Enhanced capillary imbibition by dispersion during surfactant flood for dual-porosity and dual-permeability models

Abstract

Recovery from naturally fractured carbonate reservoirs by waterflooding leaves behind at least half of the initial oil in place. Various surfactants, which alter matrix wettability and reduce interfacial tension, can be considered as EOR for the residual oil in the matrix. In carbonate reservoirs, imbibition effect plays a significant role on oil recovery. Dispersion, which enhances imbibition effect, has to be taken into account for surfactant flood process especially under naturally fractured carbonate reservoirs. This paper presents effects of dispersion on surfactant flood process under different fracture gridding approaches. Single-porosity model represents non-fractured sandstone reservoir. Conventional dualporosity model and dual-permeability model characterize naturally fractured carbonate reservoir. Injected surfactants have promising impacts on both wettability alteration and interfacial tension reduction. Firstly, surfactant flood in single-porosity model is investigated to compare impacts of fracture systems on the dispersion. Next, the influence of capillary imbibition in surfactant flood is investigated in both conceptual fracture systems. Furthermore, quantitative assessments of enhanced capillary imbibition induced by dispersion phenomenon of surfactants in both fracture formulations have been conducted.