Effect of Dynamic Water on Oil Recovery and Relative Permeability of Siliceous Carbonates Outcrops

Abstract

Abstract In reservoir simulation, one specific input requirement is relative permeability. With the current increasing interest to use brine with modified composition (also known as dynamic water) for enhanced oil recovery, our models lack such information. Therefore, our study aims to establish relative permeability curves for multiple dynamic water injection scenarios, which should help establish better reservoir models to simulate production. Two outcrop samples which similarities after being assessed using X-ray diffractometry (XRD) and thin-section microscopy in addition to petrophysical characterization. The rock samples were initially saturated with 200 kppm NaCl brine and then desaturated using crude oil by a centrifuge to irreducible water saturation. This was followed by 15 days aging at 90 degC under confining pressure. Unsteady-state relative permeability was then conducted and the efficiency of different dynamic waters, i.e., Arabian Gulf seawater and a diluted version of it, were investigated. In addition, the potential determining ions (i.e., sulfate (SO42-) and magnesium (Mg2+) were investigated. From the reported results, and among all tested brines, diluted seawater and diluted seawater with double sulfate ions showed the highest oil recovery. Relative permeability curves reflected wettability alteration and sensitivity to a change in salinity and ionic composition. The oil relative permeability (Kro) was more sensitive and increases, while water relative permeability (Krw) was less sensitive and slightly decreases with dilution of solutions. Cross-over water saturation point showed a mixed-wet to weak water-wet conditions with values close to or slightly higher than 50%. The results of this work show the potential of dynamic water in enhancing oil recovery. The generated relative permeability curves can be utilized for reservoir simulators to evaluate the potential of dynamic water at a reservoir scale, as such data availability is limited in the current open literature.