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doi:10.2204/iodp.pr.321T.2009 OperationsSan Diego port callExpedition 321T began at 1715 h on 22 June 2009 in San Diego, California, with the first line ashore Berth 10-7 at the 10th Avenue Marine Facility. The Expedition 321 scientists disembarked, and personnel associated with Expedition 321T boarded the ship. These included the Expedition 321T shipboard scientific party (the Co-Chief Scientist, United States Implementing Organization Staff Scientist, logging scientist, and an additional researcher), a BJ Services cementing engineer, 15 School of Rock (SOR) school teachers, 4 SOR instructors, 1 SOR coordinator, and other Expedition 321T technical support personnel. Two vendor representatives from Hadco came aboard for the transit to inspect and certify all Transocean lifting gear. Core samples from Expedition 321 were offloaded. One empty core liner box was removed and limited other freight, including a Schlumberger transmission/gear box, were offloaded. Four P-trucks (1391 sacks; 65.4 short tons) of "blended" (contained Cello-Flake lost circulation material [LCM]) bulk cement was loaded into P-Tank 8 and 225 sacks (9.7 short tons) of neat cement was loaded to top off P-Tank 6. In addition, six 45 gallon drums of sodium silicate "cement extender" were loaded. Fresh fruit and vegetables for catering were also brought aboard. The day was busy in the afternoon, with ship tours and other public relations events taking place. Transit to Site U1301The ship departed San Diego on schedule with the last line away from the dock at 0700 h on 24 June 2009. The San Diego pilot departed the ship at 0800 h; however, the US Navy diverted the ship on a southerly and then westerly course before being allowed to transit northward on our desired route. Average speed for the remainder of the first day exceeded 11 kt. The first half of the second day of transit continued with an excellent speed of 12.6 kt. By afternoon, a weather system began moving in and ship speed slowed to an average of 8.7 kt. By the morning of the third day, the full effect of an opposing current and a Force 8 gale with heavy seas and large swells was impacting the ship. Only 156 nmi were covered on the third day at an average speed of 6.5 kt. The fourth day of transit was not much different, covering another 163 nmi at an average speed of 6.8 kt. As of midnight on Saturday, 27 June, the vessel was 431 nmi from Hole U1301B and had averaged 8.1 kt for the transit at that point. By the morning of the fifth day (Sunday), conditions began improving. Sea and swell height began to come down as the ship moved father to the north and the "fetch" shortened. Wind speed remained brisk at 25–30 kt but was expected to also diminish over time. The ship ultimately arrived on location at 0000 h on 29 June, covering the 1154 nmi distance at an average speed of 8.4 kt. This was slightly slower than the 9.0 kt originally estimated for the transit, largely as a result of encountering the gale, which had not been anticipated. Cementing operationsUpon arrival at Site U1301, the vessel was positioned using Global Positioning System input only, as cementing operations did not require a significant amount of time in the hole nor any appreciable depth below seafloor (~1–1.5 m). Cementing operations began with Hole U1301B, as reentry at this hole was somewhat less challenging through the open slot on the platform compared to reentry through a screened 12 inch diameter opening in Hole U1301A (Table T1). Hole U1301B
After lowering thrusters and stabilizing the ship over the location coordinates, the cementing bottom-hole assembly was picked up. This consisted of the cementing stinger (made from a joint of 5½ inch drill pipe cut in half at a 60° angle and with four staggered 3 inch diameter holes drilled in the lower 9 inches), 1 joint of 5½ inch transition drill pipe, crossover, two 8¼ inch diameter control length drill collars, tapered drill collar, and another joint of 5½ inch transition drill pipe. The drill string was run to 1376.2 mbrf and the vibration-isolated television (VIT)/subsea TV was deployed. There was an initial delay with the deployment because the coaxial winch-line counter stopped working. Eventually the VIT was run in using cable tension and TV video as a reference. The line counter was removed, repaired, and put back on for the later trip out. The drill string trip was then completed to 2664.3 mbrf (4.4 m above reentry cone rim) and spaced out for reentry. A drill string wiper "pig" was pumped down to clean any remnant mud from the pipe. Pump strokes were monitored and timed as a crosscheck on the calculated displacement of the drill string. The exit of the pig was marked by a large cloud of mud that billowed out of the end of the drill pipe upon its arrival. The low-torque valve and cementing system integrity was then pressure tested, and vessel maneuvering for the first reentry attempt began at 1030 h on 30 June 2009. The reentry target was a pie shaped window in the Hole U1301B CORK platform (Fig. F3B). The platform was reentered at 1215 h after 2 h and 15 min of maneuvering (Fig. F4). The driller's task was made more complicated by the fact that the top of the cone (TOC) rim was 1.1 m below seafloor depth. This meant each time the drill string left the cone/platform vicinity it would drag into seafloor and/or drill cuttings, which stirred up the mud and obscured visibility for several minutes. At 1245 h, after observing the drill string and seafloor installation for stability and heave-out potential, the decision was made to move forward with the cementing operation. Preparations began for mixing the first batch of cement. At 1300 h, the actual cementing mixing operation was initiated, and by 1350 h a total of 60 barrels (bbls) of 15.8 pound per gallon (ppg) class G neat cement blended with Cello-Flake LCM was mixed with freshwater and displaced into the pipe. This was chased with 20 bbls of freshwater using the Halliburton cementing pump and followed by 120 bbls of seawater displaced with the Triplex rig pumps. The drill string was pulled clear of the TOC at 1420 h on 30 June, with ~10 bbls of cement still falling from the drill string. This was done to avoid the potential of pumping water into the reentry cone and diluting the cement slurry. Hole U1301A
The cementing unit was cleaned and the tanks flushed while offsetting the ship 35 m to Hole U1301A. The drill pipe was also flushed and a drill string pig was pumped to wipe away any remnant cement. Maneuvering for reentry in Hole U1301A began at 1530 h on June 30. This time the reentry target was more challenging: one of eight 12 inch diameter holes in the old style "solid" CORK platform (Fig. F3B). Reentering through one of these holes required using the cement stinger to push through the steel grating that had been tack-welded in place below the platform during Expedition 301, requiring careful timing and control of weight on bit. The Hole U1301A platform was reentered at 1815 h after only 2¾ h of maneuvering time (Fig. F5). The cone rim at this site was 1.4 mbsf and covered with a layer of fine sediment. Whenever the bit dragged on the platform surface it stirred up a cloud of sediment, obscuring visibility for several minutes. For this hole, a total of 114 bbls of 15.8 ppg "blended" cement was mixed and displaced in the same manner as in Hole U1301B. Mixing ended at 2000 h, and the batch was chased with 20 bbls of freshwater using the Halliburton cementing pump followed by an additional 120 bbls of seawater using the rig pumps. The pipe was pulled clear of the TOC at 2020 h on 30 June, with another ~10 bbls of cement still falling from the drill string. Return to Hole U1301BThe cementing unit was once again cleaned and the tanks were flushed while offsetting the ship 35 m back to Hole U1301B. The drill pipe was flushed and another drill string pig was pumped. Maneuvering for reentry began at 2145 h and the Hole U1301B platform was reentered for the second time at 2250 h, requiring a mere 65 min. Preparations for mixing the second batch of cement for the hole started immediately. A total of 70 bbls of 15.8 ppg blended cement was displaced into the pipe. The cement was chased with 20 bbls of freshwater using the Halliburton cementing pump and an additional 120 bbls of seawater using the rig pumps. The pipe was pulled clear of the TOC at 2355 h on 30 June, again with ~10 bbls of cement still falling from the drill string. Visual observations at Hole U1301B indicated that cement appeared to fill the reentry cone as well as surrounding the area outside of the cone (Fig. F6). Return to Hole U1301AFor the third and final time, the cementing unit was cleaned and the tanks flushed while offsetting the ship 35 m again to Hole U1301A. The drill pipe was flushed and another drill string pig was pumped. Visual observations at Hole U1301A indicated that cement appeared to fill the reentry cone as well as the surrounding area outside of the cone (Fig. F7). The cementing equipment was rigged down, the VIT/subsea TV was recovered, and the drill pipe was tripped back to the surface, ending cementing operations at Site U1301 at 0900 h on 1 July 2009. Transit to Victoria, British Columbia, CanadaCementing operations ended three full days ahead of the projected schedule. However, because of the unavailability of berths, the ship remained on location until 4 July 2009. The vessel departed Site U1301 at 0730 h on 4 July bound for Victoria, British Columbia, Canada. The short transit was uneventful other than moderate vessel roll resulting from being crosswise to the predominant swell. The transit was made at a slightly slower speed because time was available. Expedition 321T officially ended at 0800 h on 5 July 2009 with the first line ashore Ogden Point Berth South-A, Outer Harbor, Victoria. The 195 nmi transit from Site U1301 to the Victoria pilot station was made in 1.0 day at an average "reduced" speed of 7.8 kt. |
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