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doi:10.2204/iodp.proc.347.103.2015

Operations

Transit to Hole M0059A

At 1615 h on 12 September 2013, the Greatship Manisha set sail from Kiel, Germany, and headed for the first Expedition 347 coring site (M0059) in Little Belt (proposed Site BSB-3). The vessel arrived on site at 0000 h on 13 September. Setup and preparation of the drill floor commenced and continued throughout the day until 1530 h, when coring operations began (Table T1).

Hole M0059A

The first piston corer system (PCS) core from Hole M0059A was recovered to deck at 1920 h on 13 September 2013. Piston coring was carried out using 3.3 m strokes. However, because of a dense sand lithology at 83.2 meters below seafloor (mbsf), it was necessary to switch from the PCS to the rotary extended coring system (ECS). Coring continued through 14 September. On core Run 29 (86.7 mbsf; 15 September), the lower section of the barrel was lost because of shearing of the spring spline. Attempts were made to recover the core barrel, unfortunately without success. The hole was terminated at 0900 h on 15 September.

Twenty-nine coring attempts were made in Hole M0059A to a maximum depth of 90.2 mbsf. Recovery for the hole was 94.68%.

Hole M0059B

The vessel moved under dynamic positioning (DP) with the drill string suspended in the water column to Hole M0059B, 20 m east-northeast of Hole M0059A, arriving on station at 1300 h on 15 September 2013. Operations commenced immediately. To create a composite record with Hole M0059A, noncoring assembly (NCA) drilling was conducted to 60 mbsf (having recovered almost 100% in the upper section of Hole M0059A) before recommencing piston coring. Damage to seals was observed when recovering core Runs 1 and 5. American Petroleum Institute (API) pipe was tripped to identify and remove the source of seal damage. Coring then continued until the core barrel became stuck near the mud valve, which was not fully opening. Coring continued following repairs and alternated between the PCS, ECS, and rotating core barrel as high sand concentrations and varying lithologies were encountered.

Coring operations in this hole continued through 17 September. A harder till lithology was encountered, and the main polycrystalline diamond cutting bit was replaced with a six-cone Rock Roller core bit and tricone insert bit. Open holing continued until drilling parameters indicated softer lithologies. Where these softer lithologies were encountered, spot coring using the push coring assembly or hammer sampler (HS) was conducted. The hole was terminated at 204.03 mbsf at 1355 h on 18 September upon advancing into chalk basement, after which preparations were made for downhole logging.

Downhole logging operations were run by the Petrophysics Staff Scientist and the Weatherford Engineer and Technician. Operations commenced at 1811 h on 18 September using the compact gamma ray and compact induction tools. Because of loss of tension, the maximum depth reached was 72.5 mbsf. The tool string was then run up and reached the seafloor at 1840 h. After pumping, a second attempt was made. However, the depth reached was restricted to 58 mbsf as tension was again lost. Following this, the decision was made to run in with pipe to 175 mbsf and complete a wiper trip before tripping pipe to 90 mbsf. The tools were again run into the hole at 2305 h at a speed of 9 m/min. Tension was lost at 183.5 mbsf, and the up run began at 2340 h. The tools were recovered back to the rig floor at 0027 h on 19 September. As high tensions with up to 650 lb overpull were observed during the uplog, the decision was taken to set the pipe back to 20 mbsf and run in the hole with a second tool string. At 0207 h, a further run was attempted using the compact gamma ray, compact spectral gamma, and compact sonic tools. The string was run downhole at a speed of 10 m/min, reaching the end of the pipe at 0211 h and the total depth at 0222 h. Tension was lost at 73.5 mbsf, and the up run began at 0230 h. By 0248 h, the tools were recovered back to the rig floor, the drill string was pulled, and logging operations ended at 0320 h.

The drill floor was then prepared for transit, and the vessel departed for Hole M0059C at 0600 h.

A total of 30 coring attempts were made in Hole M0059B, extending to a maximum depth of 204.03 mbsf (including six open-holing runs covering 155.6 m). The recovery for this hole was 56.51%.

Hole M0059C

The vessel then moved 40 m west-northwest under DP to Hole M0059C on the morning of 19 September 2013, establishing position at 0620 h. During the short transit, work was undertaken to check and refit the transponder device on the seabed frame following failure in Hole M0059B (possibly as a result of sinking into the sediment/being covered in drill cuttings).

Following this, pipe was run at station in Hole M0059C, where an initial attempt at passing pipe through the seabed template resulted in a bent pipe. Following removal of this pipe, the vessel moved 5 m in order to enter the seabed template correctly and establish the hole. Coring operations on this microbiology-dedicated hole commenced with the first core recovered to deck at 0850 h. The coring rate was moderated following instructions from the microbiologists on shift to ensure appropriate time for processing the microbiology samples and ensure there was no backlog of cores waiting to be processed.

Coring operations continued through 20 September. During the first part of the day, the PCS was used to recover mud/clay lithologies. Upon completion of the microbiology sampling at 83 mbsf (at 1255 h on 20 September; dictated by lithology), the underlying till material was then sampled by drilling down using the NCA and HS to recover material for optically stimulated luminescence (OSL) samples at 3 m intervals. This approach was used through 22 September, with the drilling/coring approach driven by the material encountered.

On 21 September, microbiology samples were removed from the vessel by European Consortium for Ocean Research Drilling Science Operator personnel and transferred to shore on board the Danish Naval Homeguard Vessel (which brought visiting journalists).

Hole M0059C was terminated at 158.10 mbsf at 0535 h on 22 September.

A total of 84 coring attempts were made in Hole M0059C to a maximum depth of 158.10 mbsf. Twenty-four of these involved open holing, covering 52.91 m. Hole recovery was 97.82% with these open-holed sections discounted.

Transit to Site M0059 for second phase of sampling

Following completion of Hole M0067B, the vessel returned to Site M0059 to resample at this location to complement the samples already collected and improve recovery rates in the lower sections. The vessel arrived back at Site M0059 at 0340 h on 29 October 2013 and commenced coring operations.

Hole M0059D

Coring in Hole M0059D commenced at 0350 h on 29 October 2013 and ran smoothly throughout the day, with a total of 27 piston cores and one hammer sample recovered before midnight. On recovery of sand at the base of the hole (86.60 mbsf), the hole was ended and the drill floor was readied to bump over to Hole M0059E.

A total of 28 cores were recovered in Hole M0059D to a depth of 86.57 mbsf. Recovery for the hole was 99.9%.

Hole M0059E

Coring commenced in Hole M0059E on 30 October 2013 at 0028 h and continued successfully with good recovery of the mud lithology throughout the morning. At 1330 h, the wireline rope parted on retrieving the PCS. The barrel became jammed in the bottom-hole assembly because of a broken seal. Fishing attempts failed, and the pipe was tripped. The core was recovered to deck and operations recommenced with six more cores recovered before midnight.

On 31 October, PCS coring continued through the morning until Run 27 at 0415 h. The subsequent core Runs 28–37 used a combination of ECS and hammer sampling in an attempt to maximize recovery. The hole was terminated at 100.80 mbsf following issues with hole stability. This hole was considered an important logging target, so to minimize further damage to the hole it was terminated at this depth, and setup preparations for downhole logging commenced at 1700 h.

Logging operations started in Hole M0059E on 31 October at 1800 h with rigging up the Weatherford logging setup after the drill pipe was tripped to 15 mbsf. The first tool string comprising total gamma radiation and induction tools reached ~70 mbsf, from where an uplog was performed. The second tool string comprising total gamma radiation and microimager tools and the last tool string comprising total gamma radiation, spectral gamma radiation, and sonic tools reached 60 mbsf, from where an uplog was started. Logging operations were finished at 2130 h.

A total of 37 cores were collected in Hole M0059E to a depth of 100.80 mbsf. Hole recovery was 90.02%. Completion of this hole marked the end of coring operations for Expedition 347.

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