Novel Starch Composite Fluid Loss Additives and Their Applications in Environmentally Friendly Water-Based Drilling Fluids

With increasing intensified environmental pressure and a complex drilling environment, developing high-performance fluid loss additives with environmental acceptability is becoming a research focus. Through chemical cross-linking between starch, polyphenols, and lignosulfonate, a polymer SPL was facilely synthesized and it showed good filtration performance in bentonite-water-based drilling fluids (BT-WBDFs). The BT-WBDFs containing 2.0 wt % SPL polymer had a filtration volume of 7.0 mL/30 min at 150 degrees C. Moreover, SPL can resist the effect of 0.75 wt % CaCl2 and 7.5 wt % NaCl at 150 degrees C. The polymer SPL contributed to stable bentonite dispersion and kept enough viscosity of BT-WBDFs at high temperatures. The well-dispersed bentonite and SPL formed a thin and compact filter cake, providing effective plugging and shielding effects during the filtration process. Furthermore, a WBDF based on SPL as the main fluid loss additive was prepared and it displayed excellent high-temperature resistance, rheological property, inhibition, and environmentally friendly performance. This set WBDF has promising guidance on the design of high-performance drilling fluids with excellent environmental protection property.