Minimum miscibility pressure. abbreviated as MMP, is the lowest pressure at which a gas can achieve miscibility with a reservoir oil, meaning the gas and oil mix completely into a single phase. This is critical in enhanced oil recovery (EOR) processes, particularly in gas injection methods like \(CO_2\) flooding. At or above the MMP, the injected gas dissolves into the oil, reducing viscosity and improving oil displacement efficiency, leading to higher recovery rates. MMP depends on factors like oil composition, gas type, and reservoir conditions (temperature and pressure). It’s typically determined experimentally or through simulations, as it varies for each reservoir.
Miscibility Types
First-Contact Miscibility (FCM) - This occurs when the injected gas and reservoir oil mix completely upon their initial contact, forming a single phase immediately. This requires a specific gas composition and pressure, where the gas is fully soluble in the oil without needing intermediate steps. For example, certain light hydrocarbons or CO2 at very high pressures can achieve first-contact miscibility with light oils.
Multiple-Contact Miscibility (MCM) - This is a dynamic process where miscibility develops through repeated contacts between the injected gas and reservoir oil. It involves mass transfer (vaporization or condensation) over multiple interactions, gradually forming a single phase. This can be divided into two types: Vaporizing Gas Drive - The injected gas (e.g., lean gas) vaporizes lighter components from the oil, enriching the gas until it becomes miscible with the oil. and Condensing Gas Drive - The injected gas (e.g., enriched gas) transfers heavier components into the oil, enriching the oil until miscibility is achieved.
