メタンハイドレート開発に向けての掘削技術の挑戦

抄録

The resource development of marine methane hydrate deposits will require drilling of considerable numbers（tens to hundreds）of wells in relatively shallow and unconsolidated formations beneath deepwater due to limited area of drainage of each well. Safety and cost reduction of drilling operation could be a critical technical challenge of the development of the unconventional energy resource. The Japanese national gas hydrate resource program lead by MH21 research consortium performed twice gas production tests from gas hydrate deposits in the eastern Nankai Trough in 2013 and 2017 and drilling engineers have encountered many technical challenges and solved them for the successful testing. Among them, three technical challenges; pressure corning technology that allowed the sampling of high quality gas-hydrate bearing samples, an attempt of wash over operation for the recovery of a sand control device that had been buried with produced sand in the previous year, and screw back troubles happened on drilling strings due to ocean currents and countermeasures to them are reported in this article.