Study of a novel cross linked graft copolymer starch in water-based drilling fluid

Abstract In the drilling industry, demand for environmentally friendly additives with high thermal stability is increasing due to dual factors of environmental pressure and high-temperature oil layers. However, commonly used non-toxic biodegradable additives, such as etherified modified starch, cannot withstand temperatures higher than 150 °C. Additionally, natural polymers better obtained through graft modification sulfonated monomers face challenges in meeting standards toxicity biodegradability. To address these technical problems, a novel crosslink copolymer, St-AA/AM/NVP/MBA (SAANM), was synthesized from corn starch by combining non-sulfonated monomer cross-linking modification. Laboratory evaluation results confirm that SAANM nitrogen atmosphere close 300 °C, it exhibits excellent temperature resistance up 170 °C bentonite-based mud, while also retaining characteristics starch. The water-based fluid (WBDF), added SAANM, demonstrated outstanding rheological properties, loss control performance, friendliness after aging at being polluted concentrations NaCl or CaCl 2 . successful application directional well an offshore field confirms its potential borehole cleaning wellbore stability.