Abstract
In recent years, the depth of submarine oil wells and gas wells has increased quickly. The depth of an oil production well reached 1500-2000 meters in practical use, and will be 3000 meters in the next stage. Moreover, geophysical scientists plan to use the science drilling ship“Chikyu”to drill the earth from a seafloor of 4000-meter depth to the Mohorovicic discontinuity. This paper describes deep-sea drilling technology. Although a new method, dual gradient drilling, is proposed, I think that the riser drilling system will still be used in the future. Present techniques of riser drilling are therefore summarized briefly, and problems in deep-sea operation are pointed out. Lastly, I describe the new technology in which development is needed in order to adapt the present riser drilling system to deep-sea operation.
