Pore Scale Investigation of Oil Displacement Dynamics by Smart Waterflooding using Synchrotron X-ray Microtomography

Abstract

Abstract Smart waterflooding is an economic and effective method to improve oil recovery in carbonate oil reservoirs. Recent studies show controlling the salinity and ionic composition of injection water can alter the wettability of carbonate mineral surfaces. The pore-scale oil displacement by smart waterflooding in heterogeneous carbonate reservoirs, especially the dynamics at the early stage, is still unclear. The goal of this study is to examine the role of ion concentrations and types in the oil displacement efficiency and investigate the impact of smart waterflooding on the pore-scale dynamics of oil displacement. A carbonate rock sample was flooded with synthetic high salinity water and other smart water solutions with different sulfate concentrations. The flooding processes were visualized with synchrotron X-ray microtomography. Experimental results show that the smart water with lower sulfate concentration and high salinity water did not change the wettability of the pore surfaces. Higher sulfate ion concentrations in the smart water, in contrast, altered the wettability of carbonate pore surfaces from oil-wet to neutral-wet within the first few minutes of waterflooding. Novel insight was gained on the unique ability of smart water to displace oil in the small pores and through abundant oil channels, which consequently lead to higher oil recovery from the carbonate rock.