Site 1121
Hole 1121A
The 95-nmi voyage to Site 1121 (proposed site SWPAC-7B) was accomplished at an average speed of 10.4 kt. The vessel proceeded directly to the GPS coordinates of the location. The positioning beacon was dropped at 2025 hr on 1 September. A backup beacon with a higher output setting had to be launched because the first beacon signal was marginal. The hydrophones and thrusters were lowered and the APC/XCB BHA was assembled using a 9-7/8-in PDC bit and deployed. A drill pipe swab (pig) was pumped down the pipe to clean out rust that had accumulated in the additional drill pipe that was brought for this deep-water site. Hole 1121A was spudded with the APC at 1554 hr on 2 September. The recovery indicated that the water depth was 4492 mbsl. The hole was scheduled for only a mudline sample and the single APC Core 181-1121A-1H was taken from 0 to 8.4 mbsf.

Hole 1121B
The second hole of the site was spudded with the APC at 1710 hr on 2 September. The sea-floor depth inferred from recovery was 4487.9 mbsl. APC coring advanced to 23.0 mbsf when Core 181-1121B-3H did not achieve a full stroke. The XCB barrel was run in with a soft formation cutting shoe and experienced considerable difficulty advancing with high torque and a very low penetration rate. After advancing only 0.5 m in 30 min of rotation, the core barrel was recovered to investigate why the coring was so difficult. The core proved to contain chert fragments. A hard-formation cutting shoe was deployed, and coring continued with the XCB in slow and occasionally difficult conditions.

XCB coring deepened the hole to 139.7 mbsf when operations were terminated because the scientific objectives were reached. The bit cleared the seafloor at 0120 hr on 4 September, ending operations at Hole 1121B. The bit was at the plane of the rotary table at 1040 hr and by 1045 hr the drilling equipment was secured for the voyage to the next site. Both beacons were recalled and recovered. At 1045 hr on 4 September, the vessel was under way on a northeasterly course to Site 1122.

To 181 Summary of Engineering and Drilling Operations: Site 1122

To 181 Table of Contents