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OPERATIONS (continued)

Site 1220
Transit to Site 1220 (PAT-9D)

The 149-nmi voyage to proposed Site PAT-9D was accomplished in 13.3 hr at an average speed of 11.2 kt. At 1800 hr on 28 November, the vessel slowed to 5 kt and a short 3.5-kHz survey was made from east to west across the site. Upon conclusion of the 1-hr survey, the vessel came about and returned to site as the thrusters were lowered and the DPS was activated. The GPS receiver interface to the DPS was employed to situate the vessel over the coordinates of the new location by 1915 hr. A beacon was deployed at 2006 hr. The corrected PDR depth was 5234.4 mbrf.

Hole 1220A

After the drill string was deployed to a depth of 5215 mbrf, the driller lowered the bit until the heave compensator appeared to activate, suggesting contact with a firm seafloor. The contact was at a bit depth of ~5233 mbrf. Hole 1220A was spudded with the APC at 0500 hr on 29 November with the bit at 5229.0 mbrf. The seafloor depth that was indicated by the recovery of the initial core was 5229.1 mbrf. This depth was 5.3 m shallower than the PDR depth. Piston coring advanced routinely to 95.0 mbsf (Cores 1H through 10H) with excellent recovery (Table T1). Cores were oriented starting with Core 3H.

During the process of obtaining Core 11H, the overshot shear pin parted and the Tensor tool was recovered without the core barrel. The Tensor tool was set aside, and a second wireline trip with the sinker bars was made to retrieve the core barrel. Upon retrieval, the core barrel was momentarily stuck but quickly came free and was recovered. Core 12H was taken in the customary manner with a full bleed-off of pressure, indicating a full stroke. The sinker bars and Tensor tool were retrieved by the wireline but without the core barrel. The Tensor tool was laid down and the wireline jars were deployed to recover the core barrel. The core barrel could not be released by alternately applying overpull and upward impacts with the wireline jars. The effort was given up after 45 min, the overshot shear pin was intentionally parted, and the wireline was recovered. The drill string was then retrieved and the hole was terminated.

APC operations in Hole 1220A resulted in 114.0 m cored with 118.7 m recovered (average recovery of 104.1%).

Hole 1220B

After the BHA was redeployed, the vessel was offset 20 m west of Hole 1220A in preparation for the spudding of Hole 1220B. The drill string was deployed to a depth of 5215.5 mbrf, and Hole 1220B was spudded at 2215 hr on 30 November. After the bit was drilled to 34.0 mbsf, APC operations were initiated and the hole was deepened to 152.0 mbsf. The interval from 62.5 to 64.5 mbsf was drilled to maintain an appropriate stratigraphic overlap with Hole 1220A. The cored interval was 116.0 m with 126.8 m recovered (109.3% recovery). All piston cores were oriented. The Adara temperature tool was deployed at 53.0 mbsf (Core 2H), 83.5 mbsf (5H), and 102.5 mbsf (7H). The developmental methane tool (APCM) was deployed and appeared to have successfully obtained data.

Hole 1220B was deepened from 152.0 to 202.0 mbsf with XCB coring (Table T1) and penetrated basaltic basement with the last core (Core 20X). XCB operations deepened the hole 50.0 m and recovered 17.8 m of sediment (35.6% recovery). The total recovery for the hole was 144.7 m, representing 87.1% of the cored interval.

Hole 1220B was terminated when the bit cleared the seafloor at 1530 hr on 2 December. The vessel was then offset 20 m west of Hole 1220B.

Hole 1220C

Hole 1220C was spudded at 1600 hr on 2 December. After the bit was drilled to 25.0 mbsf, one piston core was obtained spanning the O/M boundary (25.0–34.5 mbsf). The hole was then drilled from 34.5 to 60.0 mbsf, where continuous piston coring was initiated and the hole advanced to 145.5 mbsf. The APC cored interval was 95.0 m with 98.0 m recovered (103.2% recovery) (Table T1). All APC cores were oriented. Hole 1220C was deepened from 145.5 to 204.1 mbsf with XCB coring operations. Basaltic basement was reached with the last core (Core 17X). The XCB cored interval was 58.6 m with 18.13 m recovered (30.9%). The total recovery for the hole was 153.6 m, representing 75.6% of the cored interval (Table T1).

Following the end of coring operations in Hole 1220C, the drill string was pulled to the deck, the beacon was retrieved, and the drilling equipment, hydrophones, and thrusters were secured. The vessel departed location at 0930 hr on 4 December.

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