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Port call

Expedition 330 began when the ship arrived at Wynard Wharf in Auckland, New Zealand, at 0636 h on 13 December 2010 (all times are New Zealand Daylight Time, Universal Time Coordinated [UTC] + 13 h). Both Overseas Drilling Limited and IODP crews were changed subsequent to the conclusion of immigration and custom formalities.

Several outstanding maintenance items were addressed during this port call as a result of incidents that occurred during the previous expedition. The defective field coils in Propulsion Motors 14A, 14B, and 18A were replaced with rebuilt units, and repairs were made to the I/O modules of the dynamic positioning system acoustic processors. A pacing item during the port call was the replacement of the damaged aft piston rod on the passive heave compensator with a spare unit. This labor-intensive activity continued for the entire port call. Another important issue required offloading the entire inventory (22 units) of 20 ft and 30 ft knobbies to dockside. Critical dimensions were then measured and compared with the clearance requirements of the 430 and 250 ton elevators used on the drill floor. Once an upper level of acceptable outer diameter was established, the tubular measurements were analyzed. It was determined that four knobbies had to be transported to a local machine shop (Titan Marine), where the outer diameter would be reduced to conform to specifications. These tubulars were retrieved at the conclusion of Expedition 330.

The last port call item of note was loading 1450 MT of marine gas oil, which was completed at 0035 h on 18 December. The scheduled departure to the first expedition site was delayed 1.5 h when the scheduled tug had to divert to assist an arriving cruise ship. The last line was released at 0806 h on 18 December.

On-site operations

The 824 nmi transit from Auckland to the first site of Expedition 330 was accomplished without incident at an average speed of 10.3 kt. The vessel was positioning at Site U1372 by 1700 h on 21 December. The corrected precision depth recorder water depth referenced to the dual elevator stool on the rig floor was 1960.3 meters below rig floor (mbrf).

The drill string was deployed in routine fashion to 1885 mbrf, at which point operations were suspended in order to perform a pressure test on the newly built nonmagnetic aluminum sinker bar for the third-party Göttingen Borehole Magnetometer. The sinker bar was deployed in the drill string via the logging cable at 0300 h on 22 December and was recovered by 0550 h. The unit did not leak.

After the driller tagged the seafloor with the bit at 1968.5 mbrf (1957.6 meters below sea level [mbsl]), the top drive and knobbies were picked up, and Hole U1372A was spudded with the rotary core barrel at 0850 h on 22 December (Table T1). Initially, the driller could not apply very much weight on bit because the bottom-hole assembly (BHA) was not buried. As a consequence, the rate of penetration (ROP) was very slow for the first few cores (Fig. F3). Eventually, the ROP began to pick up as the hole was deepened and more bit weight was applied. Basaltic basement (i.e., the first lava flow) was penetrated at 45.6 mbsf. The hole was deepened to 145.0 mbsf (99.4 meters subbasement [msb]) by the early morning of 26 December. At this juncture the bit had accumulated 64.4 rotating hours and it was time for a fresh bit. The average ROP for the hole was 2.3 m/h and 2.2 m/h into basement. The average recovery was 68.9% for the entire hole and 64.8% while coring into basement.

Prior to the deployment of the free-fall funnel (FFF), the vibration-isolated television (VIT) frame was launched to observe the hole and the nature of the seafloor. The hole could not be seen because a cloud of heavy mud was suspended over the site. Following the recovery of the VIT frame, a FFF was made up and deployed at 1010 h on 26 December. The VIT frame was then launched again to monitor the position of the FFF, which was still mostly obscured by a cloud of heavy mud. However, it was obvious that the FFF was upright because the three flotation balls were clearly visible. While being observed via the VIT camera, the bit was withdrawn from the hole at 1140 h on 26 December. The VIT frame was recovered concurrent with the retrieval of the drill string. The bit cleared the rotary table at 1700 h and was found to be in very good condition and only undergauge by inch. Once a new Type C-4 bit and a rebuilt mechanical bit release were made up, the BHA was deployed with an extra stand of drill collars. The FFF was reentered at 0100 h on 27 December, and rotary coring was resumed by 0430 h at 145.0 mbsf.

Coring advanced to 175.4 mbsf, at which depth ~3 h was expended working the tight hole by pulling back from 174 to 163 mbsf with a maximum overpull of 40,000 lb and circulating frequent mud flushes. Once the drill string was free, rotary coring advanced from 175.4 to 228.9 mbsf. At this depth, the drill string again had to be worked free for 5.5 h. Coring then resumed and advanced slowly and smoothly from 228.9 to 232.9 mbsf. At this juncture the hole was flushed with a 20 bbl mud sweep in preparation for a wiper trip. When the drill string was pulled back from 232.9 to 204.5 mbsf it became irretrievably stuck. Unlike the previous stuck pipe episodes when both circulation and rotation were maintained, the top drive stalled out at 800 A, making extrication even more problematic even though circulation was still possible. From 2130 h on 29 December until 0800 h on 30 December all attempts to free the drill string and salvage the hole failed. The only remaining course of action was to sever the first 5½ inch joint of drill pipe directly above the tapered drill collar in the BHA at 83 mbsf. This was successfully accomplished at 1950 h on 30 December. Left in the hole were one 9 inch core bit, one mechanical bit release, two modified head subs, eleven controlled length drill collars, one modified top sub, one tapered drill collar, and the lower end of one joint of 5½ inch drill pipe. This operation left only ~40 m of (possibly) open hole above the severed BHA for downhole logging. After considering the probable condition of the hole following the use of explosives and the potential risk to the logging tools, downhole logging was not attempted in Hole U1372A.

In summary, coring in Hole U1372A penetrated 232.9 m, with an average recovery of 60.0% (Fig. F3). Total penetration into basement was 187.3 m, with an average recovery of 55.8% and an average ROP of 2.2 m/h. There was one bit change during the 227 h (9.5 days) on site.

After the pipe was recovered and the beacon was retrieved, the vessel departed for approved alternate Site LOUI-6A at 0300 h on 31 December.