Deliverability Projection Model for Overpressured Gas-Condensate Reservoirs

Abstract

ABSTRACT During the depletion history of an abnormally pressured reservoir, pressure is initially maintained by a decrease in the pore volume. The P/Z vs cumulative gas produced graph in such reservoirs shows two distinct slopes and the initial gas in place can be estimated by extrapolation of P/Z straight line after the reservoir gradient has been reduced to normal. This decrease in pore volume also results in a reduction in the effective permeability of the rock thus affecting the formation in-flow performance. In the gas-condensate reservoirs, hydrocarbon liquids drop out of the gas phase below the dewpoint pressures increasing the total liquids saturation. An increase in the liquid saturation decreases the relative permeability to gas. The paper develops a high pressure gas-condensate reservoir deliverability calculation incorporating the effect of gas permeability reduction due to a decrease in pore volume and increase in oil saturation.