We spudded Hole 1139A at 1525 hr on 15 January 1999. The seafloor depth adjusted to the rig floor was estimated at 1427.0 m. The 3.5-kHz PDR had indicated an adjusted seafloor depth of 1431.4 m.
Continuous wireline coring proceeded in foraminifer-bearing diatom ooze and nannofossil ooze through Core 7R to a depth of 66.5 mbsf. No chert was encountered. Recovery for this interval averaged 52.0% and the average ROP was 40.3 m/hr. The formation then graded into gray nannofossil clay to a depth of 104.7 mbsf. The average recovery in this interval was 39.1%, whereas the average ROP was 41.7 m/hr. Coring continued through gray nannofossil claystone (78.4% average recovery and 38.4 m/hr average ROP) and into packstone and grainstone with abundant shell fragments. The penetration rate through this unit was very fast (43.2 m/hr), and the average recovery dropped dramatically to 7.9%. Basement was encountered at ~460 mbsf. The uppermost basement unit consisted of cobbles of dense felsic volcanic rock, underlain by deposits of pumice breccia, welded tuff, and intensely altered felsic volcanic breccia. This unit drilled quite fast at 35.4 m/hr, but recovery remained very poor at 6.5%. From Core 51R to 62R, more altered felsic volcanic and volcaniclastic rocks were recovered, coring at 12.4 m/hr with 20.7% average recovery. Basaltic basement was finally reached at the base of Core 62R at ~595 mbsf. Recovery in the basalt improved remarkably to an average of 61.0%. The ROP averaged 4.0 m/hr but varied from a low of 3.0 m/hr to as much as 7.8 m/hr. Coring was terminated with the recovery of Core 73R from a depth of 694.2 mbsf. This was ~99 m into basaltic basement, or ~204 m into acoustic basement, and exceeded the scientific depth objective for this site. A total of 356.63 m of core was recovered for an overall average of 51.4%.
During the coring operation, mud sweeps were pumped as needed. In basement, sweeps were consistently pumped during every core. During the wiper trip made in preparation for wireline logging, the pipe was pulled to 525.0 mbsf using the top drive. Overpull was 20,000-40,000 lb and torque ranged from 300-600 A. Until that point, circulation was not possible. While running the drill bit back into the hole, the driller noted little trouble other than slight hole drag of 20,000-30,000 lb. A hard bridge was identified ~8.0 m above the basalt contact at a depth of 587.0 mbsf. Drilling and reaming from that point required 5 hr to reach a point 25 m above bottom, where progress slowed considerably. The hole was swept with sepiolite mud, and the bit was released. After displacing the hole with sepiolite mud, the end of the pipe was placed at a depth of 101.7 mbsf for logging.
The first wireline logging run included the NGT, the DSI, the dual induction tool (DIT-E), and the LDEO TAP. The loggers decided not to deploy a nuclear source because of questionable hole conditions, and the deteriorating weather would not allow use of the wireline heave compensator. This logging run reached a depth of 593.0 mbsf but could not pass below the basalt contact. Once logging had begun, this tool string failed and had to be recovered. After troubleshooting, the problem was determined to be the sonic tool. The DSI tool was replaced with the Long Spaced Sonic (LSS) Tool, and the tools were run into the hole for a second time. After once again reaching the basalt contact, the hole was logged up from that point.
The weather and sea state rapidly began to deteriorate as the logging tools reached the end of the drill pipe. At this point, further logging considerations were abandoned, and all effort went into getting the drill string above the seafloor. By then the wind speed was consistently blowing in the mid-40s with gusts over 50 kt, and the swells had grown to nearly 20 m. Once at the rig floor, the logging tools were quickly hung off, the logging electric line was pulled back out of the way, and the circulating head was removed from the top of the drill string. A total of 5 stands of drill pipe were pulled. With the pipe hung off ~118 m above the seafloor, we began WOW.
This weather was the worst we experienced during Leg 183. The force 10/11 storm resulted in a maximum average sustained wind from the west-southwest of 48 kt gusting to >60 kt. The maximum average seas were 10-16 ft, and the maximum average swell height was 20-30 ft. Maximum pitch/roll was 9° and 6°, respectively. By 1300 hr on 21 January 1999, the sea state improved enough to safely allow resumption of the drill string trip. A total of 16 hr were spent WOW.
While the drill string was being tripped, the positioning beacon was released and recovered. The end of the drill string reached the rig floor at 1625 hr. The ship was immediately secured for transit, and at 1630 hr on 21 January 1999, we got under way for Site 1140.
Leg 183 Operations - Site 1140
Leg 183 Table of Contents