Well Deliverability Forecasting of Gas Condensate and Volatile Oil Wells below Saturation Pressure

Abstract

Abstract Development of a condensate bank in gas condensate wells producing below the dew point pressure causes productivity losses as gas mobility at the wellbore is reduced. The same is true in volatile oil wells producing below the bubble point pressure due to the existence of a gas bank. Using compositional simulation, this paper investigates the use of back-pressure plots expressed in terms of pressure, singlephase pseudo-pressure, and two-phase pseudo-pressure to describe well productivity losses below saturation pressure for gas condensate or volatile oil wells. It is shown that the theoretical stabilized back-pressure deliverability straight line at krg =krgi cannot be obtained using pressure and single-phase pseudo-pressure back-pressure plots whereas it can matched with two-phase pseudo-pressures, provided that non-Darcy and capillary number effects are included in the two-phase pseudo-pressure calculations. Bottom-hole back-pressure plots using two-phase pseudo-pressures can then be used to quantify productivity and mobility reductions and to separate the effect of the bank from other effects such as multi-layering, thus allowing identification of appropriate remediation measures. These results are verified with data from actual gas condensate and volatile oil reservoirs.