Experimental Study of Effective Amphiphilic Graphene Oxide Flooding for an Ultralow-Permeability Reservoir

Current displacing agents for enhanced oil recovery (EOR), i.e., water, gas, foam, and common nanofluid, suffer plenty of problems in ultralow-permeability reservoirs, with a limited oil recovery. A novel agent, amphiphilic graphene oxide (H–GO), is confirmed to be effective in EOR under such unconventional conditions. We present the fundamental mechanisms for the improved performance by H–GO. Specifically, the effectiveness of H–GO is experimentally verified from multiple perspectives, including emulsifying ability, interfacial activity, and wettability alteration action. Experimental observations show that H–GO has excellent emulsifying ability that the amphiphilic Janus nanosheet is inclined to move onto the oil–water interface. Pickering emulsion formed by H–GO and oil, with an average droplet diameter of only 2.66 μm, is considerably stable, which can be maintained for at least 30 days. Besides, H–GO reduces the oil–water interfacial tension to 0.493 mN/m, 1 order of magnitude lower than that between the common nanoparticle and oil. H–GO shows better wettability alteration efficiency compared to a common nanoparticle. Consistently, micromodel tests show that H–GO gives a promising sweep and displacement efficiency to oil. As a result of these advantages of H–GO, the oil on the rock surface can be separated and form the emulsion or oil zone easily, leading to the incremental recovery of 10.83% using only H–GO (1 mg/mL) in an ultralow-permeability core. The study provides a novel approach for EOR in ultralow-permeability reservoirs. The high performance, convenient operation, and environmental protection make H–GO flooding have great potential for oilfield practice.