Degradation behavior and mechanism of P(AM/AA/AMPS)@PLA core-shell self-degrading temporary plugging agent

Shielding temporary plugging is a simple and effective technology to protect oil–gas formation drilling fluid, with temporary plugging material as its core. However, the existing temporary plugging agents have problems such as a too-fast degradation rate under high-temperature conditions, poor degradation performance, and reservoir damage resulting from degradation products. Aiming at these problems, and with acrylamide (AM), 2-Acrylamido-2-methylpropanesulfonic acid (AMPS), acrylic acid (AA), and polylactic acid (PLA) as raw materials to prepare the self-degradation shielding temporary plugging agent DSTPA by reverse suspension polymerization, this paper has characterized its chemical composition, chemical structure and thermal stability, and studied its compatibility with drilling fluid and plugging performance. The influence of temperature, pH, and salinity on the degradation behavior of DSTPA is also investigated, and the degradation process of DSTPA is analyzed by electron microscopy (SEM) and infrared spectroscopy (FT-IR) scanning. The results show that DSTPA boasts good pressure-bearing and plugging performance, with its plugging rate above 90 % and the core damage rate lower than 5 %; DSTPA demonstrates good compatibility with drilling fluid and insignificant effect on the rheology of drilling fluid system; a small amount of DSTPA can remarkably reduce the filtration loss of drilling fluid: 1 % DSTPA addition reduces the filtration loss by 24 mL. The degradation experiments of DSTPA show that increased temperature and pH can promote the self-degradation of DSTPA, but increased salinity inhibits its self-degradation. DSTPA boasts good temperature resistance, with its complete degradation lasting 144 h under 180 ℃. FT-IR analysis and SEM analysis showed that the degradation of DSTPA was mainly due to the breaking of amide bonds and ester bonds, resulting in the collapse of the three-dimensional network structure of its molecular structure, thereby degrading into an aqueous solution with a viscosity comparable to water.