Position: 32º43.3236'S, 57º15.8544'E
Start hole: 1925 hr, 29 April 1998
End hole: 0700 hr, 30 April 1998
Time on hole: 11.58 hr
Seafloor (drill-pipe measurement from rig floor, mbrf): 740.0
Distance between rig floor and sea level (m): 11.0
Water depth (drill-pipe measurement from sea level, m): 729.0
Total depth (drill-pipe measurement from rig floor, mbrf): 741.50
Penetration (mbsf): 1.50
Position: 32º43.3236'S, 57º15.8544'E
Start hole: 0700 hr, 30 April 1998
End hole: 1630 hr, 30 April 1998
Time on hole: 9.50 hr
Seafloor (drill-pipe measurement from rig floor, mbrf): 739.0
Distance between rig floor and sea level (m): 11.0
Water depth (drill-pipe measurement from sea level, m): 728.0
Total depth (drill-pipe measurement from rig floor, mbrf): 741.0
Penetration (mbsf): 2.00
Position: 32º43.3236'S, 57º15.8544'E
Start hole: 1630 hr, 30 April 1998
End hole: 0430 hr, 1 May 1998
Time on hole: 12.00 hr
Seafloor (drill-pipe measurement from rig floor, mbrf): 739.0
Distance between rig floor and sea level (m): 11.0
Water depth (drill-pipe measurement from sea level, m): 728.0
Total depth (drill-pipe measurement from rig floor, mbrf): 741.0
Penetration (mbsf): 2.00
Position: 32º43.3236'S, 57º15.8544'E
Start hole: 0430 hr, 1 May 1998
End hole: 0905 hr, 1 May 1998
Time on hole: 4.58 hr
Seafloor (drill-pipe measurement from rig floor, mbrf): 739.0
Distance between rig floor and sea level (m): 11.0
Water depth (drill-pipe measurement from sea level, m): 729.0
Total depth (drill-pipe measurement from rig floor, mbrf): 739.0
Penetration (mbsf): 0
Position: 32º43.3236'S, 57º15.8544'E
Start hole: 0905 hr, 1 May 1998
End hole: 0700 hr, 2 May 1998
Time on hole: 21.92 hr
Seafloor (drill-pipe measurement from rig floor, mbrf): 740.0
Distance between rig floor and sea level (m): 11.0
Water depth (drill-pipe measurement from sea level, m): 729.0
Total depth (drill-pipe measurement from rig floor, mbrf): 741.50
Penetration (mbsf): 1.50
Site 1104 is located at a water depth of 731 m on the east rim of the Atlantis II Fracture Zone, ~200 m northwest of Hole 735B. This site was selected based on a video survey beginning at Hole 735B, by which we sought to find a reasonably flat, large outcrop to initiate the first spud tests of the hammer drill. During the transit from Cape Town, South Africa, the water hammer was successfully deck tested. The initial assembly of the drill string included just the SDS Digger Tools hammer and a concentric arm bit to test the spudding capability of the system. A frequency analyzer for monitoring hammer operations was built and installed during the transit.
After a 4-hr video survey starting at the Hole 735B guide base, we selected a location with an extensive, relatively flat-appearing outcrop and set the bit down on the outcrop to see how the hammer functioned without rotation. Several spud tests indicated the hammer was performing as expected, so we decided to recover the camera and begin hammer drilling Hole 1104A. After ~45 min, it appeared from rig floor observation that we had made about 1.5 m of penetration, so we deployed the camera to inspect the hole. We also noted excessive vibration of the stand pipe and derrick during hammer operations. A clean, circular hole appeared on the video image, so we recovered the camera and initiated a second test hole (Hole 1104B). After ~2 hr of rotation, we had made ~2 m of penetration but also noted increasing torque and slower rate of penetration (ROP). Another camera trip revealed a second clean, circular hole, but some apparent obliquity indicated that the hole had been initiated on a small local slope. We recovered the camera and attempted to spud a third hole, but the hammer would not actuate, so it was pulled to the surface.
Inspection of the concentric arm bit indicated that the reaming arms were damaged and that a valve had cracked in the hammer. The hammer was rebuilt, a new concentric arm bit installed, and we ran the assembly back to the seafloor. After a short video survey to inspect the site, we recovered the camera and spudded Hole 1104C. In <2 hr, although we noted about 2 m of penetration, there was an indication of high, erratic torque and the ROP effectively ceased. We attempted to initiate another hole (Hole 1104D) but made no advancement and experienced high, erratic torque. This hammer test was terminated, and we pulled the drill string. During the pipe trip, we deployed the two United States Geological Survey ocean bottom seismometers (OBS), ~100 and 300 m, respectively, from our drill site to monitor the noise transmitted through the outcrop that was generated by the hammer.
When inspection of the second concentric arm bit indicated once again that the underreamer arms had experienced excessive wear, a bit was modified by trimming the concentric arms to match the outside diameter of the pilot bit. After this modification, however, the bit did not appear robust enough to cut through the hard rock, so this modification was abandoned. A second modification removed the concentric arms, cut the bit shank, and welded the interval where the arms had been closed. We had hoped to test the drilling capability of the bit without the added challenge of attempting to ream out the hole. Unfortunately, during the modification of the bit, a crack developed, and the bit was set aside. We then modified a third bit by welding the concentric arms closed. This bit was tripped to the seafloor, and we initiated Hole 1104E. After ~1 hr, we had made ~1.5 m of penetration, but the bit stuck in the hole. We were able to free the bit with left-hand rotation, indicating that the arms had broken free and were causing the bit to stick. Having exhausted all the bits we had on board for hammer testing, and with the promise of delivery of a different bit design in a few days from a supply vessel, we chose to commit to conventional rotary coring while we waited for the equipment transfer. The OBS and positioning beacons were recovered, thus ending operations at Site 1104.
1Examples of how to reference the
whole or part of this volume can be found under "Citation" in the preliminary
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2Shipboard
Scientific Party addresses can be found under "Leg 179 Participants" in the
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Ms 179IR-102