 |
|||
| IODP publications Expeditions Data & samples Policies News & photos Search | |||
|
doi:10.2204/iodp.pr.330.2011 OperationsPort callExpedition 330 began when the ship arrived at Wynard Wharf in Auckland, New Zealand, at 0636 h on 13 December 2010. Both Overseas Drilling Limited (ODL) 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 (DP) 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 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 ton 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 will be 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 operationsSite U1372The 824 nmi transit from Auckland to the first site of Expedition 330 was accomplished at an average speed of 10.3 kt and without incident. The vessel was positioning at Site U1372 (prospectus Site LOUI-1C on Canopus Guyot) by 1700 h on 21 December. The corrected precision depth recorder (PDR) 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 GBM. The GBM 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 at 1968.5 mbrf with the bit (1957.6 mbsl), the top drive and knobbies were picked up, and Hole U1372A was spudded with the RCB at 0850 h on 22 December. 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. 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, an 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 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 9⅞ inch core bit, one MBR, two modified head subs, 11 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 for Hole U1372A. In summary, coring in Hole U1372A penetrated 232.9 m, with an average recovery of 60.0% (Fig. F68). Total penetration into basement was 187.7 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 retrieved, the vessel departed for approved alternate Site LOUI-6A at 0300 h on 31 December. Site U1373The vessel arrived at Site U1373 on Rigil Guyot (prospectus Site LOUI-6A) at 1730 h on 31 December after a 146 nmi voyage from Site U1372 that was accomplished at an average speed of 10.1 kt. A new BHA with a Type C-4 RCB bit and MBR was made up and deployed. The corrected PDR depth for this site was 1455 mbrf. The VIT frame was deployed with the drill string, and by 0200 h on 1 January 2011 a seafloor strewn with large boulders and outcrops of hard rock was displayed on the monitor. From 0230 to 0445 h a VIT survey was made around the periphery of the site until a clear area was found that appeared to be able to support an FFF deployment. After the driller tagged the seafloor at 1458.0 mbrf (1447.0 mbsl), the top drive was picked up and Hole U1373A was spudded at 0700 h on 1 January (Fig. F69). The hole was routinely advanced to 64.0 mbsf, at which point the bit had accumulated 69.7 rotating hours and required replacement. Basaltic basement was encountered at 33.9 mbsf. At this juncture the penetration into basement was 30.1 m, with an average penetration rate of 0.9 m/h. The strategy of pulling half-cores helped to increase the average basement recovery to 91%. The average recovery for the entire hole at this point was 72%. In order to keep it clean of cuttings, the hole was flushed with 20 bbl mud sweeps prior to recovering each core. An additional 40 bbl mud sweep was circulated before initiating the bit trip. An FFF was made up and deployed at 1845 h on 4 January. The VIT frame was launched and the FFF was monitored as the bit was withdrawn from the hole. The bit cleared the lip of the funnel at 2005 h and was on deck by 1210 h on 5 January. The used bit was found to be in excellent condition, exhibiting slight cone wear, no missing inserts, and tight bearings, and was ⅛ inch undergauge in spite of having accumulated 70 rotating hours. A new bit was made up to the BHA and deployed along with an additional stand of drill collars. From 0630 to 0845 h the driller attempted a reentry into the FFF, but the bit appeared to bind about 1 ft into the throat of the funnel and could not be advanced any farther. The mud pump flow was increased on the chance that any obstruction would be hydraulically dislodged, but the end result was that the FFF tipped over on its side. It was surmised that the 2.7 m FFF casing was not lodged firmly in the hole when the old bit was withdrawn and that the only element that was holding the FFF vertical was the pile of cuttings. Although the open hole was not visible on the camera, the driller attempted a blind stab into the hole by lowering the bit into the sediment cover around the periphery of the FFF. This course of action was terminated after 2.25 h, and the decision was made to offset to a recently approved alternate site (prospectus Site LOUI-6B) located on the other side of the seamount's summit. After the drill string was picked up to 1111 mbrf, the vessel was offset in DP mode to Site U1374 in the afternoon hours of 5 January. Site U1374After Hole U1373A on the eastern side of the summit plain of Rigil Guyot had to be abandoned, the vessel was offset in DP mode to a recently approved alternate site (prospectus Site LOUI-6B) located on the western side of the summit plain. The 5.6 nmi offset was accomplished in 3.25 h, and by 1630 h on 5 January the ship was positioning at the new location. The VIT frame was deployed and used to monitor the bit tagging the seafloor at 1570.0 mbrf (1559.0 mbsl), 2.6 m shallower than the corrected PDR depth. Hole U1374A was spudded with the Type C-4 RCB bit at 2035 h on 5 January (Fig. F70). After penetrating a thin sedimentary cover, the bit penetrated igneous basement at 16.7 mbsf. Rotary coring slowly advanced to 130.4 mbsf, with an average recovery of 84%, by 0345 h on 10 January. At this time, the bit had acquired 81.3 rotating hours, and preparations were made to recover the drill string and replace the bit with a fresh unit. Penetration into basement was 113.7 m, with an average recovery of 85%. The average ROP while coring basement was 1.6 m/h.
An FFF was made up and deployed at 0550 h on 10 January. The VIT frame was launched, and the bit extraction from the hole was monitored with the VIT system to ensure that the FFF was not dislodged during the process. The used bit was at the rotary table at 1145 h and was replaced with a new Type C-4 RCB bit. The latch sleeve was also inspected, and the MBR was replaced with a rebuilt unit. The used bit was found to be in excellent condition and The FFF was reentered at 1635 h. The BHA was run in the hole without incident while the driller maintained slow rotation and a low pump rate. There was no fill at the bottom of the hole. Coring resumed at 1900 h on 10 January. During the course of the week, the scientific party decided to core with the present bit until destruction and forego a second bit trip at this site. Rotary coring continued until 0545 h on 18 January, when erratic pump pressure indicated that there was a problem at the bottom of the drill string. Instead of continuing to core with a bit that had far outlasted its expected life with 133.4 rotating hours, it was decided to end coring at a final depth of 522.0 mbsf. Penetration into basement was 505.3 m, with an average recovery of 88.0% and an average ROP of 2.5 m/h. The average recovery for the entire hole was 87.8%, with an average penetration rate of 2.4 m/h. After a routine wiper trip, which suggested that the hole was in good condition, an attempt was made to release the bit with the rotary shifting tool (RST). There was no positive indication that the window sleeve in the MBR was shifted, and it was initially thought that there was an obstruction in the throat of the bit that prevented the RST from engaging the window latch. To possibly remedy this, a bit deplugger was pumped down, but there was no indication by a change in pump pressure that it had landed. The deplugger had to be jarred free and was recovered on the coring line. There were multiple abrasions on the deplugger, indicating that it was mechanically prevented from landing in the throat of the bit. Since downhole logging in this particular deep hole was considered important, it was decided to trip the drill pipe, remove the bit and MBR, and make up a shorter logging BHA with a 9¼ inch diameter logging/clean-out bit that would allow more of the open hole to be logged. As the drill pipe was recovered, sepiolite-laden mud was discharged under pressure on the rig floor with each connection. In order to remedy this, the circulating head was made up and the pipe was flushed out. It is speculated that during this process the bit may have been released and fallen to the seafloor because no further mud was discharged as the remaining pipe was recovered. The exact time and position of the bit release can only be speculated. The end of pipe cleared the rotary table at 2015 h on 18 January. A shorter logging BHA was made up with the cleanout bit and deployed at 0145 h. The bit entered the FFF at 0430 h and was positioned at a logging depth of 101.2 mbsf. The standard triple combo suite was made up and run in at 1045 h. The tool was not able to advance into the open hole because of a bridge just ~7 m below the end of the drill pipe. The tool was recovered, and the bit was lowered to 143.6 mbsf to clear the bridge. The bit was then pulled back and placed at 110.8 mbsf. When the triple combo tool string was unable to advance below 138.0 mbsf, the tool was again recovered and reconfigured to a shorter assembly using only the density and gamma ray sensors in the hope that this tool string would more easily negotiate hole entry. After this attempt was unsuccessful, the drill pipe was recovered with the bit, clearing the rotary table at 1115 h. A four-stand RCB coring assembly was made up with a new MBR and a used Type C-4 bit (recovered from Hole U1373A). The drill string entered the FFF at 1540 h on 20 January. From 1730 to 2315 h the hole was washed and reamed to bottom (522 mbsf), flushed with mud, and then displaced with 165 bbl of heavy (10.5 ppg) mud. The bit was dropped at the bottom of the hole, and the end of pipe was placed at a logging depth of 128.1 mbsf, ~18 m deeper than the previous logging attempt and below a potentially unstable zone in the formation. An extra stand of drill collars was added to the BHA to keep the tapered drill collar as close to the seafloor as possible, as that is the usual "choke point" where a BHA gets stuck. The triple combo logging tool string was made up (in its standard extended version) and deployed again at 0540 h on 21 January and succeeded in logging the hole up from 520 mbsf. The tool suite was recovered and laid out. The second instrument deployed was the GBM, which made one full pass down from the rig floor to 520 mbsf and back up. Communication with the GBM was lost while it was being retrieved in the pipe; however, because a sighting of the tool was carried out at the start of deployment, the rotation history of the GBM was still obtainable. The third logging run was performed with the FMS-sonic tool string, which also successfully came within 2 m of the bottom of the hole. The fourth log was conducted with the UBI. The fifth log was a redeployment of the GBM tool. All runs were successful. While the GBM was being deployed for the second time, the driller noticed that the suspended string weight was decreasing slightly, indicating that the formation was starting to squeeze the BHA. In order to compensate for this, the driller picked up the string an additional 3 m. When the logging tool was being retrieved the vessel had to be offset 75 m in order to lower the pipe connection the additional 3 m so that the slips could be set. From 2215 h on 22 January to 0930 h on 23 January the driller attempted to free the drill string. Although circulation was maintained, there was no rotation and the drill pipe could not be raised or lowered. Realizing that further efforts would be fruitless, the crew made the necessary preparations to sever the drill string directly above the tapered drill collar. The top of the tapered drill collar was ~13 m below the seafloor. The drill pipe was severed at 1500 h on 23 January. Once the drill pipe was recovered and the beacon was retrieved, the vessel was secured for sea. The vessel departed for prospectus Site LOUI-2B at 1945 h on 23 January, with an estimated time of arrival of 0500 h on 25 January. Site U1375The 322 nmi voyage to Site U1375 (prospectus Site LOUI-2B) on Achernar Guyot was accomplished at an average speed of 10.2 kt. During the transit the vessel pitched and rolled moderately in rough sea conditions, with a wave breaking across the deck at times. As the transit progressed, improving weather and course adjustments made the transit more comfortable. The vessel was on station above Hole U1375A at 0330 h on 25 January. In accordance with the established routine of the expedition, the VIT frame was deployed prior to spudding the hole. The bit tagged seafloor at 1269.0 mbrf (1258 mbsf), which was 0.9 m shallower than the corrected PDR depth. Hole U1375A was spudded with the RCB assembly outfitted with a Type C-4 bit at 1345 h on 25 January. Almost immediately, the driller experienced erratic high torque, indicating that we were attempting to core through loose rocks and boulders. Frequent overpulls of up to 90,000 lb were required to keep the drill string rotating freely. At 2130 h, coring of Hole U1375A was terminated at 11.5 mbsf because of unstable hole conditions. The average recovery for just two cores was 13%. The vessel was offset 300 m at 315°, and a second attempt at coring this site was initiated when Hole U1375B was spudded at 2345 h. The water depth was again 1269.0 mbrf. After penetrating 8.5 m with increasing difficulty and constantly fighting unstable hole conditions, operations in this hole were terminated as well. The lone core retrieved had an average recovery of 7%. It was concluded that the formation on the top of this seamount consisted of a sedimentary breccia loosely held together in a "soft" carbonate matrix that quickly disintegrated during drilling, leaving mainly loose pebbles behind. The vessel departed for the approved alternate Site LOUI-7A, located 91 nmi north-northwest from Site U1375 at 1945 h on 26 January. The total time spent on Site U1375 was 34.3 h or 1.4 days. Site U1376The 91 nmi transit to alternate prospectus Site LOUI-7A on Burton Guyot was accomplished at an average speed of 10.1 kt. The vessel was on station at 2300 h on 26 January. A three-stand RCB coring assembly was made up with a new C-4 coring bit and MBR and deployed. The VIT frame was launched before the hole was spudded to observe the character of the seafloor and the tagging of the bit on the bottom. A rocky seabed devoid of any appreciable sediment was observed on the VIT camera. From 0300 to 0515 h on 27 January a VIT survey was undertaken to look for an area containing sediment that could support an FFF installation (should one be later required). After 2.3 h, a spot with a very small sediment pond was located. The driller tagged the seafloor at 1514.3 mbrf (1503.3 mbsl) and spudded Hole U1376A at 0705 h on 27 January. This was 5.5 m deeper than the corrected PDR measurement. Operations continued without incident until 1530 h on 30 January, when coring was suspended at 86.8 mbsf to change the bit, which had accumulated 72.4 rotating hours. Because of the absence of sediment cover needed to support an FFF installation, a hole marker composed of a weight, tether, and single glass float was placed on the seafloor from the VIT frame via an acoustic release. The bit cleared the seafloor at 1800 h on 30 January and was on deck at 2215 h. A new Type C-4 RCB bit was made up to the BHA, along with a refurbished MBR, and deployed. After the drill string was tripped to 1131 mbrf, the VIT frame was deployed and both were run in to 1512 mbrf. The open hole was successfully reentered at 0435 h on 31 January. Coring resumed in Hole U1376A at 0630 h and continued without incident until the allocated coring time for this site expired at 1630 h on 2 February, leaving the hole at a final depth of 182.8 mbsf. The total average recovery for the hole was 74.5%, with an excellent average recovery in basement of 75.6%. The average ROP in basement was 1.8 m/h. In accordance with expedition routine, nonmagnetic core barrels were used to obtain all cores. One microsphere packet was deployed in the core catcher of Core 330-U1376A-19R at 144.4 mbsf. Prior to the recovery of all cores except 2R, 3R, and 10R, 20 bbl mud sweeps were circulated. Following a wiper trip, which included displacing the borehole with 42 bbl of heavy (10.5 ppg) mud, the bit was released at the bottom of the hole. The end of pipe was positioned at the logging depth of 80.4 mbsf by 2115 h on 2 February. The first log was conducted with the triple combo tool string, which logged the hole up from 181 mbsf in two passes. After the triple combo tool string was recovered at 0350 h on 3 February, the second logging run was conducted with the third-party GBM tool. The last tool string deployed was the FMS-sonic, which was run between 1335 and 1655 h and made two passes in the open hole. Once logging was concluded, the drill string was recovered, with the end of the pipe clearing the seafloor at 1850 h on 3 February. Once the drill collars were set back in the derrick, the beacon recovered, and the drilling equipment secured, the vessel departed at 2200 h for the 391 nmi voyage to the final Site U1377 (prospectus Site LOUI-4B) on Hadar Guyot, the youngest seamount targeted during Expedition 330. The total time on Hole U1376A was 191 h or 8.0 days (Fig. F71). Site U1377The 392 nmi transit to Site U1377 (prospectus Site LOUI-4B on Hadar Guyot) was made without incident at an average speed of 11.2 kt. By 0930 h on 5 February the vessel was positioning on the coordinates of Hole U1377A. After a three-stand RCB drilling assembly was made up with a new Type C-4 bit and refurbished MBR and was deployed to 988 mbrf, the VIT frame was launched. Tagging of the seafloor at 1262.0 mbrf (2050.8 mbsl) was observed at 1435 h. The seabed appeared to be mostly covered by a fine layer of sediment and a few scattered rocks, which did not generate any anxiety regarding the spudding of the hole. After the VIT frame was recovered and the top drive was picked up, Hole U1377A was spudded at 1510 h. Rotary coring advanced with increasingly difficult hole conditions and overall poor recovery. Finally, after coring to a depth of 53.3 mbsf, the hole became too unstable and had to be abandoned. The bit cleared the seafloor at 1815 h on 6 February and was picked up to 1103 mbrf. Average recovery for Hole U1377A was 16.4%. The time expended at Hole U1377A was 12.5 h. It was decided to slightly offset the vessel 500 m south of Hole U1377A and attempt to spud another hole at this site. The vessel was positioned after a 30 min offset with the bit 159 m above the seafloor. The VIT frame was deployed and showed a seafloor covered with soft sediment. The driller tagged seafloor at 1262.0 mbsl. Hole U1377B was spudded with the RCB at 2325 h on 6 February, and rotary coring advanced to 18.1 mbsf. At this time, during the retrieval of the core barrel for Core 330-U1377B-2R, unstable parts of the formation fell into the hole and were subsequently recovered in the core barrel of Core 330-U1377B-3G. Because the recovered material cannot be assigned to a specific depth, this core was curated as a "ghost core" indicated by the suffix "G" (instead of "R"). Below 18.1 mbsf the formation was stable enough to allow further drilling advancement to a final depth of 37.0 mbsf, when the allocated time on site expired. As the last core barrel was being retrieved, the coring line was coated with a rust inhibitor in accordance with routine. After the drill string was recovered, the beacon was retrieved, and the vessel was secured for transit, the vessel departed Site U1377 for Auckland at 0730 h on 8 February. The time on Hole U1377B was 57.5 h, and the total time on site was 70.0 h (2.9 days). Because of concerns of moderate headwinds and rough seas on the transit to Auckland, the vessel departed approximately 18 h earlier than originally planned. |
||
inch. Once a new Type C-4 bit and a rebuilt mechanical bit release (MBR) 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.