Wireline Standard Data Processing

ODP logging contractor: LDEO-BRG
Hole: 1149B
Leg: 185
Location: Nadezhda Basin (NW Pacific)
Latitude: 31° 20.5320' N
Longitude: 143° 21.0600' E
Logging date: June, 1999
Bottom felt: 5829.3 mbrf
Total penetration: 445.2 mbsf
Total core recovered: 36.72 m (12.9%)

Logging Runs

Logging string 1: DIT/APS/HLDS/HNGS
Logging string 2: GST/ACT/NGT (upper and lower sections)
Logging string 3: FMS/DSI/GPIT/NGT (1 pass, DSI not working)
Logging string 4: FMS/SDT/GPIT/NGT (2 passes: FMS working on first pass)

The wireline heave compensator was working for all logging runs.

Bottom-hole Assembly

The following bottom-hole assembly and pipe 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: Bottom-hole assembly at ~62 mbsf
GSTA/ACT/NGT: Bottom-hole assembly at ~68 mbsf (upper section).
GSTA/ACT/NGT: Bottom-hole assembly at ~159 mbsf (lower section).

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 (-5827 mbrf). This amount corresponds to the mudline depth as observed on the logs; it differs 2.3 m from the "bottom felt" depth given by the drillers (see above).

An interactive, graphical depth-match program was used to visually correlate the 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/HSGR) from the NGT/HNGS tool run on each logging string is used to correlate the logging runs. 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/DSI/GPIT/NGT and FMS/SDT/GPIT/NGT runs have been processed to correct for borehole size and type of drilling fluid. HNGS data were corrected for hole size during the recording.

Acoustic data processing: The sonic data were of moderately good quality between 248 mbsf and the base of the logs; anomalous spikes in the travel-time data were patched and the velocity record is reliable. Between 248 mbsf and the pipe, however, the sonic data are very noisy; the data have been patched as well as possible, but the resulting velocity log is not very reliable and should be used with caution.

High-resolution data: Neutron porosity data were recorded at a 5.08 cm sampling rate.

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.

The small amount of NGT/HNGS data recorded through the BHA should not be used for lithological interpretation, because of variable attenuation of the incoming signal.

Hole diameter was recorded by the calipers on the HLDS tool (LCAL) and FMS string (C1 and C2). The hole varies between 10 and 14 inches from the base of the logs up to 240 mbsf. The hole is very wide (>18 inches) over three intervals (BHS to 92 mbsf, 120 to 128 mbsf, and 170 to 180 mbsf). Swelling clays resulted in a very narrow hole (to <9 inches) between 128 and 160 mbsf, and prevented logging of the upper section with the FMS-Sonic tool strings.

APS (and probably HLDS) data are unreliable between the BHA and 160 mbsf, due to poor contact with the borehole wall, as indicated by anomalously high porosity readings.

As stated above, SDT Sonic data is very poor between 248 mbsf and the pipe.

Additional information about the logs can be found in the "Explanatory Notes" and Site Chapter, ODP IR Volume 185. For further questions about the logs, please contact:

Cristina Broglia
phone: 845-365-8343
fax: 845-365-3182
email: Cristina Broglia