CN105277464B - Recover the method for shale air content - Google Patents
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- CN105277464B CN105277464B CN201510699029.8A CN201510699029A CN105277464B CN 105277464 B CN105277464 B CN 105277464B CN 201510699029 A CN201510699029 A CN 201510699029A CN 105277464 B CN105277464 B CN 105277464B
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- 238000000034 method Methods 0.000 title claims abstract description 47
- 238000001179 sorption measurement Methods 0.000 claims abstract description 114
- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical compound C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 claims abstract description 96
- 238000012360 testing method Methods 0.000 claims abstract description 20
- 230000015572 biosynthetic process Effects 0.000 claims abstract description 14
- 239000011148 porous material Substances 0.000 claims abstract description 11
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 5
- 238000004458 analytical method Methods 0.000 claims description 54
- 238000003795 desorption Methods 0.000 claims description 20
- 239000007788 liquid Substances 0.000 claims description 8
- 229920006395 saturated elastomer Polymers 0.000 claims description 5
- 238000006467 substitution reaction Methods 0.000 claims description 3
- 239000000203 mixture Substances 0.000 claims description 2
- 229920000642 polymer Polymers 0.000 claims description 2
- CREMABGTGYGIQB-UHFFFAOYSA-N carbon carbon Chemical compound C.C CREMABGTGYGIQB-UHFFFAOYSA-N 0.000 claims 1
- 239000006185 dispersion Substances 0.000 abstract description 4
- 238000005381 potential energy Methods 0.000 abstract description 3
- 238000010521 absorption reaction Methods 0.000 abstract 3
- 230000003993 interaction Effects 0.000 abstract 1
- 239000011435 rock Substances 0.000 abstract 1
- 239000007789 gas Substances 0.000 description 146
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 14
- 229910002092 carbon dioxide Inorganic materials 0.000 description 8
- 229910052757 nitrogen Inorganic materials 0.000 description 6
- 229910001873 dinitrogen Inorganic materials 0.000 description 5
- 238000011084 recovery Methods 0.000 description 5
- 238000011161 development Methods 0.000 description 4
- 230000002349 favourable effect Effects 0.000 description 4
- 238000005259 measurement Methods 0.000 description 4
- CURLTUGMZLYLDI-UHFFFAOYSA-N Carbon dioxide Chemical compound O=C=O CURLTUGMZLYLDI-UHFFFAOYSA-N 0.000 description 3
- 238000004364 calculation method Methods 0.000 description 3
- 239000003245 coal Substances 0.000 description 3
- 230000036982 action potential Effects 0.000 description 2
- 239000001569 carbon dioxide Substances 0.000 description 2
- 238000006243 chemical reaction Methods 0.000 description 2
- 238000011156 evaluation Methods 0.000 description 2
- 230000007547 defect Effects 0.000 description 1
- 238000005553 drilling Methods 0.000 description 1
- 238000004836 empirical method Methods 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 238000004868 gas analysis Methods 0.000 description 1
- 238000004817 gas chromatography Methods 0.000 description 1
- 238000005065 mining Methods 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- QJGQUHMNIGDVPM-UHFFFAOYSA-N nitrogen(.) Chemical compound [N] QJGQUHMNIGDVPM-UHFFFAOYSA-N 0.000 description 1
- 238000010998 test method Methods 0.000 description 1
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Abstract
The present invention provides a kind of method for recovering shale air content, this method recovers the original air content of mud shale by adsorbing air content and pore volume air content, wherein, the absorption air content is recovered using Polanyi absorption potentials, London dispersion interactions potential energy theory and the equation of gas state as theoretical foundation, with reference to rock core cylinder methane adsorption isothermal curve, the test data of gas component, shale porosity and water saturation, change to obtain by absorption air content of the gas between formation temperature and 95 DEG C of resolvings；The pore volume air content is recovered to obtain by state equation using porosity, the test data of water saturation.The air content restoration methods theoretical foundation is more perfect, and can recover the original amount of each gas component of mud shale, is advantageous to mineability that is more accurate, objective, comprehensively assessing shale gas reservoir.
Description
Technical Field
The invention relates to an unconventional oil and gas exploration and development technology, in particular to a method for recovering shale gas content.
Background
Shale gas is a popular unconventional oil and gas resource nowadays, so the development of shale is crucial to the acquisition of shale gas resources. Before shale development, in order to avoid economic loss of exploration and development or loss of recoverable resources, evaluation is generally required to be carried out on shale, and the gas content of the shale is an important reference index for evaluating the potential of shale gas resources and predicting favorable areas, so that accurate total gas content of the shale can provide a reliable basis for resource potential evaluation and favorable area prediction.
At present, the total gas content of shale gas is obtained by adding a lost gas amount and a gas analysis amount, and the shale gas lost amount estimation method mainly adopts a USBM method adopted by the United states mining agency for coal seam gas loss estimation and a plurality of fitting formulas derived on the basis of the USBM method to estimate the gas lost amount of the shale gas. According to the USBM method, at the initial stage of desorption, the accumulated analysis gas content and the secondary evolution of the analysis time are in a linear relationship, the analysis gas amount data at the initial time is extrapolated to zero time, and the lost gas is recovered by a least square method or a graphical method. Because the depth of the shale layer is far greater than the depth of the coal bed, the shale layer has great difference with the coal bed in the aspects of coring mode, drilling mud and the like, so that the popularization of the method has many problems in the recovery of the shale gas loss amount, and the practice proves that the USBM method and various derived fitting formulas are inaccurate under the condition of long loss time. Meanwhile, the USBM method is established on the basis of various assumed conditions, and the USBM method also belongs to a semi-empirical method, and the principle is not perfect.
Disclosure of Invention
The invention provides a method for recovering shale gas content, which overcomes the defect of inaccurate recovery of shale gas content caused by overlarge theoretical basic deviation of shale gas content recovery in the prior art.
The invention provides a method for recovering gas content of shale, which comprises the following steps:
1) from a pressure of P0Temperature of T1Taking shale from the formation of (A) at a temperature T1And normal pressure P1Performing first analysis on the obtained shale until no gas is generated, and collecting first analysis gas;
2) at a temperature T2And normal pressure P1Secondly resolving the shale subjected to the first resolving until no gas is generated, collecting the second resolving gas and obtaining the volume V of the second resolving gas under the standard condition2Wherein, T2Is 95 ℃;
3) mixing the first analytic gas and the second analytic gas to obtain a mixed gas containing methane, and analyzing the mixed gas to obtain the volume percentage content a of each component in the mixed gasi；
4) Obtaining the adsorption gas content V of each component in the second analysis gas under the standard condition according to the formula 12i，
Formula 1
In the formula 1, V0Is the volume of the shale, q is the porosity of the shale, w is the moisture content of the shale;
5) obtaining the gas content V of each gas component in the shale under the standard condition from the stratum to the second analysis after the second analysis is finished according to the formula 21i，
Formula 2
In the formula 2, Vi0The test adsorption volume, V, corresponding to the adsorption potential of the ith component gas at the formation leveli1Is the test adsorption volume, V, corresponding to the adsorption potential of the ith gas component at the first desorptioni2A test adsorption volume corresponding to the adsorption potential of the ith gas component at the second desorption;
6) obtaining the gas content V under the standard condition generated by gas expansion in the pore volume after the shale is completely decomposed from the stratum to the second analysis according to the formula 3p，
Formula 3
The gas content of the shale is the gas content V absorbed by each gas component in the shale1iAnd gas content VpThe sum of (a) and (b).
The shale gas content recovered by the method is the total gas content of the shale in the process calculated after the shale is analyzed from the stratum layer to the second analysis end.
Because the shale generally takes tens of hours from the stratum to the process of taking out the shale to the ground, the volume of the gas released by the shale in the process of taking out the shale cannot be collected and measured, the shale after taking out the stratum is analyzed twice under the condition of set temperature and pressure, the volume of the gas generated by the shale in the process of analyzing twice can be accurately measured, and therefore the total volume of the gas released by the shale from the stratum to the second analysis is calculated by utilizing the gas volume which can be accurately measured and the Polanyi adsorption potential theory.
In the second analysis, the total volume of the gas released by the shale includes the change of the gas content adsorbed by the shale in the process and the change of the gas in the pore volume of the shale, specifically, the second analysis is an isobaric temperature change process, so that formula 1 is obtained by using a gas state equation PV ═ nRT and the percentage content of each component in the gas, and the adsorption content of each component gas generated by the shale in the second analysis is calculated by using formula 1.
The formula 2 in the step 5) of the present invention is obtained by combining the adsorption content of each component gas generated in the second desorption of shale with the adsorption potential of Polanyi. Namely, the adsorption gas content of each component gas generated after shale passes from the stratum to the second analysis is obtained according to the adsorption content of each component gas generated by the shale in the second analysis by adopting the adsorption potential theory.
Because the shale is in the temperature and pressure changing process after the second analysis from the stratum, the formula 3 in the step 6) of the invention can be obtained by using the gas state equation, and the variable quantity of the gas generated in the pore volume after the second analysis from the stratum of the shale is finished is calculated by using the formula 3.
And adding the sum of the adsorption contents of the gas components generated in the process from the stratum to the second analysis end of the shale and the variation of the gas generated in the pore volume from the stratum to the second analysis end of the shale, and finally obtaining the total gas content of the shale from the stratum to the second analysis end.
In order to express the gas content of shale more objectively, the gas volumes in the invention are unified into the gas volume under the standard condition, namely the gas volume under the pressure of 101325Pa and the temperature of 0 ℃, and when the calculation is carried into the equation, the temperature is the thermodynamic temperature, the unit is K, and the pressure unit is Pa. Specifically, the volume of the gas under standard conditions can be calculated according to equation 7.
Formula 7
Wherein, VComputingIs a gas in PComputingAnd TComputingThe gas volume below. It should be noted here that the temperature of the shale during the analysis is not consistent with the temperature of the collected gasTaking the second analysis as an example, the shale is at the temperature T2And normal pressure P1Is performed in a second analysis chamber, but the environment in which the gas is collected, i.e. the environment in which the gas volume is read, is at the field temperature T3And the field pressure P3The gas to be analyzed is collected outside the analysis tank and read, so that P in the above formulaComputingAnd TComputingIs to collect and read out VComputingPressure P of the environment3And temperature T3。
In the measuring method, the total gas amount generated by the shale is divided into two parts, one part is the variable quantity generated after the second analysis of the adsorbed gas of the shale from the stratum layer, and the other part is the variable quantity generated after the second analysis of the gas in the pore volume of the shale from the stratum layer. The volume of gas released from the shale in the process from the stratum to the ground is not collected and measured, so that the shale after the stratum is taken out is analyzed twice under the set temperature and pressure, the volume of the gas released from the shale in the process of the two times of analysis can be accurately measured, and the gas content of the shale is finally obtained by utilizing the data which can be accurately measured twice and combining the Polanyi adsorption potential and the gas state equation potential.
Further, an adsorption characteristic curve of the ith gas component is obtained from the adsorption characteristic curve of methane and equation 4, and the V is obtained from the adsorption characteristic curve of the ith gas component and equation 5i0、Vi1And Vi2，
Formula 4
Formula 5
In the formula 4, the first step is,ifor the ith gas component at a temperature T and a pressure PAt willThe adsorption potential of the mixture during the process,methaneFor methane at a temperature T and a pressure PAt willAdsorption potential of time, VmiIs the liquid molar volume, V, of the ith gas componentm methaneIs the molar volume of liquid methane.
Wherein the adsorption characteristic curve is a V (volume) - (adsorption potential) curve. In the application process, the adsorption characteristic curve of the ith gas component is drawn by using N2For example, the following steps are carried out: first, the density of the liquid methane was 426kg/m3The density of the liquid nitrogen is 808kg/m3Respectively removing the molar mass to obtain the molar volume V of the liquid methanem methane＝0.037558685m3Obtaining the molar volume V of liquid nitrogenm nitrogen gas＝0.034653465m3(ii) a Then, n points with specific test number are obtained according to the adsorption characteristic curve of the methane, and n points can be obtainedMethaneAnd corresponding n numbers of VMethane(ii) a Finally, n are addedMethaneCarry over to n in formula 4Nitrogen gasThen according to nNitrogen gasCorresponding to n number of VMethaneThe adsorption characteristic curve of nitrogen is plotted. Wherein n is more than or equal to 13 in order to ensure the accuracy of the adsorption characteristic curve.
It is to be noted that the adsorption characteristic curve of the i-th gas component of the present invention is converted from the adsorption characteristic of methane, and the conversion principle, i.e., formula 4, is obtained from the London dispersion potential.
Also with N2For example, calculate Vi0While, the formation temperature T1Formation pressure P0And nitrogen at T1The adsorption potential of nitrogen at the stratum position can be obtained in the pressure-pressing type 5 of the saturated steam, then the test adsorption volume corresponding to the adsorption potential under the condition is found on the adsorption characteristic curve of the nitrogen, and similarly, the test adsorption volume V corresponding to the adsorption potential of the nitrogen in the first analysis can be obtained according to the methodi1And a test adsorption volume V corresponding to the adsorption potential at the second resolutioni2。
Further, the adsorption characteristic curve of methane is obtained according to the isothermal adsorption curve of methane to the shale and the formula 6,
formula 6
In the formula (6), the first and second polymers,methaneFor methane at a temperature T and a pressure PAt willAdsorption potential of PSaturation ofIs the saturated vapor pressure of methane at the temperature T.
Wherein methane is isothermal with respect to shale (the present invention does not limit the test temperature, and formation temperature T may generally be selected1) The adsorption curve is a P (pressure) -V (volume) curve. In the application process, the method for drawing the adsorption characteristic curve of the methane comprises the following steps: firstly, the methane is passed through m test points on the isothermal adsorption curve of methane, namely, m PAt willAnd VAt will(ii) a Then, m P are addedAt willIn formula 6, T in formula 6 is the test temperature, PSaturation ofThe saturated vapor pressure of methane at the test temperature is used to obtain mMethane(ii) a Finally, according to mMethaneCorresponding to m number of VAt willThe adsorption characteristics of methane are plotted. Wherein m is more than or equal to 13 in order to ensure the accuracy of the adsorption characteristic curve.
In the invention, the isothermal adsorption curve of methane to shale is a P (pressure) -V (volume) curve which is drawn according to m (P-V) points measured by an isothermal adsorption test method of a volume method or a mass method. Therefore, when the adsorption characteristic curve of methane is plotted, the m (P-V) points can be used.
The software for drawing the adsorption characteristic curve of each component is not limited, and MATLAB is used as the software for drawing.
According to the method for recovering the gas content of the shale, the shale gas is divided into two parts, namely the adsorption gas content of different components in the shale gas and the gas content of the pore volume, the gas content of the shale is finally reduced through a Polanyi adsorption potential theory, a London dispersion action potential energy theory, a gas state equation and truly measurable data, uncertainty caused by a semi-empirical formula in measurement of the gas content of the shale is avoided, the measurement of the gas content of the shale gas is established on the basis of a real background of mass conservation, and the theoretical basis is more perfect. Meanwhile, the recovery method of the invention considers the characteristics of different component gases, thereby not only avoiding the irrationality of unified calculation of different component gases, but also determining the content of effective component methane in the shale gas, and providing an objective reference basis for the resource potential of shale and the prediction of a favorable area.
Drawings
FIG. 1 shows CH in an embodiment of the present invention4Isothermal (30 ℃) adsorption curves for shale;
FIG. 2 shows CH in an embodiment of the present invention4Adsorption characteristic curve of (1);
FIG. 3 shows an embodiment of the present invention N2Adsorption characteristic curve of (1);
FIG. 4 is a CO of an embodiment of the present invention2Adsorption characteristic curve of (1).
Detailed Description
Examples
The embodiment is directed at the shale of southeast yu and carries out shale gas content measurement, and includes the following steps:
1) first analysis: from pressure P07100751.744Pa, temperature T1Taking shale from a stratum at 30 ℃, putting the shale in an analysis box for first analysis, and setting the pressure P of the analysis box1＝99665Pa (normal pressure)) Temperature T1Collecting first desorption gas until no gas is generated at 30 ℃;
2) second analysis: setting temperature T of analysis box2At 95 deg.C under pressure P1The shale subjected to the first desorption was subjected to the second desorption until no gas was generated (99665 Pa), and 31mL of the second desorption gas (the ambient pressure P of the collected gas) was collected3＝99665Pa，T312 deg.C), the volume of the second desorption gas in the standard condition was 29.2089cm as obtained by equation 73，
Formula 7
Wherein, VComputing＝31cm3，PComputing＝99665Pa，TComputing＝(12+273.15)＝285.15K；
3) Mixing the first desorption gas and the second desorption gas to obtain a mixed gas containing methane, and analyzing the mixed gas by using a gas chromatography to obtain the mixed gas mainly containing CH492.0150952％，N24.3717564％，CO23.6131484％。；
4) The volume of the shale of the embodiment is 786.63896cm when the analyzed shale is measured by a He porosity method3Porosity 2.71%, percent water content 15.3% (water saturation data from depth ± 0.0625m on the well interpretation curve).
According to the formula 1, the process is carried out,
formula 1
Obtaining CH in the second analytic gas4Adsorbed gas content V under standard conditions2i＝24.27695436cm3，N2Adsorbed gas content V under standard conditions2i＝0.953280966cm3，CO2Adsorbed gas content V under standard conditions2i＝1.153429558cm3。
In the formula 1, V2＝29.2089cm3，T1＝303.15K，T2＝368.15K，P1＝99665Pa。
5) About CH4、N2、CO2The adsorbed gas content V under the standard condition from the formation to the end of the second analysis1iAnd (4) calculating.
For CH4：
FIG. 1 is CH in an exemplary embodiment of the present invention4Isothermal (30 ℃) adsorption curves for shale. In fig. 1, 16 (P-V) points of the test (see table 1 below) were used, and the pressure data for the 16 points was taken into 6,
formula 6
Wherein, R is 8.314J/mol/K, T is (273.15+30) K, CH4P at 30 ℃Saturation of118955626.1Pa, 16 correspondences were obtained by calculationMethane(see Table 1 below), based on 16 (V-)Methane) Plotting CH4FIG. 2 is CH of an example of the present invention4Adsorption characteristic curve of (1).
According to formula 5, CH is obtained4Adsorption potential at formation horizoni07.103842385kJ/mol, adsorption potential at the first analysisi117.85617861kJ/mol and adsorption potential at the second analysisi2＝23.84523157kJ/mol，
Formula 5
Wherein R is 8.314J/mol/K, calculatingi0When T is (30+273.15) K, PAt will＝7100751.744Pa，PSaturation of(30 ℃ C.) 118955626.1 Pa; computingi1When T is (30+273.15) K, PAt will＝99665Pa，PSaturation of(30 ℃ C.) 118955626.1 Pa; computingi2When T is (95+273.15) K, PAt will＝99665Pa，PSaturation of(95℃)＝240948730.1Pa。
In CH4Finding the adsorption characteristic curves ofi0、i1Andi2corresponding Vi0、Vi1And Vi2Then, the second desorption gas is treated with CH4Adsorbed gas content V under standard conditions2i＝24.27695436cm3In the formula 2, obtaining CH in shale4The adsorbed gas content V under the standard condition from the stratum to the end of the second analysis1iIs 1198.634446cm3
Formula 2
TABLE 1 CH4P-V-corresponding table of
| P/Pa | V/mL/g | ε/kJ/mol | |
| 1 | 497370 | 0.085253486 | 13.80460359 |
| 2 | 997690 | 0.157478579 | 12.05013959 |
| 3 | 2006580 | 0.276784838 | 10.28903169 |
| 4 | 3008740 | 0.368973954 | 9.268048261 |
| 5 | 4000350 | 0.438711297 | 8.550089036 |
| 6 | 6007760 | 0.548348252 | 7.525122124 |
| 7 | 7999520 | 0.625451639 | 6.803460189 |
| 8 | 9993440 | 0.681440624 | 6.242554305 |
| 9 | 12994210 | 0.746515673 | 5.580763147 |
| 10 | 14992660 | 0.777594849 | 5.22020416 |
| 11 | 19005210 | 0.825542862 | 4.622487826 |
| 12 | 22001260 | 0.853601255 | 4.253536705 |
| 13 | 24993480 | 0.87519557 | 3.932148617 |
| 14 | 28992510 | 0.898992461 | 3.558066091 |
| 15 | 32004300 | 0.912945995 | 3.30896911 |
| 16 | 34995490 | 0.925716947 | 3.083775048 |
For N2：
Formula 4
Wherein,
16 in Table 1MethaneIn formula 4, 16 correspondences are obtainedNitrogen gas(see Table 2 below), 16 will be calculatedNitrogen gasCorresponding to 16V in Table 1, N is plotted2FIG. 3 is N of an example of the present invention2Adsorption characteristic curve of (1).
According to formula 5, N is obtained2Adsorption potential at formation horizoni06.515046199kJ/mol, adsorption potential at the first analysisi117.26738242kJ/mol and adsorption potential at the second analysisi2＝22.23513894kJ/mol，
Formula 5
Wherein R is 8.314J/mol/K, calculatingi0When T is (30+273.15) K, PAt will＝7100751.744Pa，PSaturation of(30℃)＝94173358.6567508Pa；Computingi1When T is (30+273.15) K, PAt will＝99665Pa，PSaturation of(30 ℃ C.) 94173358.6567508 Pa; computingi2When T is (95+273.15) K, PAt will＝99665Pa，PSaturation of(95℃)＝142386826.245744Pa。
In N2Finding the adsorption characteristic curves ofi0、i1Andi2corresponding Vi0、Vi1And Vi2Then N in the second desorption gas2Adsorbed gas content V under standard conditions2i＝0.953280966cm3In the formula 2, N in shale is obtained2The adsorbed gas content V under the standard condition from the stratum to the end of the second analysis1iIs 43.93983546cm3
Formula 2
TABLE 2N2Adsorption characteristic curve V-corresponding table
| V/mL | ε/kJ/mol | |
| 1 | 0.085253486 | 12.73612727 |
| 2 | 0.157478579 | 11.11745879 |
| 3 | 0.276784838 | 9.492660636 |
| 4 | 0.368973954 | 8.550701326 |
| 5 | 0.438711297 | 7.888312144 |
| 6 | 0.548348252 | 6.942677672 |
| 7 | 0.625451639 | 6.276872371 |
| 8 | 0.681440624 | 5.759380602 |
| 9 | 0.746515673 | 5.14881208 |
| 10 | 0.777594849 | 4.816160358 |
| 11 | 0.825542862 | 4.264707268 |
| 12 | 0.853601255 | 3.924312964 |
| 13 | 0.87519557 | 3.627800314 |
| 14 | 0.898992461 | 3.282671775 |
| 15 | 0.912945995 | 3.052854901 |
| 16 | 0.925716947 | 2.845090859 |
For CO2：
Formula 4
Wherein,
16 in Table 1MethaneIn formula 4, 16 are obtainedCorresponding toCarbon dioxide(see Table 3 below), 16 will be calculatedCarbon dioxideCorresponding to 16V in Table 1, CO is plotted2FIG. 4 is a CO adsorption characteristic curve of an example of the present invention2Adsorption characteristic curve of (1).
According to formula 5, CO is obtained2Adsorption potential at formation horizoni03.555438835kJ/mol, adsorption potential at the first analysisi114.30777505kJ/mol and adsorption potential at the second analysisi2＝22.79913562kJ/mol，
Formula 5
Wherein R is 8.314J/mol/K, calculatingi0When T is (30+273.15) K, PAt will＝7100751.744Pa，PSaturation of(30 ℃ C.) 29103873.35 Pa; computingi1When T is (30+273.15) K, PAt will＝99665Pa，PSaturation of(30 ℃ C.) 29103873.35 Pa; computingi2When T is (95+273.15) K, PAt will＝99665Pa，PSaturation of(95℃)＝171196497Pa。
In CO2Finding the adsorption characteristic curves ofi0、i1Andi2corresponding Vi0、Vi1And Vi2Then, the CO in the second desorption gas is introduced2Adsorbed gas content V under standard conditions2i＝1.153429558cm3Carrying out the reaction in a formula 2 to obtain CO in the shale2The adsorbed gas content V under the standard condition from the stratum to the end of the second analysis1iIs 2.406723147cm3
Formula 2
TABLE 3 CO2Adsorption characteristic curve V-corresponding table
| V/mL | ε/kJ/mol | |
| 1 | 0.085253486 | 27.11638284 |
| 2 | 0.157478579 | 23.6700892 |
| 3 | 0.276784838 | 20.21074495 |
| 4 | 0.368973954 | 18.2052272 |
| 5 | 0.438711297 | 16.79493989 |
| 6 | 0.548348252 | 14.78159739 |
| 7 | 0.625451639 | 13.36403685 |
| 8 | 0.681440624 | 12.26224942 |
| 9 | 0.746515673 | 10.96229305 |
| 10 | 0.777594849 | 10.25404703 |
| 11 | 0.825542862 | 9.079952837 |
| 12 | 0.853601255 | 8.355222149 |
| 13 | 0.87519557 | 7.723919529 |
| 14 | 0.898992461 | 6.989109222 |
| 15 | 0.912945995 | 6.499808023 |
| 16 | 0.925716947 | 6.057459326 |
6) Obtaining the gas content V under the standard condition generated by gas expansion in the pore volume after the shale from the stratum to the second analysis is finished according to the formula 3p＝1126.966038cm3，
Formula 3
Wherein, P0＝7100751.744Pa，P1＝99665Pa，T2＝368.15K，T1＝303.15K。
Therefore, in this embodiment, the shale gas content V is equal to the gas content V absorbed by each gas component1i+ gas content Vp＝1198.634446+43.93983546+2.406723147+1126.966038＝2371.947043(cm3)
According to the method for recovering the gas content of the shale, the shale gas is divided into two parts, namely the adsorption gas content of different components in the shale gas and the gas content of a pore volume, the gas content of the shale is finally reduced through a Polanyi adsorption potential theory, a London dispersion action potential energy theory, a gas state equation and truly measurable data, the uncertainty caused by a semi-empirical formula in the measurement of the gas content of the shale is avoided, the recovery of the gas content of the shale gas is built on the basis of a real background of mass conservation, the theoretical basis is more perfect, and an objective reference basis is provided for the resource potential of the shale and the prediction of a favorable area.
Finally, it should be noted that: the above embodiments are only used to illustrate the technical solution of the present invention, and not to limit the same; while the invention has been described in detail and with reference to the foregoing embodiments, it will be understood by those skilled in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some or all of the technical features may be equivalently replaced; and the modifications or the substitutions do not make the essence of the corresponding technical solutions depart from the scope of the technical solutions of the embodiments of the present invention.
Claims (3)
1. A method for recovering gas content of shale is characterized by comprising the following steps:
1) from a pressure of P0Temperature of T1Taking shale from the formation of (A) at a temperature T1And normal pressure P1Performing first analysis on the obtained shale until no gas is generated, and collecting first analysis gas;
2) at a temperature T2And normal pressure P1Secondly resolving the shale subjected to the first resolving until no gas is generated, collecting the second resolving gas and obtaining the second resolving gas under the standard conditionVolume V2Wherein, T2Is 95 ℃;
3) mixing the first analytic gas and the second analytic gas to obtain a mixed gas containing methane, and analyzing the mixed gas to obtain the volume percentage content a of each component in the mixed gasi；
4) Obtaining the adsorption gas content V of each component in the second analysis gas under the standard condition according to the formula 12i，
In the formula 1, V0Is the volume of the shale, q is the porosity of the shale, w is the water content of the shale;
5) obtaining the gas content V of each gas component in the shale under the standard condition from the stratum to the second analysis after the second analysis is finished according to the formula 21i，
In the formula 2, Vi0A test adsorption volume, V, corresponding to the adsorption potential of the ith gas component at the formation leveli1Is the test adsorption volume, V, corresponding to the adsorption potential of the ith gas component at the first desorptioni2A test adsorption volume corresponding to the adsorption potential of the ith gas component at the second desorption;
6) obtaining the gas content V under the standard condition generated by gas expansion in the pore volume after the shale is completely decomposed from the stratum to the second analysis according to the formula 3p，
The gas content of the shale is the gas content V absorbed by each gas component in the shale1iSum and gas content VpThe sum of (a) and (b).
2. According to the claimsThe method for recovering the shale gas content in the solution 1 is characterized in that the adsorption characteristic curve of the ith gas component is obtained according to the adsorption characteristic curve of methane and the formula 4, and the V is obtained according to the adsorption characteristic curve of the ith gas component and the formula 5i0、Vi1And Vi2，
In the formula 4, the first step is,ifor the ith gas component at a temperature T and a pressure PAt willThe adsorption potential of the mixture during the process,methaneFor methane at a temperature T and a pressure PAt willAdsorption potential of time, VmiIs the liquid molar volume, V, of the ith gas componentm methaneIs the molar volume of liquid methane, in formula 5, PSaturation ofIs the saturated vapor pressure of the ith gas component at the temperature T;
the adsorption characteristic curve of the methane is V of the methane gasMethane-MethaneA curve showing an adsorption characteristic of the ith gas component as VMethane-iA curve;
the obtaining of the adsorption characteristic curve of the ith gas component from the adsorption characteristic curve of methane and equation 4 includes: obtaining n pieces of methane according to the adsorption characteristic curve of the methaneMethaneAnd VMethaneN is to be providedMethaneAndsubstitution into formula 4 to obtain niAccording to n number ofiAnd n number of VMethaneObtaining the adsorption characteristic curve of the ith gas component, wherein n is more than or equal to 13;
the V is obtained from the adsorption characteristic curve of the ith gas component and formula 5i0、Vi1And Vi2The method comprises the following steps: respectively measure the formation temperature T1Formation pressure P0And the ith gas component is at T1P of (1)Saturation ofIn substitution 5, the adsorption potential of the ith gas component at the formation level is obtainediAdsorption potential of the ith gas component at formation leveliObtaining the adsorption potential of the ith gas component at the stratum level according to the adsorption characteristic curve of the ith gas componentiCorresponding test adsorption volume Vi0；
Respectively will be at temperature T1Pressure P1And the ith gas component is at T1P of (1)Saturation ofSubstituting in formula 5 to obtain the adsorption potential of the ith gas component at the first desorptioniThe adsorption potential of the ith gas component at the first desorptioniObtaining the adsorption potential of the ith component gas in the first analysis according to the adsorption characteristic curve of the ith gas componentiCorresponding test adsorption volume Vi1；
Respectively will be at temperature T2Pressure P1And the ith gas component is at T2P of (1)Saturation ofSubstituting in formula 5 to obtain the adsorption potential of the ith gas component at the second desorptioniThe adsorption potential of the ith gas component at the second desorptioniObtaining the adsorption potential of the ith component gas in the second analysis according to the adsorption characteristic curve of the ith gas componentiCorresponding test adsorption volume Vi2。
3. The method for recovering the gas content in the shale according to claim 2, wherein the adsorption characteristic curve of the methane is obtained according to an isothermal adsorption curve of the methane to the shale and formula 6,
in the formula (6), the first and second polymers,methaneFor methane at a temperature T and a pressure PAt willAdsorption potential of PSaturation ofIs the saturated vapor pressure of methane at the temperature T.
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| CN106290057B (en) * | 2016-07-26 | 2018-12-04 | 中国石油大学(北京) | The measuring method of shale absorption tolerance |
| CN106370260B (en) * | 2016-08-16 | 2019-02-15 | 中国石油天然气股份有限公司 | Method for measuring gas loss in shale gas content test |
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