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doi:10.2204/iodp.proc.320321.104.2010

Operations

Unless otherwise noted, times are local ship time, which was Hawaii Standard Time (UTC – 10 h) for Site U1332.

Transit to Site U1332

Following completion of Site U1331, we started heading east to Site U1332. The vessel made slow progress into a 20 kt wind and against a strong current with moderate pitching and rolling into a 6–8 ft swell with spray occasionally over the bow. This reduced the average speed of the 66.1 nmi voyage to Site U1332 to 7.1 kt.

Site U1332

Hole U1332A

After the 9.25 h transit, we began positioning over the site at 1445 h on 22 March 2009. We assembled the BHA, and spaceout of the colletted delivery system was verified. Because the precision depth recorder (PDR) was still not working, it was necessary for the driller to carefully lower the bit and tag the seafloor to verify the exact depth. As the driller was preparing to spud the hole, the display that indicates coring line position relative to the rig floor failed. Because it is imperative for the core winch operator to know where the coring line is at all times, operations had to be suspended for 3 h while the defective unit was replaced.

Hole U1332A was spudded with the APC at 1050 h on 23 March. The water depth calculated from the recovery of the first core was established as 4935.1 m drilling depth below rig floor (DRF) (4923.9 mbsl) (Table T1). APC Cores 1H through 14H penetrated from 0 to 125.9 m DSF, and we recovered 131.9 m (104%) (Table T1). All piston cores were oriented with the FlexIt tool. Because of the potential presence of chert horizons, no downhole temperature measurements were attempted in Hole U1332A. Core 14H required 70,000 lb of overpull to extract the core barrel from the sediment, after which we switched to XCB coring.

We recovered 13.8 m (51%) in XCB Cores 15X through 18X (125.9 to 152.4 m DSF). Coring was terminated when Core 18X was recovered with a piece of basaltic basement. Hole U1332A was cored to 152.4 m, and we recovered 145.6 m (96%).

After coring was finished, we prepared the hole for logging by flushing it with 65 bbl of attapulgite mud and then dropping a go-devil to open the lockable float valve (LFV). We then displaced the hole with 80 bbl of attapulgite mud and raised the bit to 78 m DSF.

We then deployed a tool string consisting of the magnetic susceptibility, GRA density, and NGR tools. This tool string acquired good downhole logs over the entire open hole interval. Unfortunately, the tool string parted from the logging wireline when attempting to recover the tool and the tool string was lost in the hole.

We spent ~18 h conducting three unsuccessful coring line fishing attempts to recover the logging tool string. After acknowledging that spending more time fishing for the tool string would not be productive, the decision was made to seal Hole U1332A with 15 bbl of cement (from 125 to 90 m DSF) above the lost logging tool. Deploying the cement had to be delayed for 4 h while the cement pumps were repaired.

After the cementing operations were completed, the bit was pulled free of the seafloor at 0800 h on 26 March and the vessel was offset 20 m north of Hole U1332A. Before coring could resume, the drill string was flushed with seawater to remove any cement from the tubulars and bit nozzles.

Hole U1332B

Hole U1332B was spudded at 1230 h on 26 March. We started coring Hole U1332B with the bit offset 5 m deeper than the seafloor depth established for Hole U1332A but only penetrated to 2.1 m CSF below the mudline. We recovered 118.4 m (107%) in APC Cores 1H through 13H (0–110.1 m DSF). In an attempt to maintain an offset with the first hole, there were short advances with Cores 3H (8.0 m) and 11H (5.0 m). The APCT-3 was deployed while taking cores at six different depths: 11.6, 19.6, 38.6, 57.6, 76.6, and 100.6 m DSF (Cores 2H, 3H, 5H, 7H, 9H, and 12H, respectively). Nonmagnetic core barrels were used on all cores except 13H.

We then switched to the XCB and took Cores 14X to 18X from 110.1 to 148.6 m DSF and recovered 23.4 m (61%). Coring was terminated when we recovered ~2.4 m of dark brown sediment above several small pieces of basalt in Core 18X.

In Hole U1332B we cored a total of 148.6 m and recovered 141.8 m (95%). The drill string was pulled out of the hole and the bit cleared the seafloor at 2230 h on 27 March.

Hole U1332C

Hole U1331C was designed to provide stratigraphic overlap and confirm stratigraphic correlations with Holes U1332A and U1332B. After the vessel was offset 30 m north of Hole U1332B, Hole U1332C was spudded at 0105 h on 28 March. The seafloor depth calculated from the recovery of the first core was 4934.0 m DRF (4922.8 mbsl). Piston coring then routinely proceeded to 85.0 m DSF, during which the advances of Cores 6H (4.0 m advance) and 8H (7.0 m advance) were adjusted to maintain overlap with previous holes. At ~1330 h on 28 March, while retrieving Core 10H, an electrical transient attributed to the rotating condenser caused two of the three main generators to trip off the main bus and resulted in a load shedding sequence to various systems on the vessel, which included loss of control voltage to all Thyrig bays for ~10 min. The consequence of the loss of Thyrig control voltage was a short-term loss of power to thrusters, propulsion, and drilling motors. During this short event, the dynamic positioning (DP) 3% watch circle (percentage of water depth or ~150 m off the hole) was not exceeded. The main breakers quickly reset and power was restored to all main systems by 1341 h. We thought the switching circuit for removing the rotating condenser from the main bus was defective.

Because of the power loss, the coring line parted while attempting to recover Core 10H, and we had to make two fishing trips with the coring line to recover the sinker bars and the full core barrel. Unfortunately, this APC core was near the Eocene/Oligocene boundary and was very disturbed. APC coring continued to 113.5 m DSF, where coring was switched to the XCB. All the APC cores were obtained with nonmagnetic core barrels and with the FlexIt core orientation tool except Core 13H, for which we used a standard steel core barrel. APCT-3 formation temperature measurements were made at 36.0 m DSF (Core 4H) and 75.5 m DSF (Core 9H). APC Cores 1H through 13H extended from 0 to 113.5 m DSF, and we recovered 122.04 m (108%). XCB Cores 14X through 18X extended from 113.5 to 155.5 m DSF, where basement was encountered, and we recovered 26.02 m (62%). The total core interval with both coring systems was 155.5 m with 148.1 m recovered (95%).

Once the final core was on deck, we started recovering the drill string. The seafloor beacon was successfully recovered on deck at 1202 h on 29 March. At 1930 h on 29 March, the drilling equipment had been secured and we departed for Site U1333.

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