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doi:10.2204/iodp.pr.334.2011 OperationsSite U1378Two holes were drilled or cored at this site (Table T1). The first hole was drilled with a 8½ inch drill bit with LWD tools in the BHA to 456.9 mbsf. The next hole was cored with the APC/XCB coring system to 523.9 mbsf. The APCT-3 was deployed four times and useable data was recovered four times. The Flexit tool was deployed on all 16 piston cores in Hole U1378B. All APC holes were cored with nonmagnetic core barrels. Recovery for Site U1378 was 101.4% with the APC system and 100.3% with the XCB system. Overall core recovery for Site U1378 was 100.5%. A total of 63 cores were recovered after coring 523.9 m. The total length of core recovered at this site was 526.69 m. Hole U1378B was terminated after Core 334-U1378B-63X when hole conditions deteriorated and could not be remediated. First transit to Site U1378After an 8.6 h transit from Puntarenas, Costa Rica, covering 94 nmi and averaging 10.8 kt, speed was reduced and thrusters and hydrophones were lowered. Dynamic positioning was initiated over Site U1378 at 1000 h (UTC – 6 h) on 17 March 2011. The position reference was a combination of GPS signals and a single acoustic beacon. The positioning beacon was deployed at 1109 h on 17 March. The beacon was left on site for our return after Site U1379. On reoccupation, the beacon was nonresponsive and declared "lost." Another beacon was deployed at 1204 h on 2 April and was recovered at 2042 h on 6 April. Hole U1378ARig floor operations commenced at 1000 h on 17 March. The trip to the seafloor was uneventful. The top drive was picked up, the drill string was spaced out, and the LWD hole was spudded at 0425 h on 18 March. After 37.5 h of drilling, Hole U1378A was terminated at 456.9 mbsf. High standpipe pressures, lost circulation, and high torque contributed to the decision to abandon the hole. A wiper trip was attempted, but given the time available versus the progress made to date, the decision was made to terminate Hole U1378A and move to Site U1379 and complete LWD drilling at the second site. After picking up off bottom, the hole was displaced with heavy drilling mud (10.5 ppg) and the drill string was tripped out of the hole to ~640 meters below rig floor (mbrf) while experiencing high torque and significant overpull. The top drive was set back and the drill string was tripped the rest of the way to surface. The 6½ inch drill collars were set back in the derrick. The LWD tools were stored for transit and the rig floor was secured. Thrusters and hydrophones were pulled and the vessel was put into cruise mode, ending Hole U1378A at 0230 h on 20 March. Second transit to Site U1378After a 1.25 h transit from Site U1379 covering 6 nmi and averaging 4.8 kt, speed was reduced and thrusters and hydrophones were lowered. Dynamic positioning was initiated over Site U1378 at 1100 h (UTC – 6 h) on 2 April. The position reference was a combination of GPS signals and a single acoustic beacon. On reoccupation of Site U1378, the beacon which had been left on bottom was nonresponsive and declared "lost." Another beacon was deployed at 1204 hours on 2 April and was recovered at 2042 h on 6 April. Hole U1378BAfter offsetting the vessel 20 m west, Hole U1378B was spudded at 1515 h on 2 April and advanced with the APC coring system to 127.8 mbsf before refusal. All cores after the fifth core were partial strokes and the hole was advanced by recovery. The coring system was switched to the XCB coring system and coring continued from Core 334-U1378B-17X through 63X. Temperature measurements were taken with the APCT-3 on Cores 4H, 7H, 10H, and 13H. Microspheres were run on Cores 20X, 30X, 40X, 50X, and 60X. A total of 16 APC cores were taken with a total recovery of 129.56 m for an overall APC recovery in Hole U1378B of 101.4%. A total of 47 XCB cores were taken over a 396.1 m interval, recovering 396.83 m of core for a XCB recovery of 100.3%. Coring was terminated after Core 334-U1378B-63X when it became impossible to continue advancing. High top drive torque and lost circulation were major factors. A wiper trip was done to try to clean up the hole, but it was impossible to return to bottom. The hole was terminated, plugged, and then abandoned. Total cored interval in Hole U1378B was 523.9 m with 526.69 m of core recovered for an APC/XCB combined recovery of 100.5%. Last core on deck for Hole U1378B was at 0035 h on April 6. After trying to condition the hole for 14.5 h, the decision to abandon the hole was made. The hole was displaced with 10.5 ppg mud and the drill string was pulled back to 960 mbrf with the top drive in place. The top drive was set back and the remainder of the drill pipe and BHA were tripped back to the surface. The seafloor was cleared at 1850 h and the bit cleared the rotary table at 2030 h. The rig was secured for transit and the beacon was recovered at 2042 h, ending Hole U1378B at 2045 h on 6 April. Transit to Site U1379After a 1.25 h transit from Site U1378 covering 6 nmi and averaging 4.8 kt, speed was reduced and thrusters and hydrophones were lowered. Dynamic positioning was initiated over Site U1379 at 0345 h (UTC – 6 h) on 20 March 2011. The position reference was a combination of GPS signals and a single acoustic beacon. The positioning beacon was deployed at 1109 h on 17 March and recovered at 0940 h on 2 April. Site U1379Three holes were drilled or cored at this site (Table T1). The first hole was drilled with a 8½ inch drill bit with LWD tools in the BHA. The next hole was drilled with the APC coring system to recover a mudline core and one additional core. The third hole was drilled with the APC coring system to refusal at 91.2 mbsf followed by XCB coring to refusal at 949.0 mbsf (1087.8 mbrf). The APCT-3 was deployed six times and useable data was recovered five times. The Flexit tool was deployed on all APC cores in Hole U1379C, but data was lost from the first 10 cores when a critical computer was turned off during the first tool's deployment, causing the tool to lose synchronization with the computer. All APC holes were cored with nonmagnetic core barrels. Recovery for Site U1379 was 100.3% with the APC system and 84.4% with the XCB system. Overall core recovery for Site U1379 was 85.9%. A total of 120 cores were recovered after coring 959.5 m. Total length of core recovered at this site was 824.17 m. Hole U1379ARig floor operations commenced at 0345 h on 20 March 2011. The trip to the seafloor was uneventful in the very shallow water. The top drive was picked up, the drill string was spaced out, and the LWD hole was spudded at 0955 h on 20 March. After 73 h of drilling, Hole U1379A was terminated at 962.8 mbsf. After picking up off bottom, the hole was displaced with heavy drilling mud (10.5 ppg) and the drill string was tripped out of the hole to ~500 mbrf while experiencing high torque and significant overpull. The top drive was set back and the drill string was tripped the rest of the way to surface. The 6½ inch drill collars were laid out for offloading in Puntarenas. Data was downloaded from the LWD tools as they were broken down at the rig floor. The LWD tools were then stored for transit and the rig floor was secured. Thrusters and hydrophones were pulled and the vessel was put into cruise mode, ending Hole U1379A at 2254 h on 23 March. The vessel transited to Puntarenas to offload the LWD tools and equipment. Hole U1379BAfter offloading the LWD tools in Puntarenas, the vessel made the 9 h transit back from Puntarenas, covering 97.2 nmi and averaging 11.8 kt. Speed was reduced and thrusters and hydrophones were lowered. Dynamic positioning was initiated over Site U1379 at 0530 h (UTC – 6 h) on 25 March. After offsetting the vessel 20 m west of Hole U1379A, Hole U1379B was spudded at 1030 h. The mudline core established seafloor depth at 138.5 mbrf. APC coring continued until 10.5 mbsf. Two cores were taken with a total recovery of 8.72 m for an overall recovery in Hole U1379B of 83.0%. The drill string was tripped to just above the mud line, clearing the seafloor at 1030 h on 25 March, ending Hole U1379B. Hole U1379CAfter offsetting the vessel 20 m north, Hole U1379C was spudded at 1255 h on 25 March and advanced with the APC coring system to 91.2 mbsf before refusal. All cores after the second core were partial strokes and the hole was advanced by recovery. The coring system was switched to the XCB coring system and coring continued from Core 334-U1379C-18X through Core 118X. Temperature measurements were taken with the APCT-3 on Cores 4H, 7H, 10H, 12H, 13H, and 16H. Microspheres were run on Cores 20X, 30X, 40X, 50X, 60X, 75X, 92X, 105X, and 107X. A total of 17 APC cores were taken with a total recovery of 91.92 m (100.8%). A total of 101 XCB cores were taken over a 857.8 m interval, recovering 723.64 m of core (84.4%). After reviewing the LWD penetration rates, which remained high into the basement section of Hole U1379A, and given the high recovery rates of the XCB system, a decision was made to push the XCB system into the basement section of Hole U1379C. XCB core recovery continued to be excellent until basement was reached. After Core 334-U1379C-104X, the recovery dropped off as we experienced soft to hard to soft formation changes. Average recovery after Core 103X through 118X at 949 mbsf was 19.8%. Average XCB recovery prior to Core 104X was 89.2%. Total cored interval in Hole U1379C was 949.0 m with 815.56 m of core recovered for an APC/XCB combined recovery of 85.9%. Last core on deck for Hole U1379C was at 0130 h on 2 April 2. The hole was displaced with 10.5 ppg mud and the drill string was pulled back to 565 mbrf with the top drive in place. High torque (>500 amps) and overpull were observed all the way to 565 mbrf. At 565 mbrf, the top drive was set back and the remainder of the drill pipe and BHA were tripped back to the surface. The seafloor was cleared at 0755 h and the bit cleared the rotary table at 0910 h. The rig was secured for transit and the beacon was recovered at 0941 h, ending Hole U1379C at 0945 h on 2 April. Transit to Site U1380After a move in dynamic positioning mode from Site U1378, the vessel stabilized over Site U1380 (proposed Site CRIS-10A) at 2130 h (UTC – 6 h) on 6 April 2011. The position reference was a combination of GPS signals and a single acoustic beacon. The positioning beacon was deployed at 2142 h on 6 April and recovered at 1930 h on 8 April. Site U1380
A single hole was drilled at this site to a depth of 397.0 mbsf (Table T1) with a 9 Hole U1380ARig floor operations commenced at 2135 h on 6 April 2011. The RCB BHA was made up with a Rock Bit International (RBI) C-4 RCB bit and mechanical bit release. The trip to the seafloor was uneventful. The top drive was picked up, the drill string was spaced out, and the hole was spudded at 0215 h on 7 April. After 19.5 h of drilling with the center bit installed, the center bit was pulled and a RCB core barrel was dropped and coring began. Coring was terminated after Core 334-U1380A-10R when it became impossible to continue advancing. High top drive torque and lost circulation were major factors. A wiper trip was done to try to clean up the hole, but it was impossible to return to bottom and the hole was terminated, plugged, and then abandoned. Total drilled interval was 397.0 m. Total cored interval in Hole U1380A was 85.4 m with 52.37 m of core recovered for an RCB system recovery of 61.3%. Last core on deck for Hole U1380A was at 1005 h on 8 April. After trying to condition the hole for 5.0 h, the decision to abandon the hole was made. The hole was displaced with 10.5 ppg mud and the drill string was pulled back to 824 mbrf with the top drive in place. The top drive was set back and the remainder of the drill pipe and BHA were tripped back to the surface. The seafloor was cleared at 1730 h and the bit cleared the rotary table at 1905 h. The beacon was recovered at 1930 h and the rig was secured for transit at 2000 h, ending Hole U1380A and Site U1380 on 8 April. Transit to Site U1381After a 11.4 nmi transit to Site U1381 from Site U1380, the vessel stabilized over Site U1381 (proposed Site CRIS-1A) at 2133 h (UTC – 6 h) on 8 April 2011. The position reference was a combination of GPS signals and a single acoustic beacon. The positioning beacon was deployed at 2152 h on 8 April and recovered at 1527 h on 12 April. Site U1381
Two holes were cored at this site (Table T1). Hole U1381A was cored to 164.1 mbsf with a 9 Hole U1381ARig floor operations commenced at 2133 h on 8 April 2011. The RCB BHA was made up with a RBI C-4 RCB bit and mechanical bit release. The trip to the seafloor was uneventful. The top drive was picked up, the drill string was spaced out, and the hole was spudded at 0330 h on 9 April. Coring continued for 69.25 h and was terminated after Core 334-U1381A-26R to move to Hole U1381B. Total cored interval in Hole U1381A was 164.1 m with 73.86 m of core recovered for an RCB system recovery of 45.0%. Last core on deck for Hole U1381A was at 0045 h on 12 April. The hole was displaced with 50 bbl of 10.5 ppg mud, and the drill string was pulled back to just above the seafloor with the top drive in place. The seafloor was cleared at 0220 h, ending Hole U1381A. Hole U1381BAfter offsetting the vessel 20 m west, Hole U1381B was spudded at 0325 h on 12 April and advanced with the RCB coring system to 29.0 mbsf before running the SET-P tool. Three RCB cores were taken in Hole U1381B with a 15.98 m recovery. The cores were taken without circulation and were essentially punch cores. At 29.0 mbsf, the SET-P tool was run on wireline and the first measurement was taken. The hole was then advanced without recovery to 50 mbsf. The core barrel was pulled and the SET-P was again lowered by wireline to take the second measurement. The procedure was repeated for measurements at 71 and 91 mbsf. After the last temperature measurement was taken, the hole was displaced with 10.5 ppg heavy mud and the drill string was pulled back to surface. The rotary bit cleared the seafloor at 1440 h and cleared the rotary table at 1835 h. The beacon was recovered at 1527 h and the rig was secured for transit at 1857 h, ending Hole U1381B and Site U1381 on 12 April. The vessel left Site U1381 on a 100.6 nmi transit to Puntarenas after completing operations during Expedition 334. |
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inch RCB core bit with the center bit installed. The center bit was pulled and RCB coring began at 397.0 mbsf. Coring continued through Core 334-U1380A-10R to 482.4 mbsf. At that point, it became difficult to circulate and high torque was observed on the top drive. A decision was made to make a wiper trip to remediate the poor hole conditions. It was necessary to pull back from 997.4 to 853.0 mbrf before normal circulation and torque were restored. After attempting to return to bottom from 853.0 mbrf, the bit started taking weight at 920.0 mbrf. High torque and lost circulation made it impossible to return to bottom. At 1500 h, preparations began to abandon Hole U1380A. The core barrel was retrieved and the hole was displaced with 120 bbl of 10.5 ppg mud. Overall core recovery for Site U1380 was 61.6%. Nine cores were recovered after coring 85.4 m. The total length of core recovered at this site was 52.37 m. Hole U1380A was terminated after Core 334-U1380A-10R when hole conditions deteriorated and could not be remediated.