Press Releases

July 18, 2007
The Japan Agency for Marine-Earth Science and Technology

The Deep-sea Drilling Vessel "Chikyu"
Completion of Overseas Drilling Shakedown and Future Plan

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.

1.Details of the overseas drilling shakedown

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.

Off Kenya (Approximate depth)
Water depth: 2,200m    Drilling depth: 2,700m under the sea-floor.
Test of riser drilling in strong currents.
Northwest Australian Continental Shelf (Approximate depth)
i.   Water depth: 500m    Drilling depth: 3,700m under the sea-floor
ii.   Water depth: 1,000m   Drilling depth: 2,200m under the sea-floor

Other six non Riser Drilling operations for openings of boreholes (installation of casing and equipments to a borehole) are conducted as follows. (Approximate depth)

iii.   Water depth: 1,340m    Drilling depth: 1,200m under the sea-floor
iv.   Water depth:1,440m   Drilling depth:1,860m under the sea-floor
v.   Water depth:1,400m   Drilling depth:560m under the sea-floor
vi.   Water depth:830m    Drilling depth:700m under the sea-floor
vii.   Water depth:470m   Drilling depth:3,200m under the sea-floor
viii.   Water depth:640m   Drilling depth:1,000m under the sea-floor

2.Achievements from the overseas drilling shakedown

Accumulated riser drilling skills and techniques
Verified installation and operation of Blow-out Preventer (BOP)
Carried out riser drilling under a strong current with average of 2.5knot (about 4.6km/h) and confirmed stability.
Performed drilling angle control (slant hole) required for deep ocean drilling.
Carried out drilling in the complicated layers including alternate layers of sandstone, mudstone and limestone.
Improved crews’ skills and techniques Raised availability of equipments by tuning up

3. Partly Damage of Riser Tensioner

On May 19, during the drilling operation at Northwest Australian Continental Shelf, small peeling of surface coating was found on the lower part of cylinder rod of one of six Riser Tensioners (Photograph 3). On May 22, the operations were suspended since the peeling got worse and the same type of peeling and coating abnormality on two cylinders of other Tensioners were found (Photograph 4).
Drilling operations were conducted that did not require use of the Riser Tensioner, which was drilling of upper part of borehole and construction of its opening.
The damaged Riser Tensioner will be unloaded at Singapore on the way to Japan and transported to the manufacturer in Norway. It will be restored after the cause was clarified.
Furthermore, as for clarification of the cause and how to restore, review and response team including experts are discussing now.

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.

4.Future Plan

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.


*1 Riser Drilling

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.

*2 Riser Tensioner

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.

*3 Integrated Ocean Drilling Program (IODP)

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.

*4. NanTroSEIZE

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.


(For Chikyu)
Mr. Takeo Tanaka, e-mail:
Manager, Planning and Coordination Department
The Center for Deep Earth Exploration (CDEX)
Japan Agency for Marine-Earth Science and Technology
(For Publication)
Mr. Shinji Oshima, e-mail:
Manager, Planning Department Press Office
Japan Agency for Marine-Earth Science and Technology