WELL PERFORMANCE UNDER SOLUTION GAS DRIVE

A fully implicit black-oil simulator was written to predict the drawdown and buildup responses for a single well under Solution Gas Drive. The model is capable of handling the following reservoir behaviors: Unfractured reservoir, Double-Porosity system, and Double Permeability-Double Porosity model of Bourdet. The accuracy of the model results is tested for both single-phase liquid flow and two-phase flow.;New definitions of pseudopressure and dimensionless time are presented. By using these two definitions, the multiphase flow solutions correlate with the constant rate liquid flow solution for both transient and boundary-dominated flow. These definitions can be used for constant oil rate and constant pressure production.;For pressure buildup tests, an analogue for the liquid solution is constructed from the drawdown pseudopressure, similar to the reservoir integral of J. Jones. The utility of using the producing gas-oil ration at shut in to compute pseudopressures and pseudotimes is documented.;The influence of pressure level and skin factor on the Inflow Performance Relationship (IPR) of wells producing solution gas drive systems is examined. Examination of the synthetic deliverability curves suggests that the exponent of the deliverability curve is a function of time. It is shown that the methods given in the literature can be used to predict future performance provided that the exponent of the deliverability curve is known and extrapolations over large time ranges are avoided. Although, relative permeability and PVT data are required, the Muskat materials balance equation and the assumption that gas-oil ration is independent of distance can be used to predict production rates. This method avoids problems associated with other methods in the literature and always yields reliable results.;The results presented here provide a basis for the empirical equations presented in the literature.;A new definition of flow efficiency that is based on the structure of the deliverability equations is proposed. This definition avoids problems that result when the presently available methods are applied to heavily stimulated wells.;The need for using pseudopressures to analyze well test data for fractured reservoirs is shown. Expressions to compute sandface saturations for fractured systems are presented.