Site 1123
Hole 1123A
The 384-nmi voyage to Site 1123 (proposed site SWPAC-5B) was accomplished at an average speed of 11.1 kt. The vessel proceeded directly to the GPS coordinates of the location. The positioning beacon was deployed at 1848 hr on 13 September. The hydrophones and thrusters were lowered and the APC/XCB BHA was assembled using a 9-7/8-in PDC bit and deployed. Hole 1123A was spudded with the APC at 0425 hr on 14 September. The recovery indicated that the water depth was 3290.1 mbsl. APC coring advanced to refusal at 158.1 mbsf. The bit cleared the seafloor at 2355 hr on 14 September.

Hole 1123B
To obtain stratigraphic overlap with the previous hole, the bit was raised by 3 m from the spudding depth of Hole 1123A, and Hole 1123B was spudded with the APC at 0110 hr on 15 September. The recovery of the mudline core indicated a seafloor depth of 3289.9 mbsl. APC Cores 181-1123B-1H through 15H were recovered from 0 to 136.4 mbsf. While attempting to retrieve Core 181-1123B-16H from a depth of 145.9 mbsf, the wireline parted at the sinker bar assembly socket. An eight-finger hard formation core catcher was used as an overshot in order to latch onto the core barrel. The overshot was run in and engaged on the first attempt and the core barrel was retrieved to the surface. Piston coring resumed in Hole 1123B with a full stroke of Core 181-1123B-17H. The core barrel could not be extracted from the sediment and had to be drilled over. The Adara heat-flow shoe was deployed with Cores 181-1123B-5H (41.4 mbsf), 6H (60.4 mbsf), 7H (79.4 mbsf), and 11H (98.4 mbsf). These runs failed to provide heat-flow data because of the frictional heat that was generated by the vertical motion of the vessel (heave). Coring was switched to the XCB and advanced without incident to 182.0 mbsf with >100% recovery. While retrieving Core 181-1123B-21X the core-winch operator noticed that the line on the drum was slack and that there was no line tension on the weight indicator. This was an obvious indication that the wireline and sinker bars were caught on an obstruction in the drill pipe. The obstruction turned out to be the core barrel which had stuck in the pipe 124 m below the drill floor. As a result of running into the core barrel, the wireline on the drum backlashed. After respooling the line and after various attempts to free the stuck XCB barrel the drill string had to be retrieved to the level of the stuck core barrel. There was nothing found on the inside of the drill pipe to suggest the cause of the jamming. The drill string was run back in to the bottom and XCB operations recommenced at 0545 hr on 16 September. Coring advanced to 374.1 mbsf. While pumping down the XCB core barrel to cut Core 181-1123B-41X, the barrel stopped at an obstruction in the bore of the drill pipe at 645 mbrf. On tagging the stuck barrel with the sinker assembly, a number of loose wraps were produced on the forward core winch drum before the brakes could be applied. Approximately 50 m of wire was spooled from the drum to remove the loose wraps. A fishing assembly was deployed, and the core barrel was tagged at 645 mbrf. After the first hit of the wireline jars, the stuck core barrel was freed and recovered to the rig floor. XCB coring again resumed at 0900 hr on 17 September and advanced to 489 mbsf, which was the revised depth objective for this hole.

Logging Operations in Hole 1123B
In preparation for logging, an aluminum go-devil was dropped and the hole swept with 60 barrels of high viscosity mud. The bit was pulled back in the hole to 520 mbsf and the hole was displaced with 175 barrels of sepiolite mud. The bit was then positioned at the logging depth of 83 mbsf. Logging operations began at 1100 hr and lasted for 20 hr. Logging was conducted from the bottom of the hole at 489 mbsf to the bit at 84 mbsf. Three standard tool-string configurations were run: the triple combination, the FMS-sonic (two passes), and the GHMT. The NMRS (total field) tool on the GHMT failed to work. The condition of the borehole was good and the quality of the data was excellent. After the logging equipment was disassembled, the bit was pulled out of the hole and cleared the seafloor at 0955 hr on 19 September, ending operations at Hole 1123B.

Hole 1123C
The vessel was offset by 30 m to the north and Hole 1123C was spudded with the APC at 1130 hr. Piston coring advanced to 151.5 mbsf. A core barrel with a center bit was dropped and the hole was deepened by drilling ahead to 230.0 mbsf. The center bit was retrieved and one XCB core (Core 181-1123C-17X) was obtained from 230.0 to 239.6 mbsf with 67% recovery to provide overlap with an interval of poor recovery in Hole 1123B. Following the recovery of the XCB core barrel, the center bit was dropped again and the hole was drilled ahead from 239.6 to 484.0 mbsf. After the center bit was recovered, XCB coring resumed and advanced from 484.0 mbsf to the modified depth objective of 632.8 mbsf (Cores 181-1123C-18X to 33X), with excellent recovery.

Logging Operations in Hole 1123C
In preparation for logging, an aluminum go-devil was dropped and the hole swept with 60 barrels of high viscosity mud. The bit was pulled back in the hole to 629 mbsf and the hole was displaced with 213 barrels of sepiolite mud. The bit was then pulled back to logging depth of 68 mbsf. By the time the drill crew was preparing to rig up for logging, there were wind gusts of over 60 kt, seas of 3–4 m, and up to 12-m-high swells, which forced the decision to abandon planned logging. At 1050 hr on 22 September, the bit was pulled clear of the seafloor. The pipe was partially recovered, but by 1300 hr the maximum vessel pitch was over 9°. Pipe tripping was suspended because of the hazard to men and material, and operations were placed in weather standby. The storm abated by 0330 hr on 24 September, which allowed the drill crew to recover the drill string and beacon. By 1000 hr the drilling equipment was secured and the thrusters and hydrophones retracted as the vessel began the 269-nmi transit to Site 1124.

To 181 Summary of Engineering and Drilling Operations: Site 1124

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