| This work describes the development of a mechanistic model to predict the effect that transient two-phase gas-oil flow in the wellbore has on pressure drawdown and buildup behavior. A one-dimensional drift-flux model is used to derive the partial differential equations governing the two-phase flow in the wellbore. The black-oil approach, which accounts for a variable bubble-point pressure, is used to account for the effect of interphase mass transfer. After obtaining the pertinent finite-difference equations, solutions are computed by a sequential, iterative calculation procedure. We present the development of a wellbore simulator that implements the proposed model and the finite-difference solution procedure.; A procedure was developed to couple the wellbore model with a two-phase flow reservoir simulator in order to allow two-phase flow in both the wellbore and the reservoir. The coupled model should prove useful for the design of well tests and allows one to understand the physics of complex wellbore phenomena including phase redistribution.; In addition, a subplex method was implemented to calculate the bottom-hole pressures and flow rates from wellhead conditions. The procedure uses a time-dependent linear temperature gradient in the wellbore to reduce computational time. Except at early shut-in times, the method yields reasonable estimates of bottom-hole pressure during buildup tests, but is not sufficiently accurate to be used with confidence to predict bottomhole pressures during drawdown tests. |
