Wireline Standard Data Processing

 

ODP logging contractor: LDEO-BRG

Well name: 655B

Leg: 107

Location: central Tyrrhenian Basin (Tyrrhenian Sea)

Latitude: 40° 11.32' N

Longitude: 12° 27.93' E

Logging date: February, 1986

Bottom felt: 3330.8 mbrf (used for depth shift to sea floor)

Total penetration: 196.1 mbsf

Total core recovered: 49.4 m (43 %)

 

Logging Runs

 

Logging string 1: DIT/LSS/GR

         Wireline heave compensator was not used to counter ship heave.

 

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/LSS/GR: Bottom-hole assembly at ~82 mbsf.

 

Processing

 

         Depth shift: No differential depth shift necessary as only one run was recorded. The data has been depth shifted to the sea floor (-3330.8).

 

         Acoustic data processing: The long-spacing (8-10-10-12') 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. Because of the very poor quality of the data in the 82-125 mbsf interval, no processing could be performed in this section.

 

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).

         During the processing, quality control of the data is mainly performed by cross-correlation of all logging 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 the 3-arm mechanical caliper device (MCD).

 

         Additional information about the logs can be found in the "Explanatory Notes" and Site Chapter, ODP IR volume 107. For further questions about the logs, please contact:

 

Cristina Broglia
Phone: 845-365-8343
Fax: 845-365-3182
E-mail: Cristina Broglia