Wireline Standard Data Processing

ODP logging contractor: LDEO-BRG

Well name: 739C

Leg: 119

Location: Prydz Bay (Antarctic Ocean)

Latitude: 67° 16.57' S

Longitude: 75° 4.91' E

Logging date: January, 1988

Bottom felt: 422.9 mbrf

Total penetration: 486.8 mbsf

Total core recovered: 168.5 m (34 %)

Logging Runs

Logging string 1: DIT/LSS/GR (2 sections)

         The wireline heave compensator was not used to counter ship heave.

Bottom-hole Assembly

         The logs show the bottom-hole assembly at ~25 mbsf. Any discrepancy with the original depth given by the drillers onboard may be due to ship heave and drill string and/or wireline stretch.

Processing

         Depth shift: No depth shift necessary. The original logs have been depth shifted to the sea floor (- 422.5 m). This amount differs 0.4 m from the "bottom felt" depth given by the drillers.

 

         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.

 

Quality Control

         Null value=-999.25. This value may replace recorded log values or results which are considered invalid (ex. processed sonic data).

         During the processing, quality control of the data is mainly performed by cross-correlation of all logging data. The data recorded in Hole 739C is generally of good quality.

         Data recorded through bottom-hole assembly should be used qualitatively only because of the attenuation on the incoming signal.

         Hole diameter was recorded by the 3-arm mechanical caliper device (MCD).

         The data from the three sections has been merged as follows:

gamma ray: merged at 80 and 250 mbsf

resistivity: merged at 90 and 250 mbsf

caliper: merged at 80 and 250 mbsf

sonic: merged at 74 and 254 mbsf

spontaneous potential: merged at 91.5 and 270 mbsf.

         Additional information about the logs can be found in the "Explanatory Notes" and Site Chapter, ODP IR volume 119.

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