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doi:10.2204/iodp.proc.339.109.2013

Operations

The 115 nmi voyage from Site U1390 to Site U1391 (proposed Site WI-01B) was made at an average speed of 11.5 kt. The vessel was positioned on the last site of the expedition at 1230 h on 8 January 2012.

Three holes were drilled at Site U1391 (Table T1). Hole U1391A was cored using the advanced piston corer (APC) to 171.1 meters below seafloor (mbsf) and then with the extended core barrel (XCB) to 353.1 mbsf. Hole U1391B was cored using the APC to 171 mbsf and then with the XCB to 353.5 mbsf. Hole U1391C was drilled without recovery to 340 mbsf and then cored using the rotary core barrel (RCB) to 671.5 mbsf. Downhole logging was carried out in Hole U1391C using the triple combination (triple combo) and Formation MicroScanner (FMS)-sonic tool strings (see “Downhole logging at Site U1391”). Overall recovery at Site U1391 was 342.1 m (104.7% recovery) with the APC, 230.7 m (90.7% recovery) with the XCB, and 269.02 m (81.15% recovery) with the RCB. The total cored interval at Site U1391 was 1038.1 m and total recovery was 958.57 m (92.3%).

Hole U1391A

The APC/XCB bottom-hole assembly (BHA) was made up, and a routine survey of the seafloor was conducted using a 30 m grid pattern. No significant obstructions were observed. Hole U1391A was spudded with the APC at 1080.0 meters below sea floor (mbrf; 1078.3 meters below sea level [mbsl]) at 2035 h on 8 January. Seafloor depth was established at 1085.4 mbrf (1073.7 mbsl). Piston coring advanced to a final depth of 171.1 mbsf, with a recovery of 106%. Cores were oriented starting with Core 4H. Temperature measurements were made at 32.6 (Core 4H), 61.1 (Core 7H), 89.6 (Core 10H), 118.1 (Core 13H), and 146.6 (Core 16H) mbsf. Nonmagnetic core barrels were used to obtain all piston cores. XCB coring deepened the hole to the depth objective of 353.1 mbsf by 0345 h on 10 January. Average recovery for the 182 m XCB interval was 88.8%. Combined recovery in Hole U1391A was 97%. The drill string was pulled out of the hole, clearing the seafloor at 0520 h on 10 January. The vessel was offset 20 m south of Hole U1391A.

Hole U1391B

Hole U1391B was spudded with the APC at 1085 mbrf at 0815 h on 10 January. Although the mudline core was 9.65 m, the desired vertical offset (5 m deeper) with the previous hole was maintained and piston coring continued to a final depth of 171 mbsf with a recovery of 104%. Cores were oriented starting with Core 3H. Temperature measurements were made at 19 (Core 2H), 47.5 (Core 5H), 76 (Core 8H), 104.5 (Core 11H), and 133 (Core 14H) mbsf. All cores were obtained with nonmagnetic core barrels. XCB coring deepened the hole to the depth objective of 353.5 mbsf. Average recovery for the XCB interval of 182.5 m was 93%. Combined recovery for Hole U1391B was 98%. The drill string was recovered with the bit clearing the seafloor at 1350 h and the rotary table at 1850 h on 11 January. The trip out of the hole was suspended 1.5 h for the routine maintenance procedure of slipping and cutting the drilling line.

Hole U1391C

A four-stand RCB BHA was made up with a new CC-4 Rock Bit International bit and mechanical bit release and deployed. After the driller tagged the seafloor at 1085 mbrf (1073.3 mbsl), Hole U1391C was spudded with the RCB at 2345 h on 11 January. The hole was drilled with a wash barrel to 340 mbsf by 1400 h on 12 January. The empty wash barrel was recovered and a fresh core barrel dropped at 1430 h, when rotary coring was initiated. Rotary coring advanced to a final depth of 671.5 mbsf by 1645 h on 14 January. Recovery for the 331.5 m cored interval in Hole U1391C was 81%. Recovery percentage was adversely affected by the absence of recovery in Cores 26R, 29R, and 35R, which was assumed to be formation related. The average rate of penetration for the 331.5 m cored interval was 14.2 m/h.

Downhole logging at Site U1391

Following the wiper trip, Hole U1391C was flushed with sepiolite mud and the bit was released at the bottom. The hole was displaced with 248 bbl of 10.5 ppg heavy mud, and the end of pipe was placed at the logging depth of 98.9 mbsf. The first log of the hole was made with the triple combo tool string, which was made up of the natural gamma radiation (NGR), density, and resistivity tools and deployed at 0330 h on 15 January. The tool string succeeded in reaching 668 mbsf. The tool string was recovered and rigged down by 0815 h. The second and final log was made with the FMS-sonic tool string. The tool string reached 666 mbsf and recorded resistivity images of the borehole, sonic velocities, and NGR data. The hole contained many thin washouts. As at previous sites, all the logs have medium-amplitude alternations on the several-meter scale. Sonic velocity, density, and resistivity all show a downhole compaction trend. Logging equipment was rigged down by 1915 h, concluding all science operations of the expedition. We departed Site U1391 at 0200 h on 16 January.

Expedition 339 ended at 1342 h on 16 January, with the first line ashore in Lisbon, Portugal.

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