Construction and degradation mechanism of polylactic acid-pH-responsive microgel composite system plugging system

Polylactic acid (PLA) is often used as a degradable temporary plugging agent for bridging plugging, but its particles are rigid, resulting in lax plugging. Based on the acidic properties of the polylactic acid (PLA) degradation solution, pH-responsive microgels were used as flexible filler particles to construct a completely degradable polylactic acid (PLA)-pH-responsive microgel composite temporary plugging system. Using diethylaminoethyl methacrylate (DEAEMA) and acrylamide (AM) as functional monomers, pH-responsive flexible microgel particles were prepared by soap-free emulsion polymerization. The microgels were characterized by FT-IR, SEM, particle size distribution, Zeta potential, electrical conductivity, and surface tension at different pH conditions. The results showed that microgel particles could be completely dissolved in acidic environment. Furthermore, the plugging experiment showed that the plugging rate of the polylactic acid-microgel system reached more than 99%, which was 5.91% higher than that of polylactic acid particles. The addition of pH-responsive microgel could catalyze the degradation of polylactic acid, and the degradation speed was accelerated with the increase of the dosage. Meanwhile, the microgel was completely dissolved by the degradation solution of polylactic acid, forming a clear and transparent solution. Finally, the synergistic degradation mechanism of the polylactic acid-pH-responsive microgel composite system plugging agent system was summarized. This system provides a new idea for the design of a temporary plugging agent and has a broad application prospect in acid fracturing.