1、5.4 Fundamentals of Pressure Transient Testing in Gas Wells a slightly compressible liquid at a constant rate is:2162.6 l g( ) 3.23 0.86 9w f itwqB k tp p sk h C r Compressible gas in which the properties are strongfunctions of pressureMethod: using pressure and time transformation variables thatacc
2、ount for the variation of gas properties with pressure. Pseudopressure and Pseudotime Variables 0tapgtdttpC Real gas pseudopressure, pp, psi2/cpPseudotime, tap, 02ppgpdppz tpkcrprrrptp 1 Problems: variables pp and tap typically have values of 105 to108, to make the magnitudes comparable with those o
3、fpressure and time, define normalizes variable as012pggnpgrrzz pdpppp p z tt 0( ) ( )tn g r a p g rgtdtt C t CC 012pggnpgrrzz pdpppp p z Normalized variables:Reference pressure: ippOriginal reservoir pressureCurrent static drainage area pressureUsing buildup test by extrapolated to a Horner time rat
4、io of unity Adjusted Variables012pggapgzz pdpppzpp 012pggnpgrrzz pdpppp p z gttCC, 21 6 2 .6 l g ( ) 3 .2 3 0 .8 6 9 gga w f a ig g wqB ktp p skh Cr 2162.6 l g( ) 3.23 0.86 9w f itwqB k tp p sk h C r Adjusted pressure and Time Variables11 DrDDrp0 eDD rrDDrpDDDDDDD tprprrr )(1 00, DDD trptpkcrprrr t
5、0 0 0 2 6 3 7.0)(1 p(r,t=0)= pikhqBrpr wrr 0 0 7 0 8 2.0 0/ errrp qBppkh0 0 7 0 8 2.0p iD 20 0 0 2 6 3 7.0wtD rcktt DDD trEip421 2tpkcrprrr t 0 0 0 2 6 3 7.0)(1 iptrp )0,(scscrr p k h TzTqprprw1 5 0,250 errrp Pressure and Time VariablesIf p/z is constant012pggapgzz pdpp p pzpp , 21 6 2 .6 l g ( ) 3
6、.2 3 0 .8 6 9 gga w f a ig g wqB ktp p skh Cr 2162.6 l g( ) 3.2 3 0.8 69 ggw f ig g wqB ktp p skh Cr Pressure - Valid Only for High Pressures ( 3000 psi) Pressure-Squared and Time VariablesIf z is constant2012 2pggapgzz p d p pppzp p p , 21 6 2 .6 l g ( ) 3 .2 3 0 .8 6 9 gga w f a ig g wqB ktp p skh
7、 Cr 2221 6 2 .6 2 l g ( ) 3 .2 3 0 .8 6 9 wfg g gig g wq p B ktp p skh Cr 2221 6 2 .6 2 l g ( ) 3 .2 3 0 .8 6 9 wfg g gig g wq p B ktp p skh Cr scgsc sczT pBz T p1 4 .7scp psia 520 RoscT 2221637 l g ( ) 3 .2 3 0 .8 6 9 wfggig g wq T z ktp p skh Cr 00.160 2,000 4,000 6,000 8,000 10,000Pressure, psiam
8、u*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) Summary2162.6 l g( ) 3.23 0.86 9w f itwqB k tp p sk h C r , 21 6 2 .6 l g ( ) 3 .2 3 0 .8 6 9 gga w f a ig g wqB ktp p skh Cr 2162.6 l g( ) 3.2 3 0.8 69 ggw f ig g wqB ktp p skh Cr 2221637 l g ( ) 3 .2 3 0 .8 6 9 wfggig g wq T z ktp p skh Cr 5.4 Fundamentals of Pressure-Transient Testing in Gas Wells （ End)
