Chikyū is a Japanese scientific drilling ship built for the Integrated Ocean Drilling Program. The vessel is designed to ultimately drill seven kilometres beneath the seabed, where the Earth's crust is much thinner, and into the Earth's mantle, deeper than any other hole drilled in the ocean thus far. While the planned depth of the hole is significantly less than the Russian Kola Superdeep Borehole, the scientific results are expected to be much more interesting since the regions targeted by Chikyū include some of the most seismically-active regions of the world. Other deep holes have been drilled by the drill ship JOIDES Resolution during the Deep Sea Drilling Project and the Ocean Drilling Program.
Operation
The Japanese part of the IODP program is called Chikyū Hakken, Japanese for "Earth Discovery". Chikyū is operated by the Centre for Deep Earth Research, a subdivision of the Japan Agency for Marine-Earth Science and Technology. JAMSTEC also operates the DSV Shinkai, Earth Simulatorsupercomputer and other marine scientific research projects. CDEX is responsible for the services to support activities including on-board staffing, data management for core samples and logging; implements engineering site surveys; and conducts engineering developments. CDEX contracts with the Mantle Quest Japan Company for the navigation of the ship. The Chikyū Hakken program is part of an international scientific collaborative effort with scientists from the United States, ECORD, a consortium consisting of several European countries and Canada, China, South Korea, Australia and New Zealand, and India.
Design
D/V Chikyū was built by the Mitsui Engineering & Shipbuilding and launched on 18 January 2002 in Nagasaki, Nagasaki. The ship was outfitted by the Mitsubishi Heavy Industries and delivered to JAMSTEC on 29 July 2005. The hull of the ship is 210 meters long, 38 meters in width, 16.2 meters high, and has an approximate gross tonnage of about 57,000 tons. The ship has a draft of 9.2 meters and a maximum cruising speed of 12 knots. The amidships derrick is 121 m above sea level, and the top drive has a lifting capacity of 1,000 tons. Its complement of 150 crew are divided between 100 operators and 50 science personnel, with at sea crew changes handled by helicopter transfer. Key innovations include a GPS system and six adjustable computer controlled azimuth thrusters that enable precise positioning to maintain a stable platform during deep water drilling. The maximum drilling water depth for riser drilling is 2,500 meters and can support a drill string up to 10,000 meters long. The helipad can serve very large helicopters transporting as many as 30 persons per landing.
History
The D/V Chikyū was built for deep-sea geological scientific research, which now includes not only research of earthquake-generating zones in the Earth's crust but also hydrothermal vents and subseamethane hydrate research. On 16 November 2007Chikyū began drilling the NanTroSEIZE transect as planned, reaching 1,400 meters at the site of a future deep subsea floor observatory. The first stage of four NanTroSEIZE Stages was completed in February 2008. The whole project was envisioned to be completed by 2012. The ship was damaged by the 2011 Tōhoku earthquake and tsunami on 11 March 2011. The ship was moored 300 m off the coast of Hachinohe, Aomori, but was cut loose by the tsunami and collided with a pier of Hachinohe port. One of the six stabilizers was damaged and a 1.5 meter hole was made in the bottom. Local preliminary school children who were visiting the ship at the time of the earthquake spent one night on board and were rescued by Japan Self-Defense Forces helicopters next day. The ship was repaired at a dock in Shingū, Wakayama and returned to service in June 2011.
World record
According to the IODP, on 27 April 2012, Chikyū drilled to a depth of 7,740 meters below sea level, setting a new world record for deep-sea drilling. This record has since been surpassed by the ill-fated Deepwater Horizonmobile offshore drilling unit, operating on the Tiber prospect in the Mississippi Canyon Field, United States Gulf of Mexico, when it achieved a world record for total length for a vertical drilling string of 10,062 m. The previous record was held by the U.S. vessel Glomar Challenger, which in 1978 drilled to 7,049.5 meters below sea level in the Mariana Trench. On 6 September 2012 Scientific deep sea drilling vessel Chikyū set a new world record by drilling down and obtaining rock samples from deeper than 2,111 meters below the seafloor off the Shimokita Peninsula of Japan in the northwest Pacific Ocean. In addition, the 27 April 2012 drilling set a record for the depth of water for drilling of 6960 m. That record still stands.
