Wireline Standard Data Processing

Well name: 718E

Leg: 116

Location: Bengal Fan (central tropical S Indian Ocean)

Latitude: 1° 1.252' S

Longitude: 81° 24.065' E

Logging date: August, 1987

Bottom felt: 4730.2 mbrf (used for depth shift to sea floor)

Total penetration: 961.6 mbsf

Total core recovered: 9.9 m (34.8 %)

Logging Runs

Logging string 1: DIT/SDT/NGT

         No information available about use of wireline heave compensator.

 

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 and drill string and/or wireline stretch.

         DIT/SDT/NGT: bottom hole assembly at ~166 mbsf.

Processing

         Depth shift: No differential depth shift necessary as only one logging string was recorded. The original logs have been depth shifted to the sea floor (- 4741.6 m).

         Gamma-ray processing: Data have been processed to correct for borehole size and type of drilling fluid.

         Acoustic data processing: The array sonic tool was operated in standard depth-derived borehole compensated mode, including long-spacing (8-10-10-12') logs. The 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 generally appears in discrete core measurement files and also it 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.

         Due to telemetry problems the SFLU curve is invalid through the entire logged interval. Also, invalid acoustic data were recorded between 365 and 374 mbsf.

         Additional information about the logs can be found in the "Explanatory Notes" and Site Chapter, ODP IR volume 116.

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