DEEPER THAN EVER

The Japan Agency for Marine-Earth Science and Technology's deep-drilling vessel Chikyu began test drilling off the Shimokita Peninsula in Aomori Prefecture in August 2006. The ship will drill 2,200 meters below the sea floor, which is 1,200 meters below the surface of the ocean. Through this record-breaking deep drilling, researchers are hoping to achieve such results as clarifying the ecology of microorganisms that live deep underground.
Riser Drilling
The 57,000-ton Chikyu, which means earth, was completed in July 2005 at a cost of ¥60 billion ($515 million at ¥116 to the dollar). It will be used in the hope of discovering the mechanisms that trigger huge earthquakes where continental and sea plates come into contact, and also to sample the mantle underneath the earth's crust. With a drilling capacity of 7,000 meters - the deepest in the world - the vessel will make use of a unique technology called riser drilling, in which deep drilling is achieved using dual pipes to circulate mud. When digging deep below the sea floor, high pressure may cause holes to collapse or water and gas to suddenly spout. This riser drilling technology is being implemented on a scientific drilling ship for the first time ever as a safeguard against such occurrences.

A diagram of the Chikyu's drilling plan (c) JAMSTEC

A team comprised of 30 researchers and engineers from Japan, the United States, and Europe will participate in this test drilling. Over a three-month period beginning in August, Chikyu will be positioned at a point 80 kilometers off the Shimokita Peninsula, and the team will attempt riser drilling while checking their precise position using data from man-made satellites. According to the agency, four years went into hammering out a painstaking drilling plan, including selecting a suitable location and undertaking geological surveys. The agency is also hopeful of extracting methane hydrate, which some anticipate may one day be used as a source of energy.
International Drilling Effort
Up to now, the deepest scientific drilling on record was by the US driller JOIDES Resolution, which achieved a depth of 2,111 meters below the Pacific Ocean sea floor off the coast of Costa Rica in Central America. Chikyu is scheduled to undertake riser drilling in the 2,000- to 4,000-meter range from November 2006 to August 2007.

The Chikyu at night (c) JAMSTEC / CDEX

Operations using Chikyu and headed by the Integrated Ocean Drilling Program will begin in September 2007, with researchers from 21 nations participating. The IODP's first task will be to drill faults in the Nankai Trough off the Kii Peninsula, which scientists believe is the source for earthquakes occurring in the Tonankai (literally "southeastern sea") area. Over the next several years, expeditions will survey geological structures, enhance the network of observation stations by setting up seismographs, and gather samples of the earth's mantle.