Wireline Standard Data Processing
ODP logging contractor: LDEO-BRG
Well name: 638B
Location: Galicia Bank (NE Atlantic)
Latitude: 42° 9.2' N
Longitude: 12° 11.8' W
Logging date: May, 1985
Bottom felt: 4673 mbrf (used for depth shift to sea floor)
Total penetration: 431.1 mbsf
Total core recovered: 210.5 m (49 %)
Logging string 1: DIT/LSS/GR
Logging string 2: Multichannel Sonic Tool
Wireline heave compensator was not used to counter ship heave (0.3-0.9 m).
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, lack of wireline heave compensator, and drill string and/or wireline stretch.
DIT/LSS/GR: Bottom-hole assembly at ~99 mbsf.
Depth shift: Because only one run was recorded, no differential depth shift was required. The original logs have been depth shifted to the sea floor (- 4673 m).
Acoustic data processing: The long-spacing sonic logs have been processed to eliminate some of the noise and cycle skipping experienced during the recording. Using two sets of the four transit time measurements and proper depth justification, four independent measurements over a -2ft interval centered on the depth of interest are determined, each based on the difference between a pair of transmitters and receivers. The program discards any transit time that is negative or falls outside a range of meaningful values selected by the processor.
null value=-999.25. This value may replace recorded log values or results which are considered invalid (ex. processed sonic data).
Data recorded through bottom-hole assembly should be used qualitatively only because of the attenuation on the incoming signal.
Hole diameter was recorded by 3-arm mechanical caliper device.
Additional information about the logs can be found in the "Explanatory Notes" and Site Chapter, ODP IR volume 103. For further questions about the logs, please contact:
E-mail: Cristina Broglia