Abstract
Gas condensate reservoirs exhibit complexities due to the production of gas, condensates and many times, in situ oil phase. As the average reservoir pressure in a gas condensate reservoir continues to decline on production, condensate drop out occurs across the reservoir. Pressure decline between the reservoir boundaries and the well bore could lead to condensate formation near the well bore.
This paper considers the flow behavior in gas condensate reservoir and presents an approach for calculating the pressure depletion performance of a gas condensate reservoir from the original reservoir fluid composition using the vapor – liquid equilibrium calculations, the fluid properties, dimensionless properties, and retrograde liquid accumulation as guides.
The results correspond to drawdown analysis of a condensate reservoir where flow of the phase occurs. It is also a compositional analysis and includes the composition of the hydrocarbon fluid up to and including C7+. The presence of non-hydrocarbon impurities such as Carbon dioxide, Nitrogen and Hydrogen Sulphide are also considered. The comparison with other standard work on transient pressure analysis from gas condensate reservoirs showed that the approach is satisfactory.
A principal use of the method would be for the initial estimation of pressure depletion pattern after discovery of a gas condensate reservoir, where the compositional analysis of the reservoir fluid may be only approximate and the dew point if not known, is assumed to be the reservoir temperature and pressure. It is also a valuable tool during the production period for reservoir surveillance and monitoring.
