Hysteresis Effects for Gas Condensate Wells Undergoing Buildup Tests below the Dew Point Pressure

Abstract

ABSTRACT An increasing liquid saturation is observed in gas condensate reservoirs when they undergo drawdown. This liquid saturation is not reversible when the well is subjected to a pressure buildup thus resulting in a hysteresis effect. Hence, once reduced, the effective reservoir permeability does not recover and in a subsequent drawdown, the flow rate remains at largely the same level as before the shut in. This hysteresis effect is examined and quantified. An existing method to interpret the pressure behavior of gas condensate reservoirs is critiqued and is found appropriate for the time when "steady-state" saturation emerges and as long as relative permeability data are available. A new method allows the calculation of the "apparent" reservoir permeability at steady state and when employing a step-pressure test then relative permeability data may be obtained from the interpretation.