JA Daily Science Report for Expedition 308, 16 June 2005
LOCATION: Site U1323
SCIENCE UPDATE: The day was spent in MWD/LWD operations at Hole U1323A. The first lithologies encountered consisted of mud, and MWD progresses were good until 207 mbsf. At 207 mbsf, a 1.5 m layer of sand was encountered, and pressure readings on the MWD tool suddely increased by 150 psi. Following the safety protocol, drilling was stopped and pressure was monitored. Since the pressure did not go down, we pumped 50 barrels of 10.5 ppg mud to control it. Once the pressure was controlled, we drilled down to 247 mbsf where a second sand layer was encountered. Although no increase in pressure was recorded, we decided that to maximize the amount of science we could gain and to conserve our mud, we should move to the URSA-1B location. The hole was filled with 13.5 ppg mud, and cemented from 40 to 140 mbsf. A VIT survey confirmed that no flow was present at the surface. Drilling in Hole U1323A has provided two important conclusions: 1) IODP has successfully applied "Controlled Riserless drilling" to prevent flow out of overpressured pockets of sand at shallow depth, and thus proved that the technique was valid for this and future expeditions, and 2) sand layers or pockets at URSA basin are overpressured at sediment depths shallower than previously thought.