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doi:10.2204/iodp.proc.340.105.2013

Operations

Transit to Site U1395

After a 10 nmi transit from Site U1394 in cruise mode, the vessel arrived at Site U1395. The vessel stabilized over Site U1395 at 0258 h on 13 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 1030 h on 13 March. At the end of operations at Site U1395, the beacon was sent an acoustic command to release. Although it indicated that it had released, the beacon failed to surface and was declared lost.

Site U1395

Two holes were cored at Site U1395 (Table T1). The original plan called for two holes cored to ~244 mbsf. Because coring was challenging and took longer than we originally anticipated, the first hole (U1395A) was only drilled to 231.3 mbsf. The second hole (U1395B) was only drilled to 203.3 mbsf because of time constraints. Hole U1395B was successfully logged with both the Formation MicroScanner (FMS)-sonic and triple combination (triple combo) logging strings. Fifty-three cores were recorded for the site. The extended core barrel (XCB) was deployed 23 times, and the advanced piston corer (APC) was deployed 30 times. The interval cored with the XCB was 189.7 m with a recovery of only 32.02 m of core (17%). The interval cored with the APC was 244.9 m with a recovery of 251.80 m of core (103%). Overall recovery for Site U1395 was 65%.

Hole U1395A

The vessel arrived at Site U1395 and was in position at 0258 h on 13 March 2012. After an uneventful pipe trip, the top drive was picked up and the bit was spaced out to spud Hole U1395A. The hole was spudded at 0852 h. Seafloor depth was calculated from the length of the first core: 1212.4 meters below rig floor (mbrf; 1200.9 mbsl). Orientation was performed with the FlexIt tool on the first nine cores with good results. Nonmagnetic core barrels were used for APC coring for Cores 340-U1395A-2H through 9H. APC refusal in Hole U1395A came on Core 15H at 120.8 mbsf. The entire piston coring sequence was punctuated by frequent partial strokes. Cores 11H and 12H required drilling over to release them from the formation. The XCB system was then deployed, and coring continued through Core 28X without problems but with generally poor recovery. Fifteen piston cores were taken over a 120.8 m interval with a total recovery of 124.29 m of core. Thirteen XCB cores were cut over a 110.5 m interval with a recovery of 19.99 m of core. Overall core recovery for Hole U1395A was 144.18 m for the 231.3 m interval (62%). After the completion of XCB coring, the top drive was set back and the bit cleared the seafloor at 1800 h on 14 March, ending Hole U1395A. The total time spent on Hole U1395A was 39 h.

Hole U1395B

After clearing the seafloor from Hole U1395A, the vessel was offset 20 m east and Hole U1395B was spudded at 1930 h on 14 March 2012. Seafloor depth was calculated from the mudline recovery: 1211.6 mbrf (1200.2 mbsl). Nonmagnetic core barrels were used for APC coring for Cores 340-U1395B-2H through 10H. APC refusal was encountered during Core 15H at 124.1 mbsf. The entire piston coring sequence was punctuated by frequent partial strokes. Cores 10H–12H required drilling over to release them from the formation. The XCB system was then deployed, and coring continued through Core 25X without problems but with generally poor recovery. The Sediment Temperature Tool (SET) was deployed after Core 17X. Although the deployment seemed flawless, a seal within the tool leaked during deployment and no data was recovered from the tool. Fifteen piston cores were taken over a 124.1 m interval with a total recovery of 127.51 m of core. Ten XCB cores were cut over a 79.2 m interval with a recovery of 12.03 m of core. Overall core recovery for Hole U1395B was 140.21 m for the 203.3 m interval (69%). At the conclusion of coring, Hole U1395B was conditioned with a 25 bbl high-viscosity mud sweep and displaced with 85 bbl of 10.5 ppg mud for logging. The drill string was then pulled back, the top drive was set back, the bit was set at 82.3 mbsf, and the pipe was hung from the blocks. The Schlumberger wireline was then rigged up for logging, and the triple combo was deployed. Two successful passes were made to 201.3 mbsf. There was some difficulty getting the tool string back into the drill string, but after several attempts the tool string entered the drill string and was pulled back to surface and rigged down. The FMS-sonic tool string was then picked up. The tool string was run to 200.4 mbsf, and two passes were made over the length of the open hole. The tool string was then pulled back to the surface and rigged down. The knobbies were laid out, and the drill string was pulled from the hole. The bit cleared the rotary table at 1930 h, and the drill floor was secured at 2000 h, ending Site U1395 and Hole U1395B. The vessel then proceeded underway to Site U1395. The total time spent on Hole U1395B was 50 h.

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