Previous   |    Next

doi:10.2204/iodp.proc.344.104.2013

Operations

Transit to Site U1414

After a 5.8 nmi transit from Site U1412, the vessel stabilized over Site U1414 (proposed Site CRIS-19A) at 0015 h on 3 December 2012. The position reference used for dynamic positioning was a combination of GPS signals and an acoustic beacon, which was deployed at 0010 h. During the transit, an advanced piston corer (APC)/extended core barrel (XCB) bottom-hole assembly (BHA) was assembled with a nonmagnetic drill collar and the drill string was lowered to 1858 meters below rig floor (mbrf).

Hole U1414A

Upon arrival, the drill string was lowered to just above the seafloor, and Hole U1414A (8°30.2304′N, 84°13.5298′W; 2459 m water depth) was spudded at 0805 h on 3 December 2012. Cores 344-U1414A-1H through 22H were taken with the APC from 0 to 200.1 meters below seafloor (mbsf) (Table T1). Nonmagnetic core barrels and the FlexIT orientation tool were used with all APC cores. Advanced piston corer temperature tool (APCT-3) formation temperature measurements were taken with Cores 3H, 5H, 7H, and 9H. The coring system was switched to the XCB system after having to drill over Core 22H. Cores 23X–35X were taken with the XCB from 200.1 to 311.9 mbsf, by which point penetration rates and recovery had decreased drastically. The decision was made to stop XCB coring, drop a free-fall funnel (FFF), change the XCB coring assembly to a rotary core barrel (RCB) assembly, and reenter Hole U1414A. The hole was swept with a 30 bbl high-viscosity mud sweep, and the bit was pulled back to 113.7 mbsf. The FFF and subsea camera were deployed at 0025 h. The remainder of the drill string was pulled from the hole while the camera recorded the position of the FFF on the seafloor and the bit as it cleared the FFF. The drill string was then raised to the surface, with the bit clearing the rotary table at 0740 h on 5 December. An RCB BHA was assembled with a new bit, and the BHA was lowered to just above the seafloor by 1415 h. The subsea camera was deployed, and after searching for the FFF for ~1.5 h, Hole U1414 was reentered at 1543 h. The bit was slowly lowered into the hole without encountering any obstruction, and coring resumed. RCB Cores 36R–44R recovered sediment from 311.9 to 374.6 mbsf. Basement was contacted with Core 45R at ~375.25 mbsf. Coring continued through Core 63R at 471.6 mbsf until coring time expired.

In preparation for logging, the hole was swept clean with mud and the bit was released. The end of the drill string was set at 96 mbsf, and the logging tools were rigged up. The first logging run was with the triple combination (triple combo)–Ultrasonic Borehole Imager (UBI) tool string and reached 421 mbsf, where it encountered an obstruction. The second logging run was with the Formation MicroScanner (FMS)-sonic tool string, and it reached the same depth. Logging activities were completed by 1200 h on 10 December. The drill string cleared the rig floor at 1955 h on 10 December, ending Site U1414. The vessel began the 95 nmi transit to Puntarenas, Costa Rica, at 2015 h. First line ashore was at 0502 h on 11 December 2012, ending Expedition 344.

A total of 63 cores were recovered at this site: 22 APC, 13 XCB, and 28 RCB. The APC cored interval was 200.1 m, with 206.2 m recovered (103%). The XCB cored interval was 111.8 m, with 94.1 m recovered (84%). The RCB cored interval was 159.7 m, with 84.5 m recovered (53%). Overall recovery for Site U1414 was 81%. Total time spent on Site U1414 was 191.0 h or 8 days.

Top of page   |    Previous   |    Next