Effect of In-situ Dual Surfactant Formulation on Spontaneous Oil Deformation: A Comprehensive Study from Mechanism Discovery to Oil Recovery Application

Abstract

An in-situ dual-surfactant formulation is developed by using a novel cationic surfactant adsorbing the in-situ acid components in crude oil. As a result, various oil deformation patterns are first revealed and applied to control the viscous instabilities for oil recovery application. To this end, four dynamic oil displacement tests are conducted via camera snapshotting or X-ray microtomography in two and three dimensions, without and with porous media, in single to multipore-throat structures as well as through pore-scale and macroscale visualizations. As suggested in the results, displacing the oil phase using a 20 mmol/L cationic surfactant is the most effective method to suppress interfacial instability. The preferential flow path is frequently diverted by the repeated change of oil shape at a low flow rate. By contrast, emulsification plays a key role when the flow rate is high. It depends on which is dominant between the oil deformation and shearing velocity. From a deep insight into the pore spaces, oil deformation patterns are classified into oil spreading, shrinking, splitting, film detachment, and bridge breakup. The most significant oil deformation in the tortuous pore spaces occurs after 10 min of aging. Based on this time, we propose a new injection−alternate− stop scenario to suppress the viscous fingering and maximize the oil recovery efficiency to 80% in a large-scale reservoir.