Study on Preparation and Mechanism of High Temperature and High Salt Resistance Fluid Loss Reducer

As global oil and gas exploration gradually shifts toward deeper and ultradeep reservoirs, the performance of fluid loss control additives in high-temperature and high-salinity environments faces significant challenges. In this study, a fluid loss control agent, DMAPAN, suitable for high-temperature and high-salinity conditions, was synthesized using <i>N</i>,<i>N</i>-dimethylacrylamide (NNDMA), 2-acrylamido-2-methylpropanesulfonic acid (AMPS), maleic anhydride (MA), and <i>N</i>-vinylpyrrolidone (NVP) as monomers via aqueous solution polymerization. Structural characterization and performance testing showed that DMAPAN exhibits good thermal stability and significantly reduces fluid loss at 230 °C. It also demonstrates excellent resistance to high temperature and high salinity, being able to withstand 20% NaCl and 2% CaCl₂. Mechanistic analysis reveals that DMAPAN reduces the clay particle size, forms a spatial network structure, and enhances the Zeta potential, thereby improving the stability of the drilling fluid and reducing fluid loss. This study provides theoretical support and practical guidance for optimizing the performance of deep-well drilling fluids.