In-situphase and thermodynamic properties of resident brine and acid gases (CO2 and H2S) injected into geological formations in western Canada

Publisher Summary This chapter presents first methodology for evaluating the density and viscosity of native fluids and acid gas at in-situ conditions, and then applies this methodology to the case of acidgas injection operations in western Canada that cover a wide range of acid-gas composition, pressures and temperatures. The chapter implies algorithms for estimating the density and viscosity of formation water, and new algorithms have been developed for estimating the acid-gas density and viscosity at in-situ conditions. These algorithms are based on a volume-shifted Peng-Robinson equation of state and combining rules for mixtures. Calculation of the density and viscosity at in-situ conditions of the acid gas and formation water or reservoir oil or gas shows that, on average, the acid gas currently injected in western Canada is half as dense and 15 times less viscous than the formation water, and only 1.3 times lighter and 17 times less viscous than light and medium oils. With respect to hydrocarbon gas, the acid gas is approximately twice as heavy and viscous than reservoir gas. These properties affect the behavior of the injected acid gas and may lead to different strategies with regard to acid-gas disposal.