Optimization and Application of Oil-Based Drilling Fluid for Extended-Reach Wells in Shale Oil and Gas Reservoirs

Abstract

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.