ODP logging contractor: LDEO-BRG
Hole: 1150B
Leg: 186
Location: Japan Trench (NW Pacific
Ocean)
Latitude: 39°10.9145' N
Longitude: 143°19.9470' E
Logging date: July, 1999
Bottom felt: 2692 mbrf (used for
depth shift to sea floor)
Total penetration: 1181.6 mbsf
Total core recovered: 269.39 m (56.32
%)
Logging
Runs
Logging string 1: DIT/APS/HLDS/HNGS (upper
section)
Logging string 2: FMS/GPIT/DSI/NGT (upper section)
Logging string 3: DIT/APS/HLDS/HNGS (lower section)
Logging string 4: FMS/SDT/GPIT/NGT (lower section)
Logging string 5: BHTV/GPIT/NGT (lower section)
Wireline heave compensator was used to
counter ship heave.
Bottom-hole
Assembly
The following bottom-hole assembly depths are
as they appear on the logs after differential depth shift (see "Depth shift"
section) and depth shift to the sea floor. As such, there might be a
discrepancy with the original depths given by the drillers onboard. Possible
reasons for depth discrepancies are ship heave, use of wireline heave
compensator, and drill string and/or wireline stretch.
DIT/APS/HLDS/HNGS (upper section):
Bottom-hole assembly at 112.5 mbsf
DIT/APS/HLDS/HNGS (lower section): Bottom-hole assembly at 744.5 mbsf
FMS/GPIT/DSI/NGT (upper section): Recorded open hole.
FMS/GPIT/SDT/NGT (lower section): Bottom-hole assembly at 744.5 mbsf.
Processing
Depth shift: The original logs have been interactively
depth-shifted with reference to HNGS from DIT/APS/HLDS/HNGS run and to the sea
floor (-2692 m). This amount corresponds to the mudline depth as observed on
the logs; in this case the same as the "bottom felt" depth given by
the drillers (see above). The program used is an interactive, graphical
depth-match program, which allows to visually correlate logs and to define
appropriate shifts. The reference and match channels are displayed on the
screen, with vectors connecting old (reference curve) and new (match curve)
shift depths. The total gamma ray curve (SGR) from the NGT tool run on each
logging string is used to correlate the logging runs most often. In general, the
reference curve is chosen on the basis of constant, low cable tension and high
cable speed (tools run at faster speeds are less likely to stick and are less
susceptible to data degradation caused by ship heave). Other factors, however,
such as the length of the logged interval, the presence of drill pipe, and the
statistical quality of the collected data (better statistics are obtained at
lower logging speeds) are also considered in the selection. A list of the
amount of differential depth shifts applied at this hole is available upon
request.
Gamma-ray processing: NGT data from the FMS/GPIT/DSI/NGT and
FMS/GPIT/SDT/NGT runs have been processed to correct for borehole size and type
of drilling fluid. The HNGS data were corrected for hole size during the recording.
Acoustic data processing: The DSI data were re-processed onboard to give a valid
DTCO (compressional wave slowness). The SDT recorded good data in DDBHC long-spacing mode, with only a few small spikes in the DTLN and DTLF
slownesses that were edited onshore. The slownesses were then converted to
velocities.
High-resolution data: Neutron porosity data were recorded at a sampling
rate of 5.08 cm.
Quality
Control
null value=-999.25. This value may replace
invalid log values or results.
Large (>12") and/or irregular
borehole affects most recordings, particularly those that require
eccentralization (APS, HLDS) and a good contact with the borehole wall. Hole
deviation can also affect the data negatively; the FMS, for example, is not
designed to be run in holes deviated more than 10 degrees, as the tool weight
might cause the caliper to close. Hole deviation at this hole was about 5
degrees.
Above 357 mbsf, the hole was severely washed
out to 18 inches or larger; much of the APS data is of bad quality. From 357
mbsf to the obstruction at 643 mbsf, the hole is generally between 10 and 14
inches wide, with a great deal of rugosity; about 25% of the APS data in this
interval is badly affected by standoff. In the lower section, the hole is oval
in shape, generally 10 inches in the short axis, and 14 in the long, with a
great deal of rugosity; APS and HLDS logs in this lower section are good apart
from a few abrupt and deep washouts.
Additional information about the logs can be
found in the "Explanatory Notes" and Site Chapter, ODP IR volume 186.
For further questions about the logs, please contact:
Trevor Williams
Phone: 845-365-8626
Fax: 845-365-3182
E-mail: Trevor Williams
Cristina Broglia
Phone: 845-365-8343
Fax: 845-365-3182
E-mail: Cristina Broglia