IODP NanTroSEIZE Stage 1:
Expedition 315: NanTroSEIZE "Megasplay Riser Pilot"
Weekly Report #5 (Final report)
Date 19/Dec/2007
Drilled and cored from 976.5 meter below seafloor (mbsf), and cut 8 RCB cores in Hole C0002B. Stuck around 1029 mbsf at 16:50 p.m. and 1715 p.m. Came free with 300 kN over pull and worked pipe with pumping 10m3 hi-vis drilling fluid each time. After cutting 66R core, encountered hole problem below 1057 mbsf. Despite repeated reaming, hole condition did not improved. Abandoned the hole and pull out of hole.
Moved the Chikyu 6 miles upstream and made up 11-7/16" HPCS coring assembly. Run in hole the assembly to 1965 m water depth, and performed two surface HPCS cores on Hole C0002C. Moved the Chikyu 10m to next location of C0002D and perform HPCS coring. Cored to 204 mbsf and cut 18 cores (16 HPCS and 2 ESCS). Attempted downhole temperature measurement on every second cores and obtained temperature profile to 159 mbsf.
Half of the Science Party of Expedition 315 disembarked on 13 Dec and half of the next Expedition 316 Science Party came onboard instead. Cross-over between two Science Parties was being proceeded through processing of cores from the Hole C0002B, C and D. Cores from the Hole D are dedicated mainly to geoengineering assessments for riser BOP deployment. As well as sampling of whole-rounds and shear strength measurements, non-destructive core measurements were carried out as usual. Temperature measurements by APCT3 were successfully conducted down to 159 mbsf in the Hole C0002D.
Four lithostratigraphic units were defined (Unit I–III for Kumano Basin sediments, Unit IV for accretionary prism). Clear differences were observed between Unit IV and other units in terms of structure, chemistry, physical properties, etc.
Since C0002 was a contingency site, and there was no specific sample request, only time critical whole-round sampling, non-destructive measurements and description on split surface were done for cores from Hole C0002B. Cores from Hole C0002D were basically dedicated to geoengineering purpose, therefore, only non-destructive WR measurements and WR sampling for IW, microbiology and geotechnical tests were carried out.
On Dec 18, retrieved transponders by ROV and finished all operations for expedition 315. The Chikyu left the location to the next drilling site by the midnight.
The weekly report about the Expedition 315 was reported by the Co-Chief Scientists (Dr. Siegfried Lallemant and Dr. Juichiro Ashi), CDEX Operations Superintendent (Mr. Ikuo Sawada and Tsuyoshi Abe) and CDEX Expedition Project Manager (Dr. Hideki Masago).
