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doi:10.2204/iodp.proc.347.109.2015

Operations

Transit to Hole M0065A

The vessel left Hole M0064D for Site M0065 (proposed Site BSB-7) in the Bornholm Basin at 1200 h on 23 October 2013. Position was established over Hole M0065A at 1400 h on 23 October, and operations commenced with a camera survey (Table T1).

Hole M0065A

A remotely operated vehicle survey was carried out on a transect over the locations for Holes M0065A, M0065B, and M0065C. This was required by the risk assessment for this site because of the possibility of chemical contaminants being present at the seabed. Following the survey, coring operations commenced. The uppermost 2 m was washed down, to avoid contamination, and additional personal protective equipment (PPE) was worn for the first run. The first run was recovered at 1850 h, and coring continued smoothly, with eight cores recovered before midnight.

Coring in Hole M0065A continued on 24 October 2013. Initially, piston coring was used to recover the clay lithologies before switching to a combination of open holing and hammer sampling in order to maximize recovery in the sandier lithologies. This continued to 73.90 mbsf, when bedrock was encountered. The hole was then flushed with mud and prepared for downhole logging, with the pipe tripped back to 14 meters below seafloor (mbsf).

Logging operations started in Hole M0065A on 24 October with rigging up the Weatherford logging setup. The first tool string comprised the total gamma ray and induction tools and reached 42 mbsf, where the uplog commenced. The second tool string comprising total gamma ray and spectral gamma ray tools reached only 16 mbsf. The decision was taken to run in hole with the drill pipe to 45 mbsf and do a wiper trip of the hole. After this, rig up for logging started again. The tool string with total gamma ray and spectral gamma ray was deployed again but only reached 20 mbsf. Following this attempt, downhole logging operations terminated.

A total of 28 cores and 15 open-hole sections were recovered from Hole M0065A to a maximum depth of 73.90 mbsf. Hole recovery was 99.19% when the open-hole sections were discounted.

Hole M0065B

The vessel moved under dynamic positioning to Hole M0065B, arriving on site at 2230 h on 24 October 2013, when operations commenced. To avoid potential chemical contamination at the surface, the hole was washed down to 3 m before coring commenced.

On the morning of 25 October (to 1010 h) coring operations ran smoothly, with 13 piston cores recovered and 2 hammer samples conducted in sandier material at the base of the hole. The final hammer sample recovered a smear of sand, and it was decided that no further penetration was required at this hole.

A total of 16 cores were recovered from Hole M0065B to 49.30 mbsf, with two open-hole sections. Hole recovery was 99.28% when the two open-hole sections (5 m) were removed from the calculation.

Hole M0065C

The vessel bumped over to begin coring Hole M0065C at 1110 h on 25 October 2013. Again, the hole was washed down to 2 mbsf and appropriate PPE was worn for the initial core run. Piston coring continued until 0010 h on 26 October, when the hole ended at 47.9 mbsf. The drill floor was then prepared for downhole logging operations.

Logging operations started in Hole M0065C on 26 October at 0105 h with rigging up the Weatherford logging setup after the drill pipe was tripped to 14 mbsf. The first tool string comprising total gamma ray, spectral gamma ray, and sonic tools reached ~40 mbsf, where an uplog was started. The second tool string with total gamma ray and microimager tools reached 40 mbsf, and a high-resolution uplog was performed. Logging operations were finished at 0330 h.

A total of 14 cores were recovered from Hole M0065C to 47.9 mbsf, with one open-hole section at the top of the hole. Hole recovery was 99.61% when the open hole-section was discounted.

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