Natural gas hydrate is a potential alternative rich source of energy, which is efficient and environmentally friendly. The efficient development of natural gas hydrate resources is of great strategic significance to our country, especially in meeting our growing energy consumption needs, ensuring national energy security and promoting green development. On the basis ofthe review of natural gas hydrate mining technology and research status at home and abroad, this paper puts forward a new idea of using a cavitation jet drilling radial horizontal well and screen completion integrated method to develop deep sea natural gas hydrate buried in shallow layers. The paper mainly introduces the research foundation and research progress of key technologies including the overall process flow, jet drilling capacity, jet bit feeding method and extension limit, wellbore trajectory measurement and control. Then, the open source simulator HydrateResSim is used to perform depressurization induced gas production simulation by applying vertical and radial wells. This paper also discusses the main research directions of the technology in thefuture, which includes the pore-forming characteristics of hydrate reservoirs under the action of high-pressure water jets, the law of multiphase flow in the wellbore of hydraulic jet drilling, the evaluation and control of the wellbore stability of micro-holes inhydrate reservoirs, gas hydrate radial horizontal well stimulation mechanisms and effect evaluation, parameter optimization ofradial horizontal well exploitation in argillaceous silt hydrate reservoirs, etc. The study found that the cavitation jet drilling radialhorizontal well method has the characteristics of pure hydraulic high-efficiency drilling, ultra-short radius steering, precise target drilling, fine sand control of the main wellbore, and flexible liner coarse protection of the radial well. The formed multi-layerand multi-lateral wellbores can be combined with a depressurization method or thermal excitation method to greatly expand thecontact front of the reservoir and improve the efficiency of heat utilization. The research results are expected to lay the foundation for the early realization of the commercial exploitation of natural gas hydrates.
LI Gensheng, TIAN Shouceng, ZHANG Yiqun. Research progress on key technologies of natural gas hydrate exploitation by cavitation jet drilling of radial wells. Petroleum Science Bulletin, 2020, 03: 349-365.
