ODP logging contractor: LDEO-BRG
Japan Trench (NW Pacific Ocean)
39°10.9145' N
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.


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