Abstract:Drilling is the most direct means of natural gas hydrate exploration and the necessary procedure of natural gas hydrate development. Natural gas hydrate, especially the exploration and development of marine natural gas hydrate, raises a higher demand to drilling technology. On the basis of summarizing the present drilling status and drilling technology of natural gas hydrate in the world, the challenges and future development directions of natural gas hydrate drilling are analyzed. It is summarized as below. The exploration and trial production of natural gas hydrate have been carried out in many permafrost areas and oceanic areas around the world, showing a better prospect of natural gas hydrate exploration and development. Natural gas hydrate drilling usually combines with logging-while drilling data (LWD) and employs conventional drilling equipment and water-based drilling fluids. The completion methods employed in natural gas hydrate test wells are different, with having not formed effective completion technology series yet. The characteristics of natural gas hydrate, such as temperature-pressure characteristics, reservoir characteristics, burial depth characteristics, mechanical characteristics and so on, commonly determines the challenges of natural gas hydrate drilling in terms of wellbore instability and narrow safety window of drilling fluid density. In the future, the application of managed pressure drilling, underbalanced drilling, drilling with casing, insulated riser drilling, drilling and completion of horizontal wells in shallow and unconsolidated formations, combination of submersible drilling equipment and economically, environmentally friendly and efficient low-temperature drilling and completion fluid in natural gas hydrate drilling should be further explored.