Outline of scientific ocean drilling and specifications of riser drilling

发布时间：2014-10-07 16:56:46

J Mar Sci Technol (2003) 7:101–108Original articlesOutline of scientific ocean drilling and specifications of riser drilling vessel ChikyuYusuke Yano, Shinichi Takagawa, and Kazuyasu WadaJapan Marine Science and Technology Center, OD21 Program Department, 2-15 Natsushima-cho, Yokosuka 237-0061, JapanJOIDES Resolution . However, this program is sched-uled to finish at the end of September 2003. The USA has started to think about the structure of a post-ODP and a modern, nonriser, dynamically positioned drill-ship, a successor to the JOIDES Resolution , to be sup-plied and operated by the USA. In addition to these two vessels, several European nations are establishing ini-tiatives to provide “mission-specific” drilling platforms (e.g., drilling barges, jack-up rigs, and seafloor drilling systems). These plural platforms have different specifi-cations to allow optimum scientific drilling under the Integrated Ocean Drilling Program (IODP). Thus,scientific ocean drilling will proceed seamlessly after the ODP.At the beginning of this paper, the significance and history of ocean drilling is briefly described. Then the technological aspects of the Chikyu and the drilling/coring method are explained (Fig. 1).2What is “scientific ocean drilling”?2.1History and results of scientific ocean drilling After World War II, extensive studies in a very deep region at the bottom of the sea started for research into geophysics, mineralogy, and biology, and to search for submarine cable routes, etc. Although the surface sedi-ment on the sea bottom had previously been collected by a dredge (a bag net with an opening) or a piston corer, the first ocean drilling project for scientific research was the “Mohole Project” in 1959.The propagation velocity of seismic waves varies on the boundary between the crust and the mantle. This has been called the “Mohorovicic discontinuity” or “Moho.” The word “Mohole” means to drill a “hole” to “Moho.” It seemed easier to approach the boundary plane by ocean drilling than by continental drilling sim-ply because the crust is thinner in the bathyal area. TheAddress correspondence to: Y. Yano (e-mail: yanoy@jamstec.go.jp)Received: June 15, 2002 / Accepted: November 11, 2002Abstract The Japan Marine Science and Technology Center (JAMSTEC) has been, and is now promoting the “OD21”program (i.e., “Ocean drilling in the 21st century”). This is the first plan in the world to utilize deep-water riser-drilling tech-nologies for scientific drilling. One of the important factors for the success of this program is the development of a high-performance drilling vessel. Since 1990, JAMSTEC has been continuing a technological study of a riser-drilling vessel for scientific studies with an operational capability in waters up to 4000m deep. It was decided to start the construction with a two-phase plan: a vessel with a riser operation for waters up to 2500m deep will be constructed in the initial stage, and then the vessel will be modified to a 4000-m depth capability. In the development process of the vessel, named Chikyu , many new technical developments have taken place, such as drilling/coring equipment, a dynamic positioning system, etc. Thus,the Chikyu is expected to contribute to ocean engineering and other work, in addition to scientific advances.Key words Riser · Mud circulation · IODP · OD21 · Chikyu1IntroductionMost of the active processes that create and shape the Earth’s crust take place under the ocean. Seafloor sedi-ment and extrusive volcanic rock represent the most recent environmental conditions. Drilling is the only way to access the deep layers within the Earth to inves-tigate directly the processes of earthquake generation,or the dynamics of the global environmental system.The present ocean drilling program (ODP) has been carried out through the international cooperation of 21countries, led by the USA, and many outstanding re-sults have been achieved by the riser-less drilling vessel

Outline of scientific ocean drilling and specifications of riser drilling

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