A Study of Miscible Displacement Mechanism of Alcohol Mixture by Coreflooding

Alcohol flooding is one of miscible flooding techniques and the major benefit over others is that the miscibility can be achieved at very low pressure. The ability of alcohol to create miscibility with both oil and water results in single-phase flow, yielding the maximum flow ability at absolute permeability. Oil soluble alcohol and water soluble alcohol are selected and mixed at appropriate proportion to create maximum miscibility region on ternary phase diagram. From the study, a mixture of methanol and butanol with a ratio of 4:6 results in the best miscibility power in oil-brine-alcohol system. Correction of miscibility due to pressure is performed in coreflood machine and moreover, effects of alcohol slug size and initial oil saturation are investigated. Pressure difference across core sample is observed as it is related to number of flowing phase in core sample. From the experiment, it is observed that alcohol slug size of 0.4 pore volume yields the best miscibility condition as it can prevent loss of miscibility from chasing water. High initial oil saturation is not desirable condition as it can quickly deplete butanol from alcohol slug. Higher portion of butanol would be required in case of high initial oil saturation.