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doi:10.2204/iodp.proc.324.107.2010

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 h). No further adjustments to the clock were made during the expedition.

The 53 nmi transit from Site U1349 to Site U1350 proceeded at an average speed of 10.6 kt. At 0115 h on 13 October 2009, the vessel was positioned on the new drill site. The driller tagged the seafloor at 4067.0 m drilling depth below rig floor (DRF) (4055.9 meters below sea level [mbsl]) (Table T1) at 1030 h. This was 12 m shallower than the corrected precision depth recorder depth of 4079.0 m DRF. Hole U1350A was spudded with a wash barrel in place and drilled to 104.6 m drilling depth below seafloor (DSF), where rotary coring was initiated at 1115 h. The sediment portion (48.0 m) of the hole was cored with the usual poor recovery (1.6%) because of soft ooze and chalk sediments mixed with chert layers. Igneous basement was reached with Core 324-U1350A-6R at 143.1 m DSF, which was slightly shallower than the expected depth of ~ 157 mbsf, calculated from the site survey seismic data.

Rotary coring deepened the hole to a final depth of 315.8 m DSF at 2015 h on 18 October when operating time expired. The final depth corresponds to a total penetration of 172.7 m in basement, which was cored with an average recovery of 43.2% and an average rate of penetration (ROP) of 2.0 m/h. A total interval of 211.2 m was cored with an average recovery of 35.6% at an average ROP of 3.5 m/h. When coring was halted, the bit had accumulated 91.2 rotating hours and was still viable.

In preparation for logging, the hole was flushed with a 50 bbl mud sweep followed by a wiper trip up to 84 m DSF and back down to 316 m DSF. Following another 50 bbl sweep, the bit was released with the rotary shifting tool and the hole was displaced with 90 bbl of 10.5 ppg heavy mud. The pipe was then pulled back in the hole with the end of pipe placed at the logging depth of 117 m DSF (4184 m DRF).

The first of potentially two logging runs was attempted with the triple combination (triple combo) tool string, which was deployed at 0640 h on 19 October and lowered at a speed of 2200 m/h to 3600 m DRF. At this depth, the head tension decreased dramatically and the cable speed was reduced to ~90–120 m/h to avoid potential damage to the wireline. The slow progress required pumping pressure down the drill pipe to aid the descent. After making very slow progress to 4000 m DRF, it was decided to pull out of the hole to check the tool string and cable for damage. With the tool string on the rig floor it was decided to pump down high volumes of water through the pipe to remove any potential obstruction. The tool string was deployed a second time with similar results, reaching 4122 m DRF. As time was expiring, the weather was progressively deteriorating (initial ship heave conditions of ~2 m changed to ~4 m with wind gusts of up to 56 kt). Without knowing the cause of the low-tension problem, it was decided to terminate logging operations. The tool was recovered at 2330 h, and after the logging equipment was rigged down the drill string was pulled out of the hole, clearing the seafloor at 0125 h on 20 October. After securing the drilling equipment and hydrophones and recovering the beacon, the vessel departed for its transit to Townsville at 1245 h on 20 October. The total time at Site U1350 was 7.5 days (Fig. F3).

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