We spudded Hole 1137A at 0215 hr on 1 January 1999 using the RCB coring assembly and an RBI C-4 core bit. Accurate identification of the seafloor is quite difficult with the RCB system. The driller believed he saw some weight loss around the 3.5-kHz PDR depth of 1020.4 meters below rig floor. The bit was advanced a full 9.5 m from the last connection at 1016.0 m, and, when recovered, the core barrel had 9.62 m of recovery. Because an accurate seafloor depth was not considered essential to the science objectives, we did not take the time to attempt recovering mudline. Coring continued with a seafloor depth adjusted to the rig floor of 1016.0 m.
Continuous wireline coring proceeded in homogenous white foraminifer-bearing nannofossil ooze through Core 21R to a depth of 1215.5 m (199.5 mbsf). No chert was encountered. Recovery for this interval averaged 53.8% but was highly variable, ranging from 0% to 108%. The average ROP was 40.1 m/hr. The formation became glauconite-bearing sandy packstone with abundant shell fragments until contacting basement at ~1240 m (~224 mbsf). The average recovery in this 24.5-m interval was an extremely poor 10.7%, whereas the average ROP dropped to 30.5 m/hr. Basement consisted of a series of basalt flows interspersed with volcaniclastic sandstone, conglomerate, and crystal-vitric tuff.
After recovering Core 37R from 327.5 mbsf, a short trip was made to recover five knobby drilling joints. This was to enable the drilling depth objective of 374.0 mbsf to be reached using knobby joints. These joints were required because of the slow ROP and frequent severe sea states experienced while on site. Upon returning to the bottom of the hole, ~1.3 m of hard fill was found. While attempting to ream through this material, the weather and sea state continued to deteriorate to the point where the heave compensator was exceeding its stroke length. In addition, the yellow (2%) DP warnings were becoming more frequent. The pipe was pulled to the top of the hole and hung off using knobby joints at a depth of 1336.0 m (320.0 mbsf). After waiting on weather (WOW) for 6.75 hr, the weather conditions moderated and the pipe was run back to the bottom of the hole. Only 30 min were required to clean out the hole and resume coring. Coring was terminated with Core 46R at a TD of 371.2 mbsf. This was ~150 m into basement and satisfied the scientific depth objective for this site. Average recovery in basement was 69.2%, but recovery was quite variable, ranging from 19% to 102%. A total of 14 half cores were cut to maximize recovery. The overall ROP averaged 4.5 m/hr; however, it varied considerably from 5.5 to 1.7 m/hr.
A wiper trip was initiated to prepare the hole for wireline logging; however, this was halted when the pipe reached a depth of 120.3 mbsf because of deteriorating weather conditions. After WOW for 10.75 hr, the wiper trip was completed. The hole was swept with a 25-barrels (bbl) sepiolite mud pill, the bit released, and 112 bbl of sepiolite mud were displaced into the hole for logging. The pipe was pulled to a depth of 100.3 mbsf, and preparations for logging began. The first logging run was with the triple combo suite of tools, which includes the dual laterolog (DLL) for resistivity, the accelerator porosity sonde (APS) for porosity, and the high temperature lithodensity tool (HLDT). Also included in this tool string was the hostile environment natural gamma-ray sonde (HNGS) and the Lamont Doherty Earth Observatory (LDEO) high temperature/acceleration/pressure tool (TAP). This run was very successful, reaching a depth of 367.0 mbsf (~4 m above bottom). The next run was with the Formation MicroScanner (FMS) and dipole shear sonic imager (DSI) tool suite. A natural gamma ray tool (NGT) was included for calibrating between logging runs. This deployment was also very successful, reaching the same depth as the first run. During the second pass with the FMS-DSI, the tool would not pass a tight spot at ~174 mbsf. After 30 min of working the tool, a decision was made to log upward from the tight spot. Unfortunately, the tool was stuck at that point, requiring ~3500 lb overpull to free it. In looking at the FMS caliper log, it appeared that a fairly large portion of the hole (~75 m) had closed in significantlyin places to a diameter of ~4 in. Because it was not likely that the well seismic tool (WST) would pass this spot, the remainder of the wireline logging program was canceled for this hole. Opening up the hole with open-ended pipe was unlikely to be successful and would have put the drill string/bottom-hole assembly (BHA) at risk.
While the drill string was being recovered, several attempts were made to release the positioning beacon. Although it acknowledged the commands, on each occasion the beacon failed to release and was ultimately left on the seafloor. The pipe trip was completed when the mechanical bit release reached the rig floor at 1645 hr. The ship was immediately secured for transit, and at 1645 hr on 6 January 1999, we were under way for Site 1138.
Leg 183 Operations - Site 1138
Leg 183 Table of Contents