Compositional Change of Reservoir Fluid in CO₂ Flooding

Abstract

A multicell model was used to investigate phase behavior in the reservoir during CO₂ injection. This numerical model computes the compositional changes that occur in the reservoir between the in-place oil and the injected fluid. The Peng-Robinson Equation of State was employed for these calculation. A mixture of methane, n-butane and n-decane was used as the in-place oil and CO₂ was used as the injected fluid. Three injection pressures were considered, each of them correspondending to the first contact miscible, the multicontact miscible and the immiscible flooding respectively. The generation of the multicontact miscibility was discussed based on K value profiles, density profiles, composition profiles and composition histories. Distinct differences were observed among the immiscible flooding process and the multicontact miscible process.