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OPERATIONS

Transit to Site U1316

The 302 nmi transit from Dublin, Ireland, to Site U1316 was accomplished at an average speed of 9.7 kt in just under 32 h. During the transit, drilling and coring equipment was prepared (Table T1).

Site U1316

Hole U1316A

Once on site, the thrusters were lowered and the vessel was placed in dynamic positioning (DP) mode. The hydrophones were lowered and the positioning beacon was deployed at 0410 h on 30 April, officially marking the beginning of on-site operations. The precision depth recorder (PDR) provided a seafloor depth of 956.4 m, corrected to the rig floor dual elevator stool (DES). The drill string deployment for Hole U1316A was initiated by picking up drill collars and strapping (measuring) and drifting (verifying minimum internal bore diameter) all tubular components. A two-stand APC/XCB bottom-hole assembly (BHA) was used for coring. After tripping the drill string to bottom, the top drive was picked up and the drill string was spaced out for spudding. Hole U1316A was spudded with the APC at 1120 h on 30 April, and a seafloor depth of 959.2 meters below rig floor (mbrf) was established.

Eight APC cores advanced to 66.3 mbsf (1025.5 mbrf) (recovery = 95%). APC temperature measurements were taken at 26.3 and 54.8 mbsf, and the Tensor orientation tool took measurements from 26.3 to 64.3 mbsf. Core 8H short-stroked and became stuck at 66.3 mbsf, and a maximum of 80 klb overpull was not able to free it. The core barrel was released after overdrilling 1.5 m. The coring assembly was switched to XCB, and 13 XCB cores advanced an additional 67.7 m to a total depth (TD) of 134.0 mbsf (1093.2 mbrf) (recovery = 80%). XCB coring times were long and recovery erratic. The XCB coring shoe on Core 18X failed in torsion but remained on the core barrel, and heat checking was evident on other coring shoes. The average penetration rate was <3 m/h. Coring was suspended at 2015 h on 1 May because of the slow penetration rate.

Hole U1316A was prepared for logging. A wiper trip was run from bottom up to 30 mbsf and back to bottom using the top drive, fill (1 m) was circulated out, and the hole was displaced with 45 bbl of sepiolite mud. The bit was then pulled up to logging depth of 30 mbsf.

The Schlumberger wireline logging sheaves were rigged up, and the triple combo tool string was assembled deployed. On the way down the pipe it encountered an obstruction at 45 mbsf, which left 5 m of the logging string still inside the drill pipe. The logging string was picked up and run back down but would not pass beyond 30 mbsf, which was coincident with the lockable float valve. It was speculated that vessle heave and the shallow engagement of the drill pipe in the hole (30 m) allowed the pipe to "walk around" and wallow out the top of the hole. The logging program was suspended and the tools recovered. The Schlumberger logging sheaves were rigged down and the drill string was pulled clear of the seafloor at 0640 h on 2 May, officially ending operations in Hole U1316A.

Hole U1316B

The drillship was offset 20 m north of Hole U1316A, and the drill string was spaced out for spudding. Hole U1316B was spudded with the APC at 0830 h on 2 May, and a seafloor depth of 959.0 mbrf was established.

Eight APC cores advanced to a TD of 59.5 mbsf (1018.5 mbrf) (recovery = 103%). Perfluorocarbon tracer (PFT) and microsphere tracers were run on all cores, and the Tensor orientation tool took measurements from 24.5 to 59.5 mbsf. The drill string was pulled clear of the seafloor at 1500 h on 2 May, officially ending operations in Hole U1316B.

Hole U1316C

Note: Hole U1316C was drilled out of sequence to take advantage of the logistics of APC/XCB coring at nearby Site U1317. Before starting Hole U1316C, a pipe trip was made to change out the BHA from APC/XCB to RCB.

The ship moved back from Site U1317 on 7 May. The location coordinates for Hole 1316C were 20 m south-southeast of Hole U1316A. The RCB BHA was made up with a mechanical bit release (MBR) and three stands of drill collars. Hole U1316C was spudded at 0800 h on 7 May, and seafloor was established at 959.0 mbrf. The RCB was initially run with a center bit and the hole was drilled ahead to 40.0 mbsf (999.0 mbrf). The center bit was retrieved and 11 RCB cores advanced an additional 103.1 m to a TD of 143.1 mbsf (1102.1 mbrf) at 0010 h on 8 May (recovery = 68%). PFT and microsphere tracers were run on all cores.

Hole U1316C was prepared for logging. A wiper trip was run from bottom up to 58 mbsf and back to bottom. There was no fill. The RCB bit was released by a wireline releasing tool and dropped to the bottom. The hole was displaced with 44 bbl of sepiolite mud, and the drill pipe was tripped to the logging depth of 59 mbsf.

The Schlumberger wireline logging sheaves were rigged up, and the triple combo tool string was assembled. The logging string was run in the hole to TD at 143 mbsf and logged uphole. After a single pass, the tools were pulled out of the hole and laid out at 0715 h on 8 May.

The second logging run was with the FMS-sonic tool string. The FMS-sonic tool string was assembled and run to bottom. Two logging passes were made from bottom to 59 mbsf. With logging complete, the string was pulled out of the hole and laid out at 1135 h on 8 May. The Schlumberger wireline logging sheaves were rigged down, ending the logging operation at 1330 h on 8 May.

The drill pipe was tripped to the surface, the beacon was released at 1350 h and recovered, and the MBR cleared the rotary at 1515 h on 8 May, ending operations at Site U1316.

Site U1317

The vessel was moved 0.5 nmi in DP mode with the drill string in the water from Site U1316 to Site U1317. A positioning beacon was deployed at 1837 h on 2 May. The PDR provided a seafloor depth of 830.4 mbrf, and the vessel moved in DP mode to position over the site coordinates.

Hole U1317A

There was some difficulty obtaining an accurate reading from the PDR because of the steep bathymetric slopes of the carbonate mound. The PDR tended to give readings shallower, by as much as 40 m, than the actual depth of the rig floor. This caused several hours delay. After the drill string was spaced out, Hole U1317A was spudded with APC at 2335 h on 2 May, and a seafloor depth of 832.5 mbrf was established.

Sixteen APC cores advanced to 130.8 mbsf (956.8 mbrf) (recovery = 105%). PFT and microsphere tracers were run on all cores. APC temperature measurements were taken at 25.5, 63.5, and 110.0 mbsf, and the Tensor orientation tool took measurements from 25.5 to 63.5 mbsf. Overpulls were required on all temperature runs, 70 klb at 110.0 mbsf. The coring assembly was switched to XCB, and two XCB cores advanced an additional 8.0 m to a TD for Hole U1317A of 138.8 mbsf (964.8 mbrf) (recovery = 63%). The drill string was pulled clear of the seafloor at 1815 h on 3 May, officially ending operations in Hole U1317A.

Hole U1317B

The vessel was offset 25 m southeast of Hole U1317A. After the drill string was spaced out, Hole U1317B was spudded at 1920 h on 3 May, and a seafloor depth of 809.0 mbrf was established.

Sixteen APC cores advanced to 145.2 mbsf (954.2 mbrf) (recovery = 101%). No tracer material was run in Hole U1317B, and the Tensor orientation tool took measurements from 24.5 to 110.0 mbsf. Overpulls were required on six cores, with 80 klb needed for two of them. At 110.5 mbsf, the core barrel had to be drilled over. The coring assembly was switched to XCB for one core, which advanced only 3 m, for a TD for Hole U1317B of 148.2 mbsf (957.2 mbrf). The drill string was pulled clear of the seafloor at 0815 h on 4 May, officially ending operations in Hole U1317B.

Hole U1317C

The vessel was offset 15 m south of Hole U1317B. After the drill string was spaced out, Hole U1317C was spudded at 1000 h on 4 May, and seafloor depth was established at 802.7 mbrf.

Seventeen APC cores advanced to 150.8 mbsf (953.5 mbrf) (recovery = 103%). No tracer material was run in Hole U1317C, and the Tensor orientation tool took measurements from 19.8 to 95.8 mbsf. Overpulls were required on four cores. The coring assembly was switched to XCB for one core, which advanced only 2.2 m, for a TD for Hole U1317C of 153.0 mbsf (955.7 mbrf). The drill string was pulled clear of the seafloor at 2130 h on 4 May. The drill string was tripped back to the surface, and the bit cleared the rotary at 2330 h on 4 May, officially ending operations in Hole U1317C. The bit, seal bore drill collar, and nonmagnetic drill collar were laid out.

Hole U1317D

The vessel was offset 25 m southeast of Hole U1317B. An RCB BHA with an MBR and three stands of drill collars was made up. Hole U1317D was spudded at 0400 h on 5 May, and seafloor was established at 805.0 mbrf. The RCB was initially run with a center bit, and the hole was drilled ahead to 110.0 mbsf (915.0 mbrf). The center bit was retrieved, and 18 RCB cores advanced an additional 160 m to a TD of 270.0 mbsf (1075.0 mbrf) at 0420 h on 6 May (recovery = 64%). PFT and microsphere tracers were run on all cores.

Hole U1317D was prepared for logging. A wiper trip was run from bottom to 30 mbsf and back to bottom. During the wiper trip up, overpulls of 70 klb at 242 mbsf and 30 klb at 185 mbsf were experienced. On the wiper trip down, the bit took weight at 222 mbsf. A core barrel was dropped, and the hole was reamed and washed down to TD (270 mbsf). Fill (2 m) was circulated out, and hole-cleaning sweep with 30 bbl of sepiolite mud was pumped around. The RCB bit was released and dropped to the bottom. The hole was displaced with 84 bbl of sepiolite mud, and the drill pipe was tripped to the logging depth of 88 mbsf.

The Schlumberger wireline logging sheaves were rigged up, and the triple combo tool string was assembled. The logging string was run in the hole, and took weight at 246 mbsf. The attempt to work the tools down was not successful, and the hole was logged up from that depth. After the single pass the tools were pulled out of the hole and laid out at 0600 h on 6 May.

The second logging run was with the Well Seismic Tool (WST). Preparation for this run required following the Marine Mammal Policy for seismic sources. The watch for marine mammals began an hour before the air gun was put through a soft start. The soft start required ramping up the firing pressure to operational levels over a 30 min period. No mammals were sighted. The WST tool string was assembled and run into the hole to 246 mbsf. Check shots were taken at 13 stations on the way up. The signals were good and the WST string was pulled out of the hole and laid out at 2000 h on 6 May.

The third logging run was with the FMS-sonic tool string, which was assembled and run to 246 mbsf. Two logging passes were made from 246 to 88 mbsf. With the logging complete, the string was pulled out of the hole and laid out at 0100 h on 7 May. The Schlumberger wireline logging sheaves were rigged down, ending the logging operation at 0230 h on 7 May.

The drill pipe was tripped to surface, and the beacon was released at 0326 h and recovered. The MBR cleared the rotary at 0430 h on 7 May, ending operations in Hole U1317D.

Hole U1317E

Note: Hole U1317E was drilled out of sequence because it was a late add-on that required approvals from both the IODP safety panel and the Irish government.

The transit from Site U1318 to Site U1317 occurred on 11 May and took 1.5 h. As the vessel came on site, the thrusters were lowered and the vessel was positioned over the site coordinates. The positioning beacon was dropped at 1138 h on 11 May. The vessel was offset 50 m south-southeast of Hole U1317D, and the drill string was spaced out for spudding. Hole U1317E was spudded at 1430 h on 11 May, and a seafloor depth was established at 792.2 mbrf.

Eighteen APC cores advanced to 158.6 mbsf (950.8 mbrf) (recovery = 103%). No tracer material was run, and the Tensor orientation tool took measurements from 25.7 to 139.7 mbsf. Overpulls were required on nine cores with 80 klb needed for Core 17H. Cores 17H and 18H had incomplete stroke, and Core 17H had to be drilled over. The core catcher of Core 17H held the prize of the hole, the boundary interval where coral growth initiated.

The drill pipe was tripped out of the hole, pulling clear of seafloor at 0100 h and continuing to the surface. The beacon was released and recovered at 0111 h on 12 May. The collars were laid out and the rig was secured for transit. The ship was under way to Ponta Delgada, Azores (Portugal), at 0429 h on 12 May, ending operations at Site U1317.

Site U1318

The rig was secured for transit and the vessel was under way from Site U1316 to Site U1318 on 8 May. After a 7 nmi transit the vessel came on site and the thrusters were lowered and the vessel was positioned over the site coordinates.

Hole U1318A

A positioning beacon was dropped at 1649 h on 8 May, beginning Hole U1318A. The PDR provided a seafloor depth of 430.4 mbrf. An APC/XCB BHA was made up with two stands of collars. Hole U1318A was spudded at 2045 h on 8 May, and a seafloor depth was established at 420.3 mbrf.

Fifteen APC cores advanced to TD at 142.2 mbsf (562.5 mbrf) (recovery = 90%). PFT and microsphere tracers were run on all cores, APC temperature measurements were taken at 28.2, 56.7, 85.2, and 113.7 mbsf, and the Tensor orientation tool took measurements from 28.2 to 123.2 mbsf. Overpulls were required on five cores, two of those on the temperature runs. The drill string was pulled clear of the seafloor at 0905 h on 9 May, officially ending operations in Hole U1318A.

Hole U1318B

The drillship was offset 20 m south of Hole U1318A. After the drill string was spaced out, Hole U1318B was spudded at 1010 hr on 9 May, and the seafloor was established at 419.8 mbrf.

Fourteen APC cores advanced to 128.5 mbsf (548.3 mbrf) (recovery = 94%). No tracers were run during APC coring, and the Tensor orientation tool took measurements from 24.0 to 128.5 mbsf. Overpulls were required on two cores. The coring assembly was switched to XCB. PFT and microsphere tracers began on Core 19X (176.5 mbsf) and ended on Core 26X (235.0 mbsf). Thirteen XCB cores advanced an additional 116.1 m to TD at 244.6 mbsf (644.4 mbrf) at 0630 h on 10 May (recovery = 79%).

Hole U1318B was prepared for logging. A wiper trip was run from bottom up to 60 mbsf and back to bottom. There were no hole problems, and only 1 m of fill was circulated out. The hole was displaced with 102 bbl of sepiolite mud, and the drill pipe was tripped to the logging depth of 70 mbsf.

The Schlumberger wireline logging sheaves were rigged up and the triple combo tool string was assembled. As the logging string was run in the hole, it took weight at 70 and 96 mbsf. The tools worked their way through the restrictions and were able to get to TD at 244.6 mbsf. From TD the triple combo logged upward to 70 mbsf. The data quality was good, so a second pass was not necessary. The tools were pulled out of the hole and laid out.

The second logging run was with the FMS-sonic tool string. The FMS-sonic string was assembled and run to bottom with no problems. Two passes were made from 244 to 87 mbsf. The logging string was pulled out of the hole and laid out. The Schlumberger wireline logging sheaves were rigged down, ending the logging operations at 1855 h on 10 May.

The drill pipe was tripped out of the hole and pulled clear of seafloor at 2110 h on 10 May, ending operations in Hole U1318B.

Hole U1318C

The vessel was offset 25 m south of Hole U1318B, and the drill string was spaced out for spudding. Hole U1318C was spudded with the APC at 2245 h on 10 May, and a seafloor depth of 420.9 mbrf was established.

A center bit was dropped and the hole was washed/drilled down to 70.0 mbsf. The center bit was retrieved with the wireline, and seven APC cores advanced an additional 58.6 m to 125.7 mbsf (546.6 mbrf) (recovery = 93%). No PFT or microsphere tracers were run, and the Tensor orientation tool took measurements from 79.5 to 125.7 mbsf. Overpulls were required on two cores, so the coring assembly was switched to XCB. Three XCB cores advanced an additional 28.8 m to TD at 154.5 mbsf (575.4 mbrf). The drill string was pulled clear of the seafloor at 0900 h on 11 May. The positioning beacon was released and recovered on deck at 0920 h, the drill pipe was tripped to surface, and the BHA was racked back. The rig was secured for transit to Site U1317 at 1015 h on 11 May, ending operations at Site U1318.

Transit to Dublin

Expedition 307 ended with first line ashore on 30 May 2005.

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