COMPUTATION AND ANALYSIS OF SINGLE WELL RESPONSES FOR GAS CONDENSATE SYSTEMS (TWO-PHASE FLOW, PSEUDOPRESSURE, STEADY-STATE)

A fully implicit compositional simulator was written to predict the drawdown and buildup responses for a single well in a gas condensate reservoir. The model uses the Redlich-Kwong equation of state to compute fluid properties and to determine phase equilibrium. The accuracy of the model predictions in the two-phase flow regime is tested using the results of a steady-state theory developed here.;These two theoretical functions are shown to reduce to a computable pseudopressure function by using the results of the steady-state theory. The usefulness of this pseudopressure function for computing the permeability-thickness product and the skin factor is documented.;For pressure buildup tests, analogues for the liquid solution are constructed from the reservoir integral and the sandface integral. It is shown that the analogue based on the reservoir integral follows closely the liquid solution. Pseudopressure reductions of this analogue based on the steady-state theory and the single-phase gas theory are presented. The accuracy of buildup analysis performed using these reductions is studied in detail. In general, permeability-thickness products and estimates of average pressure can always be obtained using these reductions. Estimates of skin factors are correct only if the saturation profile at shut-in can be approximated accurately. However, upper and lower bounds for the skin factor are available from these reductions.;Two new correlating functions for transient flow--the reservoir integral and the sandface integral--are presented. The reservoir integral is shown to be a good liquid analogue during transient flow (drawdown). That is, the reservoir integral follows the semilog approximation to the liquid solution closely. The sandface integral correlates with the liquid solution only in slope.