Risk analysis on the blowout in deepwater drilling when encountering hydrate-bearing reservoir

Significant risks are associated with deepwater drilling when encountering hydrate-bearing reservoir. This paper analyses the influencing factors of geologic, environmental and drilling risk as well as their impacts on safety operations in drilling of hydrate-bearing reservoir. A fault tree is established based on a large-scale blowout as the top event. The key risk factors are analysed and the methods used to control these risks are identified. Drilling design, well control design and risk control measures must maintain precise wellbore pressure and temperature in drilling hydrate-bearing reservoir under deepwater conditions, which inhibit hydrate dissociation and reduce the risk of large-scale blowout.