079 shale oil Substances 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
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Abstract
A method for representing the full size of the bore diameter of an unconventional tight reservoir comprises the steps of dividing a core after drying treatment into two parts so as to avoid pore structure representation errors possibly caused by heterogeneity of the unconventional tight reservoir and carry out a high-pressure mercury intrusion test and a low-temperature nitrogen adsorption test on a columnar core; based on a fractal method, dividing the pore size distribution obtained by mercury intrusion test into a micrometer-level crack, a normal pore and a compressed nm-level pore; calculating the compression coefficient of the rock core by combining the low-temperature nitrogen adsorption test result of the rock core, and correcting the real pore size distribution of the compressed nm-level pores in the mercury intrusion test; drawing the corrected mercury intrusion test pore size distribution curve and the low-temperature nitrogen adsorption test pore size distribution curve in the same graph, finding out an intersection point of the curves, and taking the nano-scale pores obtained by the low-temperature liquid nitrogen adsorption test as a reference to obtain the full-size representation of the pore size of the unconventional compact reservoir; the method can accurately and effectively represent the full-size distribution characteristics of the pore diameter of the unconventional tight reservoir.
Description
Technical Field
The invention relates to the technical field of oil and gas development, in particular to a method for representing the full size of the pore diameter of an unconventional tight reservoir.
Background
The proportion of unconventional oil and gas resources such as coal bed gas, tight sandstone gas, shale gas and shale oil in a world energy structure is gradually improved, the pore structures in unconventional tight reservoirs such as a coal reservoir, a tight sandstone reservoir and a shale reservoir corresponding to the unconventional oil and gas resources are complex, and micron-level pores-fractures and nm-level pores are developed. The μm-scale pore-fractures favor the seepage of unconventional hydrocarbons, while the nm-scale pores favor the adsorption of unconventional hydrocarbons. Therefore, quantitative research on the ratio of seepage holes and adsorption holes in the unconventional tight reservoir is realized by performing full-size fine characterization on the mu m-level holes-fractures and the nm-level holes in the unconventional tight reservoir, and the unconventional tight oil and gas enriched dessert region can be effectively evaluated.
In the existing research, CN201810260408.0 discloses an evaluation method for hydrogen-containing components, porosity and pore diameter of shale rich in organic substances, CN201710238534.1 discloses a method for determining pore diameter distribution of a tight reservoir based on mercury intrusion-nitrogen adsorption joint measurement data, CN201910237931.6 discloses a method for quantitatively characterizing full-size pores of the tight reservoir based on NMT and LTNA, CN201810571899.0 discloses a method for analyzing pore characterization of the tight sandstone reservoir based on Matlab, and CN201711026567.6 discloses a method for characterizing pore throat characteristics of the tight reservoir based on high-pressure mercury intrusion multi-scale. In 2015, 9 months, the natural gas geosciences, lie soar and the like represent the shale pore size by using a low-pressure gas adsorption method; 2016, 3 months, geology front (university of geology, Beijing); university of Beijing), Jones, et al, conducted a study of the full pore size characterization of the shale pore structure of Longmaxi groups; in 2016, 6 months, geological science of colleges and universities, Yang-Qin and the like research the full-aperture pore structure of shale by utilizing a field emission scanning electron microscope, a high-pressure mercury pressing experiment and a low-temperature low-pressure adsorption experiment; in 2017, in 4 months, in the China mining industry, Wangkai and other people characterize the pore structure of the coal rock by utilizing carbon dioxide adsorption, liquid nitrogen adsorption, high-pressure mercury pressing and low-field nuclear magnetic resonance; in 7 months in 2018, the full-aperture pore structure of the ultra-low permeability compact sandstone is researched by using high-pressure mercury pressing, constant-speed mercury pressing and nuclear magnetic resonance by people in petroleum experimental geology, Europe Ciqi and the like; in 2019, 1 month, journal of the university of western's safety science and technology, forest sea flying and the like research the pore structure of the coal rock by using a low-temperature liquid nitrogen adsorption method and a mercury pressing method; in 2019, in oil and natural gas geology, tsukudani and other people, the pore structure of shale reservoirs is characterized by low-temperature carbon dioxide adsorption, nitrogen adsorption, nuclear magnetic resonance, mercury intrusion, a scanning electron microscope and the like in 12 months.
The main problems that exist are: (1) although the existing research adopts a plurality of methods for combined test, the pore size distribution characteristics measured by different test methods are analyzed based on the development of different test samples, and the pore structure characterization error possibly brought by the strong heterogeneity of an unconventional compact reservoir is not considered; (2) in the existing research, when a high-pressure mercury porosimetry is adopted for pore size distribution characterization, the maximum test pressure reaches 170MPa, and the compressibility of pores under a high-pressure condition (>10MPa) is not considered.
Disclosure of Invention
In order to solve the defects in the prior art, the invention aims to provide a method for characterizing the full size of the pore diameter of an unconventional compact reservoir, which is used for realizing fine quantitative characterization of different pore diameter distribution characteristics of the unconventional compact reservoir at a nm level-mum level by respectively carrying out a high-pressure mercury intrusion test and a low-temperature nitrogen adsorption test on the same sample and correcting the pore diameter distribution characteristics of the sample according to the typical characteristic of pore compressibility under the high-pressure mercury intrusion test condition of the compact reservoir.
In order to achieve the purpose, the invention is realized by the following technical scheme:
a method for full-size characterization of pore size of unconventional tight reservoirs, comprising the steps of:
placing an unconventional tight reservoir rock core in an oven until the sample weight is constant, and cutting the rock core into a columnar rock core block with the diameter of 2.5cm and the length of 3cm by using a wire cutting machine; cutting a columnar core with the diameter of 2.5cm and the length of 2cm, and crushing the columnar core with the diameter of 2.5cm and the length of 2cm into granular samples with the size of 0.18-0.25 mm;
step two, carrying out a high-pressure mercury intrusion test on a columnar rock core with the diameter of 2.5cm and the length of 3cm, and carrying out a low-temperature nitrogen adsorption test on a granular sample crushed to be 0.18-0.25mm in size;
step three, carrying out fractal processing on pore structure data of the high-pressure mercury intrusion test to determine the filling pressure P of the inter-granular poresfAnd the matrix contraction pressure PcCorrecting the pore size distribution obtained by the high-pressure mercury intrusion test by combining the low-temperature liquid nitrogen adsorption test result;
drawing the corrected high-pressure mercury intrusion aperture distribution curve and the corrected low-temperature nitrogen adsorption aperture distribution curve on the same graph to obtain an intersection point of different aperture distribution curves;
and fifthly, taking the junction as a boundary, removing the repeated pore size distribution of the junction based on the nm-level pore distribution characteristics obtained by the low-temperature nitrogen adsorption test, thus obtaining the pore size full-size distribution curve of the unconventional tight reservoir sample and realizing the fine quantitative characterization of the pore size full-size distribution of the unconventional tight reservoir.
The high-pressure mercury injection test and the low-temperature nitrogen adsorption test procedures in the step two are developed according to the following conditions:
high-pressure mercury intrusion test flow: firstly, placing a sample in a drying box, and drying for 24 hours at 85 ℃; then putting the sample into a sample cabin of a mercury porosimeter, evacuating under low pressure, and evacuating the cabin and the adsorbed gas on the surface of the particles; finally, a balance method is adopted to carry out mercury intrusion test on the coal sample, the balance time is 90s, and the experimental result is automatically recorded by a computer;
low-temperature nitrogen adsorption test flow: firstly, drying the coal for 12 hours at 105 ℃ to remove moisture in the coal; then, 1-2g of coal sample is selected to be treated for 12 hours under the conditions of vacuum and 105 ℃, and possible adsorbed gas on the surfaces of coal particles is removed; finally, high purity N2Used as adsorbate, the adsorption process was tested at a temperature of 77K under relative pressure conditions of 0.01 to 0.995.
The third step is specifically as follows: fractal processing is carried out on pore structure data of a high-pressure mercury intrusion test, and filling pressure P of inter-granular pores is determined based on formula (1) and formula (2)fAnd the matrix contraction pressure PcAnd correcting the pore size distribution obtained by the high-pressure mercury intrusion test by combining the formulas (3) to (10);
dV/dP∝P4-D(1)
in the formula, V is the mercury feeding amount of the coal sample under the pressure P, and D is the fractal dimension of pores;
obtaining the fractal dimension corresponding to the coal rock pore under different mercury inlet pressures by taking logarithm of the formula (1):
lg(dV/dP)∝(4-D)lgP (2)
dividing the coal rock pore structure into three sections by taking the fractal dimension of pores in different pressure ranges as a reference, and taking the corresponding mercury inlet pressure at the position with the fractal dimension less than 2 as the filling pressure P of the interparticle poresfTaking the corresponding mercury inlet pressure with fractal dimension larger than 3 as the matrix contraction pressure Pc(ii) a Interparticle pore filling pressure PfThe prior mercury intrusion test obtains the mum-level cracks of unconventional compact reservoir and the matrix shrinkage pressure PcThen mercury injection testing is carried out to obtain the compressed part of nm-level pores of the unconventional compact reservoir, and normal pores are arranged between the nm-level pores and the unconventional compact reservoir;
the compressibility of a tight reservoir at high pressure can be expressed as:
in the formula, KcIs the coefficient of matrix shrinkage, m2/N；VcIs the volume of the matrix, cm3/g；
Wherein rho is the true density, g/cm3；VN2Pore volume, cm, measured by low temperature liquid nitrogen method3/g；
For compressible porous media, the mercury inlet amount is mainly represented by two parts together, namely:
ΔVobs＝ΔVp+ΔVc(5)
in the formula,. DELTA.VobsAccording to the amount of mercury in cm3/g；ΔVpFilling the pores with mercury in cm3/g；ΔVcIs the shrinkage of the matrix, cm3/g；
The matrix shrinkage effect mainly occurs at the mercury inlet pressure of Pcthen, in the pressure range, the mercury feeding amount and the mercury feeding pressure are approximately a linear straight line, and the slope of the straight line is β;
the compound of formula (7) is introduced into formula (3),
in the formula,. DELTA.VpThe pore volume measured by low-temperature liquid nitrogen adsorption can be used for substitution, and the shrinkage coefficient of the matrix can be calculated and obtained according to the pore volume;
assuming that the matrix shrinkage factor is constant during the pressure increase, the volume of the matrix at different pressures is:
Vci＝Vc-K*Vc*(Pi-P0) (9)
in the formula, VciIs a pressure PiVolume of lower coal matrix, cm3/g；
Accordingly, the actual mercury intake of the pores in the sample under different pressure conditions can be obtained:
Vpi＝Vobsi-(Vc-Vci) (10)
in the formula, VpiIs a pressure PiActual mercury intake in cm of lower pores3/g；VobsiIs a pressure PiLower pores according to mercury amount, cm3/g。
Compared with the prior art, the invention has the following advantages:
unconventional compact reservoirs such as coal rock, compact sandstone, shale and the like have abnormally complex pore structures, the diameters of pores are distributed from nm level to mum level, the traditional research aiming at the pores with different sizes and apertures mostly adopts a method of comprehensively researching by various testing means, and multiple methods are developed aiming at different test samples and the characteristics of the pore size distribution corresponding to different testing methods are analyzed. Especially, when a high-pressure mercury intrusion method is adopted to analyze a pore structure, the understanding of the compressibility of the pore of the compact reservoir under the high-pressure condition in the high-pressure mercury intrusion method is insufficient, so that a certain error region exists in the understanding of the accurate distribution characteristics of partial pore diameters. The invention relates to a non-conventional tight reservoir pore size full-size characterization method, which aims at the typical characteristic of strong heterogeneity of a non-conventional tight reservoir, carries out high-pressure mercury intrusion test and low-temperature nitrogen adsorption test on the same non-conventional tight reservoir core, and avoids the difference of reservoir pore structures caused by the self heterogeneity of the non-conventional tight reservoir; in addition, the pore size distribution distortion phenomenon caused by pore compression under high-pressure conditions in a high-pressure mercury intrusion test is corrected, the distribution characteristics of the nm-mum-level pores in the compact reservoir are more accurately characterized, and the fine characterization of the full-size pore size distribution of the unconventional compact reservoir is realized.
Drawings
FIG. 1 is a graph of pore size distribution obtained for high pressure mercury intrusion.
FIG. 2 is a graph of pore size distribution obtained by cryogenic liquid nitrogen adsorption.
FIG. 3 is a fractal characteristic diagram of the pore diameter of high-pressure mercury intrusion.
fig. 4 is a graph showing calculation of the high-pressure mercury intrusion correction constant β.
FIG. 5 is a plot of corrected pore size distribution for high pressure mercury intrusion.
FIG. 6 is a cross-sectional view of pore size distribution based on high pressure mercury intrusion and low temperature nitrogen adsorption.
FIG. 7 is a graph of pore size full-scale distribution characterization of unconventional tight reservoirs.
Detailed Description
The invention is further described in detail below with reference to the drawings and examples, but the invention is not limited thereto.
The invention is described in detail below by selecting a block of unconventional tight reservoir core sample and combining the drawing.
A method for full-size characterization of pore size of unconventional tight reservoirs, comprising the steps of:
placing a compact reservoir core with the diameter of 2.5cm and the length of 5cm in an oven, setting the drying temperature to be 80 ℃, weighing a sample once every 6 hours by using a high-precision balance, and considering that the core is in a dry state when the mass variation of the core measured continuously three times is less than 0.01 g; cutting a columnar core with the diameter of 2.5cm and the length of 3cm into one piece by using a wire cutting machine, cutting a columnar core with the diameter of 2.5cm and the length of 2cm into one piece, and crushing the columnar core with the diameter of 2.5cm and the length of 2cm into granular samples with the size of 0.18-0.25 mm;
step two, carrying out a high-pressure mercury intrusion test on a columnar core with the diameter of 2.5cm and the length of 3cm, and obtaining a core high-pressure mercury intrusion test pore size distribution curve as shown in figure 1; carrying out nitrogen adsorption test on a granular sample crushed to 0.18-0.25mm in size to obtain a core nitrogen adsorption test pore size distribution curve, as shown in figure 2;
the high-pressure mercury-pressing test and the low-temperature nitrogen adsorption test flow are developed according to the following conditions:
high-pressure mercury intrusion test flow: firstly, placing a sample in a drying box, and drying for 24 hours at 85 ℃; then putting the sample into a sample cabin of a mercury porosimeter, evacuating under low pressure, and evacuating the cabin and the adsorbed gas on the surface of the particles; finally, a balance method is adopted to carry out mercury intrusion test on the coal sample, the balance time is 90s, and the experimental result is automatically recorded by a computer;
low-temperature nitrogen adsorption test flow: firstly, drying the coal for 12 hours at 105 ℃, and mainly removing moisture in the coal; then, 1-2g of coal sample is selected to be treated for 12 hours under the conditions of vacuum and 105 ℃, and possible adsorbed gas on the surfaces of coal particles is removed; finally, high purity N2Used as adsorbate, testing the adsorption process at a relative pressure of 0.01 to 0.995 at a temperature of 77K;
step three, carrying out fractal processing on pore structure data of the high-pressure mercury intrusion test, and determining the filling pressure (P) of the inter-granular pores based on the formula (1) and the formula (2)f) And the matrix contraction pressure (P)c) And correcting the pore diameter distribution obtained by the high-pressure mercury intrusion test by combining the formulas (3) to (10):
dV/dP∝P4-D(1)
in the formula, V is the mercury feeding amount of the coal sample under the pressure P, and D is the fractal dimension of pores;
by taking logarithm of the formula (1), fractal dimensions corresponding to coal rock pores under different mercury inlet pressures can be obtained.
lg(dV/dP)∝(4-D)lgP (2)
Dividing the coal rock pore structure into three sections by taking the fractal dimension of pores in different pressure ranges as a reference, and taking the corresponding mercury inlet pressure at the position with the fractal dimension less than 2 as the filling pressure P of the interparticle poresfTaking the corresponding mercury inlet pressure with fractal dimension larger than 3 as the matrix contraction pressure Pc(ii) a Interparticle pore filling pressure PfThe prior mercury intrusion test obtains the mum-level cracks of unconventional compact reservoir and the matrix shrinkage pressure PcThen mercury intrusion test is carried out to obtain the compressed part of nm-level pores of the unconventional tight reservoir, and normal pores are arranged between the nm-level pores and the unconventional tight reservoir, and the reference is made to the graph shown in FIG. 3;
the compressibility of a tight reservoir at high pressure can be expressed as:
in the formula, KcIs the coefficient of matrix shrinkage, m2/N；VcIs the volume of the matrix, cm3/g；
Wherein rho is the true density, g/cm3；VN2Pore volume, cm, measured by low temperature liquid nitrogen method3/g；
For compressible porous media, the mercury inlet amount is mainly represented by two parts together, namely:
ΔVobs＝ΔVp+ΔVc(5)
in the formula,. DELTA.VobsAccording to the amount of mercury in cm3/g；ΔVpFilling the pores with mercury in cm3/g；ΔVcIs the shrinkage of the matrix, cm3/g；
The matrix shrinkage effect mainly occurs at the mercury inlet pressure of Pcthen, the mercury inlet amount and the mercury inlet pressure in the pressure range are approximately a linear straight line, the slope of which is β, and fig. 4 is referred to;
the formula (7) is introduced into the formula (3) to obtain:
in the formula,. DELTA.VpThe pore volume measured by low-temperature liquid nitrogen adsorption can be used for substitution, and the shrinkage coefficient of the matrix can be calculated and obtained according to the pore volume.
Assuming that the matrix shrinkage factor is constant during the pressure increase, the volume of the matrix at different pressures is,
Vci＝Vc-K*Vc*(Pi-P0) (9)
in the formula, VciIs a pressure PiVolume of lower coal matrix, cm3/g；
Accordingly, the actual mercury intake of the pores in the sample under different pressure conditions can be obtained, as shown in fig. 5:
Vpi＝Vobsi-(Vc-Vci) (10)
in the formula, VpiIs a pressure PiActual mercury intake in cm of lower pores3/g；VobsiIs a pressure PiLower pores according to mercury amount, cm3/g。
Step four, referring to fig. 6, drawing the corrected high-pressure mercury intrusion aperture distribution curve and the corrected low-temperature nitrogen adsorption aperture distribution curve on the same graph to obtain the intersection points of different aperture distribution curves;
and step five, referring to fig. 7, with the junction as a boundary, and based on the nm-level pore distribution characteristics obtained by the low-temperature nitrogen adsorption test, removing the repeated pore size distribution of the junction, namely obtaining the pore size full-size distribution curve of the unconventional tight reservoir sample, and realizing the fine quantitative characterization of the pore size full-size distribution of the unconventional tight reservoir.
Description of the principles of the Experimental methods
The high-pressure condition in the high-pressure mercury intrusion test easily causes the compression of pores in a compact reservoir to cause the reduction and distortion of pore size distribution, the pore size distribution characteristics measured by the high-pressure mercury intrusion test are used blindly, the error recognition of the pore size distribution characteristics of a part of nm-level and mum-level in an unconventional compact reservoir is easily caused, the pore size distribution characteristics obtained by the high-pressure mercury intrusion test are correctly recognized, and the fine characterization of the pore size distribution characteristics of the unconventional compact reservoir is realized by combining the pore size distribution characteristics of the unconventional compact reservoir obtained by low-temperature liquid nitrogen adsorption.
According to the invention, the precise characterization of the pore size distribution in the high-pressure mercury intrusion is realized through the precise characterization of the shrinkage effect of the matrix in the high-pressure mercury intrusion process, and the full-size characterization of the pore size of the unconventional compact reservoir is realized by combining the nm-level pore size distribution characteristics of the same sample obtained by the low-temperature gas adsorption test, so that the method has guiding significance for the effective evaluation of the unconventional compact oil-gas enriched dessert area.
While the invention has been described in further detail with reference to specific preferred embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims.
Claims (3)
1. A method for full-size characterization of pore size of unconventional tight reservoirs, comprising the steps of:
placing an unconventional tight reservoir rock core in an oven until the sample weight is constant, and cutting the rock core into a columnar rock core block with the diameter of 2.5cm and the length of 3cm by using a wire cutting machine; cutting a columnar core with the diameter of 2.5cm and the length of 2cm, and crushing the columnar core with the diameter of 2.5cm and the length of 2cm into granular samples with the size of 0.18-0.25 mm;
step two, carrying out a high-pressure mercury intrusion test on a columnar rock core with the diameter of 2.5cm and the length of 3cm, and carrying out a low-temperature nitrogen adsorption test on a granular sample crushed to be 0.18-0.25mm in size;
step three, carrying out fractal processing on pore structure data of the high-pressure mercury intrusion test to determine the filling pressure P of the inter-granular poresfAnd the matrix contraction pressure PcCorrecting the pore size distribution obtained by the high-pressure mercury intrusion test by combining the low-temperature liquid nitrogen adsorption test result;
drawing the corrected high-pressure mercury intrusion aperture distribution curve and the corrected low-temperature nitrogen adsorption aperture distribution curve on the same graph to obtain an intersection point of different aperture distribution curves;
and fifthly, taking the junction as a boundary, removing the repeated pore size distribution of the junction based on the nm-level pore distribution characteristics obtained by the low-temperature nitrogen adsorption test, thus obtaining the pore size full-size distribution curve of the unconventional tight reservoir sample and realizing the fine quantitative characterization of the pore size full-size distribution of the unconventional tight reservoir.
2. The method for full-size characterization of pore diameter of unconventional tight reservoir according to claim 1, wherein the high-pressure mercury intrusion test and low-temperature nitrogen adsorption test procedures in the second step are developed according to the following conditions:
high-pressure mercury intrusion test flow: firstly, placing a sample in a drying box, and drying for 24 hours at 85 ℃; then putting the sample into a sample cabin of a mercury porosimeter, evacuating under low pressure, and evacuating the cabin and the adsorbed gas on the surface of the particles; finally, a balance method is adopted to carry out mercury intrusion test on the coal sample, the balance time is 90s, and the experimental result is automatically recorded by a computer;
low-temperature nitrogen adsorption test flow: firstly, drying the coal for 12 hours at 105 ℃ to remove moisture in the coal; then, 1-2g of coal sample is selected to be treated for 12 hours under the conditions of vacuum and 105 ℃, and possible adsorbed gas on the surfaces of coal particles is removed; finally, high purity N2Used as adsorbate, the adsorption process was tested at a temperature of 77K under relative pressure conditions of 0.01 to 0.995.
3. The method for full-size characterization of pore diameters of unconventional tight reservoirs according to claim 1, wherein the third step is specifically:
fractal processing is carried out on pore structure data of a high-pressure mercury intrusion test, and filling pressure P of inter-granular pores is determined based on formula (1) and formula (2)fAnd the matrix contraction pressure PcAnd correcting the pore diameter distribution obtained by the high-pressure mercury intrusion test by combining the formulas (3) to (10):
dV/dP∝P4-D(1)
in the formula, V is the mercury feeding amount of the coal sample under the pressure P, and D is the fractal dimension of pores;
obtaining fractal dimensions corresponding to coal rock pores under different mercury inlet pressures by taking logarithm of the formula (1);
lg(dV/dP)∝(4-D)lgP (2)
dividing the coal rock pore structure into three sections by taking the fractal dimension of pores in different pressure ranges as a reference, and taking the corresponding mercury inlet pressure at the position with the fractal dimension less than 2 as the filling pressure P of the interparticle poresfTaking the corresponding mercury inlet pressure with fractal dimension larger than 3 as the matrix contraction pressure Pc(ii) a Interparticle pore filling pressure PfThe prior mercury intrusion test obtains the mum-level cracks of unconventional compact reservoir and the matrix shrinkage pressure PcThen mercury injection testing is carried out to obtain the compressed part of nm-level pores of the unconventional compact reservoir, and normal pores are arranged between the nm-level pores and the unconventional compact reservoir;
the compressibility of a tight reservoir at high pressure can be expressed as:
in the formula, KcIs the coefficient of matrix shrinkage, m2/N；VcIs the volume of the matrix, cm3/g；
Wherein rho is the true density, g/cm3；VN2Pore volume, cm, measured by low temperature liquid nitrogen method3/g；
For compressible porous media, the mercury inlet amount is mainly represented by two parts together, namely:
ΔVobs＝ΔVp+ΔVc(5)
in the formula,. DELTA.VobsAccording to the amount of mercury in cm3/g；ΔVpFilling the pores with mercury in cm3/g；ΔVcIs the shrinkage of the matrix, cm3/g；
The matrix shrinkage effect mainly occurs at the mercury inlet pressure of Pcthen, the mercury feeding amount and the mercury feeding pressure are approximately a linear straight line in the pressure range, and the slope of the straight line is β;
the compound of formula (7) is introduced into formula (3),
in the formula,. DELTA.VpThe pore volume measured by low-temperature liquid nitrogen adsorption can be used for substitution, and the shrinkage coefficient of the matrix can be calculated and obtained according to the pore volume;
assuming that the matrix shrinkage factor is constant during the pressure increase, the volume of the matrix at different pressures is:
Vci＝Vc-K*Vc*(Pi-P0) (9)
in the formula, VciIs a pressure PiVolume of lower coal matrix, cm3/g；
Accordingly, the actual mercury intake of the pores in the sample under different pressure conditions can be obtained:
Vpi＝Vobsi-(Vc-Vci) (10)
in the formula, VpiIs a pressure PiActual mercury intake in cm of lower pores3/g；VobsiIs a pressure PiLower pores according to mercury amount, cm3/g。
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| CN114428043A (en) * | 2020-09-18 | 2022-05-03 | 中国石油化工股份有限公司 | Porous medium pore size distribution characterization method and electronic equipment |
| CN112304841A (en) * | 2020-09-24 | 2021-02-02 | 青岛石大华通科技有限公司 | Rock pore structure simulation test system and simulation test method |
| CN112284999A (en) * | 2020-10-26 | 2021-01-29 | 中国石油大学(华东) | Sandstone pore size distribution determination method and application thereof |
| CN112284999B (en) * | 2020-10-26 | 2022-06-17 | 中国石油大学(华东) | Sandstone pore size distribution determination method and application thereof |
| CN114018780A (en) * | 2021-10-11 | 2022-02-08 | 北京市科学技术研究院分析测试研究所(北京市理化分析测试中心) | Method for measuring porosity and fractal dimension of ceramic coating and application |
| CN114894692A (en) * | 2022-04-26 | 2022-08-12 | 重庆大学 | Method for determining full-scale pore diameter of compact reservoir |
| CN115235977A (en) * | 2022-07-22 | 2022-10-25 | 中国石油大学(华东) | Method and system for calculating shale multi-scale pore size distribution based on fractal characteristics |
| 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 |
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