CN108460219A - Shale adsorbed gas air content method is calculated based on overcritical mono layer adsorption model - Google Patents
Shale adsorbed gas air content method is calculated based on overcritical mono layer adsorption model Download PDFInfo
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- 238000001179 sorption measurement Methods 0.000 title claims abstract description 205
- 239000002356 single layer Substances 0.000 title claims abstract description 39
- 238000000034 method Methods 0.000 title claims abstract description 26
- 239000011148 porous material Substances 0.000 claims abstract description 30
- 238000001514 detection method Methods 0.000 claims abstract description 19
- 238000002474 experimental method Methods 0.000 claims abstract description 12
- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical compound C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 claims description 46
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 22
- 239000010410 layer Substances 0.000 claims description 19
- 239000007788 liquid Substances 0.000 claims description 15
- 239000007787 solid Substances 0.000 claims description 13
- 229910052770 Uranium Inorganic materials 0.000 claims description 10
- JFALSRSLKYAFGM-UHFFFAOYSA-N uranium(0) Chemical group [U] JFALSRSLKYAFGM-UHFFFAOYSA-N 0.000 claims description 10
- ZSLUVFAKFWKJRC-IGMARMGPSA-N 232Th Chemical compound [232Th] ZSLUVFAKFWKJRC-IGMARMGPSA-N 0.000 claims description 7
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- 238000007796 conventional method Methods 0.000 description 1
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Abstract
The invention discloses one kind calculating shale adsorbed gas air content method based on overcritical mono layer adsorption model, the rock-electric test data of core sample are obtained in advance, adsorption isotherm experiment data and nuclear-magnetism experimental data, and utilize adsorption isotherm experiment data, excess adsorption in pipe pore model is converted into absolute adsorption amount, establish overcritical mono layer adsorption model, then, determine the parameter in the overcritical mono layer adsorption model, later, error-detecting is carried out to the overcritical mono layer adsorption model, as detection passes through, then shale adsorbed gas air content in practical logging is calculated using the overcritical mono layer adsorption model.Shale adsorbed gas air content method, which should be calculated, based on overcritical mono layer adsorption model can more truly reflect subsurface picture, can more accurately evaluate shale reservoir.
Description
Technical Field
The invention relates to a method for calculating the gas content of shale gas reservoir adsorbed gas, and particularly provides a method for calculating the gas content of shale adsorbed gas based on a supercritical monomolecular layer adsorption model.
Background
The adsorption model of the shale gas is generally referred from the coal bed gas, and the common adsorption models at present mainly comprise a subcritical adsorption model and a supercritical adsorption model. Although the subcritical adsorption model calculates the gas content based on a monolayer adsorption theory, the maximum experimental temperature does not exceed 100 ℃, the maximum pressure does not exceed 20Mpa, and the actual temperature and pressure of the formation are far higher than the maximum experimental temperature and pressure, so that the method is only suitable for general qualitative evaluation, and a large error exists in quantitative calculation. Whereas the supercritical adsorption model is established in consideration of the critical temperature and critical pressure of methane, shale is considered to be supercritical adsorption when adsorbing methane. Multi-layered adsorption occurs on the open surface. However, in a real formation, no liquid state is possible above the critical temperature, and therefore the saturated vapor pressure in the pore filling model is of no practical significance. Meanwhile, in the application process of the method, when the pressure of the model is increased, the error is increased, and the application range of the model is limited.
Therefore, how to establish a more accurate adsorption model to truly reflect the underground situation and accurately evaluate the shale reservoir becomes a problem to be solved urgently.
Disclosure of Invention
In view of the above, the invention aims to provide a method for calculating gas content of shale adsorbed gas based on a supercritical monomolecular layer adsorption model, so as to solve the problems that the application range of the existing adsorption model is small, the underground condition cannot be truly reflected, the shale reservoir cannot be accurately evaluated, and the like.
The technical scheme provided by the invention is as follows: a method for calculating gas content of shale adsorbed gas based on a supercritical monomolecular layer adsorption model comprises the following steps:
s1: acquiring rock electricity experimental data, isothermal adsorption experimental data and nuclear magnetic experimental data of a rock core sample in advance, converting the excessive adsorption quantity in the circular tube hole model into absolute adsorption quantity by using the isothermal adsorption experimental data, and establishing a supercritical monomolecular layer adsorption model;
s2: determining parameters in the supercritical monolayer adsorption model, the parameters includingWater saturation, fill factor α, Langmuir pressure P of gas-liquid interface, specific surface A of microtubetubeAnd a maximum methane adsorption K per unit area of the gas-solid interface;
s3: performing error detection on the supercritical monolayer adsorption model, and if the supercritical monolayer adsorption model passes the error detection, executing S4;
s4: calculating the gas content of shale adsorption gas in the actual logging by using the supercritical monomolecular layer adsorption model;
wherein, S1 includes the following steps:
s11: the excess adsorption capacity obtained by using the isothermal adsorption experimental data is as follows:
wherein V is an excess adsorption amount in m3T; v' is the volume of the adsorption space in m3； VaIs the volume of the adsorption phase in m3；ρgIs gas phase density, in kg/m3(ii) a ρ (r) is the density distribution of the adsorption phase in the adsorption space,
the density of the adsorption phase is (V-V)a) And (3) the density of the medium phase is approximately equal to that of the gas phase, and the formula (1.1) is simplified to obtain a formula (1.2):
s12: the influence of the volume of the adsorption phase on the adsorption phase gives the formula (1.3):
V＝Va(ρa-ρg).............................(1.3)
where ρ isaThe adsorption phase density is equal to the absolute adsorption amount divided by the volume of the adsorption phase, and therefore, formula (1.4) can be obtained by formula (1.3):
wherein, VabRepresents the absolute adsorption amount in m3/t；
S13: solving the gas phase density by adopting a P-R gas state equation:
wherein:m＝0.37464+1.54226w-0.26992w2(ii) a R is a molar gas constant; a. b is the attraction coefficient and the repulsion coefficient respectively; t iscIs the critical temperature in K; pcIs the critical pressure in MPa; w is an eccentricity factor and is a substance characteristic constant for representing the eccentricity or non-sphericity of a substance molecule,
s14: the adsorption phase density was calculated using the Dubinin formula:
wherein M is the gas molar mass and the unit is kg/mol;
s15: based on the calculation, the excess adsorption capacity in the supercritical monomolecular layer adsorption model of the circular tube hole model is converted into the absolute adsorption capacity to obtain a new adsorption model:
wherein A istubeIs the specific surface of a microtube, and the unit is m2(ii)/g; k is the maximum methane per unit area of gas-solid interfaceAdsorption capacity in m3T; p is reservoir pressure in MPa; pLIs Langmuir pressure, expressed in MPa, and represents half of the pressure corresponding to the maximum adsorption capacity; gamma-shaped*The maximum methane adsorption capacity in mmol/m per unit area of the gas-liquid interface2，Vab-d、Vab-mixAnd Vab-wAbsolute adsorption capacity under different water saturation conditions; sWIs the water saturation, SwonThe water saturation when the water molecules in the tubular pores reach monolayer adsorption;
the method for determining the parameters in the supercritical monolayer adsorption model in the step S2 is as follows:
s21 calculation of Water saturation and fill factor α
The flood coefficient α is an approximation of the water saturation, wherein the water saturation is calculated using petro-electric experimental data;
s22: calculating the Langmuir pressure P of the gas-liquid interface
The Langmuir pressure P at the gas-liquid interface is related to the temperature T as follows:
P*＝17.059e0.011T.........................(1.8)
wherein T has the unit of;
s23: calculating the specific surface A of the microtubetube
Obtaining transverse relaxation time T through nuclear magnetic experiment data and isothermal adsorption experiment data2Relationship to aperture d:
T2'＝0.38d...................................(1.9)
wherein, T2' is the transverse relaxation time corresponding to the aperture, with the unit of ms, after the corresponding aperture is calculated, the T is passed2Calculating the percentage of the pore volume occupied by the pore diameter by distribution to obtain a weighted average pore diameter, and setting the T corresponding to the 6nm pore diameter2Cutoff value of T2'(6)Nuclear magnetic porosity of less than 6nmAnd a porosity of greater than 6nmComprises the following steps:
wherein,is the porosity calculated by nuclear magnetic experimental data, and has the unit of percent,
the pore volume V' of less than 6nm is:
the cross section area S' corresponding to the aperture is as follows:
S'＝π·(dm/2)2............................(2.3)
the section perimeter C' corresponding to the aperture is:
C’＝π·dm...............................(2.4)
then the above formula, A, is combinedtubeExpressed as:
wherein, VSIs a sampleVolume in m3(ii) a m is the sample mass in g; dmIs the weighted average pore diameter in m;
s34: calculating the maximum methane adsorption K of the unit area of the gas-solid interface
Obtaining the maximum adsorption quantity of the sample by using isothermal adsorption experimental data obtained by laboratory measurement, obtaining the specific surface of the sample by using a formula (2.5), obtaining the maximum adsorption quantity K of methane in unit area of a gas-solid interface of the sample by using a formula (2.6),
wherein the unit of K is mmol/m2，VmaxThe maximum adsorption quantity of methane in the isothermal adsorption experiment is expressed in mmol/g;
s4 further includes a step of judging whether the actual logging data include nuclear magnetic logging data, if yes, the shale adsorbed gas content is calculated according to the supercritical monolayer adsorption model (formula (1.7)) of which the parameters in the supercritical monolayer adsorption model are determined through S2, and if not, the parameter A in S2 is calculated through formula (2.7)tubeThen calculating the gas content of shale adsorption gas by using the formula (1.7),
Atube＝-10.22TH/U+0.22U+37.23....................(2.7)
wherein TH is thorium content, U is uranium content, and TH/U is the ratio of thorium content to uranium content.
Preferably, the method for performing error detection on the supercritical monolayer adsorption model in S3 specifically includes:
s31: calculating the gas content of shale adsorbed gas by using the supercritical monomolecular layer adsorption model;
s32: comparing the calculation result in the step S31 with the isothermal adsorption data measured in the laboratory, if the error is within a preset acceptable range, passing the detection, and performing a step S4, if the error is not passed, indicating that the supercritical monolayer adsorption model is invalid in the detection area.
The method for calculating the gas content of shale adsorbed gas based on the supercritical monolayer adsorption model is based on a Langmuir (Langmuir) adsorption model of gas-solid-liquid three-phase action of a slit and a circular tube hole, establishes the supercritical monolayer isothermal adsorption model based on a monolayer adsorption theory, and introduces a concept of excess adsorption quantity. A solid-liquid-gas three-phase adsorption model of predecessors is expanded to a supercritical region, and a pore structure model is combined, so that the underground condition can be reflected more truly, and the shale reservoir can be evaluated more accurately. Meanwhile, each parameter in the adsorption model can be accurately solved, and the method has the characteristic of convenience in application.
Drawings
The invention is described in further detail below with reference to the following figures and embodiments:
fig. 1 is a flowchart of a method for calculating gas content of shale adsorbed gas based on a supercritical monolayer adsorption model.
Detailed Description
The invention will be further explained with reference to specific embodiments, without limiting the invention.
As shown in fig. 1, the present invention provides a method for calculating gas content of shale adsorbed gas based on a supercritical monolayer adsorption model, comprising the following steps:
s1: acquiring rock electricity experimental data, isothermal adsorption experimental data and nuclear magnetic experimental data of a rock core sample in advance, converting the excessive adsorption quantity in the circular tube hole model into absolute adsorption quantity by using the isothermal adsorption experimental data, and establishing a supercritical monomolecular layer adsorption model;
s2, determining parameters in the supercritical monolayer adsorption model, wherein the parameters comprise water saturation, a flooding coefficient α, a Langmuir pressure P of an air-liquid interface and a specific surface A of a microtubetubeAnd a maximum methane adsorption K per unit area of the gas-solid interface;
s3: performing error detection on the supercritical monolayer adsorption model, and if the supercritical monolayer adsorption model passes the error detection, executing S4;
s4: calculating the gas content of shale adsorption gas in the actual logging by using the supercritical monomolecular layer adsorption model,
wherein, S1 includes the following steps:
s11: the excess adsorption capacity obtained by using the isothermal adsorption experimental data is as follows:
wherein V is an excess adsorption amount in m3T; v' is the volume of the adsorption space in m3； VaIs the volume of the adsorption phase in m3；ρgIs gas phase density, in kg/m3(ii) a ρ (r) is the density distribution of the adsorption phase in the adsorption space,
the density of the adsorption phase is (V-V)a) And (3) the density of the medium phase is approximately equal to that of the gas phase, and the formula (1.1) is simplified to obtain a formula (1.2):
s12: the excess adsorption was investigated by the influence of the volume of the adsorption phase on the adsorption phase to give formula (1.3):
V＝Va(ρa-ρg).............................(1.3)
where ρ isaTo suckThe density of the adsorbed phase is equal to the absolute adsorption amount divided by the volume of the adsorbed phase, and therefore, formula (1.4) can be obtained by formula (1.3):
wherein, VabRepresents the absolute adsorption amount in m3/t；
S13: solving the gas phase density by adopting a P-R gas state equation:
wherein:m＝0.37464+1.54226w-0.26992w2(ii) a R is a molar gas constant of 8.3144J/(mol.K); a. b is the attraction coefficient and the repulsion coefficient respectively; t iscIs the critical temperature in K; pcIs the critical pressure in MPa; w is an eccentricity factor which is a substance characteristic constant for representing the eccentricity or non-sphericity of a substance molecule, the eccentricity factor of methane is generally 0.008,
s14: the adsorption phase density was calculated using the Dubinin formula:
wherein M is the gas molar mass, the unit is kg/mol, and M is 0.016 kg/mol; pc＝4.59MPa； TcThe adsorbed phase density was calculated to be about 0.375g/cm (-82.4 ℃ C.) when the temperature was 190.7K3，
S15: based on the calculation, the excess adsorption capacity in the adsorption model of the circular tube hole model is converted into the absolute adsorption capacity, and a new adsorption model is obtained:
wherein A istubeIs the specific surface of a microtube, and the unit is m2(ii)/g; k is the maximum methane adsorption capacity of the gas-solid interface in unit area and is m3T; p is reservoir pressure in MPa; pLIs Langmuir pressure, expressed in MPa, and represents half of the pressure corresponding to the maximum adsorption capacity; gamma-shaped*The maximum methane adsorption capacity in mmol/m per unit area of the gas-liquid interface2，Vab-d、Vab-mixAnd Vab-wAbsolute adsorption capacity under different water saturation conditions; sWIs the water saturation, SwonThe water saturation when the water molecules in the tubular pores reach monolayer adsorption;
the method for determining the parameters in the supercritical monolayer adsorption model in the step S2 is as follows:
s21 calculation of Water saturation and fill factor α
The flood coefficient is independent of logging response, is a parameter which only represents the ratio of the pore surface covered by a water film to the pore surface, is similar to coverage rate and is related to the distribution of fluid in pores, but the data is difficult to establish connection with logging data;
s22: calculating the Langmuir pressure P of the gas-liquid interface
The integral Langmuir pressure of the gas-liquid interface is in a positive correlation with the temperature, an exponential law is obeyed, the fitting R2 is 0.9995, the fitting effect is good, and the relational expression is as follows:
P*＝17.059e0.011T.........................(1.8)
wherein T is temperature in units of;
S23: calculating the specific surface A of the microtubetube
The storage space in the shale is divided into two types of circular tubes, the aperture of one type of circular tube is smaller than 6nm, the aperture of the other part of circular tube is larger than 6nm, the adsorption phase gas is only adsorbed in micropores smaller than 6nm, so the specific surface of the circular tube is only calculated, the calculation of the part needs to combine the nuclear magnetic resonance data of the sample and the aperture data calculated by using the isothermal adsorption curve, and the most probable aperture in the aperture data is used for determining the transverse relaxation time T corresponding to the peak value in the nuclear magnetic resonance data2Further obtain the aperture d and T2The distribution relationship is used to determine the T corresponding to the 6nm aperture2Cutoff value, nuclear magnetic T2Dividing the nuclear magnetic response into two parts, respectively using the nuclear magnetic response of the two parts as the response values of two circular tubes in the shale reservoir space model, respectively integrating to obtain the percentage of the total volume, calculating the total pore space volume by utilizing the porosity and the sample volume to further obtain the pore volume corresponding to each circular tube, and finally obtaining the specific surface A of the micro-circular tube smaller than 6nm by combining the volume and the pore diameter information obtained by calculationtubeThe method comprises the following steps:
obtaining transverse relaxation time T through nuclear magnetic experiment data and isothermal adsorption experiment data2Relationship to aperture d:
T2'＝0.38d...................................(1.9)
wherein, T2' is the transverse relaxation time corresponding to the aperture, with the unit of ms, after the corresponding aperture is calculated, the T is passed2Calculating the percentage of the pore volume occupied by the pore diameter by distribution to obtain a weighted average pore diameter, and setting the T corresponding to the 6nm pore diameter2Cutoff value of T2' (6), nuclear magnetic porosity less than 6nmAnd a porosity of greater than 6nmComprises the following steps:
wherein,is the porosity calculated by nuclear magnetic experimental data, and has the unit of percent,
the pore volume V' of less than 6nm is:
the cross section area S' corresponding to the aperture is as follows:
S'＝π·(dm/2)2............................(2.3)
the section perimeter C' corresponding to the aperture is:
C’＝π·dm...............................(2.4)
then the above formula, A, is combinedtubeExpressed as:
wherein, VSIs the sample volume in m3(ii) a m is the sample mass in g; dmIs the weighted average pore diameter in m;
s34: calculating the maximum methane adsorption K of the unit area of the gas-solid interface
Obtaining the maximum adsorption quantity of the sample by using isothermal adsorption experimental data obtained by laboratory measurement, obtaining the specific surface of the sample by using a formula (2.5), obtaining the maximum adsorption quantity K of methane in unit area of a gas-solid interface of the sample by using a formula (2.6),
wherein K is the maximum methane adsorption capacity of the unit area of the gas-solid interface and the unit is mmol/m2，VmaxThe maximum adsorption quantity of methane in the isothermal adsorption experiment is expressed in mmol/g;
s3: performing error detection on the supercritical monolayer adsorption model, and if the error detection is passed, executing S4;
the error detection method specifically comprises the following steps:
s31: calculating the gas content of shale adsorbed gas by using the supercritical monomolecular layer adsorption model;
s32: comparing the calculation result in the step S31 with isothermal adsorption data measured in a laboratory, if the error is within a preset acceptable range, passing the detection, and executing a step S4, if the error detection is not passed, indicating that the supercritical monolayer adsorption model is invalid in the detection area;
s4: and calculating the gas content of shale adsorbed gas actually measured by using the supercritical monomolecular layer adsorption model.
Wherein, S4 further includes a step of determining whether the actual logging data includes nuclear magnetic logging data, if so, calculating the shale adsorbed gas content according to the supercritical monolayer adsorption model (formula (1.7)) with the parameters in the supercritical monolayer adsorption model determined through S2, and if not, calculating the parameter a in S2 using formula (2.7)tubeThen calculating the gas content of shale adsorption gas by using the formula (1.7),
Atube＝-10.22TH/U+0.22U+37.23....................(2.7)
wherein TH is thorium content, U is uranium content, and TH/U is the ratio of thorium content to uranium content.
The microporosities in the shale are mainly organic microporosities which are mainly provided by organic matter kerogen, and in general, a certain positive correlation relationship exists between uranium elements and organic matter in a shale stratum, because the shale contains a large amount of organic matter, the stratum has high radioactivity and is higher than that of a general non-hydrocarbon source rock stratum, so that the uranium content and thorium-uranium ratio curves in natural gamma and gamma energy spectrum logging are commonly used in the exploration process to qualitatively identify the positions of the organic matter-rich shale reservoir stratum. As mentioned above, AtubeThere should be some correlation with the uranium content, thorium to uranium ratio, so when there is no nuclear magnetic log data, equation (2.7) can be used to calculate this parameter.
The traditional Langmuir adsorption model aiming at the gas-solid-liquid three-phase action of the slits and the round pipe holes does not consider the condition that the reservoir temperature is higher than the critical temperature of methane, in the condition, the excessive adsorption quantity and the absolute adsorption quantity have large deviation, and the difference of physical quantities before and after balance and the adsorption quantity are calculated by adopting a Kerbelon equation at each pressure point in the process of isothermal adsorption experimental data. Because the volume is assumed to be unchanged during calculation, and actually, an adsorption phase is formed on the surface of the adsorbate after the adsorbate adsorbs gas and occupies a certain volume, when adsorption is balanced, the volume of a gas phase is reduced, and the volume of the adsorption phase is still reduced as the gas phase during data processing, so that the volume of the gas phase is overestimated, the adsorption phase is underestimated, and the excess adsorption quantity and the absolute adsorption quantity have a certain difference. Therefore, to accurately calculate the adsorbed gas content, it is necessary to accurately convert the process adsorption amount into an absolute adsorption amount.
At the parameter microtube specific surface AtubeIt is generally not true that the conventional method uses empirical constants, i.e. a given value, which is obviously not true. In the invention, the specific surface A of the microtube is calculated by combining the nuclear magnetic resonance data of the shale sample and the aperture data obtained in the isothermal adsorption experimenttubeThus highlighting individual variability.
Claims (2)
1. A method for calculating gas content of shale adsorbed gas based on a supercritical monomolecular layer adsorption model is characterized by comprising the following steps:
s1: acquiring rock electricity experimental data, isothermal adsorption experimental data and nuclear magnetic experimental data of a rock core sample in advance, converting the excessive adsorption quantity in the circular tube hole model into absolute adsorption quantity by using the isothermal adsorption experimental data, and establishing a supercritical monomolecular layer adsorption model;
s2: determining parameters in the supercritical monolayer adsorption model, wherein the parameters comprise water saturation and coefficient of fullnessα Langmuir pressure P of gas-liquid interface, specific surface A of microtubetubeAnd a maximum methane adsorption K per unit area of the gas-solid interface;
s3: performing error detection on the supercritical monolayer adsorption model, and if the supercritical monolayer adsorption model passes the error detection, executing S4;
s4: calculating the gas content of shale adsorption gas in the actual logging by using the supercritical monomolecular layer adsorption model;
wherein, S1 includes the following steps:
s11: the excess adsorption capacity obtained by using the isothermal adsorption experimental data is as follows:
wherein V is an excess adsorption amount in m3T; v' is the volume of the adsorption space in m3；VaIs the volume of the adsorption phase in m3；ρgIs gas phase density, in kg/m3(ii) a ρ (r) is the density distribution of the adsorption phase in the adsorption space,
the density of the adsorption phase is (V-V)a) And (3) the density of the medium phase is approximately equal to that of the gas phase, and the formula (1.1) is simplified to obtain a formula (1.2):
s12: the influence of the volume of the adsorption phase on the adsorption phase gives the formula (1.3):
V＝Va(ρa-ρg)…………………..……(1.3)
where ρ isaThe adsorption phase density is equal to the absolute adsorption amount divided by the volume of the adsorption phase, and therefore, formula (1.4) can be obtained by formula (1.3):
wherein, VabRepresents the absolute adsorption amount in m3/t；
S13: solving the gas phase density by adopting a P-R gas state equation:
wherein:m＝0.37464+1.54226w-0.26992w2(ii) a R is a molar gas constant; a. b is the attraction coefficient and the repulsion coefficient respectively; t iscIs the critical temperature in K; pcIs the critical pressure in MPa; w is an eccentricity factor and is a substance characteristic constant for representing the eccentricity or non-sphericity of a substance molecule,
s14: the adsorption phase density was calculated using the Dubinin formula:
wherein M is the gas molar mass and the unit is kg/mol;
s15: based on the calculation, the excess adsorption capacity in the supercritical monomolecular layer adsorption model of the circular tube hole model is converted into the absolute adsorption capacity to obtain a new adsorption model:
wherein A istubeIs the specific surface of a microtube, and the unit is m2(ii)/g; k is the maximum methane adsorption capacity of the gas-solid interface in unit area and is m3T; p is reservoir pressure in MPa; pLIs Langmuir pressure, expressed in MPa, and represents half of the pressure corresponding to the maximum adsorption capacity; gamma-shaped*The maximum methane adsorption capacity in mmol/m per unit area of the gas-liquid interface2，Vab-d、Vab-mixAnd Vab-wAbsolute adsorption capacity under different water saturation conditions; sWIs the water saturation, SwonIs the water saturation when the water molecules in the tubular pores reach monolayer adsorptionDegree;
the method for determining the parameters in the supercritical monolayer adsorption model in the step S2 is as follows:
s21 calculation of Water saturation and fill factor α
The flood coefficient α is an approximation of the water saturation, wherein the water saturation is calculated using petro-electric experimental data;
s22: calculating the Langmuir pressure P of the gas-liquid interface
The Langmuir pressure P at the gas-liquid interface is related to the temperature T as follows:
P*＝17.059e0.011T………·……………(1.8)
wherein T has the unit of;
s23: calculating the specific surface A of the microtubetube
Obtaining transverse relaxation time T through nuclear magnetic experiment data and isothermal adsorption experiment data2Relationship to aperture d:
T2'＝0.38d……………………··………(1.9)
wherein, T'2The transverse relaxation time corresponding to the aperture is in ms, and after the corresponding aperture is calculated, T is passed2Calculating the percentage of the pore volume occupied by the pore diameter by distribution to obtain a weighted average pore diameter, and setting the T corresponding to the 6nm pore diameter2The cut-off value is T'2(6) Nuclear magnetic porosity of less than 6nmAnd a porosity of greater than 6nmComprises the following steps:
wherein,is the porosity calculated by nuclear magnetic experimental data, and has the unit of percent,
the pore volume V' of less than 6nm is:
the cross section area S' corresponding to the aperture is as follows:
S'＝π·(dm/2)2…………………·……(2.3)
the section perimeter C' corresponding to the aperture is:
C’＝π·dm…………………………·(2.4)
then the above formula, A, is combinedtubeExpressed as:
wherein, VSIs the sample volume in m3(ii) a m is the sample mass in g; dmIs the weighted average pore diameter in m;
s34: calculating the maximum methane adsorption K of the unit area of the gas-solid interface
Obtaining the maximum adsorption quantity of the sample by using isothermal adsorption experimental data obtained by laboratory measurement, obtaining the specific surface of the sample by using a formula (2.5), obtaining the maximum adsorption quantity K of methane in unit area of a gas-solid interface of the sample by using a formula (2.6),
wherein the unit of K is mmol/m2，VmaxThe maximum adsorption quantity of methane in the isothermal adsorption experiment is expressed in mmol/g;
s4 further comprises the step of judging whether the actual logging data contain nuclear magnetic logging data, if yes, the supercritical monomolecular layer adsorption model is determined according to the step S2Calculating the gas content of shale adsorption gas by using a supercritical monomolecular layer adsorption model (formula (1.7)) of the parameters, and if the gas content of the shale adsorption gas is not included, calculating the parameter A in S2 by using the formula (2.7)tubeThen calculating the gas content of shale adsorption gas by using the formula (1.7),
Atube＝-10.22TH/U+0.22U+37.23………..………(2.7)
wherein TH is thorium content, U is uranium content, and TH/U is the ratio of thorium content to uranium content.
2. The method for calculating the gas content of shale adsorption gas based on the supercritical monolayer adsorption model according to claim 1, wherein:
the method for performing error detection on the supercritical monolayer adsorption model in the S3 specifically includes:
s31: calculating the gas content of shale adsorbed gas by using the supercritical monomolecular layer adsorption model;
s32: comparing the calculation result in the step S31 with the isothermal adsorption data measured in the laboratory, if the error is within a preset acceptable range, passing the detection, and performing a step S4, if the error is not passed, indicating that the supercritical monolayer adsorption model is invalid in the detection area.
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