Method for simulating fluid flows, a computer program and a computer readable medium

A method for improving a recovery of a hydrocarbon from a petroleum reservoir, wherein the method comprises:

• creating a model of said petroleum reservoir in which a reservoir fluid can be split in a plurality of physical phases, said plurality of physical phases comprising a gas phase, an oil phase, a water phase and a microemulsion phase, each physical phase comprising a plurality of components, the plurality of components comprising at least water, a hydrocarbon, and a surfactant,
• performing a simulation on the model with a flash step for calculating at least compositions of each physical phase by evaluating a concentration and a quantity of each component in said physical phases,
• wherein the flash step comprises:
• a first stage comprising at least a first flash to determine compositions of a group of phases, said group of phases being the water phase, the oil phase and the gas phase, and said first flash being performed by omitting the surfactant component in the fluid,
• a second stage wherein, in case the water phase and the oil phase are simultaneously present in the group of phases determined at the first stage, said second stage comprises at least a second flash to determine a microemulsion composition of the microemulsion phase,
• optimizing a surfactant flooding procedure in the petroleum reservoir using the simulation output obtained after the flash step to optimize the timing for injection and the amount of injected surfactant;
• initiating the optimized surfactant flooding procedure;
• and
• recovering the hydrocarbons from the petroleum reservoir utilizing the optimized surfactant flooding procedure.