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doi:10.2204/iodp.proc.314315316.116.2009

Operations

Hole C0004A

After confirming the position at 0430 h on 31 October 2007, an 8½ inch pilot hole was spudded without logging tools at 0445 h on 1 November. The hole was jetted-in from the seafloor to 75.5 m drillers depth below seafloor (DSF), and rotary drilling began from that depth. During drilling, a short wiper trip was made between 2888 and 2736 m drillers depth below rig floor (DRF). Total depth (TD) of 400 meters below seafloor was reached at 1845 h and the bottom-hole assembly (BHA) was pulled out of the hole and reached the rig floor at 0345 h on 2 November.

Hole C0004B

The drill string was made up in preparation for drilling from 0515 to 0800 h on 2 November 2007. Like the previous LWD-measurement while drilling (MWD)-annular pressure while drilling (APWD) holes, the LWD tools (6¾ inch [17.15 cm] collars) included the geoVISION resistivity tool with a 23.18 cm button sleeve, sonicVISION tool, MWD (PowerPulse) tool, seismicVISION tool, and adnVISION tool run without a radioactive source for ultrasonic caliper only (see Fig. F1 in the “Expedition 314 methods” chapter). A summary of operations is given in Table T1, and the full BHA is described in Table T2.

Following the standard procedure, the tools were assembled, and a first shallow communication and function check was conducted between 0830 and 0845 h. The BHA was immediately lowered while the remotely operated vehicle (ROV) was launched (1415 h on 2 November) and the D/V Chikyu moved 2000 m upcurrent. From 1415 to 1845 h, the Chikyu slowly drifted to the spud-in position while the bit was lowered. After tagging the seafloor at 2665.5 m DRF (2637 meters below sea level), the hole position was located and surveyed by ROV.

Hole C0002B was jetted-in from 2666.5 to 2726 m DRF (0–60.5 m LWD depth below seafloor [LSF]) at 1845 h on 2 November with an initial surface pump rate of 500–510 gpm (~1900 L/m) and surface pump pressure of 8–9 MPa. Drilling continued with an average rate of penetration (ROP) of ~40 m/h above 100 m LSF and reduced to 30 m/h below. Surface weight on bit (SWOB) was set to minimal values (mostly <150 kkgf) and no torque was observed (<3 kNm). Drilling progressed with normal collar rotation (80 rpm) while surface pump flow progressively increased with depth (700 gpm; ~2650 L/m) with pump pressure (SPPA; 8–12 MPa). At 234 m LSF (2900 m DRF) a short wiper trip was conducted to 99 m LSF (from 0330 to 0430 h on 3 November; 2765 m DRF). Drilling resumed from 234 m LSF to TD (400 m LSF; 3065 m DRF) with localized increase in SWOB (20 kkgf) and no increase in torque. At 1230 h on 3 November, two joints of pipe were removed to create an offset in uphole check shots at every pipe disconnection, and tools were pulled out of the hole. All LWD tools were recovered on the rig floor at 0000 h on 4 November, and all memory data were successfully downloaded. Time versions of the surface drilling parameters and downhole equivalent circulating density (ECD), average annular pressure (APRS), and real-time resistivity-at-the-bit gamma ray (GR_RAB_RT) values are given in Figure F4.

Transit to Site C0005

After recovering the ROV, the Chikyu moved to proposed Site NT2-01G over a distance of ~600 m with average speed of 0.3 kt at 0240 h on 6 November 2007 and checked the communication with beacons at the site at 0500 h.

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