Objective  In response to the demand for small-sized and high-performance profile control agent particles for high water content well groups in Bohai Oilfield, solid core structure submicron-micron swellable particle profile control agent (PAS) was synthesized through free radical polymerization using acrylamide (AM) and 2-acrylamido-2-methylpropanesulfonic acid (AMPS) as main agents, N, N'-methylenebisacrylamide (MBA) and polyethylene glycol diacrylate (PEGDA) as crosslinking agents, and nano silica as the modifying agent.

Methods  The two-step process of pre-grinding-ball milling was used for grinding, and its molecular structure was characterized by infrared spectroscopy. The effects of temperature and salinity on its properties were studied. The injection performance, deep sealing ability, erosion resistance, and enhanced oil recovery of PAS were studied using a sand-filled pipe model displacement experiment.

Results  PAS is evenly distributed in an aqueous solution, with a median particle size of 17.3 μm, and the strength of the gel was still high after 90 days of aging at 120 ℃ and 200 000 mg/L. The experiment on plugging and enhanced oil recovery showed that at a permeability of 3 000×10⁻³ μm², the plugging rate reached over 98.0%, and the enhanced oil recovery of heterogeneous cores was increased by more than 22.8%.

Conclusion  Field tests with an average daily oil production of 28.31 m³ on high porosity and permeability oil reservoirs were carried out, which showed significant effects on oil production rate and water control.