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IODP Expedition 330 Louisville Seamount Trail

Daily Report 19 -- Thursday, 30 December 2010 -- What About Getting Stuck on a Seamount?



Site U1372 on 26.5°S Guyot 26° 29' 35.9988" S, 174° 43' 45.0012" W
Louisville Seamount Trail
0 m above sea level

All good things end - at least a pessimist would argue so. Generally I would disagree, but things were turning worse with every new core we were getting on deck. The first bad signs came when the recovery started going from 19% to 115% and vice versa. And it kept fluctuating. We quickly noticed that every time we had poor recovery, we also had a few basaltic clasts or pebbles "jamming" the core catcher. As soon as a few of these pebbles decided to block the core catcher they evidently didn't allow any more new core to come into the core liner and hence we got poor recovery. Basically we were now simply grinding through the seamount formation and not coring any of the basalts. That of course was not such a good thing.

The drillers now started to note that because of the high number of uncemented volcaniclastic sediment that many of the loose pebbles or clasts were getting stuck between the drill collars and the borehole wall. To keep the hole in good condition for further penetration and later downhole logging, they kept sweeping the hole, they pumped drilling mud and water, all with the intent to get rid of the drilling rubble that we were now generating by grinding through the rocks. The first attempts were successfull and we kept pushing on. However, in the afternoon things started to go wrong and it didn't get better anymore. Now the hole conditions started to deteriorate more quickly and just before midnight on December 30 the drill pipe got stuck and the drillers couldn't rotate the pipe anymore. Despite 20 hours of trying to unstuck the drill pipe, the drillers had to give up and we needed to severe the drill pipe with an explosive just above the obstruction. If you think about it, that is in fact the only way to decouple almost 2 km of drill pipe that is irretrievably stuck in the ocean floor. It is the only thing to do if you like to move on to another drill site and so we did.

After a carefull operation taking all safety precautions necessary, the drill string was severed at a depth of about 90 mbsf and thus this left only a short interval of open hole for logging. Together with the fact that the explosion likely further weakened the condition of the borehole, it was decided not to attempt any downhole logging at this site and to move on. A science meeting was held at noon to discuss the situation. The science party agreed to a proposal by the co-chiefs to go to the approved Alternate Site LOUI-6A, which is located on a similar old seamount just 146 nautical miles to the SE. We were steaming by the afternoon of December 31, the last day of 2010.