CN105277464A - Method for recovering gas content of shale - Google Patents

Abstract

The invention provides a method for recovering gas content of shale. According to the method, the original gas content of the shale is recovered according to adsorption gas content and pore volume gas content, wherein on the theoretical bases of Polanyi adsorption potential, the London chromatic dispersion interaction potential energy theory and a gas state equation in combination of a core column methane isothermal adsorption curve, test data of gas components as well as porosity and water saturation of the shale, recovery of the adsorption gas content is acquired through adsorption gas content change of gas at the formation temperature and at the temperature of 95 DEG C in the analytical process and; recovery of the pore volume gas content is acquired by adopting test data of the porosity and the water saturation through the state equation. According to the method for recovering the gas content of the shale, the theoretical bases are further perfected, the original content of each gas component of the shale can be recovered, and mineability of a shale gas reservoir can be evaluated more accurately, more objectively and more comprehensively.

Description

Recover the method for shale air content

Technical field

The present invention relates to unconventionaloil pool exploratory development technology, particularly relate to a kind of method recovering shale air content.

Background technology

Shale gas is current popular unconventional petroleum resources, and therefore the exploitation of shale is most important for the acquisition of shale gas resource.Before shale exploitation, in order to avoid the economic loss of exploratory development or the loss of mining resources, usually need to evaluate shale, and the air content of shale evaluates the important references index of shale gas resource potential and prediction Favorable Areas, therefore, the total air content of shale can provide reliable foundation for resource potential evaluation and favorable accurately.

At present total air content of relevant shale gas loss tolerance is conciliate gassing rate to be added and to obtain, and the evaluation method of shale loss tolerance mainly adopt United States Bureau of Mines (USBM) to coal seam lose gas estimate the USBM method that adopts and in this way based on the multiple fitting formula that derives to estimate the loss tolerance of shale gas.According to USBM method, at the initial stage of desorption, accumulative resolution gas content is linear with the secondary evolution of the time of parsing, by parsing tolerance Data Extrapolation to zero moment of initial time, recovers loss gas by least square method or graphical method.Because the degree of depth of shale bed is much larger than the coal seam degree of depth, it has huge otherness with coal seam in the mode of coring, drilling mud etc., therefore the method is promoted and there is a lot of problem in the recovery of shale gas loss tolerance, and facts have proved, when lost time is longer, USBM method and derivative multiple fitting formula thereof are inaccurate.Meanwhile, USBM method is based upon on the basis of multiple hypotheses condition, and itself also belongs to semi-empirical approach, principle imperfection.

Summary of the invention

The invention provides a kind of method recovering shale air content, overcome theoretical foundation deviation that shale air content in prior art recovers excessive and cause shale air content to recover inaccurate defect.

The invention provides a kind of method recovering shale air content, comprise the steps:

1) from pressure be P ₀, temperature is T ₁stratum in get shale, at temperature T ₁with normal pressure P ₁under the first parsing is carried out to the shale obtained, until without gas produce, collect first resolve gas;

2) at temperature T ₂with normal pressure P ₁under the second parsing is carried out to the shale of resolving through described first, until produce without gas, collect second and resolve gas and obtain its volume V at standard conditions ₂, wherein, T ₂it is 95 DEG C;

3) mix described first and resolve gas and the second parsing gas, obtain the mixed gas containing methane, described mixed gas is analyzed, obtain the volumn concentration a of each component in described mixed gas _i;

4) according to formula 1, obtain described second and resolve each component absorption air content V at standard conditions in gas _2i,

$V_{2i}=\[V_2-(\frac{T_2}{T_1}-1)\·V_0\·q\·(1-w).\frac{273.15\·P_1}{101325\·T_2}\]\·a_i$ Formula 1

In formula 1, V ₀for the volume of described shale, q be described shale factor of porosity, w is the water cut of described shale;

5) according to formula 2, obtain each gas composition in described shale from stratum to second resolve terminate after absorption air content V at standard conditions _1i,

$V_{1i}=\left(\frac{V_{i2}-V_{i0}}{V_{i2}-V_{i1}}\right)\·V_{2i}$ Formula 2

In formula 2, V _i0be test adsorption volume corresponding to the i-th component gas adsorption potential when stratigraphic horizon, V _i1be the i-th gas composition test adsorption volume that adsorption potential is corresponding when described first resolves, V _i2it is the i-th gas composition test adsorption volume that adsorption potential is corresponding when described second resolves;

6) according to formula 3, obtain described shale from stratum to second resolve terminate after air content V under the status of criterion that produced by the gas expansion volume of voids _p,

$V_p=(\frac{P0\·T2}{P1\·T1}-1)\·V_0\·q\·(1-w).\frac{273.15\·P1}{101325\·T2}$ Formula 3

Shale air content is each gas composition absorption air content V in shale _1iand with air content V _psummation.

The shale air content that the present invention recovers refers to after shale terminates from stratigraphic horizon to the second parsing, calculates the shale total tolerance produced in this process.

Because shale generally can experience dozens of hour from stratum to the process being taken out to ground, therefore cannot carry out collection at the gas volume getting shale release in rock process to measure, so the present invention has carried out twice parsing under taking out the condition of the shale behind stratum under design temperature pressure, the gas volume that shale produces in the process of twice parsing can Measurement accuracy, therefore utilizes and the gas volume of Measurement accuracy and Polanyi Adsorption Potential Theory can go to calculate shale and resolve from stratum to second the cumulative volume terminating rear release gas.

In resolving second, the variable quantity that the gas in the change and shale volume of voids that in this process, shale absorption air content produces produces is contained in the cumulative volume of shale release gas, concrete, second resolves to isobaric variable temperature process, therefore utilize the percentage composition of each component in equation of gas state PV=nRT and gas to obtain formula 1, utilize formula 1 to calculate the absorption content of each component gas that shale produces in the second parsing.

Step 5 of the present invention) in formula 2, be that the absorption content of each component gas produced in being resolved second by shale obtains in conjunction with Polanyi adsorption potential.That is, the absorption content of each component gas produced in adopting Adsorption Potential Theory to resolve second according to shale obtain shale from stratum to second resolve terminate after the absorption air content of each component gas that produces.

Because shale is in alternating temperature transformation process from stratum after the second parsing terminates, therefore utilize the equation of gas state can obtain step 6 of the present invention) in formula 3, utilize formula 3 to calculate shale and resolve from stratum to second the variable quantity terminating gas rear volume of voids and produce.

Shale is resolved the absorption content sum of each component gas that produces the process after terminating and shale from stratum to second resolves to second the variable quantity that the gas terminated rear volume of voids produces from stratum and be added, finally acquisition shale terminate from stratum to the second parsing after total air content.

In order to more objectively express the air content of shale, the gas volume in the present invention is all unified is the gas volume under the status of criterion, and namely pressure is 101325Pa, gas volume when temperature is 0 DEG C, when bringing above-mentioned equation into and calculating, temperature is thermodynamic temperature, unit is K, and pressure unit is Pa.Particularly, gas volume at standard conditions can calculate according to formula 7.

formula 7

Wherein, V _calculatethat gas is at P _calculateand T _calculateunder gas volume.It is noted herein that the temperature of shale when resolving is inconsistent with the temperature of collection gas, and resolve to example with second, shale is at temperature T ₂with normal pressure P ₁parsing case in carry out the second parsing, but collecting the environment of gas and the reading conditions of gas volume is temperature T at the scene ₃and site pressure P ₃under carry out, the gas of namely resolving is collected outward and reading at parsing case, P therefore in above-mentioned formula _calculateand T _calculatecollect and read V _calculatethe pressure P of environment ₃with temperature T ₃.

In measuring method of the present invention, total tolerance that shale produces is divided into two large divisions, the adsorbed gas that a part is shale is resolved from stratigraphic horizon to second and is terminated rear produced variable quantity, and the gas in the volume of voids that another part is shale is resolved from stratigraphic horizon to second and terminated rear produced variable quantity.Because shale cannot carry out collection measurement from stratum to being taken out to the gas volume discharged the process on ground, so the present invention carries out the parsing under twice design temperature pressure to the shale behind taking-up stratum, in the process of twice parsing, the gas volume of shale release can Measurement accuracy, the present invention utilize this twice can Measurement accuracy data and finally obtain the air content of shale in conjunction with Polanyi adsorption potential and equation of gas state gesture, therefore the theoretical foundation of the method for measurement shale air content provided by the present invention is perfect, and the original amount of each component gas in shale gas can be measured, be conducive to more accurate, objective, assess the mineability of shale gas reservoir all sidedly.

Further, obtain the adsorpting characteristic curve of the i-th gas composition according to the adsorpting characteristic curve of methane and formula 4, and obtain described V according to the adsorpting characteristic curve of the i-th gas composition and formula 5 _i0, V _i1and V _i2,

formula 4

formula 5

In formula 4, ε _ibe the i-th gas composition temperature be T, pressure is P _arbitrarilytime adsorption potential, ε _methanefor methane temperature be T, pressure is P _arbitrarilytime adsorption potential, V _mibe the liquid molar volume of the i-th gas composition, V _{m methane}for the molar volume of liquid methane.

Wherein, adsorpting characteristic curve is V (volume)-ε (adsorption potential) curve.Specifically in application process, the adsorpting characteristic curve method for drafting of the i-th gas composition is, with N ₂for example: first, the density of liquid methane is 426kg/m ³, the density of liquid nitrogen is 808kg/m ³, respectively except molal weight, obtain the molar volume V of liquid methane _{m methane}=0.037558685m ³, obtain the molar volume V of liquid nitrogen _{m nitrogen}=0.034653465m ³; Then, according to test number point of destination n concrete on the adsorpting characteristic curve of methane, n ε can namely be obtained _methaneand the n of a correspondence V _methane; Finally, by n ε _methanebring in formula 4 and obtain n ε _nitrogen, then according to n ε _nitrogenwith a corresponding n V _methanedraw out the adsorpting characteristic curve of nitrogen.Wherein, in order to ensure the accuracy of adsorpting characteristic curve, n >=13.

It should be noted that the adsorpting characteristic curve of the i-th gas composition of the present invention converts according to the characterization of adsorption of methane, this transfer principle, i.e. formula 4, is getable according to London dispersion interaction gesture.

Same with N ₂for example, calculate V _i0time, by formation temperature T ₁, reservoir pressure P ₀and nitrogen is at T ₁time saturated vapor pressure bring in formula 5 and can obtain the adsorption potential of nitrogen when stratigraphic horizon, then on the adsorpting characteristic curve of nitrogen, find the test adsorption volume that the adsorption potential under this condition is corresponding, in like manner, the test adsorption volume V that adsorption potential is corresponding when first resolves of nitrogen can be obtained according to the method _i1the test adsorption volume V corresponding with the adsorption potential when second resolves _i2.

Further, the adsorpting characteristic curve of described methane obtains for the adsorption isothermal curve of described shale and formula 6 according to methane,

formula 6

In formula 6, ε _methanefor methane temperature be T, pressure is P _arbitrarilytime adsorption potential, P _saturatedfor the saturated vapor pressure of methane when temperature T.

Wherein, for the isothermal of shale, (the present invention does not limit this probe temperature methane, generally can select formation temperature T ₁) adsorption curve is P (pressure)-V (volume) curve.Specifically in application process, the adsorpting characteristic curve method for drafting of methane is: first, by the test point of the m on the adsorption isothermal curve of methane, i.e. and a corresponding m P _arbitrarilyand V _arbitrarily; Then, respectively by m P _arbitrarilybring in formula 6, the T in this up-to-date style 6 is probe temperature, P _saturatedfor the saturated vapor pressure of methane when probe temperature, obtain m ε _methane; Finally, according to m ε _methanewith a corresponding m V _arbitrarilydraw out the adsorpting characteristic curve of methane.Wherein, in order to ensure the accuracy of adsorpting characteristic curve, m >=13.

In the present invention, methane is P (pressure)-V (volume) curve for the adsorption isothermal curve of shale is measure m (P-V) point-rendering according to the isothermal adsorption method of testing of volumetric method or mass method.Therefore, when drawing the adsorpting characteristic curve of methane, this m (P-V) point just can be adopted.

The software for drawing of the present invention to the adsorpting characteristic curve of each component does not limit, and software for drawing adopted in the present invention is MATLAB.

The method of recovery shale air content provided by the invention, shale tolerance is divided into absorption air content and the volume of voids air content two parts of different component in shale gas, the air content of shale is finally reduced by Polanyi Adsorption Potential Theory, London dispersion interaction potential energy theory, the equation of gas state and the data that truly can survey, avoid the uncertainty that semiempirical formula is brought in shale air content is measured, the measurement of shale gas air content is based upon on the realistic background basis of the mass conservation, and theoretical foundation is more perfect.Simultaneously, the characteristic of different component gas is considered in restoration methods of the present invention, both the irrationality unifiedly calculated by different component gas had been avoided, there is the content can specifying active principle methane in shale gas, for the resource potential of shale and the prediction of Favorable Areas provide objectively with reference to basis.

Accompanying drawing explanation

Fig. 1 is the CH of the embodiment of the present invention ₄for isothermal (30 DEG C) adsorption curve of shale;

Fig. 2 is the CH of the embodiment of the present invention ₄adsorpting characteristic curve;

Fig. 3 is the N of the embodiment of the present invention ₂adsorpting characteristic curve;

Fig. 4 is the CO of the embodiment of the present invention ₂adsorpting characteristic curve.

Embodiment

Embodiment

The present embodiment carries out the measurement of shale air content for the shale of the southeast, Chongqing, comprises the steps:

1) first resolve: from pressure P ₀=7100751.744Pa, temperature T ₁get shale in the stratum of=30 DEG C, be in by shale to resolve in case and carry out the first parsing, the pressure P of case is resolved in setting ₁₌99665Pa (normal pressure), temperature T ₁=30 DEG C, until produce without gas, collect first and resolve gas;

2) second resolve: the temperature T of case is resolved in setting ₂=be 95 DEG C, pressure P ₁=99665Pa, carries out the second parsing to the shale of resolving through first, until produce without gas, collects second and resolves gas 31mL (the environmental pressure P of collection gas ₃=99665Pa, T ₃=12 DEG C), it is 29.2089cm that through type 7 obtains the second parsing gas volume at standard conditions ³,

formula 7

Wherein, V _calculate=31cm ³, P _calculate=99665Pa, T _calculate=(12+273.15)=285.15K;

3) mix described first and resolve gas and the second parsing gas, obtain the mixed gas containing methane, vapor-phase chromatography analysis is carried out to described mixed gas, obtain in described mixed gas main containing CH ₄92.0150952%, N ₂4.3717564%, CO ₂3.6131484%.；

4) measure resolving complete quarrying shale He porosity method, the volume of the shale of the present embodiment is 786.63896cm ³, factor of porosity 2.71%, moisture number percent was 15.3% (data of water saturation come from the water saturation in the scope of the degree of depth ± 0.0625m on well logging interpretation curve).

According to formula 1,

$V_{2i}=\[V_2-(\frac{T_2}{T_1}-1)\·V_0\·q\·(1-w).\frac{273.15\·P_1}{101325\·T_2}\]\·a_i$ Formula 1

Obtain described second and resolve CH in gas ₄absorption air content V at standard conditions _2i=24.27695436cm ³, N ₂absorption air content V at standard conditions _2i=0.953280966cm ³, CO ₂absorption air content V at standard conditions _2i=1.153429558cm ³.

In formula 1, V ₂=29.2089cm ³, T ₁=303.15K, T ₂=368.15K, P ₁=99665Pa.

5) about CH ₄, N ₂, CO ₂respectively since stratum to second resolve terminate after absorption air content V at standard conditions _1icalculating.

For CH ₄:

Fig. 1 is the CH that the present invention shows embodiment ₄for isothermal (30 DEG C) adsorption curve of shale.In FIG, adopt 16 (P-V) points (seeing the following form 1) of test, the pressure data of 16 some correspondences brought in formula 6,

formula 6

Wherein, R=8.314J/mol/K, T=(273.15+30) K, CH ₄at the P of 30 DEG C _saturated=118955626.1Pa, by calculating 16 corresponding ε _methane(seeing the following form 1), according to 16 (V-ε _methane) draw out CH ₄adsorpting characteristic curve, Fig. 2 is the CH of the embodiment of the present invention ₄adsorpting characteristic curve.

According to formula 5, obtain CH ₄adsorption potential ε when stratigraphic horizon _i0=7.103842385kJ/mol, described first resolve time adsorption potential ε _i1=17.85617861kJ/mol and the adsorption potential ε when second resolves _i2=23.84523157kJ/mol,

formula 5

Wherein, R=8.314J/mol/K, calculates ε _i0time, T=(30+273.15) K, P _arbitrarily=7100751.744Pa, P _saturated(30 DEG C)=118955626.1Pa; Calculate ε _i1time, T=(30+273.15) K, P _arbitrarily=99665Pa, P _saturated(30 DEG C)=118955626.1Pa; Calculate ε _i2time, T=(95+273.15) K, P _arbitrarily=99665Pa, P _saturated(95 DEG C)=240948730.1Pa.

At CH ₄adsorpting characteristic curve, find respectively with ε _i0, ε _i1and ε _i2corresponding V _i0, V _i1and V _i2, then resolve CH in gas by second ₄absorption air content V at standard conditions _2i=24.27695436cm ³bring in formula 2, obtain CH in shale ₄from stratum to second resolve terminate after absorption air content V at standard conditions _1ifor 1198.634446cm ³

$V_{1i}=\left(\frac{V_{i2}-V_{i0}}{V_{i2}-V_{i1}}\right)\·V_{2i}$ Formula 2

Table 1CH ₄p-V-ε correspondence table

	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 N ₂:

formula 4

Wherein,

By the ε of 16 in table 1 _methanebring in formula 4, obtain 16 corresponding ε _nitrogen(seeing the following form 2), by 16 ε calculated _nitrogencorresponding with the V of 16 in table 1, draw out N ₂adsorpting characteristic curve, Fig. 3 is the N of the embodiment of the present invention ₂adsorpting characteristic curve.

According to formula 5, obtain N ₂adsorption potential ε when stratigraphic horizon _i0=6.515046199kJ/mol, described first resolve time adsorption potential ε _i1=17.26738242kJ/mol and the adsorption potential ε when second resolves _i2=22.23513894kJ/mol,

formula 5

Wherein, R=8.314J/mol/K, calculates ε _i0time, T=(30+273.15) K, P _arbitrarily=7100751.744Pa, P _saturated(30 DEG C)=94173358.6567508Pa; Calculate ε _i1time, T=(30+273.15) K, P _arbitrarily=99665Pa, P _saturated(30 DEG C)=94173358.6567508Pa; Calculate ε _i2time, T=(95+273.15) K, P _arbitrarily=99665Pa, P _saturated(95 DEG C)=142386826.245744Pa.

At N ₂adsorpting characteristic curve, find respectively with ε _i0, ε _i1and ε _i2corresponding V _i0, V _i1and V _i2, then resolve N in gas by second ₂absorption air content V at standard conditions _2i=0.953280966cm ³bring in formula 2, obtain N in shale ₂from stratum to second resolve terminate after absorption air content V at standard conditions _1ifor 43.93983546cm ³

$V_{1i}=\left(\frac{V_{i2}-V_{i0}}{V_{i2}-V_{i1}}\right)\·V_{2i}$ Formula 2

Table 2N ₂adsorpting characteristic curve V-ε correspondence 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 CO ₂:

formula 4

Wherein,

By the ε of 16 in table 1 _methanebring in formula 4, obtain 16 corresponding ε _{carbon dioxide}(seeing the following form 3), by 16 ε calculated _{carbon dioxide}corresponding with the V of 16 in table 1, draw out CO ₂adsorpting characteristic curve, Fig. 4 is the CO of the embodiment of the present invention ₂adsorpting characteristic curve.

According to formula 5, obtain CO ₂adsorption potential ε when stratigraphic horizon _i0=3.555438835kJ/mol, described first resolve time adsorption potential ε _i1=14.30777505kJ/mol and the adsorption potential ε when second resolves _i2=22.79913562kJ/mol,

formula 5

Wherein, R=8.314J/mol/K, calculates ε _i0time, T=(30+273.15) K, P _arbitrarily=7100751.744Pa, P _saturated(30 DEG C)=29103873.35Pa; Calculate ε _i1time, T=(30+273.15) K, P _arbitrarily=99665Pa, P _saturated(30 DEG C)=29103873.35Pa; Calculate ε _i2time, T=(95+273.15) K, P _arbitrarily=99665Pa, P _saturated(95 DEG C)=171196497Pa.

At CO ₂adsorpting characteristic curve, find respectively with ε _i0, ε _i1and ε _i2corresponding V _i0, V _i1and V _i2, then resolve CO in gas by second ₂absorption air content V at standard conditions _2i=1.153429558cm ³bring in formula 2, obtain CO in shale ₂from stratum to second resolve terminate after absorption air content V at standard conditions _1ifor 2.406723147cm ³

$V_{1i}=\left(\frac{V_{i2}-V_{i0}}{V_{i2}-V_{i1}}\right)\·V_{2i}$ Formula 2

Table 3CO ₂adsorpting characteristic curve V-ε correspondence 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) according to formula 3, obtain shale from stratum to second resolve terminate after air content V under the status of criterion that produced by the gas expansion volume of voids _p=1126.966038cm ³,

$V_p=(\frac{P_0\·T_2}{P_1\·T_1}-1)\·V_0\·q\·(1-w).\frac{273.15\·P_1}{101325\·T_2}$ Formula 3

Wherein, P ₀=7100751.744Pa, P ₁₌99665Pa, T ₂=368.15K, T ₁=303.15K.

Therefore, each gas composition absorption of the shale air content V=in the present embodiment air content V _1i+ air content V _p=1198.634446+43.93983546+2.406723147+1126.966038=2371.947 043 (cm ³)

The method of recovery shale air content provided by the invention, shale tolerance is divided into absorption air content and the volume of voids air content two parts of different component in shale gas, by Polanyi Adsorption Potential Theory, London dispersion interaction potential energy theory, the equation of gas state and the data truly can surveyed finally reduce the air content of shale, avoid the uncertainty that semiempirical formula is brought in shale air content is measured, the recovery of shale gas air content is made to be based upon on the realistic background basis of the mass conservation, theoretical foundation is more perfect, for the resource potential of shale and the prediction of Favorable Areas provide objectively with reference to basis.

Last it is noted that above each embodiment is only in order to illustrate technical scheme of the present invention, be not intended to limit; Although with reference to foregoing embodiments to invention has been detailed description, those of ordinary skill in the art is to be understood that: it still can be modified to the technical scheme described in foregoing embodiments, or carries out equivalent replacement to wherein some or all of technical characteristic; And these amendments or replacement, do not make the essence of appropriate technical solution depart from the scope of various embodiments of the present invention technical scheme.

Claims (3)

1. recover a method for shale air content, it is characterized in that, comprise the steps:

1) from pressure be P ₀, temperature is T ₁stratum in get shale, at temperature T ₁with normal pressure P ₁under the first parsing is carried out to the shale obtained, until without gas produce, collect first resolve gas;

2) at temperature T ₂with normal pressure P ₁under the second parsing is carried out to the shale of resolving through described first, until produce without gas, collect second and resolve gas and obtain its volume V at standard conditions ₂, wherein, T ₂it is 95 DEG C;

3) mix described first and resolve gas and the second parsing gas, obtain the mixed gas containing methane, described mixed gas is analyzed, obtain the volumn concentration a of each component in described mixed gas _i;

4) according to formula 1, obtain described second and resolve each component absorption air content V at standard conditions in gas _2i,

$V_{2i}=\[V_2-(\frac{T_2}{T_1}-1)\·V_0\·q\·(1-w)\·\frac{273.15\·P_1}{101325\·T_2}\]\·a_i$ Formula 1

In formula 1, V ₀for the volume of described shale, q be described shale factor of porosity, w is the moisture ratio of described shale;

5) according to formula 2, obtain each gas composition in described shale from stratum to second resolve terminate after absorption air content V at standard conditions _1i,

$V_{1i}=\left(\frac{V_{i2}-V_{i0}}{V_{i2}-V_{i1}}\right)\·V_{2i}$ Formula 2

In formula 2, V _i0be test adsorption volume corresponding to the i-th component gas adsorption potential when stratigraphic horizon, V _i1be the i-th gas composition test adsorption volume that adsorption potential is corresponding when described first resolves, V _i2it is the i-th gas composition test adsorption volume that adsorption potential is corresponding when described second resolves;

6) according to formula 3, obtain described shale from stratum to second resolve terminate after air content V under the status of criterion that produced by the gas expansion volume of voids _p,

$V_p=\left(\frac{P_0\·T_2}{P_1\·T_1}-1\right)\·V_0\·q\·(1-w)\·\frac{273.15\·P_1}{101325\·T_2}$ Formula 3

Shale air content is each gas composition absorption air content V in shale _1isum and air content V _psummation.

2. the method for recovery shale air content according to claim 1, is characterized in that, obtains the adsorpting characteristic curve of the i-th gas composition according to the adsorpting characteristic curve of methane and formula 4, and obtains described V according to the adsorpting characteristic curve of the i-th gas composition and formula 5 _i0, V _i1and V _i2,

formula 4

formula 5

In formula 4, ε _ibe the i-th gas composition temperature be T, pressure is P _arbitrarilytime adsorption potential, ε _methanefor methane temperature be T, pressure is P _arbitrarilytime adsorption potential, V _mibe the liquid molar volume of the i-th gas composition, V _{m methane}for the molar volume of liquid methane.

3. the method for recovery shale air content according to claim 2, is characterized in that, the adsorpting characteristic curve of described methane obtains for the adsorption isothermal curve of described shale and formula 6 according to methane,

formula 6

In formula 6, ε _methanefor methane temperature be T, pressure is P _arbitrarilytime adsorption potential, P _saturatedfor the saturated vapor pressure of methane when temperature T.