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doi:10.2204/iodp.proc.331.107.2011

Operations

Arrival at Site C0017

The D/V Chikyu moved to Site C0017 and began coring on the night between 26 and 27 September 2010 (Fig. F1; Table T1). The plan was to core as deep as possible in the 2–3 days available.

Hole C0017A

After tagging the seafloor on 27 September 2010 at 1154.5 m drilling depth below seafloor (DSF), Hole C0017A was spudded with the hydraulic piston coring system (HPCS), retrieving mudline and penetrating to 8.8 mbsf. The bit pulled out of hole on core retrieval, ending Hole C0017A.

Hole C0017B

Hole C0017B was washed and drilled down to the penetration depth of Core 331-C0017A-1H on 27 September 2010 and then shot with the HPCS just 1 m south of Hole C0017A. Penetration and recovery were a perfect 9.5 m, but again the bit pulled out when we retrieved the core, ending Hole C0017B.

Hole C0017C

On 27 September 2010, the Chikyu offset ~8 m northeast to begin drilling deeper. Core 331-C0017C-1H was shot with the HPCS after washing and drilling down to the penetration depth of Core 331-C0017B-1H. Core 331-C0017C-2H was shot with the HPCS, penetrated fully, and recovered 8.5 m of sediment with a little overpull at the end. To avoid getting stuck in the formation, we switched to the extended shoe coring system (ESCS) for Core 331-C0017C-3X. However, upon retrieval of the core barrel we found the shoe and core catcher sub were missing and decided to abandon the hole. An HPCS inner barrel was run through the drill string after pulling out, to ascertain that nothing was left inside the pipe.

Hole C0017D

Hole C0017D was spudded on 27 September 2010, 5 m northeast of Hole C0017C. After washing and drilling down to 59.9 mbsf, skipping an interval of unrecoverable volcanic rubble, and recovering a failed ESCS coring attempt, Core 331-C0017D-1H was shot with the HPCS and recovered 9.5 m from a 9.2 m advance. Core 331-C0017D-2H was also shot with the HPCS, recovering 9 m from a 9.5 m advance. Core 331-C0017D-3H, however, recovered nothing from a 6.0 m advance, returning only a broken flapper and a cracked liner. Core 331-C0017D-4H likewise returned no sediment and had no advance, so we switched to the extended punch coring system (EPCS) to continue beyond 84.6 mbsf. With no recovery from a 9.5 m EPCS advance, we switched back to the ESCS, which returned 1.8 m from another advance of 9.5 m. As the formation seemed softer, we switched back to the HPCS and gained 100% recovery from an 8.5 m advance into sticky mud between 103.6 and 112.1 mbsf. Switching back to the EPCS returned only a few centimeters in the core catcher from a 9.5 m advance, so we went back to the ESCS. This change, surprisingly, gave us two good cores (331-C0017D-9X and 10X) with 107.8% and 68.4% recovery, respectively. However, during retrieval of Core 331-C0017D-11X, the sinker bar broke, leaving Core 11X in the hole at 149.6 mbsf. Fishing for Core 11X was unsuccessful because we did not have a tool onboard that would fit. The core was retrieved via a pipe trip, returning 4.8 m of core (50.5% of a 9.5 m advance) from a depth of 140.1–149.6 mbsf.

After pulling out, Hole C0017D was reentered unguided on the night of 28 September, and Core 331-C0017D-12H was taken on the morning of 29 September. This final shot penetrated 1 m to 150.6 mbsf but retrieved only a little gravel in the core catcher. The main reason for attempting the reentry and last core, however, was to get a temperature reading from either the advanced piston corer temperature tool (APCT3) shoe or one of the thermoseal strips taped to the inner barrel. The thermoseal strips returned a temperature measurement of 90° ± 5°C (three replicate strips), so Site C0017 ended very successfully at 150.6 mbsf with Core 331-C0017D-12H.

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