Abstract
Prediction of the timing and location of condensate build-up around the wellbore in gas condensate reservoirs is essential for the selection of appropriate methods for condensate recovery from these challenging reservoirs. The present work focuses on the use of a novel phase change tracking approach in monitoring the formation of condensate blockage in a gas condensate reservoir. The procedure entails the simulation of tight, low and high permeability reservoirs using global and local grid analysis in determining the size and timing of three common regions (Region 1, near wellbore; Region 2, condensate build-up; and Region 3, single-phase gas) associated with single and two-phase gas and immobile and mobile gas condensate. The results show that permeability has a significant influence on the occurrence of the three regions around the well, which in turn affects the productivity of the gas condensate reservoir studied. Predictions of the timing and location of condensate in reservoirs with different permeability levels of 1 mD to 100 mD indicate that local damage enhances condensate formation by 60% and shortens the duration of the immobile phase by 45%. Meanwhile, the global change in permeability increases condensate formation by 80% and reduces the presence of the immobile phase by 60%. Finally, this predictive approach can help in mitigating condensate blockage around the wellbore during production.
Highlights
Low-permeability tight gas condensate reservoirs, or so-called unconventional reservoirs, have been a focus for exploitation by operators across the world [1]
The lower the reservoir permeability, the more abundant the gas and the higher the pressure drawdown will be during production, which indicates a high potential for condensate blockage
The results show that permeability has a significant effect on the occurrence of the three regions around the well, which in turn influences the productivity of gas condensate reservoirs
Summary
Low-permeability tight gas condensate reservoirs, or so-called unconventional reservoirs, have been a focus for exploitation by operators across the world [1]. Condensate blockage in a gas condensate reservoir occurs due to a rapid decline in pressure below the dew point This is a common problem in tight reservoirs, which can experience severe damage near the wellbore [2,3]. Production from such reservoirs usually displays an extensive period of transient flow, during which a two-phase flow of oil and gas begins [4], where the oil phase is often referred to as “condensate” or “distillate” [5]. Condensate blockage near the wellbore can cause a substantial loss in production for low-to-moderate permeability condensate reservoirs since the main source of pressure loss in tight reservoirs depends primarily on reservoir permeability [9]
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