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doi:10.2204/iodp.proc.314315316.124.2009

Operations

Locations of holes drilled during Expedition 315 are shown in Figure F3.

Transit from Site C0001 to Site C0002

The D/V Chikyu departed IODP Site C0001 at 0230 h on 8 December 2007. The 7 nmi transit was covered at an average speed of 2.8 kt. We arrived at Site C0002 at 0530 h on the same day.

Hole C0002B

The vessel was on location at 0530 h on 8 December 2007 (Table T1). Deployment and calibration of four transponders occurred from 0530 to 1930 h. The vessel moved 4 nmi upcurrent from 1930 to 2215 h at an average speed of 1.6 kt. We started making up and running a 10⅝ inch rotary core barrel (RCB) assembly at 2215 h. In the meantime, we carried out minor troubleshooting of the dynamic positioning system. We spudded Hole C0002B at 0600 h on 9 December. After jetting to 50 mbsf, we started drilling with an RCB coring assembly with a center bit at 0745 h. While drilling to 181 mbsf, a problem with the top drive was found at 1300 h. We checked it and made repairs to the changing bolt. We started running in the hole at 1815 h, and we restarted drilling from 181 mbsf at 1830 h. We reached the starting coring depth (475 mbsf) at 0215 h on 10 December and installed an RCB core barrel and a sinker bar. We retrieved the center bit on the second run and then dropped an inner barrel and started coring at 0530 h. We continued coring until 0700 h on 11 December and cut 22 cores in the interval from 475 to 675 m core depth below seafloor (CSF). Leaking was found on a crown-mounted heave compensator booster line at 0700 h, and we spotted 10 m³ of Hi-Vis mud and retrieved an inner barrel and a sinker bar. Repairs were completed by 1530 h. After washing and reaming from 634 to 669 m drillers depth below seafloor, we installed a sinker bar and restarted coring at 1730 h. After cutting Core 315-C0002B-23R, we could not recover the inner barrel. We redressed the running tool with a new shear pin. An inner barrel swivel assembly shaft was left down the hole. We ran a fishing tool (core catcher) in the hole with the coring line and were able to retrieve the assembly at 2230 h. We restarted coring at 2315 h and cut 39 cores by 1645 h on 13 December. The drill pipe became stuck twice, once at 1029 m CSF at 1650 h and again at 1030 m CSF at 1715 h, but came free with 300 kN of overpull each time. After cutting four more cores, hole conditions became worse below 1057 m CSF at 2230 h. The drill pipe was packed off, and weight on bit increased to 200 kN. The pipe was freed with 300 kN of overpull. We washed and reamed the hole repeatedly by sweeping Hi-Vis mud until the next morning; however, hole conditions did not improve. We finally decided to stop RCB coring and abandon the hole at 1345 h on 14 December. We displaced the hole with 1.3 specific gravity kill mud and pulled out of the hole by 2100 h. The remotely operated vehicle (ROV) was recovered at 1835 h on 15 December. We moved the vessel 6 nmi upcurrent at 2100 h, at an average speed of 1.5 kt.

Hole C0002C

The vessel was on location at 0130 h on 16 December 2007 (Table T2). We made up an 11 inch hydraulic piston coring system (HPCS) assembly at 0630 h and started running in the hole at 0830 h. We installed a sinker bar and an inner barrel at 1530 h and cut two HPCS cores by 1815 h. We moved the vessel 10 m away from the hole to core the next hole.

Hole C0002D

The vessel was on location at 1830 h on 16 December 2007, and we continued HPCS coring at 1930 h (Table T3). We cut 13 cores with the HPCS until 0830 h the next morning. With 450 kN of overpull on Core 315-C0002D-13H at 120 m CSF, we overdrilled from 110 to 113 m CSF. We pulled the core line winch to the surface and found that we had not recovered the inner barrel (the sinker bar pin was sheared). We installed a new latch head and ran back in and latched. After another 2 m of overdrill, we attempted to pull free and released the inner barrel with 400 kN of overpull. We changed the latch head and replaced shear pins and V-packings on the inner barrel. We continued HPCS coring from 114 to 120 m CSF. We had high overpull (450 kN) again and overdrilled 5 m; the barrel came free with 400 kN of overpull. After recovering this core, we dropped the extended shoe coring system (ESCS) bottom-hole assembly for drilling. Having verified its landing, we started drilling at 1600 h at 120 m CSF. We ran a sinker bar assembly in the hole and recovered the ESCS. We then ran the advanced piston coring temperature tool (APCT3) in the hole and performed HPCS coring at 150 m CSF. To free the barrel, 200 kN of overpull was needed. We recovered the HPCS core and dropped the ESCS again. We verified its landing and started drilling at 159 m CSF at 2015 h. We ran the sinker bar assembly in the hole and recovered the ESCS at 2300 h. The final HPCS core was taken at 200 m CSF at 0110 h on 18 December. A total of 18 cores were cut in this hole. In situ temperature measurement with the APCT3 was attempted on Cores 315-C0002D-2H, 4H, 6H, 8H, 10H, 12H, 16H, and 18H; six attempts were successful. We displaced the hole with 26 m³ of 1.3 specific gravity kill mud and pulled up to the surface from 0215 to 0545 h. We moved the vessel and then launched the ROV at 0730 h and retrieved four transponders by 1345 h. The vessel left for IODP Expedition 316 Site C0006 at 1345 h on 18 December.

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