# Minimum Miscibility Pressure (MMP)

In this module, minimum miscibility pressure by first contact ($$MMP_{FC}$$) and multi-contact ($$MMP_{MC}$$) are calculated. The data required is:

• Reservoir fluid composition (generated with any of the available methods)
• Reservoir temperature
• Injection gas composition

## Minimum Miscibility Pressure

For a given temperature, injection gas composition, and reservoir fluid composition, the minimum miscibility pressure (MMP) is the lowest pressure at which first- or multi-contact miscibility can be achieved for a specific process, e.g. ($$MMP_{FC}$$), ($$MMP_{VGD}$$), and ($$MMP_{C/V}$$).

## Miscibility

In petroleum engineering, we consider two types of miscibility: first-contact miscibility (FCM) and multi-contact miscibility (MCM). First-contact miscibility is relevant for the gas huff-n-puff (HnP) method, while multi-contact miscibility is relevant for displacment processes.

## First-Contact Miscibility

At a given pressure and temperature, first-contact (FC) miscibility refers to the process in which two fluids mix in all proportions – at any concentration of either fluid – such that the resulting mixture remains a single phase. This is the formal, text-book definition of “miscibility”. In petroleum systems, we use the term first-contact miscibility pressure (FCMP) to define any pressure at which the injection gas and reservoir fluid mix on first contact (in any proportion), forming a single phase. The minimum first-contact miscibility pressure ($$MMP_{FC}$$) is obtained from a swell test, defined as the maximum pressure on a p-x diagram (saturation pressure vs. mol% injection gas); shown in the figure below, for a rich and a lean injection gas.

## Multi-Contact Miscibility

In a conventional displacement process, miscibility between a reservoir fluid and an injection gas develops through a dynamic process of mixing, with component exchange controlled by phase equilibria (K-values) and local compositional variation along the path of displacement. In such a process, the injection gas and reservoir fluid are said to be multi-contact miscible (MCM). Multi-contact (dynamic) miscibility investigates the mixtures that form as a result of interaction of phases with different compositions flowing at different velocities in a porous medium (Jessen & Orr, 2008).