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doi:10.2204/iodp.proc.344.107.2013

Operations

Transit to Site U1413

After a 15.0 nmi transit from Site U1412, the vessel stabilized over Site U1413 (proposed Site CRIS-13B) at 2330 h on 23 November 2012. The position reference used for dynamic positioning was a combination of GPS signals and an acoustic beacon, which was deployed at 2345 h on 23 November and retrieved at 0037 h on 1 December.

Hole U1413A

As soon as the vessel stabilized over the site coordinates, an advanced piston corer (APC)/extended core barrel (XCB) bottom-hole assembly (BHA) was assembled and lowered to just above the seafloor. Hole U1413A (8°44.4593′N, 84°6.8095′W; 540 m water depth) was spudded at 0635 h on 24 November 2012. Nonmagnetic core barrels and the FlexIT orientation tool were used for Cores 344-U1413-1H through 18H (Table T1). Advanced piston corer temperature tool (APCT-3) formation temperature measurements were taken with Cores 3H and 5H–8H. Coring continued through Core 18H at 140.6 mbsf with the APC system and through Core 26X at 189.1 mbsf with the XCB system. Because of the slow coring rate, the decision was made to pull out of the hole and change coring systems to the rotary core barrel (RCB) system. In Hole U1413A, 18 APC cores were taken over a 140.6 m interval with 143.6 m recovered (102%) and 8 XCB cores were taken over a 48.5 m interval with 43.7 m recovered (90%). Overall recovery for Hole U1413A was 187.3 m over the 189.1 m cored (99%). Hole U1413A ended when the bit cleared the seafloor at 2355 h on 25 November. Total time spent on Hole U1413A was 48.5 h.

Hole U1413B

A shallow hole was cored for geochemical analyses. The vessel was offset 20 m east, and Hole U1413B (8°44.4593′N, 84°6.7992′W; 540 m water depth) was spudded at 0055 h on 26 November 2012. The seafloor depth was established at 540 m based on the mudline core recovery. Nonmagnetic core barrels were used, but orientation was not recorded. Three APC cores were taken over a 25.6 m interval with 27.4 m recovered (107%) (Table T1). The bit cleared the rotary table at 0550 h on 26 November, ending Hole U1413B. Total time spent on Hole U1413B was 5.75 h.

Hole U1413C

After offsetting the vessel 20 m south, an RCB BHA with a new 9⅞ inch bit was made up and run in the hole to just above the seafloor. Hole U1413C (8°44.4482′N, 84°6.7993′W; 540 m water depth) was spudded at 0940 h on 26 November 2012. The seafloor depth was assumed to be 540 m based on nearby Hole U1413B. Drilling without recovery continued for 11.75 h and reached a depth of 178.0 mbsf (Table T1). A nonmagnetic RCB core barrel was dropped, and coring began. Coring continued with Cores 344-U1413C-2R through 43R to a total depth of 582.2 mbsf, which was reached at 1300 h on 29 November. Coring was terminated to allow time to complete other expedition objectives. Forty-two RCB cores were taken over a 404.2 m interval with 313.9 m recovered (78%).

In preparation for logging, the hole was swept clean with a 50 bbl high-viscosity mud sweep. A wiper trip was made from bottom to 88.4 mbsf. On the way back into the hole, we ran into an obstruction at 250.6 mbsf. The hole had to be washed and reamed down to the total depth of 582.2 mbsf. Another 30 bbl high-viscosity mud sweep was pumped, followed by a 50 bbl sweep. The RCB bit was released at 572.2 mbsf, and the hole was displaced with heavy mud. The drill string was pulled out of the hole so that the end of the pipe was set at 103 mbsf. Because hole conditions were poor, the decision was made not to run the nuclear source on the first logging run. The logging tools were rigged up, and the triple combination (triple combo) tool string was run into the hole at 1200 h, reaching 181.9 mbsf. The next logging run was with the Ultrasonic Borehole Imager (UBI) tool string. This run started at 1600 h and reached 189.9 mbsf. The final logging run was with the Formation MicroScanner (FMS) tool string. The run started at 1955 h and also reached 189.9 mbsf. The logging tools were rigged down, and the rig floor was secured for transit back to Site U1412 at 0145 h on 1 December. Total time spent on Hole U1413C was 116 h. Total time spent on Site U1413 was 170.25 h or 7.1 days.

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