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

Abstract

In the drilling industry, the demand for environmentally friendly additives with high thermal stability is increasing due to the dual factors of increasing environmental pressure and high-temperature oil layers. However, commonly used non-toxic and biodegradable additives, such as etherified modified starch, cannot withstand temperatures higher than 150 °C. Additionally, natural polymers with better thermal stability obtained through graft modification with sulfonated monomers face challenges in meeting the standards of toxicity and biodegradability. To address these technical problems, a novel graft and crosslink copolymer, St-AA/AM/NVP/MBA (SAANM), was synthesized from corn starch by combining graft modification with a non-sulfonated monomer and cross-linking modification. Laboratory evaluation results confirm that the thermal stability of SAANM in a nitrogen atmosphere was close to 300 ℃, and it exhibits excellent temperature resistance up to 170 °C in bentonite-based mud, while also retaining the non-toxic and biodegradable characteristics of starch. The water-based drilling fluid (WBDF), added with SAANM, demonstrated outstanding rheological properties, fluid loss control performance, and environmental friendliness after aging at 170 °C and being polluted by high concentrations of NaCl or CaCl2. The successful application of SAANM in a high-temperature directional well in an offshore oil field confirms its potential for borehole cleaning and wellbore stability.

A Review in Polymers for Fluid Loss Control in Drilling Operations

“…The remarkable advantages of starch nanosphere, such as insignificant influence on rheology, outstanding filtration control at elevated temperatures and high biocompatibility, make it a promising filtrate reducer in high-performance water-based drilling fluids. You et al [74] reported a novel grafted and crosslinked copolymer starch as filtrate reducer. The copolymer was obtained through grafting and crosslinking starch with acrylic acid (AA), acrylamide (AM), N-vinylpyrrolidone (NVP), and N, N-methylene bis acrylamide (MBA) in aqueous solutions.…”