Optimization and Application of Oil-Based Drilling Fluid for Extended-Reach Wells in Shale Oil and Gas Reservoirs
To address the technical challenges of wellbore instability, excessive friction and torque, and poor hole cleaning encountered in the drilling of extended-reach wells in shale oil and gas reservoirs, this paper determined the optimal formula by optimizing the emulsification system, rheological control system, and filtration and plugging system: oil-water ratio of 85:15, 1.4% emulsifier N180, 0.4% wetting agent YX-1, 1.2% calcium oxide, 0.8% organically modified bentonite, 1.2% polyamide M2000, 2.2% asphalt R45, 2.5% 800-mesh calcium carbonate, 2.5% 1500-mesh calcium carbonate, with barite to adjust the density to 1.8 g/cm3. Laboratory experiments showed that after aging the optimized system at 140 °C for 16 hours, the demulsification voltage reached 895 V, the high temperature and high pressure (HTHP) filtration loss was only 1.9 mL, the cuttings hot rolling recovery rate was 97.5%, the extreme pressure lubrication coefficient was 0.06, the resistance to bentonite contamination reached 0.8%, the resistance to salt and calcium contamination reached 0.5%, and the core permeability recovery value exceeded 94%. In field application, the rate of penetration (ROP) was increased by 18.5% compared with adjacent wells, no accidents such as wellbore collapse and stuck pipe occurred, and the qualification rate of cementing quality was 100%. The research results provide technical support for the safe and efficient drilling of extended-reach wells in shale oil and gas reservoirs and have important popularization value.