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1、 3.5 Material-Balance MethodFor Dry-Gas Reservoirs with Water Influx1 Dry-Gas Reservoirs with Water Influx1 Dry-Gas Reservoirs with Water Influx For a water-drive system can be derived:the PV occupied by the gas at initial conditions=the PV occupied by the gas at later conditions plus the change in

2、PV resulting from the water influx.1 Dry-Gas Reservoirs with Water Influx1 Dry-Gas Reservoirs with Water InfluxMethods for Estimating Water Influx:van Everdingen and Hurst method Carter-Tracy methodFetkovich method(1)edge-water drive(2)bottom-water drive2 Van Everdingen and Hurst method The reservoi

3、r/aquifer system is modeled as two concentric cylinders or sectors of cylinders.radial diffusivity equationpD:dimensionless pressureqppkhpiDrD:dimensionless radiusoDrrr 2 Van Everdingen and Hurst methodtD:dimensionless time2otDrckttwftcccCt:total aquifer compressibility2 Van Everdingen and Hurst met

4、hod Dimensionless accumulative water influx for constant pressure conditions:pDtoepQchrW36022p:pressure difference between initial aquifer pressure and the pressure at the reservoir/aquifer boundary.QpD:dimensionless water influx rate.2 Van Everdingen and Hurst method The average pressure during the

5、 first period:For the second period:2/)(212PPP2/)(11PPPi2 Van Everdingen and Hurst methodIn general,for the nth time period:2/)(1nnnPPPPressure change between the initial and first time periods:Pressure change between the first and second time periods:2/)(110PPPPPii2/)(2211PPPPPi2 Van Everdingen and Hurst methodIn general,for the(n-1)and nth time periods:2/)(21nnnnnPPPPPniDinpDinettQpBtW11)(For linear flow2119.1rtrchBor)360(119.12rtrchB 2 Van Everdingen and Hurst methodThank you for your attention!