As the JOIDES Resolution approached Site 1095, a short 3.5-kHz precision depth recorder (PDR) profile was acquired to refine the site selection. The positioning beacon was launched at 1615 hr on 17 February, beginning drilling operations for the leg. Before spudding, a drill pipe swab (pig) was pumped down to clear any rust that might have accumulated inside the drill pipe.
Hole 1095A was spudded with the first advanced hydraulic piston corer (APC) core at 0530 hr on 17 February, with the seafloor depth estimated from recovery as 3841.6 m (3852.6 meters below rig floor [mbrf]). APC coring advanced to 87.3 meters below seafloor (mbsf) with core recovery of 99.1% when operations had to be stopped because an iceberg (one of only two on the 24-mi radar screen) closed within 1.6 nmi. It had a computed closest point of approach (CPA) to the drill site of less than 0.5 nmi. The drill string was pulled above the seafloor and the vessel offset in dynamic position mode 330 m north of the location, while the iceberg passed directly over the drilling site. As the ice cleared the site, the vessel was repositioned 20 m west of Hole 1095A.
After three hours spent waiting on ice, Hole 1095B was spudded at 2145 hr on 18 February. The bit was washed down to 83.0 mbsf, where APC coring was resumed. The coring advanced from 83.0 to 205.0 mbsf and ceased when overpulls of 100 kilopounds (kips) could not dislodge the core barrel (Core 178-1095B-13H) from the formation. The stuck core barrel was drilled over to release it from the sediment. Coring continued in Hole 1095B with the extended core barrel (XCB) advancing to 483.3 mbsf (Core 43X) with 89.0% recovery. Below this, core recovery was only 18.1%. This factor, together with increasing vessel heave, influenced the decision to terminate drilling at 570 mbsf. Pump pressure was abnormally high below 483.3 mbsf, and on recovery, three of the four bit nozzles were found to be clogged with glacial debris.
In preparation for logging Hole 1095B, a wiper trip was conducted up to 89 mbsf with no drag. While running pipe back to bottom, the region from 541 to 570 mbsf was washed and reamed. The bit contacted 2 m of hard fill on the bottom, which was cleaned from the hole by circulating a 30-bbl high-viscosity mud pill. The drill string was pulled back to 95 mbsf with no drag experienced.
The Schlumberger logging equipment was rigged by 1615 hr on 22 February, and three downhole logging runs were completed in Hole 1095B: a triple combination (TC; caliper, lithodensity, porosity, resistivity, and natural gamma ray) log, a geologic high-sensitivity magnetic tool (GHMT) log, and a well seismic tool (WST) experiment. For the TC log, the vessel heave exceeded the maximum stroke of the wireline heave compensator, which was therefore turned off. At the start of the repeat TC run, the hostile environment lithodensity sonde (HLDS) caliper arm became detached, probably when the tool moved downward during a large heave. Because of concerns about tool safety, heave, and the large diameter of much of the hole (16-19 in), the Formation MicroScanner (FMS)-sonic tool string was not run. Seas were lower for the GHMT run, and the wireline heave compensator could be activated. The heave was still large enough to require slow (1000 m/hr) tool speeds through the pipe.
Holes 1095C and 1095D
Hole 1095C was spudded with the APC at 0215 hr on 24 February, 20 m west of Hole 1095B. After one mudline core, the driller repositioned the bit 5 m lower and spudded Hole 1095D at 0400 hr. APC coring advanced to the depth objective of 84.6 mbsf (Core 9H) with 93.3% recovery. The drill string was recovered, the positioning beacon released and retrieved, and the vessel departed for Site 1096 at 1930 hr on 24 February.
To 178 Site 1096
To 178 Table of Contents