Objective The sulfur remover suitable for oil-based drilling fluid was studied to solve the problems, such as pollution of oil-based drilling fluid by hydrogen sulfide and safety risk caused by hydrogen sulfide overflow in the drilling process of sulfur-bearing gas reservoir in northeastern Sichuan.

Methods The evaluation method and parameters of oil-based drilling fluid contaminated by hydrogen sulfide were established. The formulation of high efficiency sulfur removal agent and compound sulfur removal system for oil-based drilling fluid were optimized.

Results The single agents with excellent sulfur removal effect were liquid sulfur removal agent YT-1, zinc carbonate basic JD-2 and alcohol ether amide CLC, with the saturation of 56.48 mg/g, 21.13 mg/g and 5.8 mg/g, respectively, the high temperature aging sulfur removal rates of 90.10%, 82.60% and 75.23%, and they showed good compatibility with oil-based drilling fluid. The compound sulfur removal system formulation of 4%YT-1+2%JD-2 was optimized. For the 75 mg/L hydrogen sulfide contaminated oil-base drilling fluid, the time to reach the outlet concentration of 0.015 mg/L was only 1.21 min, which reached 171.8 min after adding the compound sulfur removal system. The H₂S concentration of the contaminated oil-based drilling fluid was 0.078 mg/L after high temperature aging, and the H₂S concentration was 0 mg/L after adding the compound sulfur removal system, and the sulfur removal rate reached 100%.

Conclusions The single agent of sulfur removal can improve the sulfur removal effect, providing technical support for the safe and efficient drilling in the high sulfur formation in northeastern Sichuan.