Water-Free Synthesis of Temperature-Sensitive Polyacrylamide Microgels and Pore Modeled Oil Recovery Performance

Polymer gel treatments can improve sweep efficiency and reduce water production during oil recovery operations. In this article, a novel suspension polymerization method was developed to synthesize a temperature-sensitive microgel. The microgel was prepared by suspension polymerization above the melting point of the monomer in a nonpolar solvent without water. Dry microspheres were obtained, which can be readily used without post-treatment. Two different crosslinkers were employed in the suspension polymerization synthesis to give the particles thermally responsive aqueous swelling properties. After entering pore channels, gel particles expand to engineered size to realize flow profile changes within in a reservoir formation. When dispersed into water under lower temperatures (ambient to 40 °C), the original dry particles can swell about 18 times their original size. Exposure to a harsher environment (e.g., 80 °C) resulted in cleavage of the labile crosslinking agent and some chain cleavage gave a further size expansion. A Millipore film filtration model system was adopted to evaluate pore occlusion performance of the gel particles. It was found that the nuclear pores were effectively sealed by swollen microgels only when gel particle sizes were similar to or smaller than the membrane pores and interpore separation distance.