Position: 32º43.32'S, 57º15.86'E
Start hole: 1938 hr, 10 May 1998
End hole: 2230 hr, 12 May 1998
Time on hole: 50.87 hr
Seafloor (drill-pipe measurement from rig floor, mbrf): 740.0
Distance between rig floor and sea level (m): 11.2
Water depth (drill-pipe measurement from sea level, m): 728.8
Total depth (drill-pipe measurement from rig floor, mbrf): 742.0
Penetration (mbsf): 2.00
Position: 32º43.32'S, 57º15.86'E
Start hole: 2230 hr, 12 May 1998
End hole: 1110 hr, 13 May 1998
Time on hole: 12.67 hr
Seafloor (drill-pipe measurement from rig floor, mbrf): 741.0
Distance between rig floor and sea level (m): 11.2
Water depth (drill-pipe measurement from sea level, m): 729.8
Total depth (drill-pipe measurement from rig floor, mbrf): 741.5
Penetration (mbsf): 0.50
Position: 32º43.32'S, 57º15.86'E
Start hole: 1110 hr, 13 May 1998
End hole: 2215 hr, 13 May 1998
Time on hole: 11.08 hr
Seafloor (drill-pipe measurement from rig floor, mbrf): 742.5
Distance between rig floor and sea level (m): 11.2
Water depth (drill-pipe measurement from sea level, m): 731.3
Total depth (drill-pipe measurement from rig floor, mbrf): 743.5
Penetration (mbsf): 1.00
Position: 32º43.32'S, 57º15.86'E
Start hole: 2215 hr, 13 May 1998
End hole: 0710 hr, 14 May 1998
Time on hole: 8.92 hr
Seafloor (drill-pipe measurement from rig floor, mbrf): 742.5
Distance between rig floor and sea level (m): 11.2
Water depth (drill-pipe measurement from sea level, m): 731.3
Total depth (drill-pipe measurement from rig floor, mbrf): 742.5
Penetration (mbsf): 0.00
Position: 32º43.32'S, 57º15.86'E
Start hole: 0710 hr, 14 May 1998
End hole: 2312 hr, 14 May 1998
Time on hole: 16.03 hr
Seafloor (drill-pipe measurement from rig floor, mbrf): 741.0
Distance between rig floor and sea level (m): 11.2
Water depth (drill-pipe measurement from sea level, m): 729.8
Total depth (drill-pipe measurement from rig floor, mbrf): 749.0
Penetration (mbsf): 8.00
After coring operations at Site 1105, we returned to the location of Site 1104 in anticipation of continued hammer testing. Although the supply vessel had arrived on site, heavy seas prevented the transfer after dark. Despite the same coordinates as Site 1104, because a new beacon was deployed and we wanted the record to indicate the next phase of hammer testing, this location was assigned as Site 1106. The hammer was tested on the deck in preparation for deployment, but continued deterioration of sea state prevented any transfer from the supply vessel. After waiting for the weather to improve, our operations team determined that we could continue with hammer operations if we could manage to transfer at least the bits from the supply vessel. An ingenious flotation device, created from several buoys, was assembled. The three bits were thrown overboard by the crew on the supply vessel one at a time and recovered by the crew on the Resolution despite seas that would not allow the two ships to converge.
Once the bits were transferred, we were ready to resume hammer testing. The hammer was run, and, after a brief seafloor survey, Hole 1106A was initiated. After about 2 m of penetration, the hammer ceased activity, and we tripped it back to the surface. Once again a valve had broken in the hammer, potentially from excessive heave during the continuing poor sea state. Hole 1106B was initiated on the ensuing pipe trip, which included the second of the three bits we acquired during the transfer (coincidentally, the last bit capable of drilling an overgauge hole), because the first was worn after Hole 1106A. Only ~0.5 m penetration was realized before the hammer ceased activity again, necessitating another pipe trip. Again the bit was worn, so it was replaced with the last of the bit configurations we had available, a flat-faced drilling bit. Our decision to run this bit was based on the assumption that if we could demonstrate the ability to make a hole, we could use this information in future bit design.
Hole 1106C was spudded and drilled ~1 m in <1 hr before the hammer stalled again. On the ensuing pipe trip, the piston in the hammer was replaced, and the flat-faced bit was run back to the seafloor. Hole 1106D was attempted, but the hammer would not operate, so it was pulled and rebuilt once again. Hole 1106E was initiated, and the hammer drill system performed admirably, cutting an 8-m-deep hole in <2 hr. At this time, the pressure transducer on the stand pipe gave way, so the pumps had to be shut down for repairs. Once the repair was completed, the driller noted no pressure buildup and was able to slowly lower the drill string to the total depth of the hole + 4 m, indicating we had lost some of the bottom-hole assembly. The subsequent camera trip indicated that the bit and hammer were indeed missing, and because we could not see these on the seafloor, we assume they are still in Hole 1106E. Weather conditions had still not improved, and we did not have a clear idea which of the several holes within a few m radius was Hole 1106E, so a fishing attempt was unrealistic. Given that we had exhausted all the bits and hammer spare parts, we declared the hammer test for Leg 179 complete and got under way for Ninetyeast Ridge.
In summary, while a detailed summation of all the data relevant to the hammer testing awaits postcruise development, we do have some preliminary impressions. We are encouraged by the performance of the hammer and will be able to use this series of tests for optimal design improvements. Despite the less than desired performance of the bits, again we are optimistic, particularly based on the last test where we made 8 m of penetration in <2 hr, that bit design improvements will yield improved performance in the future. Finally, as with all our operations, sea state appears to be a primary control, if not on the success of an operation, at least on its duration and ease of completion.