Evaluation of oil recovery by alkali/surfactant flooding in multi-layered carbonate reservoirs with different pore sizes

Abstract

Carbonate reservoirs can severely yield oil recovery. Major part of residual oil remains in small pores due to high capillary pressure. Waterflooding therefore ca recover oil only large. Carbonate reservoir can be found as layers with different pore sizes. This structure is naturally formed by different sediments in different environments. Surface active agents such as alkaline substances and surfactants, can be injected to overcome high capillary pressure force between residual oil and rock surface. This study involves with reservoir simulation to study the effects of several parameters on effectiveness of alkali/surfactant flooding in multi-layered carbonate reservoirs with different pore sizes. Optimized chemical flooding base case is first to be identified. From simulation results, it shows that oil recovery efficiency obtained from alkali/surfactant flooding ranges from 40 to 50%, depending on design parameters, whereas waterflooding only yield 25%. Pre-flushed water is not required since it could reduce concentration of injected chemical. Optimum chemical slug size is 0.20PV, whereas critical micelles concentration is best concentration for. High contrast of pore size and high vertical permeability yield advantage on oil recovery factor due to extension of production life. Relative permeability of immiscible mode is more sensitive to efficiency of alkali/surfactant flooding compared to ones of miscible mode.