Standard Wireline Data Processing

ODP logging contractor: LDEO-BRG

Hole: 894G

Leg: 147

Location: Hess Deep Rift Valley (tropical NE Pacific)

Latitude: 2° 17.977' N

Longitude: 101° 31.555' W

Logging date: December, 1992

Bottom felt: 3034.4 mbrf (used for depth shift to sea floor)

Total penetration: 154.5 mbsf

Total core recovered: 45.8 m (35 %)

Logging Runs

Logging string 1: HLDT/SDT/NGT (no radioactive source on HLDT)

Logging string 2: FMS/GPIT/NGT (5 passes)

The wireline heave compensator was used to counter ship heave resulting from the mild/rough sea conditions.

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.

SDT/HLDT/NGT: Bottom-hole assembly at ~ 34 mbsf

FMS/GPIT/NGT: Bottom-hole assembly at ~ 4 mbsf.

Processing

Depth shift: No depth shift could be performed at this hole because of the lack of correlation among the gamma ray curves from the different runs. This is in part due to the very low gamma ray signature and to the high logging speed (a lower logging speed could have allowed for better statistics).

Gamma-ray processing: NGT data have been processed to correct for borehole size and type of drilling fluid. Because of the low signature and the poor statistics, the gamma ray data are questionable, particularly from the LSS/NGT/HLDT run, which was recorded at the highest logging speed. The gamma ray data from the FMS/GPIT/NGT pass 4 are believed to be the most reliable because of the lower logging speed and less sticking problems (as shown by the tension curve).

Acoustic data processing: Because of the extremely poor quality of the raw sonic logs (SDT in DDBHC Long-Spaced Mode), no processing has been performed at this stage.

 

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.

Hole diameter was recorded by the hydraulic caliper on the HLDT tool (CALI). Better measurements, however, were provided by the caliper 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 147.

For any question about the data or about the LogDB database, please contact LogDB support: logdb@ldeo.columbia.edu.