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Transit to Site U1352

After a 3 h, 8 nmi move from Site U1351 in dynamic positioning (DP) mode, the R/V JOIDES Resolution was positioned at Site U1352 at 0500 h (all times are ship local time, Universal Time Coordinated [UTC] + 13 h) on 30 November 2009. The position reference was a combination of Global Positioning System (GPS) and an acoustic beacon on the seafloor, weighted heavily toward the acoustic beacon (80%). A positioning beacon (FSI BAP-547W, SN 1025, 14.0 kHz, 200 dB) was deployed at 0455 h on 30 November.

Site U1352 overview

Four holes were drilled at this site (Table T1). Hole U1352A was cored with the advanced piston corer (APC) system to 42.2 m drilling depth below seafloor (DSF) with the objective of providing whole-round samples for microbiology, chemistry, and geotechnical studies. Hole U1352B was cored with the APC/extended core barrel (XCB) coring system to XCB refusal at 830.9 m DSF. Hole U1352C was drilled and cored with the rotary core barrel (RCB) system to the target, record depth of 1927.5 m DSF. Hole U1352D was cored with the APC system to 127 m DSF while we waited for the weather to improve before transiting to the next site.

Logging was attempted with partial success in Holes U1352B and U1352C. The third-generation advanced piston corer temperature tool (APCT-3) was deployed five times with good results. Overall recovery for Site U1352 was 102% with the APC, 59% with the XCB, and 51% with the RCB. The total cored interval for Site U1352 was 2296.5 m, and total recovery was 1444.1 m (63%).

Rig floor operations commenced at 0500 h on 30 November when the vessel shifted to DP control and ended at 2100 h on 21 December when the vessel was secured for transit.

Hole U1352A

The bottom-hole assembly (BHA) was made up with an APC/XCB bit, and coring in Hole U1352A began at 1145 h on 30 November. The mudline was established at 354.8 m drilling depth below rig floor (DRF) (343.8 meters below sea level [mbsl]). APC coring continued through Core 317-U1352A-5H (42.2 m DSF), using nonmagnetic coring assemblies. Core orientation was measured on all cores, and a temperature measurement was taken with Core 317-U1352A-4H. Contamination testing was done on all cores with perfluoromethylcyclohexane (PFT) and microspheres. A total of 43.92 m of core was recovered from Hole U1352A (104%). The drill string was pulled back to the seafloor, and the bit cleared the seabed at 1530 h on 30 November, officially ending operations in Hole U1352A.

Hole U1352B

The vessel was offset 20 m south of Hole U1352A, and Hole U1352B was piston cored to Core 317-U1352B-36H at 297.0 m DSF, with a total recovery of 298.85 m (101%). Core orientation was measured with the Flexit tool on the first 17 cores before the tool was pulled because of more severe piston coring conditions. The XCB coring system was deployed for Cores 317-U1352B-37X through 94X (297.0–830.9 m DSF). Recovery with the XCB system was very good to ~500 m DSF. Below that depth, a steadily increasing number of cores had poor recovery. A total of 533.9 m was cored, and 315.02 m was recovered (59%). Toward the bottom of the hole, the XCB cutting shoe overheated and the formation caused excessive torque. The risk of damaging the core barrel was too high to continue with the XCB system. A 50 bbl high-viscosity mud sweep was pumped to clean the hole.

The drill string was tripped back to 80 m DSF, and the triple combination (triple combo) logging tool string was rigged up and run into the hole (RIH). The first logging run failed to pass 487 m wireline log depth below seafloor (WSF) because the hole evidently had collapsed during logging preparations. Two passes were successfully recorded. The caliper readings indicated that the borehole was too large to allow an adequate clamp for the Versatile Seismic Imager (VSI) tool to obtain reliable data, so the vertical seismic profile (VSP) plan was canceled. The Formation MicroScanner (FMS)-sonic tool string was subsequently deployed, and it also encountered a borehole obstruction, this time somewhat higher in the hole. FMS-sonic logs were recorded from 442 m WSF. After the logging tools were rigged down, a 12 bbl cement plug was pumped at 154.4 m DSF. The drill string was tripped back to the surface and cleared the rotary table at 1615 h on 5 December, ending operations in Hole U1352B.

PFT and microspheres were deployed every ~50 m throughout Hole U1352B for microbiological contamination testing. Temperature measurements with the APCT-3 tool were taken with Cores 317-U1352B-6H, 10H, 15H, and 20H. All temperature measurements had good decay curves. The cored interval in Hole U1352B was 830.9 m, and total recovery was 613.87 m (74%).

Hole U1352C

The ship was offset 20 m south of Hole U1352B, and operations in Hole U1352C began with the makeup of a new BHA for the RCB system, which was fitted with a mechanical bit release to facilitate logging after coring was completed. Drilling in Hole U1352C began at 2015 h with a center bit installed. At ~300 m DSF, the center bit was recovered, inspected, and reinstalled. The hole was then advanced to 574.7 m DSF, at which point the center bit was pulled and an RCB was dropped. The hole was cored with the RCB system from 574.7 to 603.6 m DSF (Cores 317-U1352C-2R through 4R), and 12.79 m of core (44%) was recovered. The center bit was reinstalled, and drilling continued to 660.0 m DSF. The center bit was again pulled, and rotary coring resumed for Cores 317-U1352C-6R through 41R (660.0–1009.9 m DSF), with 20 bbl high-viscosity mud sweeps every 50 m of coring to clean the cuttings from the hole. At 1900 h on 8 December, a 50 bbl sweep was pumped and a wiper trip of the drill string was made from 1007 to ~200 m DSF and back. Coring resumed ~8 h later for Cores 317-U1352C-42R through 118R (1009.9–1661.5 m DSF), with sections of good and poor recovery. The deplugger was run, and coring intervals were reduced to 5 m several times in attempts to improve core recovery. On 15 December at 2030 h, a 50 bbl sweep was pumped and a wiper trip of the drill string was made from 1662 to ~1000 m DSF and back; coring resumed ~7 h later. The interval for regular 20 bbl hole cleaning mud sweeps was decreased to 40 m.

On 17 December, it became evident that the scientific target for the hole, the Marshall Paraconformity, was deeper than anticipated. Permission was requested and received to exceed the original EPSP limit of 1913 m DSF by up to 250 m (to 2163 m DSF). The Marshall Paraconformity was recovered in Core 317-U1352C-140R (1851–1861 m DSF) on 18 December. Coring continued to Core 317-U1352C-148R (1927.5 m DSF) in order to provide sufficient depth to log across the Marshall Paraconformity. The last core from Hole U1352C was received on deck at 1740 h on 19 December.

Starting at 796 m DSF, PFT and microspheres were deployed at ~50 m intervals throughout Hole U1352C for microbiological contamination testing.

The penetration depth of 1928 m for Hole U1352C established a new single-bit, single-expedition record for the JOIDES Resolution and made Hole U1352C the deepest sediment hole ever drilled by IODP or its predecessor programs. The cored interval in Hole U1352C was 1296.4 m, with 655.02 m of core recovered (51%).

The hole was swept clean with a 50 bbl sweep of high-viscosity mud, the RCB coring bit was released, and the drill string was tripped out to ~900 m DSF. The top drive was picked back up, and 400 bbl of high-viscosity logging mud was displaced into Hole U1352C. The top drive was set back, and an attempt was made to continue the trip out of the hole. After one stand, excessive drag required the top drive to be reinstalled, and the trip out of the hole continued with rotation until the end of the string reached 545 m DRF. The top drive was then set back and the drill string was pulled back to 439 m DRF. The upper guide horn was removed, and the vibration-isolated television (VIT) camera was deployed to observe and document the cone of cuttings at the seafloor during logging. The drill string was set to a logging depth of 458 m DRF. The logging string was rigged up to run a modified version of the triple combo tool string. The first logging run indicated that the hole had collapsed, and the tool string was unable to pass 207.5 m WSF. The tool string was pulled back to the surface and rigged down. The drill string was tripped back to the surface, clearing the rotary table at 2200 h on 20 December, ending Hole U1352C.

Hole U1352D

When operations in Hole U1352C concluded, the winds and swells were too high to begin operations at the next site, which was in extremely shallow (<100 m) water. We anticipated a weather delay of ~24 h and decided to core Hole U1352D. An APC/XCB assembly was made up, and piston coring in Hole U1352D began at 0615 h on 21 December and continued through Core 317-U1352D-14H (0–127.0 m DSF). Core recovery totaled 130.84 m (103%).

Nonmagnetic coring assemblies were used, and core orientation was measured on all cores.

The drill string was pulled back to the rotary table, the BHA was racked back, and the rig floor was secured for transit at 2100 h on 21 December, ending Hole U1352D and Site U1352.