163 Preliminary Report

Site 988

At 1115 GMT on 8 September, we approached the survey area. After a 10-nmi seismic run with the 3.5-kHz depth sounder, we were preparing to drop the beacon on coordinates when we encountered a large iceberg bearing down on the beacon drop point. Because the iceberg was passing close to Site 988, we slowly moved on site approximately 1.4 nmi "behind" the iceberg as it moved southwest at about 1 kt. We avoided the iceberg by making a sharp turn to starboard after dropping the beacon at 1230 GMT. By 1300 GMT, the JOIDES Resolution was on site (65°42.255'N, 34°52.262'W).

Hole 988A

Hole 988A was spudded about 30 nmi offshore of the southeast Greenland coast in 262.6 m of water. The original plan for Site 988 was to core a single, deep (700 m below seafloor, or mbsf) hole into basaltic basement using a free-fall funnel or, if necessary, a reentry cone with casing. If a single deep hole proved impossible to achieve, we would drill a series of shallower offset holes.

We began coring at 2115 GMT on 8 September with a nine-collar, rotary core barrel bottomhole assembly (RCB BHA), including a new RBI C-4 bit (SN BD472). Before coring commenced, we viewed the seafloor with a TV camera and determined that there was sufficient sediment cover for an RCB spud-in by conducting a drill-string penetration test. Initial coring advanced slowly to 21.4 mbsf with 2.4 m recovered (11%). After little advance of the drill bit was made during the latter part of coring of Core 163-988A-2R, the bit was tripped to the surface and found to be jammed with a large amount of basalt in the bit throat and the bit body. Mechanical impressions on two recovered basaltic fragments suggest that the 163-988A-2R core barrel landed on basalt dropped out from the 163-988A-1R core barrel, preventing it from seating properly.

Coring resumed with a new, harder formation bit (Security H87F). Drill-string reentry of the open hole was accomplished in 15 min without requiring a free-fall funnel. RCB coring advanced in Hole 988A to 32 mbsf with an average rate of penetration (ROP) of 1.7 m/hr. After retrieving Core 163-988A-5R, the driller was unable to establish circulation and the hole began to pack off. The drill string could not be rotated and the bit became firmly stuck at 27 mbsf.

While working the stuck drill pipe in an attempt to free the drill string, a joint of 5 in. pipe approximately 30 m above the BHA and 135 m below the rig floor parted at 0515 GMT on 10 September. The recoil resulting from the pipe failing under tension caused both tilt-link pin anchors in the top drive motor frame/guide dolly assembly to be torn apart. These anchors secure the swivel to the dolly assembly and are made of 1-1.5 in.-thick steel plate. The top drive swivel also sustained damage as a result of this recoil. The immediate release of tension on the drilling line as a result of the rebound caused the drilling line to jump out of the dead-line sheave. In order to repair the top drive motor frame/dolly, we returned to Reykjavik, Iceland, arriving at 1830 GMT on 10 September.

To Operations Site 989

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