Risk Assessment and Countermeasure on Drilling and Production Process of Deep Water Gas Hydrate in the South China Sea

Abstract Deep-water natural gas hydrate has high environmental risk and high technical difficulty in drilling and production. In order to promote the development of gas hydrate, we develop the assessment methods and control technologies for the operation risk during hydrate drilling and production. The work completed includes: (1) Safety analysis of conductor and wellhead for the hydrate drilling and production Establish a pipe-wellhead stability model to determine the drilling and working conditions under different working conditions. (2) Risk assessment of wellbore blockage in hydrate drilling and production Construct a wellbore multiphase flow analysis model to determine the amount of drilling inhibitor injection; obtain the location and extent of the hydrate blockage. (3) Risk assessment of wellbore instability in hydrate production Combined with hydrate formation properties, ground stress distribution and casing mechanics model, the position of the formation instability, and the damage of casing crushing is determined. (4) Gas diffusion risk assessment due to hydrate decomposition in water Study the distribution of underwater gas diffusion formed by large-area decomposition of hydrate to get the overflow flow risk. (5) Safety model and process risk assessment of hydrate drilling operations Conduct hazard identification and operation safety analysis of hydrate drilling operations, determine the risk level of each operation stage, and support the drilling operation.