WANG Zhigang, GONG Jianyu, WU Jixiu, YIN Hao, SHI Shanshan, YAN Jia, LI Xiaoyang
Natural gas hydrate is a kind of solid crystalline substance formed by water and methane under high pressure and low temperature, which is considered as the clean energy with the most potential to replace fossil energy by all countries in the world. The status of gas hydrate pilot production in the United States, Japan, India, South Korea and China was summarized. It was pointed out that there were some technical problems for the drilling and completion of natural gas hydrate in the sea area, such as narrow drilling fluid density window, difficult bottom hole pressure control, difficult directional well deflection, poor wellbore and wellhead stability, difficult reservoir reconstruction, and difficult sand control. The research and development status of solid fluidization drilling technology, horizontal well drilling technology, dual gradient drilling technology, pressure controlled casing drilling technology, hydraulic jet micro hole drilling technology, drilling fluid technology, and completion sand control technology were reviewed, and it was proposed that the scientific research efforts such as sand production mechanism, sand production prediction, well completion, drilling and completion equipment and instrument development must be strengthened to provide technical support for large-scale exploitation of natural gas hydrate in sea area.
