| IODP Proceedings Volume contents Search | |||
 | |||
| Expedition reports Research results Supplementary material Drilling maps Expedition bibliography | |||
|
doi:10.2204/iodp.proc.314315316.113.2009 OperationsShingu, Japan, port callLoading for three expeditions that spread out over 4 months was a huge task, and Typhoon FITOW caused delays in the original loading and laboratory rearrangement schedule at dock in Yokohama, Japan. Therefore, work at Shingu, Japan, was busy. Upon arriving in Shingu on 15 September 2007, drill pipes and drill collars were checked and listed aboard the D/V Chikyu. Instruments, laboratory supplies, mud chemicals, and logging tools were loaded. An official ceremony for launching the Chikyu’s IODP operations was held in Shingu on 16 September upon arrival of the ship to port. Officials from IODP-Management International, U.S. National Science Foundation, Ministry of Education, Culture, Sports, Science and Technology of Japan, and Japan Agency for Marine-Earth Science and Technology (JAMSTEC) were in attendance. While performing maintenance on the drilling equipment, drill pipe was picked up for the first hole. The science party boarded the ship in Shingu on 19 September after undergoing helicopter underwater escape training and sea survival training at JAMSTEC headquarters in Yokosuka, Japan. A prespud meeting was held on 20 September by shipboard scientists with marine, drilling, and laboratory technical personnel. Numerous media interviews were conducted and ship tours were carried out during the port call. Transit from Shingu to Site C0001The Chikyu departed Shingu for Site C0001 at 1620 h on 21 September 2007. The 44 nmi transit was covered at an average speed of 5.06 kt. Upon arrival at the first site at 0100 h on 22 September, the ship was set in dynamic positioning (DP) mode and bighead transducers were lowered. Hole C0001AThe summary of operations at Site C0001 is shown in Table T1. The drill string was spaced out in preparation for drilling and the Schlumberger Drilling and Measurement measurement-while-drilling (MWD) and annular-pressure-while-drilling (APWD) tools were tested in preparation for drilling pilot Hole C0001A (target depth = 1000 m LWD depth below seafloor [LSF]). The bottom-hole assembly (BHA) included a polycrystalline diamond compact (PDC) bit, crossover sub, MWD (PowerPulse) and APWD tools, stabilizer and fifteen 6¾ inch drill collars, and one jar (see Fig. F1 in the “Expedition 314 methods” chapter; Table T2). Tools were assembled and started running into hole between 0230 and 1030 h on 25 September 2007. The position of the hole was located and surveyed by remotely operated vehicle (ROV). After spud-in, drilling/MWD logging operations began at 1215 h. Based on the cumulative length of drilling pipe, the seafloor depth was estimated to be 2199.5 m (2228 m drillers depth below rig floor [DRF]). A time version of the surface drilling parameters and downhole MWD measurements of equivalent circulating density (ECD), average annular pressure (APRS), and gamma ray value (GRM1) is given in Figure F4. The drillers attempted to maintain a 50 m/h rate of penetration (ROP). The instantaneous ROP averaged over 5 ft (1.52 m) (ROP_5ft) was higher for the first 1.75 h of drilling (0 to ~70 m LSF) because of the unconsolidated nature of the formation. After that, ROP was maintained close to 50 m/h while drilling, even though effective ROP was lower as a result of the time required to make pipe connections (every 38 m). From 380 m LSF (2330 h on 25 September), ECD and APRS sharply increased after each pipe connection and associated noncirculating time intervals. Normal ECD and APRS trends were recovered, at first within 5 min and further downhole with increased circulation time of up to 20 min. Pills of high-viscosity gel mud were regularly pumped to increase the density of the drilling fluid and to facilitate hole cleaning and stability. Characteristics of the high-viscosity gel mud are given in Table T3. At 0320 h on 26 September, major increases in ECD, APRS, and torque (from 5–7 to 15 kNm) before a new pipe connection were of major concern (~430 m LSF). A combination of backreaming, increasing pump pressure (standpipe pressure [SPPA]), and reducing surface weight on bit (SWOB) and ROP for ~2 h allowed a return to normal drilling conditions (0515 h; 520 m LSF). Drilling continued at lower ROP (22–30 m/h), reduced weight on bit (WOB), increased pump flow (from 500 to 570–590 gpm) and pumping time (dummy connection), and increased collar rotation speed (CRPM = 80–100 rpm) until the target total depth (TD) was reached at 1250 h on 27 September (after 49 h of drilling operations). The BHA was then pulled out of the hole and the drill bit cleared the seafloor at 1430 h on 27 September. The drill bit was recovered on the rig floor at 1200 h on 28 September. Hole C0001BPreparation for special-purpose geotechnical coring began on 29 September 2007, after a delay to change out excessively rusted drill collars. Hole C0001B was tagged at 2220 m DRF on 30 September (Table T1). Four cores were taken from the seafloor with the hydraulic piston corer system (HPCS). The top intervals of HPCS cores are as follows (total core recovery = 30.82 m): Hole C0001CHole C0001C was the first LWD-MWD-APWD (hereafter referred to as LWD) hole drilled during Expedition 314. Operations began with making up the BHA, tool initialization, and tool calibration. The BHA included a PDC bit, various subs, LWD tools, fourteen 6¾ inch drilling collars, and one jar (Table T3). From bottom to top, the LWD tools (6¾ inch [17.15 cm] collars) included the geoVISION tool with a 23.18 cm button sleeve, the sonicVISION (four-receiver array) tool, the MWD (PowerPulse) tool, the seismicVISION tool, and the Azimuthal Density Neutron (adnVISION) tool (see Fig. F1 in the “Expedition 314 methods” chapter). For the seismicVISION tool, memory and battery life are good for ~40 nonpumping hours; when circulating above 400 gpm, battery power is not used. Installing the radioactive source for density measurement was completed at 0540 h on 1 October 2007, and the BHA was lowered to run into hole. Tool communication and function checks were conducted at 320 m DRF between 0745 and 0815 h on 1 October. At ~60 m above seafloor (1550 h on 1 October), the surface air gun array was activated and the seismicVISION tool was tested again. Simultaneously, a problem with the surface IDEAL depth recording system was found (see the “Expedition 314 methods” chapter). The geolograph, which tracks the position of the top drive and in-slip or out-of-slip displacement, malfunctioned but was returned to service at 1840 h. After tagging the seafloor at 2226.6 m DRF (2198.0 m mud depth below sea level [MSL]), hole position was confirmed and surveyed by ROV (1840–1915 h) (Table T1). Hole C0001C was spudded at 1915 h with an initial pump rate of 550 gpm, ROP of 15–30 m/h, and bit rotation of 80 rpm. A graphic representation of the drilling parameters and gamma ray log is given in Figure F5. Below ~2237 m DRF (~7 m LSF), drilling proceeded with a more constant ROP of 25–30 m/h. ECD was constant at slightly <1 g/cm3 . WOB and SPPA were kept to minimum while drilling this unconsolidated upper section. From 2110 h on 1 October to 0230 h on 2 October (duration = 5.33 h) drilling stopped for maintenance of rig floor equipment (leakage of wash pipe). After repairs, drilling continued at an ROP of 25 m/h. Between 2266 and 2304 m DRF, a hole deviation survey showed that hole deviation was ~6° (6° at 2266 m and 5.45° at 2304 m). Operations stopped at 0530 h with TD at 78 m LSF. The BHA was pulled out of the hole and the hole position checked. ROV observations confirmed the pipe footprint on the seafloor was associated with pipe/hole deviation during the rig floor maintenance period while the bit was at shallow depth in unconsolidated formation. A decision to spud Hole C0001D without further delay was made at 0740 h on 2 October. Hole C0001DHole C0001D was spudded at 0800 h on 2 October 2007 with the same BHA as Hole C0001C (see Table T3) after an ROV survey. LWD-MWD drilling/logging operations were conducted from the seafloor (2226 m DRF) to TD of 3202 m DRF (974 m LSF) after >5 days of drilling operations (Fig. F6). To avoid hole deviation, the BHA was jetted in to ~40 m LSF. Drilling advanced at an average ROP of 80 m/h then reduced to 25–30 m/h. WOB was kept at a minimum and SPPA was maintained slightly higher than in Hole C0001A (1.1 versus 1.0 MPa). APRS and ECD measurements show a normal (hydrostatic) trend increasing with depth until early morning on 3 October (~2700 m DRF; 470 m LSF), where the slope of the trend increased with increased bit rotation (from 75–80 to 100 rpm). Major reaming and sweeping operations with increased pump pressure and pump flow were conducted between 1245 and 1915 h because of difficult drilling conditions (sticky hole conditions from 2730 to 2773 m DRF; 502 to 545 m LSF). High SPPA was maintained (>15 MPa) for the remaining duration of drilling. The ROV observed stick-slip rotation of the drill pipe above seafloor below this interval. At 0730 h on 4 October, the bit was raised to 2600 m DRF (372 m LSF) for rig floor maintenance of the wireline blow-out preventer line (until 1615 h; duration = 8.75 h), followed by reaming and sweeping of the hole (until 2150 h; duration = ~2.5 h). From 2600 m DRF (372 m LSF), drilling operations continued with routine hole cleaning operations at each pipe connection. ECD decreased smoothly back to 1.2 g/cm3 and remained stable while ROP was reduced to ~15 m/h. At 1200 h on 7 October, the bit reached 3202 m DRF (974 m LSF), 26 m less than the planned TD for this hole. At this point, the DP system computer experienced a series of malfunctions and a red alert DP alarm sounded at 1126 h. The decision was made to trip out of the hole as quickly as possible. Tools were pulled out of the hole and, after having removed the radioactive source (at 0100 h on 7 October), all tools were recovered on the rig floor. Transit to Site C0002After pulling out of the hole because of the DP system failure, troubleshooting of the DP system took 6 days. Finally, approval to continue operations was received on 12 October 2007. At 2100 h on 12 October, the Chikyu moved 14 nmi northwest of the Site C0001 at 3.4 kt to avoid running the LWD tool string in a strong current. After assembling the LWD BHA and drill pipes to a depth of 700 m, the ship drifted to the location of Site C0002 with 1.5 kt speed at 1430 h on 13 October. Upon arrival at Site C0002 at 2145 h, the ship was set in DP mode. |
|||
