Experimental Study on Low-Toxicity and Environment-Friendly Oil-Based Drilling Fluids

To enhance the environmental protection performance of oil-based drilling fluids, and to eliminate problems related to the biological toxicity and difficulties in the degradation of conventional drilling fluids, an innovative low-toxicity and environment friendly oil-based drilling fluid has been developed. During its development, normal raw oil was primarily processed into base oil through desulfurization and dearomatization, then composed modifiers with innovative techniques were deployed to generate modified organic clay. Eventually, a low-toxicity oil-based drilling fluid system was generated through the optimization of additives and added specific volumes of such additives in the drilling fluid. Experimental results show that the innovative drilling system has filtration losses of 3.2-9.5 mL, a maximum differential precipitation density of 0.06 g/cm3 and ES over 1 190 V under high pressure and high pressure. In addition, the emulsion system can maintain desirable stability after water or low-quality clay invasion with a secondary cutting recovery rate of 99.17%, linear expansion rate of 1.92% and permeability recovery rate 88.5%-94.6%. Research results show that the newly developed low-toxicity and environmental-friendly oil-based drilling fluid system possesses outstanding rheological properties, stability, anti immersion, lubrication, inhibition and reservoir protection performances and can meet the requirements for safe and high-efficiency drilling and environmental protection in complex formations in the drilling of deep and ultra-deep wells.