Preparation and performance evaluation of heat resistant and salt resistant anionic fluid loss reducer for water-based drilling fluid

In this investigation, a new micro-crosslinked anionic polymer resistant to elevated temperature and high salinity, PKDASN, was synthesized using 3-chloropropyltriethoxysilane (KMB703), N, N-Dimethylacrylamide (DMAM), 2-acrylamido-2-methylpropanesulfonic acid (AMPS), N-vinyl caprolactam (NVCL), and sodium (4-vinyl phenyl)methanesulfonate (SVM) employing free radical polymerization in a water-based solution. The structure of PKDASN was analyzed using Fourier-transform infrared spectroscopy, nuclear magnetic resonance spectroscopy, and X-ray photoelectron spectroscopy, while its microstructure was analyzed using scanning electron microscopy. Thermogravimetric analysis showed that the pyrolysis temperature of PKDASN was above 294°C. Adding KMB703 enables the polymer to form a dense and stable spatial network. This intensified polymer network could interact with bentonite via intermolecular force and Coulomb force and form a dual grid structure, which presents impressive stability and control of filtration in saltwater. This is mainly achieved through creating a “silane coupling layer” on the particle surface by KMB703, which facilitates the crosslinking and aggregation of the polymer, thereby reinforcing the polymer's framework. This implies that under high-temperature conditions of 230°C, 3 wt% PKDASN can improve the filtration effectiveness of drilling fluids and exhibit resistance to 15 wt% NaCl contamination. American Petroleum Institute filtration(FL API ) and High temperature and high pressure filtration(FL HTHP ) values were 4.6 and 23.0 mL, respectively. Therefore, this investigation provides a novel approach to utilizing the designated silane agent for the advancement of filtration loss additives in drilling fluids resistant to elevated temperature and high salinity.