Enumeration Approach in Condensate Banking Study of Gas Condensate Reservoir

Abstract

In this paper, enumeration method was developed to simulate gas condensate reservoir behavior based on the different condensate banking zones. Sharp increment of pressure drawdown near wellbore and description of condensate bank away the wellbore are still part of challenges in simulating gas condensate reservoir. This method allows prediction on how pressure behavior near and away wellbore and how the condensate banking will evolve in future due to the simultaneous flow of gas and condensate in the reservoir. A single well model has been developed to investigate the effect of condensate bank on pressure behavior in gas condensate reservoir. Upon production, gas condensate reservoir creates different zones based on different phase mobility, resulting from condensate banking. Enumeration initialization approach is to divide the simulation explicitly for the multiple stages. During the stops, condensate bank parameters have been modified at each zone to describe drastic change of well performance due to condensate banking. A representative matured gas condensate reservoir from Malay Basin has been selected for the purpose. The effect of the mobility changes to pressure behavior is then investigated. Comparison of pressure behavior between enumeration ways with conventional approach have been presented. It was found that enumeration method shows better prediction in investigating the pressure behavior and condensate saturation near and away wellbore during stabilized production. It is due to its ability to predict mobility changes at every zones. The change of relative permeability to variations in fluid saturation, velocity, and interfacial tension cause increment of pressure drawdown. In analytical analysis, the increment of pressure drawdown mostly demarcated as positive skin to a factor of 30 – 90. With enumeration method in place, pressure behavior can be quantified without defining the positive skin, thus improve the condensate bank characterization. This paper improves accuracy in defining complex physics of condensate banking phenomena, also providing key tool in quantifying the condensate bank. Enumeration approach screens the potential condensate banking in later well life and appropriate mitigation technique can be selected – optimize drawdown or change wettability as the positive skin term in simulation has been replaced.