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| HOME > Expedition > NanTroSEIZE > NanTroSEIZE Exp. 314 |
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IODP Nankai Trough Seismogenic Zone Experiment
Stage 1 Expedition 314 "LWD Transect" |
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OVERVIEW |
| Expedition Number |
Expedition 314 |
| Expedition Prospectus |
Riserless drilling without coring at all six Stage 1 sites
using dedicated Logging-While-Drilling (LWD) technology at unstable formations associated with accretionary
prism environment. Results from the variety of logging measurements planned in this expedition will be
crucial for optimizing the subsequent Stage 1 expeditions for coring and observatory operations,
and for planning future stages. |
| Location |
Nankai Trough, Kumano-nada, Offshore Kii peninsula, Japan |
| Duration of Expedition |
From Sept. 21 to Nov. 15 2007 |
| Drilling Vessel |
The Chikyu |
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EXPEDITION SCIENTISTS |
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Masataka Kinoshita
Institute For Research on Earth Evolution, JAMSTEC (Japan)
Harold J. Tobin
Dept. of Geology and Geophysics, The Univ. of Wisconsin-Madison (USA) |
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Summary of drilling result |
Drilling data
Proposed
Site |
Site
Name |
North
Latitude |
East
Longitude |
Water
Depth
(m) |
Drilling Depth(mbsf*) |
| Pilot Hole |
GeoTech
Hole** |
LWD Hole |
| NT2-03 |
C0001 |
33°14.3’ |
136°42.7’ |
2,180 |
1,000.0 |
30.5 |
77.5 |
| 976.0 |
| NT3-01 |
C0002 |
33°18.0’ |
136°38.2’ |
1,970 |
- |
- |
1,401.5 |
| NT2-01D |
C0003 |
33°13.4’ |
136°42.1’ |
2,453 |
- |
- |
530.0 |
| NT2-01I |
C0004 |
33°13.2’ |
136°43.2’ |
2,524 |
400.0 |
- |
400.0 |
| NT2-01E |
C0005 |
33°13.6’ |
136°43.1’ |
2,446 |
524.0 |
- |
- |
| NT2-01G |
33°13.4’ |
136°43.2’ |
2,454 |
37.0 |
- |
- |
| NT1-03 |
C0006 |
33°01.6’ |
136°47.6’ |
3,830 |
885.5 |
- |
885.5 |
*mbsf: meters below the seafloor
**GeoTech Hole: Collect core samples to evaluate soil density for upcoming riser drilling
Summary of drilling result
Proposed Drill
Site |
Drill Site
Name |
Drilling Result |
| NT2-03 |
C0001 |
Drilled into a thrust sheet in hanging wall of the mega-splay fault system. Logged and imaged deformed accretionary prism rocks and collected data on stresses in prism system. Piloted the planned first riser drilling site. |
| NT3-01 |
C0002 |
Succeeded to drill the deepest hole into an accretionary prism both in scientific and LWD drilling history. Imaged and logged data clearly identified basal layer of Methane hydrate at 400 mbsf and boundary between basin sediment and underlying accretionary prism. Piloted the 2nd planned riser drilling site to be attempted to 6,000 mbsf. |
| NT2-01D |
C0003 |
The original plan was to penetrate the splay fault zone at 710 mbsf. However, the drilling was aborted at 525 mbsf where the lower part of drill pipe disconnected because of excessive pressure and torque inside of the borehole. Abandoned retrieval (released on October 29, 2007). However the recovered data such as density, resistivity, and gamma-ray intensity are valuable to characterize properties in active accretionary prism. |
| NT2-01I |
C0004 |
Drilled through the splay fault at 300 meters below the seafloor. A pilot drilling was made first and confirmed the drillability with LWD. High quality images and log data were acquired. The splay fault zone anticipated at approximately 300 mbsf was very well-imaged and logging data detected fault properties. For the first time drilling through the mega-splay fault was made successful. |
| NT2-01E |
C0005 |
Planned to drill and log into the splay fault. A pilot drilling was made first to confirm drillability with LWD. Drilling became difficult at 524 mbsf and after attempted to remedy borehole status, abandoned because of the excessive risk. |
| NT2-01G |
Planned to drill and log into the splay fault. Determined to abandon drilling because of limited time remaining in the expedition. |
| NT1-03 |
C0006 |
Drilled the point of 1 km landward from the toe of the accretionary prism. A pilot drilling was made to confirm drillability for LWD. Drilled through early formation stage layer of the accretionary prism, including the frontal fault zone, and reached 885 mbsf. |
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