Site 1122
Hole 1122A
The 341-nmi voyage to Site 1122 (proposed site SWPAC-8A) was accomplished at an average speed of 9.6 kt. The vessel proceeded directly to the GPS coordinates of the location. The positioning beacon was dropped at 2254 hr on 5 September. The hydrophones and thrusters were extended and the vessel settled on location. The APC/XCB BHA was assembled using a 9 7/8" PDC bit. Hole 1122A was spudded with the APC at 1210 hr on 6 September. The recovery indicated that the water depth was 4435.00 mbsl. Piston coring advanced to refusal at 75.8 mbsf and Core 181-1122A-1H through 8H were taken. The hole was deepened with the XCB to 124.0 mbsf, which was considered the objective for the initial hole of the site. APC cores were oriented starting with Core 181-1122A-3H. The bit cleared the seafloor at 0415 hr on 7 September, ending operations at Hole 1122A.
Hole 1122B
The vessel was offset 20 m to the west and the second hole of the site was spudded with the APC at 0615 hr on 7 September. To obtain a stratigraphic overlap for interhole correlation, the bit was positioned 5 m higher than at Hole 1122A. However, the recovered core barrel was full, which required another attempt to obtain a mudline core.
Hole 1122C
The bit was raised at the same location by an additional 5 m and Hole 1122C was spudded with the APC at 0740 hr. The mudline core indicated that the water depth was 4431.80 mbsl. The APC was advanced by recovery to 103.7 mbsf and Cores 181-1122C-1H through 13H were obtained. The last three cores (181-1122C-11H, -12H, and -13H) did not achieve a full stroke.
Coring was switched to the XCB and advanced without incident to 204 mbsf with good to poor recovery. Very rapid XCB coring continued with recovery ranging from 1%–97% from 204 to 627 mbsf. After making a drill pipe connection following the retrieval of Core 181-1122C-68X (617.8 to 627.4 mbsf), the drill string became stuck and could not be rotated with up to 700 amps of top drive current. For over an hour, the driller worked the pipe with overpulls as large as 200 kips (200,000 lb), while maintaining a circulation rate of 1000 gallons/min at 2200 psi pressure. After working the pipe for over an hour, the drill string became free. It was considered imprudent to attempt to deepen the hole past this depth, and preparations for logging operations were started.
Logging Operations at Hole 1122C
In preparation for logging, the hole was 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 pulled back and positioned at 83 mbsf. At 0700 hr on 11 September, the logging equipment was rigged up and the first tool suite (triple combination: DITE/HLDS/APC/HNGS) was deployed in the drill pipe. The tool string was unable to pass the bit more than 12 m and after repeated attempts by the logging winch operator, it was decided to recover the logging tool in rapidly deteriorating weather conditions. After the logging tool was disassembled, we terminated operations at the site because of heavy seas and high winds. The combined sea state was exceeding 10 m and wind gusts were recorded as high as 55 kt.
When overpulls as large as 200 kips were unable to free the drill string, the top drive was picked up. For two hours, the stuck drill pipe was worked with 200 kips of overpull while maintaining a circulating rate of 1000 gallons/min. At 1530 hr on 11 September, the pipe was free and the drill string was recovered. The bit cleared the seafloor at 1625 hr. By 0800 hr the drilling equipment was secured for the voyage to the next site and the beacon was recalled and recovered. At 0800 hr on 12 September, the vessel was under way on a northeasterly course to Site 1123 (SWPAC-5B).
To 181 Summary of Engineering and Drilling Operations: Site 1123