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1、5 Calcuation relative permeability curve from 5 Calcuation relative permeability curve from capillary pressure curvecapillary pressure curveBasic Theory:By Poiseuilles Law,the flow rate in single capillary:If volume of single capillary is V,then：By definition of capillary pressure:If the porous medi
2、um is conceived to be comprised of n capillary tubes of unequal diameter,the total rate of flow is given by:Further more:V Further more:Vi i =V=VP IP I In actual rock,from Darcys law ThenThen：If the volume VpiIf the volume Vpi of each capillary can be expressed as a of each capillary can be expresse
3、d as a fraction Sfraction Si i of the total void volumeof the total void volume V Vp p of the system,so that:of the system,so that:S Si i=V=Vpi pi/V/Vp p ,V ,Vp p=V=Vpipi/S/Si i therefore:therefore:=V=Vp p/AL=V/AL=Vpipi/ALS/ALSi,i,then:V then:Vpipi=ALS ALSi i Introducing conversion factors Introduci
4、ng conversion factors Method as follows：Measured capillary pressure curve(Pc Sw),and draw 1/PC2 Sw curve，abtain intrinsic area of this curve and can calculate the relative permeability of rock。Calculate of effective permeability and relative permeability:Introduction：tortuosity of only one fluid saturation in porous medium;wttortuosity of wet phase;nwt tortuosity of non-wet phase;r wt=/wttortuosity of wet phase ratio;r nwt=/nwttortuosity of non-wet phase ratio;