SITE 1047
(ODP Site 676; Proposed Site NBR-10A)

After the drill string was pulled clear of the seafloor following Hole 1046A, the vessel was offset in DP mode over to Site NBR-10A, and a positioning beacon was deployed. During the move to Site NBR-10A, the LWD tools were changed out. A request was made to ODP/TAMU to deepen the penetration at NBR-10A from the approved 500 to 650 mbsf. The deeper penetration was intended to obtain LWD data from the turbidite sequence in the underthrust section at a location between the reference Site 1044 and Site 1046 farther to the west in the accretionary prism. This request was approved by ODP/TAMU.

Hole 1047A was spudded at 0115 hr 04 January 1997 at GPS coordinates 15°31.8344'N and 58°42.1909'W. This location is approximately 27 m south of ODP Site 676 (Leg 110). Drilling was initiated at 35 m/hr at a water depth of 5070 mbrf based on the drill pipe depth from Site 676. The final water depth was established at 5067 mbrf (5056 mbsl) based on the analysis of the LWD data.

Drilling continued at 35 m/hr down to 5353 m (286 mbsf) where high pump pressure and high torque were encountered due to penetration of the décollement zone. The zone from 283 to 350 mbsf required considerable back reaming and hole conditioning in order to alleviate elevated pump pressures and torque values. Sepiolite mud sweeps (20 to 30 bbl) were used to condition the hole during four different wiper trips through the décollement. After drilling deep enough to get the top of the BHA below the décollement, the pump pressures and torque returned to normal. Drilling continued without problems at a rate of penetration of 35 m/hr down to 5700 mbrf (633 mbsf) at which point we expended the time allotted for drilling this hole. The drill string was pulled clear of the seafloor at 2115 hr 05 January ending Hole 1047A.

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