July 18, 2007
The Japan Agency for Marine-Earth Science and Technology
The Deep-sea Drilling Vessel"Chikyu" (Photograph.1) of the Japan Agency for Marine-Earth Science and Technology (JAMSTEC; Mr. Yasuhiro Kato, President) has completed overseas drilling shakedown (Photograph.2) on July 17, commenced since last November at off Kenya and the Northwest Australian Continental Shelf, aiming to accumulate deep ocean scientific drilling experiences and technologies.
During the overseas drilling shakedown, riser drilling operations (*1) were conducted at three locations at depths that exceeded 2,000m and Well Drilling operation for opening of boreholes were conducted at six locations.
During the shakedown, the Riser Tensioner (*2) (Photograph 3), which holds the riser pipe, sustained damages. Nonetheless, all shakedown objectives were achieved, and the Chikyu will return to Japan on schedule by the end of August.
Riser drilling operations were conduced at one location offshore of Kenya and two locations offshore of Northwest Australian Continental Shelf. Water depths and drilling depths as are indicated below.
Other six non Riser Drilling operations for openings of boreholes (installation of casing and equipments to a borehole) are conducted as follows. (Approximate depth)
Note that the Nankai Trough Seismogenic Zone Experiment (NanTroSEIZE) (*3) on behalf of the Integrated Ocean Drilling Program (IODP) (*4) scheduled for this year does not entail drilling using the Riser Tensioner.
|Around July 25||Arrive in Singapore
Change the crew, unload Riser Tensioner, etc.
|Middle of August||Depart from Singapore|
|End of August||
Return to Japan, to the shipyard in Tokyo bay
Load and unload of materials and equipments
Install the improved Mud Disposal Unit
Annual inspection process, etc.
|End of September||Port call at Shingu port, Wakayama Prefecture|
|September 21||Depart from Shingu port, and commence the first research expedition "NanTroSEIZE" as the Chikyu of IODP.|
Further details of the plans and schedule for the NanTroSEIZE drilling will be announced at about the time the Chikyu returns to Japan.Notes:
Drilling method by using riser pipe (lowered from the drilling vessel to the sea floor) which guides the drill pipe inside. With the riser pipe and blow-out preventer (BOP), drilling mud is circulated from the drilling vessel and it allows drilling at greater depths than other methods such as the riser-less drilling, since the mud reinforce wall of the borehole.
This equipment supports the weight of the riser pipe and damps wave motion, allowing the riser pipe and BOP to remain fixed to the bottom of the sea during drilling operations. The Riser Tensioner on the Chikyu employs 16m long cylinder rods that, when fully extended, increase the length of the Riser Tensioner to 34m. Each cylinder weighs 31 tons, with the cylinder rod alone weighing seven tons.
The Integrated Ocean Drilling Program (IODP) is an international marine research drilling program dedicated to advancing scientific understanding of Earth by monitoring and sampling subseafloor environments. Through multiple platforms, preeminent scientists explore IODP principal themes: the deep biosphere, environmental change, and solid earth cycles. IODP has started since October 2003 led by Japan and USA. IODP now has 21 member countries.
It is an abbreviation of Nankai Trough Seismogenic Zone Experiment and the first project for the Chikyu as IODP.
From this September, at Nankai Trough off Kii Peninsula (sea of Kumano) which is a seismogenic zone of large-scale earthquakes such as Tonankai Earthquake, scientific drillings will be started to study seismogenic mechanism by core samplings and long-term borehole measurements.