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1、3.2 Volumetric method for dry gas reservoir1 Volumetric dry-gas reservoirgas expansionclosed systemNo phase changesPhase diagram for dry gas giwigigiBSAhBSAhG10000TPTzPpnRTPznRTVVBiiiiscRgiGas initially in place:1 Volumetric dry-gas reservoirGas in place at some abandonment pressure:gawiaBsAhG11 Vol
2、umetric dry-gas reservoirCummulative gas production(The recoverable reserve)apGGG the amount of gas recovered within a certain technical or economic limit.gagigiwigawigiwipBBBsAhBsAhBsAhG11111 Volumetric dry-gas reservoirGas recovery factor gagipBBGG11 Volumetric dry-gas reservoirEX.1:A new gas rese
3、rvoir was found with area of 7.4km2,the net thickness is 9.14m,the effective porosity is 0.15,the initial gas saturation is 0.70,the initial pressure is 20.68MPa,the initial temperature is 358.6k,the specific gravity of the gas is 0.60.(1)Try to calculate the GIIP.(2)If the abandonment pressure of t
4、he gas reservoir is 4.0MPa,try to calculate the recovery factor of the reservoir.1 Volumetric dry-gas reservoirSolution:(1)To calculate the pseudo-critical parameterskTMPaPgpcgpc2222.1986667.1762222.926291.42482.07780.4(2)To calculate the pseudo-reduced parameters47.4/pciprPPP81.1/pciprTTT(3)To chec
5、k the S-K correlations for Z-factorZi=0.90(4)To calculate Bgi 33300/1033.5smmTPTPzBiiigi(5)To calculate GIIP 391033.1smBSAhGgigi (6)To calculate the pseudo-reduced parameters at abandonment pressure86.0/pcaprPPP81.1/pciprTTT(7)To check the S-K correlations for Z-factorZa=0.95(8)To calculate Bga 3320
6、0/1091.2smmTPTPzBaiaga(9)To calculate the recovery factor%7.811gagipBBGG2 Dry-gas reservoirs with water influx Pore volume occupied by gas decreases as water encroaches into the gas reservoir.At initial conditions:wcgiSS1 At later conditions:wgSS12 Dry-gas reservoirs with water influxGas initially i
7、n place:giwiBsAhG12 Dry-gas reservoirs with water influxGas in place at some abandonment pressure:gawaaBsAhG1Swa-Water saturation at abandonment conditions2 Dry-gas reservoirs with water influxThe recoverable reserve:apGGGwigagrgigiwigagrgiwigawagiwipsBsBBsAhBsAhBsAhBsAhBsAhG111111ResidualGas satura
8、tion2 Dry-gas reservoirs with water influx The gas recovery factor for dry-gas reservoir with water influx:wigagrgisBsB11 Assumption:the volumetric sweep efficient for gas is 100%.1tVaVpGEGEGGTake the volumetric sweep efficiency into account,2 Dry-gas reservoirs with water influxVVgigrgagiVgiwigawiV
9、gawaVgiwipEEssBBEBsAhBsAhEBsAhEBsAhG1111111The gas recovery factor:VVgigrgagiVEEssBBEF112 Dry-gas reservoirs with water influxEX.2:As the data given in last Ex.1,if the residual gas saturation is 35%at abandonment pressure and the volumetric sweep efficiency is 100%,try to calculate the recovery factor for the dry gas reservoir with water-influx.Solution:33300/1033.5smmTPTPzBiiigi33200/1091.2smmTPTPzBaiaga2 Dry-gas reservoirs with water influx70.0giS35.0grS0.1vE92.0111gigagrgiVVgigrgagiVSBSBEEssBBEFThank you for your attention!
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