Numerical modeling on high-temperature and high-pressure gas condensate recovery considering the viscosity variation and dynamic relative permeability.

The production evaluation of high-temperature and high-pressure gas condensate remains unsatisfactory in terms of precision due to the inadequate knowledge of viscosity variation and dynamic relative permeability. Here, we first conduct phase behavior experiments to clarify the mechanisms of viscosity variation followed by core flooding experiments to reveal the dynamic relative permeability. The viscosity variation responses in different regimes to pressure and temperature increases. Besides, the carbon number of the gas condensate exhibits three influencing scenarios on viscosity variation at different pressure and temperature conditions. Moreover, the variation of relative permeability is limited within 5% as temperature decreases together with pressure decreases, but the decline rate of pressure is expected to be higher than that of temperatures. We then theoretically model the production of the gas condensate reservoir by integrating the viscosity variation and dynamic relative permeability mechanisms obtained from the experiments. Modeling results well fit the field data. We adopt the model to analyze and elucidate the effects of temperature, pressure and fracture size on water flooding recovery of ultra-deep gas condensate reservoirs. We figure out that at high temperature, the gas condensate recovery can be enhanced by a rapid pressure decline which can further accelerate the oil thinning and gas condensate production. A high gas condensate production is obtained in the early stage at high pressure, but the oil with high viscosity consumes vast amounts of reservoir energy, leading to a rapid pressure drop in the early development stage. This work pioneers in revealing the interactive mechanisms of viscosity variation and dynamic permeability of ultra-deep reservoir during water flooding development, and brings insights into more adequate gas condensate recovery evaluation. [ABSTRACT FROM AUTHOR]