(4)--4-Fundamentals of Pressure-Trans气藏工程气藏工程.ppt

5.4 Fundamentals of Pressure 5.4 Fundamentals of Pressure Transient Testing in Gas Wells Transient Testing in Gas Wells a slightly compressible liquid at a constant rate is:Compressible gas in which the properties are strong functions of pressureMethod:using pressure and time transformation variables that account for the variation of gas properties with pressure.Pseudopressure and Pseudotime VariablesReal gas pseudopressure,pp,psi2/cpPseudotime,tap,nProblems:variables pp and tap typically have values of 105 to 108,to make the magnitudes comparable with those of pressure and time,define normalizes variable asnNormalized variables:Reference pressure:Original reservoir pressureCurrent static drainage area pressureUsing buildup test by extrapolated to a Horner time ratio of unity Adjusted VariablesAdjusted pressure and Time Variables p(r,t=0)=pi Pressure and Time VariablesIf p/z is constantPressure-Valid Only for High Pressures(3000 psi)Pressure-Squared and Time VariablesIf z is constant00.1602,0004,0006,0008,00010,000Pressure,psiamu*z,psi/cpTf=200 FSG=1.2SG=1.0SG=0.8SG=0.6Fairly constant at rates 2,000 psiPressure-Squared-Valid Only for Low Pressures(2000 psi)Summary5.4 Fundamentals of Pressure-Transient Testing in Gas Wells（End)