In Situ Surface Decorated Polymer Microsphere Technology for Enhanced Oil Recovery in High-Temperature Petroleum Reservoirs

Polymer microspheres have been applied for petroleum reservoir enhanced oil recovery (EOR) in the past decade because they can overcome some drawbacks inherent in in situ polymer gel systems. A novel in situ surface decorated polymer microsphere technology was developed for chemical EOR in high-temperature reservoirs. The swelling performance of the conventional polymer microspheres at room temperature was systematically analyzed and verified by an environmental scanning electron microscope. Their swelling and degradation mechanisms at a high temperature (150 °C) were also examined. To improve the long-term thermal stability of the polymer microsphere, different concentrations of polyethylenimine (PEI) were used as an in situ surface decorating agent. The decorated microspheres remained stable at 150 °C for more than three months, and thermogravimetric analysis indicated that the in situ surface decorated polymer microspheres could remain stable at temperatures up to 310 °C. PEI-decorated 3D network structures on the surface of the microspheres prevented water molecules from entering inner structures, thereby inhibiting the polymer microspheres from swelling in aqueous solution under high temperatures. A sandpack flooding experiment showed how the in situ surface decorated polymer microspheres could effectively plug the porous media for water control and oil recovery improvement even after aging at 150 °C for two months. In situ surface polymer microspheres decorated with PEI can help petroleum engineers better apply this gel technology.