Wireline Standard Data Processing

ODP logging contractor: LDEO-BRG

Well name: 791B

Leg: 126

Location: Sumisu Rift (NW Pacific)

Latitude: 30° 54.98' N

Longitude: 139° 52.19' E

Logging date: May, 1989

Bottom felt: 2279 mbrf (used for depth shift to sea floor)

Total penetration: 1145 mbsf

Total core recovered: 114.4 m (15.5 %)

Logging Runs

Logging string 1: ACT/GST/NGT

No information available about use of wireline heave compensator to counter ship heave.

Bottom-hole Assembly/Drill Pipe

The following bottom-hole assembly and drill pipe depth are as they appear on the logs after depth shift (see "Depth shift" section) 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 and drill string and/or wireline stretch.

     

ACT/GST/NGT: Bottom-hole assembly at ~712 mbsf; data recorded through bottom-hole assembly below this depth.

Processing

Depth shift: No differential depth shift was necessary, as only one logging pass was recorded. Original logs have been interactively depth shifted to the sea floor (- 2279 m).

 

Gamma-ray processing: NGT data have been processed to correct for borehole size and type of drilling fluid. Also, a linear shift has been applied to correct for the effect of the pipe and bottom hole assembly.

Quality Control

Null value=-999.25. This value may replace invalid recorded values or results.

     

Data recorded through pipe and bottom hole assembly such as those recorded at hole 791B suffer from attenuation on the incoming signal. and should be used qualitatively only.

Additional information about the logs can be found in the "Explanatory Notes" and Site Chapter, ODP IR volume 126.

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