The offshore S oilfield has entered a high water cut development stage, yet a significant amount of residual oil remains, indicating potential for further enhanced oil recovery. This study evaluates the ultimate oil displacement efficiency of the S oilfield under typical permeability and crude oil viscosity conditions through high multiple waterflooding experiments, thus clarifying the EOR potential during this period. Using online nuclear magnetic resonance testing, the distribution pattern of residual oil during the high water cut stage is revealed. Additionally, by conducting high multiple waterflooding and online nuclear magnetic resonance displacement experiments, the study investigates the ultimate oil displacement efficiency and the mobilization pattern of residual oil in the offshore S oilfield after waterflooding, thereby determining the EOR potential with binary flooding post-waterflooding. The research indicates significant potential for enhancing oil recovery after water flooding in the offshore S oilfield. The ultimate oil displacement efficiency with high multiple water flooding reaches up to 75.2%, which is 17.6 to 25.8 percentage points higher compared to the high water cut stage. During the high water cut stage, residual oil is mainly distributed in pores with radius >10 μm and 1~10 μm, accounting for 32.4%~55.1% and 35.1%~47.7%, respectively. After injecting the binary system, the water cut decreases, and oil production increases significantly, with the ultimate oil displacement efficiency rising to 84.8%, an increase of 33 percentage points, requiring less than 2 PV of subsequent water flooding. The binary system effectively mobilizes residual oil in pores of different sizes by increasing sweep volume and oil displacement efficiency.Therefore, binary flooding after water flooding in the offshore S oilfield can effectively enhance oil recovery and significantly reduce development time costs.

Despite advances in renewable energy sources, the world's current infrastructure and consumption patterns still heavily depend on crude oil. Enhanced oil recovery (EOR) is a crucial method for significantly increasing the amount of crude oil extracted from mature and declining oil fields. Nanomaterials have shown great potential in improving EOR methods due to their unique properties, such as high surface area, tunable surface chemistry, and the ability to interact at the molecular level with fluids and rock surfaces. This study examines the potential use of incorporating ethoxylated molybdenum disulfide with a unique three-dimensional flower-like morphology for overcoming the challenges associated with oil recovery from reservoirs characterized by complex pore structures and low permeability. The synthesized nanomaterial features a chemical composition that encompasses a polar ethoxy group linking molybdenum disulfide nanosheets and an alkylamine chain. The ethoxy group promotes interactions with water molecules through hydrogen bonding and electrostatic forces, disrupting the cohesive forces among water molecules and reduction surface tension at the oil–water interface. As a result, the nanomaterial achieves an ultra-low interfacial tension of 10⁻³ mN/m. Core flooding experiments demonstrate a significant oil recovery of approximately 70% at a concentration as low as 50 ppm. This research paves the way for the design and synthesis of advanced extended surfactant-like nanomaterials, offering a promising avenue for enhancing oil recovery efficiency.