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doi:10.2204/iodp.proc.333.104.2012

Operations

Transponders were retrieved from 0600 to 1530 h on 17 December 2010. The D/V Chikyu then moved to the first transponder location at Site C0011 over a 22 nmi distance at an average speed of 5.5 kt. The ship began setting transponders at 1930 h and finished at 0700 h on 18 December.

The hydraulic piston coring system (HPCS)/extended punch coring system (EPCS)/extended shoe coring system (ESCS) coring assembly was made up, run into Hole C0011C, and tagged the seafloor at 1700 h; coring began at 1800 h on 18 December. After oil leakage from the HPCS was found, the decision was made to pull out to 13 m above the seafloor, and coring in Hole C0011C ended at 22.5 mbsf (Table T1). From 0015 h on 19 December, the bottom-hole assembly was jetted in Hole C0011D to 6 mbsf and drilled to 21 mbsf before starting HPCS coring again at 0245 h. Coring continued to 184.5 m drilling depth below seafloor (DSF) where the decision was made to switch to EPCS because of continuous partial penetrations.

EPCS coring did not bring good quality and recovery of cores, and we switched to the ESCS after three cores at 1200 h on 21 December. After reaching 380 mbsf, which is 30 m deeper than the target depth, coring was stopped at 0900 h on 24 December, and we spotted kill mud and displaced the same with seawater before pulling out. The core bit and all of the assembly were on rig floor at 2000 h.

Coring operations were smooth except for oil leakage from the HPCS, which forced us to end Hole C0011C at a very shallow depth. Core recovery was good with an overall average of 101.7% in Hole C0011C and 102.2% in Hole C0011D. HPCS cores were the best of the three core types in terms of both recovery and quality, with an average recovery of 102.4%, ranging from 117.3% to 82.8%. EPCS did not get good core recovery, ranging from 77.2% to 38.6%. ESCS cores were good in recovery with an average of 103.3%, ranging from 158.6% to 9.3%, and remarkably good cores with mild biscuiting (length of coherent pieces >10 cm) were obtained in the weakly cemented tuffaceous sandstone (e.g., Cores 333-C0011D-48X and 51X), an improvement over Expedition 322 RCB coring. The core liner was broken twice and core jammed once.

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