Abstract
The phenomenon of retrograde condensation occurs when the reservoir pressure declines below the dew-point pressure causing gas condensation and developing two-phase flow. Material Balance Equation (MBE) of gas condensate reservoirs is a challenge because of the change in fluid composition and complexity of phase behavior. Neglecting the effect of water vaporization may lead to inaccurate predictions of the material balance equation. Therefore, the main objective of this study is to develop an improved MBE model capable of describing
gas condensate reservoirs under significant vaporization of connate water and water influx driving mechanism. A new parameter is developed to consider water vaporization. This parameter is used to derive equations for gas condensate reservoirs considering vaporization effect with and without consideration of water influx. Numerical examples have been developed and used to compare the accuracy of the newly-developed model with conventional ones using actual reservoir depletion and production data. The results indicated that water vaporization has an important effect and should be considered for accurate MBE predictions. Error analysis
showed that the newly-developed equations are more accurate than previously-developed models. The accuracy of the new MBE is attributed to the additional parameter introduced considering high pressure and high temperature conditions. The application of the new material balance equation will have important impact on predictions of initial gas in place, reserve calculation and future simulation studies.