Several important reservoir engineering aspects of gas condensate well performance are investigated using an IMPES (Implicit Pressure Explicit Saturation) compositional simulator which employs a modified Redlich Kwong Equation of State to describe phase equilibria. These aspects are: total hydrocarbon fluid production rate, saturation and pressure profiles, gas-oil ratio and produced fluid compositions. The simulations are performed using a gas condensate fluid from a reservoir in the Overthrust Belt. The initial condition is a constant reservoir pressure. Simulations include transient state when two-phase flow occurs and steady-state when the flowing phase composition becomes constant. Both radial and linear systems are examined.
Excellent agreement between the results of the compositional simulator at steady-state/near steady-state conditions and the two-phase steady-state theory (Chopra and Carter1) is obtained. A step-by-step procedure to compute performance of gas condensate wells using the two-phase steady-state theory is illustrated. It is shown that the two-phase steady-state theory is a satisfactory approach for predicting the performance of gas condensate wells once the criteria for steady-state are satisfied. The conventional criteria to determine when steady-state is achieved for single phase systems are not applicable to two-phase gas condensate systems. Based on a study of the produced fluid compositions and the areal extent of the two-phase region, criteria for steady-state are suggested. A compositional simulator is needed to model transient conditions. The valuable applications of the two-phase steady-state theory are to validate a simulator and evolve new techniques for two-phase pressure transient analysis techniques.
