Wireline Standard Data Processing
ODP logging contractor: LDEO-BRG
Hole: 1171D
Leg: 189
Location: South Tasman Rise (Tasman
Sea)
Latitude: 48° 29.9975' S
Longitude: 149° 6.7222' E
Logging date: April, 2000
Bottom felt: 2159 mbrf
Total penetration: 958.8 mbsf
Total core recovered: 525.40 m (73.9
%)
Logging
Runs
Logging string 1: DIT/APS/HLDS/HNGS
The DIT/APS/HLDS/HNGS tool string reached the
bottom of the hole without problem, and recorded good logs. A malfunction of
the head tension gauge on the GHMT tool string as it was being lowered down the
hole, combined with the tool string landing on a bridge, caused the logging
cable to over-spool and kink. The kinked cable had to be cut. On lowering the
pipe to clear the bridge, the end of pipe deviated from the borehole and became
plugged. Significant over pull was required to remove the pipe, and logging
operations at Hole 1171D were terminated.
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 and drill string and/or wireline
stretch.
DIT/APS/HLDS/HNGS: Bottom-hole assembly at
151 mbsf
Processing
Depth shift: The original logs were shifted to the sea floor
(-2159 m). The sea floor depth is determined by the step in gamma ray values at
the sediment-water interface. It coincides with the "bottom felt"
depth given by the drillers (see above).
Gamma-ray processing: The HNGS data were corrected for hole size during the
recording.
High-resolution data: Bulk density and neutron porosity data were recorded
at a sampling rate of 2.54 and 5.08 cm respectively. The enhanced bulk density
curve is the result of Schlumberger enhanced processing technique performed on
the MAXIS system onboard. While in normal processing short-spacing data is
smoothed to match the long-spacing one, in enhanced processing this is
reversed. In a situation where there is good contact between the HLDS pad and
the borehole wall (low density correction) the results are improved, because
the short-spacing has better vertical resolution.
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. In
general, Hole 1171D was fairly smooth, with borehole diameter ranging from 11
to 14 inches. Above 250 m, the hole is washed out beyond the maximum extent of
the caliper arm (19 inches).
The SFLU resistivity log contains anomalous
spikes from 298 and 307 mbsf.
The wireline heave compensator stopped at
certain intervals during logging, because of excessive ship heave. Depth
control is degraded in these intervals (813-840, 851-881, 916-934 mbsf)
Data recorded through bottom-hole assembly,
such as the gamma ray data, should be used qualitatively only because of the
attenuation on the incoming signal.
Hole diameter was recorded by the hydraulic
caliper on the HLDS tool (LCAL).
Additional information about the logs can be
found in the "Explanatory Notes" and Site Chapter, ODP IR volume 189.
For further questions about the logs, please contact:
Cristina Broglia
Phone: 845-365-8343
Fax: 845-365-3182
E-mail: Cristina Broglia