Sites 1196 (proposed Site CS-06A) and 1199 (proposed Site CS-16A) are within the Great Barrier Reef Marine Park. All operations adhered to the guidelines established by the Great Barrier Reef Marine Park Authority. A beacon was dropped on Site 1196 coordinates at 0139 hr on 30 January 2001. A strong eastward current moved the beacon ~150 m from the original launching position, so the vessel was offset 140 m to the east to compensate for the displacement of the beacon. The corrected precision depth recorder indicated a water depth of 308.4 m.
Hole 1196A was spudded with the rotary core barrel (RCB) system at 0410 hr on 30 January (Table T2 in the "Leg Summary" chapter; Tables T1, T2). Penetration into the hard carbonate cap of the carbonate platform by 9.6 m required 3.8 hr. At 85.8 mbsf, the drill string became stuck during the connection of a joint of pipe. The drill string could not be pulled up without stalling the top drive, although circulation and rotation were maintained. The string was freed after 5.5 hr of slowly working the drill string back up the hole and pulling with up to 220 kilopounds (kips). The bit was reamed back to the bottom of the hole and coring resumed nearly 10 hr after the hole problems began. To reduce the risk of the pipe becoming stuck, the hole was flushed with mud sweeps following the retrieval of each core and additional wiper trips were made at 285 and 429 mbsf. The pipe became stuck and was freed again after a connection was made with the bit at 499 mbsf. Coring was terminated at 672.2 mbsf, well below the original target depth of 570 mbsf. Acoustic basement was not penetrated; attempting to do so might have compromised the potential for downhole logging. A total of 86.37 m of core was recovered (12.9% average recovery).
The wireline triple combination (triple combo) tool string was made up with the Lamont-Doherty Earth Observatory (LDEO) natural gamma spectrometry tool (NGT) on top and the LDEO temperature tool at the bottom of the string for the first run. The NGT experienced electrical problems when lowered in the pipe. The tool string was brought back on deck, and the NGT was removed. The shortened string was deployed but could not pass a tight spot at ~520 mbsf. The hole was logged up from that depth. The hole diameter was >17 in for long distances, likely a result of the wiper trips and frequent mud sweeps performed to maintain the hole. The temperature tool was recovered with loosened connections, and the brass bottom nosepiece (~4 in long) was missing. Its loss was attributed to significant vibration of the drill pipe due to a strong southwesterly current.
For the second wireline run, the Formation MicroScanner (FMS) sonic velocity tool string was deployed. The tools encountered an obstacle in the pipe at ~135 meters below rig floor (mbrf), which could have been the missing piece of the temperature tool. After pumping was not successful in moving the obstruction, the tools were recovered. The top drive was picked up, and a core barrel was lowered to force the obstacle down the hole. This effort was successful, and the FMS/Sonic combination was deployed after setting back the top drive. The tight spot at 524 mbsf encountered on the first run prevented the tool from further penetration. Logging was initiated at that depth. Two FMS/Sonic passes were logged.
The third run was a check shot survey with the well seismic tool (WST) with 13 stations successfully shot between 94.4 and 523.5 mbsf. Logging operations ended at 0700 hr on 4 February.
A new RCB bit was affixed to the bottom-hole assembly (BHA), and the vessel was offset 20 m east of Hole 1196A. The plan for Hole 1196B was to rotary core through the top of the carbonate platform to a depth of 110 mbsf, recover the RCB BHA and deploy the advanced diamond core barrel (ADCB), reenter Hole 1196B, and core to ~360 mbsf. The 110-m pilot hole was required for lateral support of the ADCB drilling assembly, which is composed of slick-profile 6-in drill collars and is not as robust as the RCB assembly. Deploying a free-fall funnel (FFF) at this point would have facilitated reentry with the ADCB. However, this would have required reaming a 4-m deep, large-diameter (14 in) pilot hole to accommodate the casing of the FFF in the hard seafloor formation (first pipe trip); reentering bare rock with the RCB to drop the FFF (second pipe trip); and deploying the ADCB (third pipe trip). Instead, attempting a bare-rock reentry directly with the ADCB into the RCB pilot hole (one pipe trip only) seemed a wiser use of time at minimal risk.
The bit tagged the seafloor at 304.2 m water depth, and Hole 1196B was spudded with the RCB at 0410 hr on 30 January. The drilling results were similar in drilling time and recovery to the first hole. Following the recovery of Core 194-1196B-6R, the vessel was forced to wait on weather, as the heave was routinely exceeding the shallow-water guideline threshold of 2 m. The bit was pulled back to 19.4 mbsf, and coring was suspended for 11.25 hr. The peak value of heave was 3 m. Coring then resumed and advanced to the target depth of 110 mbsf. Average recovery for that interval was 10%.
Once the bit was on deck, the weather was still unfavorable for shallow water operations and deemed too rough for ADCB coring. It was decided to move on to the next site (Site 1197) and return when the environmental conditions promised better success for ADCB reentry and coring. The vessel departed Site 1196 at 0415 hr on 6 February. The beacon remained on the seafloor.
After initial operations at Site 1197 (see "Operations" in the "Site 1197" chapter) and completion of Site 1198 (see "Operations" in the "Site 1198" chapter), the weather had abated and coring with the ADCB in Hole 1196B appeared feasible. ADCB coring was attempted in anticipation of achieving better recovery than that achieved with the RCB. The 8-nautical mile (nmi) trip from Site 1198 to Hole 1196B was accomplished in 40 min, and the beacon signal was reacquired at 0545 hr on 11 February.
Before reentering Hole 1196B with the ADCB after leaving it open for 5 days, the hole was reentered with the RCB and washed ahead to 110 mbsf to ensure a clean and stable hole for the ADCB reentry. It took <50 min to position the ship so that the RCB system could be reentered into the hole, which was clearly visible from the television transmission. The hole was reentered at 0950 hr on 11 February with the active heave compensator (AHC) in operation. About 1 m of soft sediment fill was cleaned from the hole above 110 mbsf.
The drill string was recovered, and the ADCB drilling assembly was deployed. A strong current made it difficult to position the bit directly over the borehole. At 2130 hr on 11 February, after 1.75 hr of maneuvering, Hole 1196B was reentered with the ADCB with the AHC in operation (Fig. F3). ADCB coring advanced from 110 to 265.3 mbsf (Cores 13Z-51Z). Unlike the standard coring systems, the ADCB does not have a float shoe to prevent the cuttings and loose material in the annulus from backing up into the BHA during the wireline retrieval and running in of core barrels. Therefore, mud was spotted at the bit after each core was cut and before withdrawing the core barrel via the wireline.
Because of diminishing returns and the interest in conserving time for use at an additional site at the end of the leg, coring was terminated before reaching the target depth of 360 mbsf. Total recovery from the 155.3 m interval cored was 17.92 m, or an average of 11.5%. The RCB recovery for a comparable interval (17 cores from 105.0 to 268.4 mbsf) from Hole 1196A was 10.4%. The ADCB recovery in the interval from 110 to 128.1 mbsf was 7.5 m, or 41.4%. This recovery was considerably better than the RCB results for a corresponding interval (26.8%) in Hole 1196A. Beyond this depth, the recovery of the ADCB was comparable with the RCB results. The heave while coring in Hole 1196B rarely exceeded 1 m.
Although this system is still in the development stage, the ADCB acquired 35 hr of continuous operation without hardware problems, broken parts, improper seating of the core barrel, or downtime of any kind. Slip and basket core catchers were both used with moderate success despite the limited recovery in this difficult hole. The operation of the ADCB with the liners worked better than expected. The handling and core extrusion problems experienced during the first deployment of the ADCB on Leg 193 were not encountered during Leg 194. The PDC bit on loan from the Japanese Drilling Company worked quite well, with the overall rate of penetration exceeding initial estimates.
Although the 6-in drill collars were an unusual size for our operation and required drill collar slips and dog collars, the drill crew worked efficiently and managed to have all of the drilling equipment secured only 6 hr after coring was terminated. The beacon was successfully recovered, and the drilling equipment was secured by 1700 hr on 13 February as the vessel began the short return transit to Site 1197.
After a revisit of Site 1197 (13-17 February), the vessel proceeded to Site 1199 (proposed Site CS-16A). This transit was accomplished with extended thrusters, using the dynamic positioning system, which took 5.9 hr. The beacon was launched at 0705 hr on 18 February while the drill string was being deployed to 313 m. Operations were suspended for 3.5 hr to wait for the maximum heave to abate from the measured 2.5 m to <2 m.
Hole 1199A was spudded with the RCB at 1235 hr on 18 February (Table T2 in the "Leg Summary" chapter; Tables T1, T2). Rotary coring advanced to a final depth of 419.5 mbsf by 0845 hr on 21 February. A maintenance wiper trip was made from 187 to 71 mbsf, and ~4 m of soft fill was found. The recovery from the top 159.8 m of the hole was 83.6 m (52.3%) and was cored with a slow average rate of penetration (ROP) at 4.7 m/hr. Part of the reason for the extended coring time in the top of the platform was that not more that 5 kips of bit weight could be applied without putting the BHA in compression. As the hole deepened, bit weight was gradually added and the ROP increased. Below 159.8 mbsf, the recovery dropped off dramatically and the ROP increased substantially. The average recovery from 159.8 to 419.5 mbsf was 3.3%. The total recovery for the hole was 92.16 m, or 22.0%.
A wiper trip was completed, the bit was released, the hole was displaced with 125 barrels of sepiolite mud, and the end of pipe was placed at the depth of 85.7 mbsf in preparation for logging. The triple combo tool string reached a depth of 418 mbsf, which was about 2 m above total depth (TD) of the hole, and a successful log was completed. The FMS/Sonic tool suite was subsequently lowered in the hole but would not move past an obstruction at 118 mbsf, presumably because of a possible karst cave. After 1 hr of countless attempts, the tool was recovered. The drill pipe was lowered to ~210 mbsf in order to widen the narrow hole, and the FMS/Sonic tool suite was lowered once more in the hole. It still was not possible to clear the interval at 118 mbsf. Logging was initiated above this horizon, and we measured a hole deviation of 7.5°, which is likely the cause of repeated failures to reenter the hole. Two sections were added to the tool suite in a final and fruitless attempt at reaching the bottom of the hole. Logging operations were terminated at 1000 hr on 19 February.
The drill string was recovered and the beacon was retrieved. The BHA was disassembled, and the vessel was secured for the extended sea voyage to Guam. The vessel left the location at 1415 hr on 22 February.