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doi:10.2204/iodp.proc.340.106.2013

Operations

Transit to Site U1396

After a 28.6 nmi transit from Site U1395 in cruise mode, the vessel arrived at Site U1396. The vessel stabilized over Site U1396 at 2245 h on 16 March 2012. All times reported in this volume are given in ship local time, which was Universal Time Coordinated (UTC) – 4 h. The position reference was a combination of GPS signals and a single acoustic beacon. The positioning beacon was deployed at 2310 h on 16 March. At the end of operations at Site U1396, the beacon was sent an acoustic command to release. The beacon was retrieved at 0730 h on 18 March.

Site U1396

Site U1396 consists of three holes (Table T1). The original plan called for two holes to a depth of ~132 mbsf. The first hole was successfully cored and was terminated at a total depth of 134.9 mbsf. Hole U1396B was a short hole designed to capture an interval in Hole U1396A that was poorly recovered because of a shattered core liner. Hole U1396C was cored to a depth of 139.4 mbsf. No logging was scheduled at Site U1396. The advanced piston corer (APC) was deployed 31 times. The cored interval with the APC was 283.8 m with a recovery of 296.38 m of core (104%). Overall recovery for Site U1396 was 104%. There was one drilled interval of 5 m in Hole U1396B. Total time spent on Site U1396 was 34.75 h.

Hole U1396A

The vessel arrived at Site U1396 and was in position at 2245 h on 16 March 2012. After an uneventful pipe trip, the top drive was picked up and the bit was spaced out to spud Hole U1396A. The bit was initially set at 789 meters below rig floor (mbrf), and the core barrel was run in on wireline. The first attempt to recover the mudline came back without core. The bit was lowered to 795 mbrf for another attempt at a mudline core. The hole was spudded at 0345 h on 17 March. Seafloor depth was calculated from the length of the first core to be 798.9 mbrf (787.4 mbsl). Orientation was performed with the FlexIt tool on the first 12 cores with good results. Nonmagnetic core barrels were used for APC coring for Cores 340-U1396A-1H through 12H. There was only one coring anomaly during the hole; Core 2H had the liner shatter when the piston fired. Advanced piston corer temperature tool (APCT-3) measurements were taken on Cores 3H through 6H. There was only one partial stroke experienced in the entire piston coring sequence. A total of 15 piston cores were taken over a 134.9 m interval with a total recovery of 140.51 m of core (104%). After the completion of APC coring, the drill string was pulled back with the top drive still installed, and the bit cleared the seafloor at 1615 h on 17 March, ending Hole U1396A. The total time spent on Hole U1396A was 17.5 h.

Hole U1396B

After clearing the seafloor in Hole U1396A, the vessel was offset 20 m east and Hole U1396B was spudded at 1650 h on 17 March 2012. Seafloor depth was used from Hole U1396A, which was 798.9 mbrf (787.4 mbsl). The uppermost 5 m of Hole U1396B was drilled, and Core 340-U1396B-2H was shot from 5 mbsf. Both the FlexIt tool and nonmagnetic core barrels were used for Core 2H. One piston core was taken over the 9.5 m interval, with a total recovery of 10.00 m of core. Overall recovery for Hole U1396B was 105%. The hole was terminated after a single core, and the drill string was pulled clear of the seafloor at 1725 h. The total time spent on Hole U1396B was 1.25 h.

Hole U1396C

After clearing the seafloor in Hole U1396B, the vessel was offset 20 m south and Hole U1396C was spudded at 1810 h on 17 March 2012. Seafloor depth was calculated from the length of the first core 798.1 mbrf (786.6 mbsl). Orientation was performed with the FlexIt tool on all 15 cores with good results. Nonmagnetic core barrels were used all cores. APCT-3 measurements were taken on Cores 340-U1396C-6H and 11H. Microspheres were run on Cores 3H, 6H, and 14H. There was only one partial stroke in the entire piston coring sequence. Two of the cores (11H and 12H) had to be drilled over to release them from the formation. A total of 15 piston cores were taken over a 139.4 m interval with a total recovery of 145.92 m of core. Overall recovery for Hole U1396C was 105%. After the completion of APC coring, the top drive was set back and the drill string was pulled back to the rig floor. Drilling equipment was secured on the rig floor at 0935 h on 18 March, ending Site U1396 and Hole U1396C. The total time spent on Hole U1396C was 16.0 h. The vessel then proceeded underway to Site U1397.

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