ODP logging contractor: LDEO-BRG
Hole: 1151D
Leg: 186
Location: Japan Trench (NW Pacific Ocean)
Latitude: 38°45.0138' N
Longitude: 143°20.0441' E
Logging date: August, 1999
Bottom felt: 2184 mbrf
Total penetration: 874 mbsf
Total core recovered: 96.19 m (103.43%)

Logging Runs

Logging string 1: FMS/GPIT/SDT/NGT (2 passes)
Logging string 2: DIT/APS/HLDS/HNGS (main pass and a short repeat pass)

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.

FMS/GPIT/SDT/NGT: Recorded open-hole (pass 1)
FMS/GPIT/SDT/NGT: Bottom-hole assembly at 104.5 mbsf (pass 2)
DIT/APS/HLDS/HNGS: Bottom-hole assembly at 105 mbsf.

Processing

Depth shift: Original logs have been interactively depth shifted with reference to HSGR log from the DIT/APS/HLDS/HNGS tool string and to the sea floor (-2182 m). ). This amount corresponds to the mudline depth as observed on the logs; in this case it differs 2 meters from 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 (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/SDT/NGT has been processed to correct for borehole size and type of drilling fluid. The HNGS data from DIT/HLDS/APS/HNGS was corrected for hole size during the recording.

Acoustic data processing: The acoustic data were recorded with the SDT in DDBHC long-spacing mode. Minor spikes were removed from the DTLN and DTLF slowness logs of both passes, and the compressional wave velocity logs (VP1 and VP2, respectively) were calculated.

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 recorded log values or results which are considered invalid. 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 105 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).

Hole conditions were very good. Between 270 mbsf and the base of the hole, the hole was in gauge at about 11.5 inches, with some very minor washouts at 9.5 m intervals maybe from where the BHA halted during drilling. Above 270 mbsf, the hole becomes more oval in shape, the short axis remaining in gauge and the long axis varying between 13 and 16 inches.

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