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doi:10.2204/iodp.proc.319.104.2010

Operations

Transit to Site C0010

After operations were completed at IODP Site C0009, the D/V Chikyu moved to Site C0010. While in transit, the drill pipe was set up and racked in preparation for running into the hole. The location was reached at 0100 h on 4 August 2009, and the remotely operated vehicle (ROV) engaged in a seabed survey.

Hole C0010A

The Chikyu moved to the new location after completing operations in Hole C0009A, and Schlumberger engineers and technicians prepared the Schlumberger LWD and MWD tools for assembly prior to drilling Hole C0010A (target depth = 560 mbsf, water depth = 2523.7 m) (Table T1). The bottom-hole assembly (BHA) included a 12¼ inch bit, RAB-8, TeleScope, stabilizer, crossover subs, 11 drilling collars, and a mechanical jar (Table T2). The mud cart and jet-in tools were prepared and hung below the Chikyu in the low-current area prior to drifting to the site. The ROV was again deployed for the jet-in, which occurred at 0745 h on 5 August. Jetting-in included placing a Mudmat and 20 inch casing to 41 m drilling depth below seafloor (DSF).

The BHA was made up of a 12¼ inch bit, with an 8¼ inch LWD geoVISION tool measuring natural gamma ray (NGR) and resistivity, and the MWD-PowerPulse measuring direction and inclination, torque, and weight on bit. After LWD and MWD drilling to 402 m DSF (Run 1), operations were suspended on 9 August to move the Chikyu to safety, out of the path of Typhoon "Etau," and wait on weather (WOW). Although the winds and wave predictions were not very severe (21–31 m/s winds and 5.9–9.5 m swells), the heave prediction was of greater concern. Heave had a detrimental influence on the LWD data quality, and the Co-Chief Scientists and Operations Superintendent (OSI) decided to ream and relog the hole from 2900 to 2970 m drilling depth below rig floor (DRF), in order to improve the data quality around the fault zone target and to better define locations for screened casing joint placement. After the storm passed, the Chikyu returned to Site C0010 to resume drilling operations to TD (Run 2), arriving at 0200 h on 12 August. Reaming operations began at 0300 h and included relogging the 2900–2970 m DRF section. TD (3107 m DRF, 555.00 m DSF) was reached at 1715 h on 12 August, when circulation and high-viscosity (Hi-Vis) mud was pumped into the hole. Operations continued with a wiper trip to the 20 inch casing shoe at 41 m DSF, and then running back to the bottom of the hole. Because the wiper trip exhibited tightness in one section of the hole below 2995 m DRF even after reaming, reaming continued from 2995 to 3107 m DRF. After spotting with kill mud, pulling out of the hole to 2584 m DRF and then washing to 2543 m DRF to clean the wellhead, pulling out of the hole continued to surface while recovering the ROV in preparation for moving the Chikyu to a low-current area. At 1700 h, the BHA was back on the drill floor.

The Chikyu moved upcurrent, and then 13 nmi northwest of Site C0010 to a low-current area to run the casing pipe, finishing preparations on 13 August. After examining the LWD data from logging Runs 1 and 2, the bottom depth of the screen casing joints was set at 2959 m DRF (407.59 m DSF) (Fig. F4). Casing was run into the water column, and the Chikyu started drifting to Hole C0010A on 14 August. At 1120 h on 15 August, the casing was run into Hole C0010A and reached 500 m DSF at ~1443 h. At 2130 h, pulling out of the hole began, and at 2230 h, the stinger was out of the hole. There was no signal from the cement dart to show that it had landed/seated properly, so a scraper run was planned. There was a break while the ROV umbilical was under repair, during which the 8½ inch drill collar was made up for a scraper run. The scraper run was cancelled after the cement dart was found when the BHA was disassembled. Instead, the hole was reentered for a sweep at 1210 h on 17 August, finishing at 1400 h, with the BHA reaching deck at 1621 h. After the sweep was completed, the dummy observatory run began. On 19 August, ocean-bottom seismometers used in conjunction with vertical seismic profile operations at Site C0009 were acoustically released and recovered by the supply ship, Kaiko, at 2020 h on 20 August.

Dummy run

The dummy run (see "Observatory") began in a low-current area at 0830 h on 18 August. This included a shipboard test to ensure the instrument carrier could be run through the 9⅝ inch casing after it was discovered that the sensor carrier was warped. After confirming that it could pass though the casing unimpeded at 0900 h on 18 August, the entire array was made up beginning at 1215 h and run into the hole at 1500 h. During these operations, the smart plug (see "Observatory") was tested in preparation for installation in Hole C0010A. There was considerable vortex-induced vibration (VIV) from the strong current (4.5 kt) during drifting in to location, and the carrier was held at 1650 meters below sea level (mbsl) for ROV inspection. At 1750 h on 19 August, the ROV was deployed, and at 2045 h, it reached the carrier. Visual inspection revealed that the strainmeter and tubing below were lost, as well as one of the two seismometers. The remaining seismometer and accelerometer remained attached, and at 2130 h, after meeting with the OSI, the Co-Chief Scientists decided to recover the carrier to the surface for further inspection. As the Chikyu moved north 9 nmi to a low-current area, the carrier was pulled up, reaching deck at 0400 h on 20 August. The carrier showed signs of polishing and cracking and required ~4 h for the ship's welder to repair. The second dummy run carrier included only the accelerometer and a dummy strainmeter with two tubing joints below the seismometer, and it was decided to stab the reentry cone 2–3 times with no attempt to pass the carrier into the hole. The carrier was returned to the water at 1500 h on 20 August and lowered below the Kuroshio Current as the Chikyu drifted back to Hole C0010A. At 0915 h on 21 August, the Chikyu returned to the site and jumped the ROV in preparation for stabbing the wellhead. At 0955 h, the carrier was ready for reentry into Hole C0010A, which began at 1010 h and was completed by 1025 h. Pulling out of the hole began at 1040 h, and the carrier reached the drill floor at 1630 h.

Smart plug

The smart plug was made up and welded to the crossover sub at 0525 h on 22 August and then run into the hole. Drifting to Site C0010 began, and at 1350 h (4 nmi from the site), the ROV was deployed. At 1709 h, the Chikyu was still 9.2 nmi from Hole C0010A, arriving at 0110 h on 23 August. There was another delay as the ROV umbilical needed work to fix a broken strand. The smart plug and packer were run into Hole C0010A at 0404 h, and the packer was set at 0850 h. The drill string was removed at 0930 h while the Chikyu moved again to a low-current area 3 nmi from Site C0010. Upon recovery, it was discovered that the bridge plug running tool had sheared off of the drill pipe in the water column at a 3½ inch tubing connection after the packer had been set. The corrosion cap was attached to the ROV carrier, in preparation for setting in at the wellhead. At 1800 h, the ROV was launched but experienced problems with the umbilical again at 2030 h. After troubleshooting was completed, the corrosion cap was finally set at 1015 h on 24 August. The ROV began recovery of the transponders, but again had trouble and was recovered on deck. It was decided to recover the remaining three transponders with the Kaiko, after acoustically releasing them from the seafloor. By 1200 h on 25 August, with all transponders recovered, the Chikyu began moving toward Site C0011 (proposed Site NT1-07).

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