Synthesis and Application of a Temperature Sensitive Poly(Acrylamide‐Co‐N‐Isopropylacrylamide‐Co‐Sodium P‐Styrene Sulfonate) as a New Water‐Based Drilling Fluid Plugging Agent

In the process of oil and gas production, the failure of drilling fluid caused it to invade the formation, leading to wellbore instability. N‐isopropylacrylamide (NIPAM), acrylamide (AM), and sodium p‐styrene sulfonate (SSS) were used as raw materials, and the P(NIPAM/AM/SSS) (abbreviated as NAS) temperature‐sensitive plugging agent was synthesized by inverse emulsion polymerization. The optimum synthesis conditions were obtained using a redox initiation system. Infrared measurements and UV–visible analysis showed that the target product was successfully prepared, and NAS exhibited a lower critical solution temperature (LCST) of 55°C, with sensitive temperature‐responsive behavior. Rheological and filtration tests, along with high‐temperature and high‐pressure (HTHP) sand tray tests, demonstrated that the temperature‐sensitive plugging agent effectively plugged the formation. Particle size analysis and Zeta potential analysis indicated that the addition of the temperature‐sensitive plugging agent increased the electrostatic stability of bentonite‐based slurry and polymer. Contact angle measurements and micro‐morphology of the mud cake revealed that a hydrophilic‐hydrophobic transition occurred at high temperatures in NAS, forming a dense hydrophobic film on the surface of the mud cake. This film effectively sealed cracks and micropores, reduced the invasion of free water, and improved wellbore stability.