10.5.15 Multiple Contact Miscibility

A multiple contact miscibility test is a specialized PVT test that represents establishment of miscibility when a gas and oil sample come in contact under a fixed condition of pressure and temperature. The test involves multiple contact of a fixed amount of gas with multiple fresh charges of an oil sample, where intermediate components from the oil sample are stripped consecutively (forward contact). In case of a backward contact test, a fixed charge of an oil sample will come in contact with multiple charges of fresh rich gas, so that intermediate components in the gas phase are transferred to the oil phase. The process continues until miscibility is achieved. During each contact, the composition of each phase is measured. Such mass transfer process and compositional change may be shown using a pseudo-ternary diagram. Results of such study are generally used to optimize an equation-of-state (EoS) model. The optimized EoS model is generally used in a compositional reservoir simulator to properly capture the miscibility process in a reservoir during a gas injection EOR process.