Application of Two-phase Pseudo-pressure in Gas-condensate Well-testing With and Without Positive Coupling and Inertia

Well-test interpretation in gas condensate system is particularly challenging when condensation happens within the reservoir. This is not only due to the natural reduction of near wellbore mobilities, but also the existence of the velocity effects (i.e. positive coupling and inertia), which compete to revamp the relative permeabilities. In this study, a set of realistic build-up tests are generated using a compositional reservoir simulator, where measured (velocity dependent) relative permeabilities and a real gas condensate fluid model are used. The transient build-up tests are analysed using the real-gas and steady-state two-phase pseudo-pressures, and the (velocity dependent) reservoir integral transforms. The results show that the application of steady-state two-phase pseudo-pressure transform can result in a remarkable over-prediction of the reservoir permeability, when the velocity dependent relative permeabilities are in effect. Moreover, the traditional real-gas pseudo-pressure transform fails to estimate the reservoir properties particularly when the reservoir is initially below the dew point pressure. However, in either of situations (i.e. with and without velocity effects), using the reservoir integral transform leads to an excellent liquid analogy solution, where the reservoir properties can be accurately estimated.