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doi:10.2204/iodp.proc.324.104.2010

Operations

Times in this chapter are given in local ship time. During transit to Site U1346, shipboard clocks were advanced 1 h, resetting local ship time to Sydney Standard Time (Universal Time Coordinated + 10). No further adjustments to the clock were made during the expedition.

After a 370 nmi transit from Site U1346, the R/V JOIDES Resolution came to position at Site U1347 at 1730 h on 21 September 2009. The average speed during the transit was 8.0 kt. The slow pace was a result of heavy seas kicked up by passing Typhoon Choi-Wan.

After the driller tagged seafloor at 3461.0 m drilling depth below rig floor (DRF) (Table T1), Hole U1347A was spudded with the rotary core barrel (RCB) at 0710 h on 22 September. The hole was drilled with a wash barrel in place to 71.0 m drilling depth below seafloor (DSF) where rotary coring was initiated. While coring the interval from 71 to 109 m DSF, the average recovery was ~5% because of chert fragments jamming in the core catcher. As the hole was extended beyond this depth, chert became much less prevalent and recovery and penetration rate improved. We reached basaltic basement at ~158 m DSF. Coring into basement continued until 2145 h on 25 September when operations were suspended in order to change to a fresh bit after the initial rotary bit had accumulated 60 rotating hours. After flushing the hole with a 50 bbl mud sweep, the drill string was pulled back to 155 m DSF and the hole displaced with 57 bbl of heavy mud.

A FFF was made up and deployed at 0130 h on 26 September. The vibration-isolated television (VIT) camera was then launched to monitor the extraction of the bit through the FFF. As the VIT frame was suspended ~10 m above the FFF, a hydraulic supply hose to the VIT winch ruptured resulting in the TV camera frame rapidly descending and coming into contact with the lip of the deployed FFF. The rig mechanic spent 1 h replacing the defective hose. Once the repairs were concluded, the VIT camera was raised into position to image the FFF and the bit was pulled off the FFF at 0515 h. After the VIT camera was recovered, an inspection of the camera assembly indicated no obvious damage except for a slightly bent compass arm.

While coring with the first bit, heave frequently exceeded 3 m making it difficult to keep the bit on the bottom of the hole. An inspection of the recovered bit indicated that the bit body was under gauge by ~3/8 inch. With the exception of two chipped teeth, the cutting structure was intact as well as the cone seals. There was some noticeable shirt tail wear, but overall the bit was in remarkably good condition for the accumulated hours.

A new RCB C-4 bit with a refurbished mechanical bit release was quickly affixed to the rotary drilling assembly and run back in the water column. Hole U1347A was successfully reentered at 2250 h on 26 September after 2 h of maneuvering against a strong current. The drill string was advanced to the bottom of the hole where the driller found only 1 m of soft fill. At 0500 h on 27 September, coring resumed but was suspended after cutting the first core with the new bit. The core barrel containing Core 324-U1347A-21R could not be recovered for 5.75 h because the core winch motor had shorted field windings and had to be replaced. Once the new motor was mounted and tested, coring resumed.

From 1530 h on 27 September to 1230 h on 30 September rotary coring deepened the hole from 242.7 m DSF to a final depth of 317.5 m DSF in routine fashion with no hole problems. Operations were concluded when the last core was able to advance only 1 m in 3 h (rate of penetration [ROP] = 0.3 m/h), possibly caused by a either a worn bit, an extremely hard formation, or a combination thereof. Because the time allotted for drilling at Site U1347 was nearly expired, it was decided to terminate drilling.

Total penetration into basement in Hole U1347A was 159.9 m DSF, cored at an average ROP of 1.5 m/h (Fig. F3). While coring basement, the ROP for individual cores ranged from a lethargic 0.7 m/h to a more energetic 4.1 m/h. The average recovery for basement coring was 64.2%. The drilled/washed interval was 71.0 m, and the total average recovery for the entire hole was 47.1%.

The hole was prepared for logging with three mud flushes and a wiper trip to 86 m DSF. Once the bit was released at the bottom of the hole, the bore was displaced with 83.5 bbl of 10.5 ppg mud. The drill string was pulled back in the hole and placed at the logging depth of 131.5 m DSF. The first logging run was made with the triple combination (triple combo) tool string, which succeeded in reaching within 2 m of the bottom of the hole. A preliminary analysis of the results of the first logging run indicated that the hole was in good condition and suitable for the additional measurement runs planned for this site. The second tool string deployed was the Formation MicroScanner (FMS)-sonic tool string, which was also successfully run (two complete passes) to within 2 m of the bottom of the hole. The third planned logging tool suite included the Ultrasonic Borehole Imager (UBI), but this run was cancelled because of hardware problems.

After the logging equipment was secured, the drill string and beacon were retrieved in routine fashion. Once the drilling equipment was secured, the vessel departed for Site U1348 at 0400 h on 2 October. The total time on site for Site U1347 was 10.4 days.