A Novel Ultrahigh-Temperature-Resistant and Multivalent-Cation-Tolerant Filtrate Reducer Based on Polysilane for Water-Based Drilling Fluids

Summary As oil and gas exploration and development progressively extend to more than 10,000 m, formation temperature rise and the complexity of downhole environments increase, which imposes more stringent requirements on the performance of water-based drilling fluids (WBDFs). Filtration loss performance has become one of the critical indicators of drilling operation safety and efficiency. Although some of the filtrate reducers exhibit satisfactory temperature resistance, they become ineffective at high temperatures in the presence of high concentrations of cations. This investigation addresses this challenge by synthesizing an inorganic/organic hybrid amphoteric nanomaterial (IOHAN) through the copolymerization of cationic and anionic monomers onto a polysilane backbone with high bond energy and flexible bond angles. The performance of IOHAN in terms of filtration loss, as well as its resistance to temperature and multivalent cations in montmorillonite (MMT) dispersions, is systematically assessed. The results indicate that the MMT dispersion containing 2 wt% IOHAN maintains uniform and stable dispersion at 240°C and demonstrates resistance to contamination from saturated sodium chloride (NaCl), saturated potassium chloride (KCl), 30 wt% calcium chloride (CaCl2), 10 wt% magnesium chloride (MgCl2), and 0.5 wt% aluminum sulfate octadecahydrate (Al2(SO4)3·18H2O) at 240°C. Through laboratory evaluation and field trials, IOHAN was successfully applied in the third interval of a Xinjiang block, where its incorporation into the WBDF reduced filtration loss to below 11 mL while maintaining favorable rheological properties. This method optimizes WBDFs under extreme conditions to meet the challenges of ultradeep formations and enhance drilling safety and efficiency.