Low-Salinity Brine Enhances Oil Production in Liquids-Rich Shale Formations

Abstract Low-salinity waterflooding has proven to be an appealing technique for enhancing oil recovery in conventional reservoirs. However, few studies have been conducted on low-salinity brines (LSBs) for hydraulic fracturing in liquids-rich shale plays with or without surfactant. Additionally, as operators tend to shift from fresh water to 100% produced water, the implications of such a switch must be understood from a production standpoint. Therefore, the effects of LSBs on oil recovery from liquids-rich shale should be investigated. In this study, LSBs with or without surfactant were injected into the crushed, oil saturated Muskwa shale from Canada. Laboratory results suggest that LSB (≤4% KCl) extracts more hydrocarbon than high salinity brine (HSB) (≥8% KCl). Notably, additional oil recovery was observed when surfactant was used in LSB. Interfacial tension (IFT) reduction decreased with increasing salinity but remained constant for LSB with surfactants across all salinities examined. Short-lived oil in water emulsions were observed in LSB in the presence of surfactant. Additionally, LSBs with surfactant were injected into a microfluidic based reservoir on a chip (ROC) device, where pore size was comparable to that of shale. The visualized oil recovery on the ROC was consistent with that found in core flooding tests. These reported results provide a potential methodology for optimizing source water before hydraulic fracturing operations. LSBs with properly tailored surfactant additives are imperative to helping enhance well productivity.