Abstract: Aiming at the risk of hydrogen sulfide leakage at the wellhead of an offshore platform, a numerical simulation model was developed to analyze the diffusion process and distribution of hydrogen sulfide leakage in order to provide guidance for prevention of hydrogen sulfide risks. The analysis reveals that following wellhead leakage, hydrogen sulfide rapidly diffuses from the middle deck to the upper deck. The concentration of hydrogen sulfide in areas such as the wellhead region, walkway, water injection manifold, wellhead control panel, and chemical injection pry can reach up to 20 mg/L; the incoming wind can dilute the concentration of leaked hydrogen sulfide in affected areas; moreover, wind direction affects both the distribution pattern of leaked gas and positioning directions of external rescue forces. Due to windshield arrangements, the dilution effect of the incoming wind on hydrogen sulfide is weakened; thus accumulation occurs after wellhead and equipment leakage incidents. In summer, employing open mobile windshields should be considered.

Key words: offshore platform, hydrogen sulfide, leakage, risk