Operations Synopsis: Site 1176 | Table of Contents

OPERATIONS SYNOPSIS

SITE 1175 (ENT-07A)

 A seafloor positioning beacon was dropped at 2230 hr on 22 June, establishing Site 1175. A new APC BHA consisting of a 9-7/8-in PDC bit, a bit sub with a lockable float valve, a seal bore drill collar, landing saver sub, modified top sub, modified head sub, nonmagnetic drill collar, seven 8-1/4-in drill collars, a tapered drill collar, a crossover sub, six joints of 5-1/2-in drill pipe, and a crossover sub to 5-in drill pipe was assembled and run in the hole. The PDR indicated a seafloor depth of 3024.4 mbrf. The bit was positioned at 3010 mbrf, and the WSTP was deployed to take a seafloor water sample prior to establishing any circulation. The WSTP was recovered with traces of sediment on it indicating that the water depth was shallower than anticipated.

Hole 1175A
After recovering the WSTP, the bit was positioned at 3006.7 mbrf and Core 1H was taken, recovering 7.12 m of core and establishing a seafloor depth of 3009.1 m. Hole 1175A was then APC cored from the mudline to 92.7 mbsf (3101.8 mbrf), where Core 11H resulted in a short stroke and recovered 2.32 m of loose sand. The bit was washed ahead without coring to 100.8 mbsf (3109.9 mbrf) in an attempt to get through the loose sand. Core 12H from 100.8 to 110.3 mbsf (3109.9—3119.4 mbrf) recovered 9.58 m of sediment. Normal APC coring operations continued without unusual overpull until Core 22H (195.8—205.3 mbsf; 3204.9—3214.4 mbrf), which could not be pulled out of the formation. The drill string space out was such that a short kelly was left after shooting the core; therefore, only 3 m of the core barrel could be drilled over. After drilling over these 3 m, the core barrel was pulled out with 120,000 lb overpull and heavy circulation.
Twenty-two APC cores were taken from Hole 1175A, recovering 197.68 m of sediment from 199.5 m of cored section (99% recovery); 5.8 m was drilled without coring. After recovering Core 22H, the XCB coring system was use to obtain Cores 23X through 47X (205.3—445.5 mbsf) and recovered 129.3 m of sediment (54%).
After terminating coring in Hole 1175A, the hole was displaced with 136 bbl of heavy mud. Because the formation contained a considerable amount of loose sand, the bit was pulled to 289.92 mbsf (3299.02 mbrf) with the top drive in place. The top drive was racked back, and the bit was pulled 153.7 m above the seafloor for the move to Site 1176. The bit cleared the seafloor at 0500 hr on 26 June and the seafloor positioning beacon was released. The beacon was recovered at 0615 hr on 26 June, ending operations at Site 1175.


Operations Synopsis: Site 1176 | Table of Contents