JA Daily Science Report for Expedition 309, 01 August 2005


LOCATION: Site 1256


SCIENCE UPDATE: Following the identification of pump pressure loss somewhere in the bottom hole assembly on 31 July the drill string was tripped back to the rig floor and the BHA inspected for cracks. Drilling collars started to be landed and inspected at 0300 and the bit was on the rig floor at 0500. Major damage was clear to the 8.5 inch bit-sub assembly, which sits directly above the drill bit. A straight horizontal gash had opened for approximately 150 degrees (11 inches) of the circumference of the 3/4 inch-thick bit-sub wall, with more ragged fracture tips propagating a further ~75 degrees (~5-6 inches) around the pipe from each end of the clean fracture. When in tension with the drill bit hanging from the sub the fracture opened up to ~1 cm and the bit was held on by only about 4.25 inches of the bit-sub wall. Such a failure of the bit-sub assembly had not been witnessed before in the shipboard memory of scientific ocean drilling and the rapid diagnosis and response of the Transocean operations team certainly averted a time consuming major equipment loss in Hole 1256D. A new BHA was made up with a new CC-9 RCB bit and Hole 1256D was re-entered for the 6th time at 1423 and coring operations recommenced at 1945 with Core 112R landed at 0200, 02 August 2005.