ODP logging contractor: LDEO-BRG
Hole: 1137A
Leg: 183
Location: Kerguelen Plateau
(Antarctic Ocean)
Latitude: 56° 49.9832' S
Longitude: 68° 5.6057' E
Logging date: January, 1999
Bottom felt: 1016 mbrf (used for
depth shift to sea floor)
Total penetration: 371.2 mbsf
Total core recovered: 219.3 m
(59.1 %)
Logging
Runs
Logging string 1: DLL/APS/HLDS/HNGS
Logging string 2: FMS/GPIT/DSI/NGT
Wireline heave compensator was used during both passes 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.
DLL/APS/HLDS/HNGS: Bottom-hole assembly at 80 mbsf
FMS/GPIT/DSI/NGT: Bottom-hole assembly at 80 mbsf.
Processing
Depth shift: Original logs have been interactively depth shifted
with reference to NGT from DLL/APS/HLDS/HNGS and to the sea floor (- 1016 m).
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
(HSGR or SGR) from the HNGS or 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 is 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 FMS/GPIT/DSI/NGT has been processed to correct for borehole size and type
of drilling fluid. The HNGS data from DLL/HLDS/APS/HNGS was corrected for hole
size during the recording.
Acoustic data processing: The
acoustic data were recorded with the Dipole Sonic Imager (DSI). The DSI
recorded lower-dipole and P&S-wave. Velocity has been computed from the
delay times.
High-resolution data: Neutron
porosity data were recorded at a sampling rate of 5.08 cm.
Quality
Control
null value=-999.25. This value generally
appears in discrete core measurement files and also it may replace recorded log
values or results which are considered invalid (ex. processed sonic data).
During the processing, quality control of the data is mainly performed by
cross-correlation of all logging data. 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.
Data recorded through bottom-hole assembly, such as the HNGS data above 80
mbsf, 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) and
on the FMS string (C1 and C2).
Additional information about the logs can be found in the "Explanatory
Notes" and Site Chapter, ODP IR volume 183. For further questions about
the logs, please contact:
Cristina Broglia
Phone: 845-365-8343
Fax: 845-365-3182
E-mail: Cristina Broglia