Operational overview of the first offshore production test of methane hydrates in the Eastern Nankai Trough

摘要

In March 2013, the world’s first field trial of gas production from marine methane hydrate deposits wasconducted in the Daini Atsumi Knoll area of the Eastern Nankai Trough off the Pacific coast of Japan asa process to bring gas hydrates under seafloor to valuable energy resource. The technique used todissociate the ice-like material was “depressurization method” that had been applied in the previousproduction test in Mallik site, the Northwest Territories, Canada in 2007-2008. Japan Oil, Gas and MetalsNational Corporation (JOGMEC) as a part of MH21, the Research Consortium for Methane HydrateResources in Japan planed and supervised the project with the funding of the Ministry of Economy, Tradeand Industry (METI), and scientific supports from the National Institute of Advance Industrial Scienceand Technology (AIST). One production well with two monitoring boreholes were drilled in the test sitefor the test. Along with the flow test operation, intensive data acquisition program was planned andimplemented to understand behavior of methane hydrate dissociation- bearing sediments against depressurization.To realize high degree of drawdown in relatively shallow formation below deepwater, severaldownhole devices were designed and installed.The flow test started in the morning of March 12 and lasted until severe sand production forced toterminate the operation six days later. During the stable production term, gas flow rate was approximately20,000m~3 under atmospheric condition, and gas liquid ratio was larger than 100. A lot of data includingformation temperatures, fluid pressure and temperature, and physical property changes in the formationwere obtained. The data taken are under studies to verify applicability of the depressurization techniqueas a methane hydrate production technologies.