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doi:10.2204/iodp.proc.314315316.123.2009 OperationsLocations of holes drilled during Expedition 315 are shown in Figure F3. Transit from Site C0006 to Site C0001The D/V Chikyu departed IODP Site C0006, the last location of Expedition 314, at 1700 h on 15 November 2007. The 14 nmi transit was covered at an average speed of 3.5 kt. Rig maintenance was carried out upon arrival at Site C0001 at 2100 h on the same day. Hole C0001E
After making up a hydraulic piston coring system (HPCS)/extended shoe coring system (ESCS) coring assembly with an 11 Hole C0001FAfter we abandoned Hole C0001E, we moved 20 m eastward and spudded Hole C0001F (Table T2) at 0945 h on 22 November 2007. After washing to 108 m drillers depth below seafloor (DSF), we started coring with ~10 m of overlap with the previous hole. We cored 121.8 m and cut 19 cores with the HPCS. Our recovery rate was >100% for most cores; however, some relatively deep cores showed obvious flow-in structures. In situ temperature measurements were carried out using the APCT3 on Cores 315-C0001F-2H, 5H, 8H, and 11H. Because the formation became stiff, we changed to the ESCS from the twentieth core and then cored an additional 19.0 m and cut two cores. Core recovery was good for both cores; however, severe drilling disturbance was observed on X-ray computed tomography (CT) scan imagery, suggesting that we could not get good samples for physical and mechanical properties. We therefore decided to stop ESCS coring and switch to the rotary core barrel (RCB). We abandoned the hole by displacing with 1.3 specific gravity kill mud and then pulled out of the hole and recovered the remotely operated vehicle (ROV) under drifting at an average speed of 0.8 kt at 0500 h on 24 November. Hole C0001GWe started making up a 10⅝ inch RCB assembly at 0845 h on 24 November 2007 and started running in the hole at 1300 h (Table T3). We spudded Hole C0001G at 0130 h on 25 November. After jetting to 74.5 mbsf, we started drilling. Just after drilling started, the ROV umbilical cable wrapped around the drill pipe. We stopped drilling and started pulling out of the hole at 1415 h. We safely recovered the ROV on board at 1500 h and confirmed it had no fatal damage. Hole C0001HAfter moving the vessel 6 nmi upcurrent at an average speed of 3.0 kt, we restarted running in the hole at 0000 h on 26 November 2007 (Table T4). We spudded Hole C0001H at 0515 h, ~10 m away from the previous hole. After jetting to 74 mbsf, we started drilling with an RCB assembly with a center bit. Washing to 230.0 mbsf, we retrieved the center bit and started RCB coring at 1445 h. The first RCB core arrived on deck at 1704 h. The ROV umbilical cable wrapped around the drill pipe at 0300 h on 27 November, but we recovered it at 0530 h without retrieving it to the surface. After cutting Core 315-C0001H-20R at 412.5 m core depth below seafloor (CSF), we observed high torque up to 18 kNm. Torque returned to normal (3–5 kNm) after we pumped 10 m3 of Hi-Vis mud twice. Round mudstone gravel, typical of borehole caving, was observed at the top of Cores 315-C0001H-18R (~15 cm) and 20R. Core recovery was generally as low as 30%–35%, except for one core that yielded almost full recovery. Correlation between drilling parameters and core recovery was uncertain. As the weather was worsening, we stopped coring at 448.0 m CSF after cutting Core 315-C0001H-24R and started free-fall funnel (FFF) installation at 1600 h on 28 November. We completed installation of the FFF by 0700 h on 29 November, and then we pulled the pipe to 35 mbsf and waited on weather for the rest of the day. As the weather improved that night, we started running in the hole at 2330 h. After washing from 152 to 381 mbsf, we swept and reamed with Hi-Vis mud from 381 to 448 mbsf. We restarted coring at 0700 h on 30 November and cut two cores from 447.2 to 457.8 m CSF. The pipe stuck while coring and was released with 350 kN overpull; we then decided to stop coring. We displaced the hole with 1.3 specific gravity kill mud and started to pull out of the hole at 1230 h. The pipe was recovered at the surface by 2145 h. As the current was too strong to retrieve the ROV, we had to wait until the current was below the operational limit. Meanwhile, we made up a 10⅝ inch RCB drilling assembly. After moving the vessel 8.6 nmi to a low-current area at 0730 h on 1 December at an average sped of 0.7 kt, we retrieved the ROV at 2045 h while drifting. We started moving the vessel 5 nmi upcurrent of the well location from 2045 h at an average speed of 3.1 kt. Meanwhile, we repaired an ROV cursor cable. We started running in the hole at 0200 h on 2 December. We launched the ROV at 0630 h and dove to the location at 0900 h. Having positioned the vessel to set the bit above the FFF at 1030 h, we reentered the hole at 1235 h. After washing and reaming from 299 to 458 m DSF, we started drilling at 1930 h. After repeating the reaming and wiper trip several times, we reached 600 m DSF, the starting depth for coring, at 2000 h on 3 December. We spotted 57 m3 of 1.3 specific gravity kill mud and then started picking up out of the hole at 2030 h and retrieved the bottom-hole assembly to the surface at 0500 h. We moved the vessel 6 mni upcurrent and meanwhile made up an RCB coring assembly without a center bit. We started running in the hole at 0900 h and launched the ROV at 1330 h. The vessel was on location at 1845 h. We reentered the hole at 2010 h and continued running in the hole to 264 m DSF. We then started washing and reaming from 268 m DSF at 2200 h. Despite repeated washing and reaming, borehole conditions did not improve. After washing and reaming to 449 m DSF, we finally decided to abandon the hole at 1300 h on 5 December. We displaced the hole with 50 m3 of 1.3 specific gravity kill mud and picked up the coring assembly to the seafloor. We moved the vessel 60 m eastward and spudded a new hole (C0001I). Hole C0001IWe dropped a center bit and then spudded Hole C0001I at 1550 h on 5 December 2007 (Table T5). After jetting to 70 mbsf, we started drilling at 1700 h with a 10⅝ inch RCB assembly with a center bit. Drilling to 425 mbsf was relatively smooth. At every pipe stand, 10 m3 of Hi-Vis mud was spotted. On 6 December, while picking up from 457 to 340 m DSF to change the wash pipe, both upper and lower inline blowout preventers were repaired. Running in the hole started at 1400 h, and we repeatedly washed and reamed to 520 m DSF. While backreaming 434 to 520 m DSF, we had a pipe stick at 464 m DSF. We managed to free the pipe with 700 kN of overpull. After escaping from this zone, we gave up further drilling and coring at 0315 h on 7 December. After displacing the hole with 35 m3 of 1.5 specific gravity kill mud, we started pulling out of the hole at 0900 h and finished at 1400 h. The ROV dove to retrieve transponders at 1600 h. Meanwhile, we changed saver subs and repaired a leak on the top drive system. Four transponders were recovered at 0230 h on 8 December. We left the location for Site C0002 at 0230 h. |
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inch bit, we started running in Hole C0001E at 0000 h on 17 November 2007 (Table