Using Nanopolymeric Microspheres for Enhanced Oil Recovery in a High-Salt Oil Reservoir in B-3 Block, Erdos Basin, China

To address the challenges of inefficient water flooding and low oil recovery in high-salinity, low-permeability reservoirs of the B-3 Block, Erdos Basin, this study developed a novel temperature-resistant and salt-tolerant nanosphere system based on an acrylamide (AM)/2-acrylamido-2-methylpropanesulfonic acid (AMPS) copolymer. Systematic physical simulation experiments were conducted to evaluate the performance and enhanced oil recovery (EOR) potential of these nanospheres under high-temperature and high-salinity conditions. Results demonstrate that the nanosphere system retains excellent swelling stability and plugging capacity at a salinity of 23,800 mg/L and 50 °C while achieving effective injectivity and in situ migration within cores possessing pore-throat sizes of 10–300 × 10–3 μm2. Oil displacement experiments confirmed that, compared to conventional water flooding (with a recovery factor of ∼45%), the nanosphere-assisted process significantly reduced water cut by 5–10% and increased the ultimate oil recovery by 15–17%. The underlying EOR mechanism is primarily attributed to effective blockage of high-permeability channels and diversion of subsequent injection fluid, thereby improving sweep efficiency. The study also identified the optimal injection parameters: a concentration of 1250 mg/L, a rate of 0.3 mL/min, and a volume of 1.0 PV, which, under conditions of a permeability of 60.61 × 10–3 μm2 and a permeability contrast of 2.29, yielded the most pronounced profile control and displacement effect. This work demonstrates that the developed nanosphere system offers a robust and effective technical solution for the efficient development of challenging high-salinity, low-permeability reservoirs.