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The main purpose of shore-based log processing is to provide scientists with a comprehensive quality controlled downhole log data set. This data set can then be used for comparison and integration with core and seismic data from each ODP leg: the Sagan in-house software is used to put cores and logs on the same depth scale; and IESX software is used to analyze seismic sections and generate synthetic seismograms from the logs. Shore-based log processing comprises:
- Depth adjustments to remove depth offsets between data from different logging runs
- Corrections specific to certain tools and logs
- Documentation for the logs, with an assessment of log quality
- Conversion of the data to a widely accessible format (ASCII for the conventional logs, GIF for the FMS images and summary diagrams)
- Assembling the data for inclusion in the ODP Logging Services on-line and tape databases.
Log analysts at ODP Logging Services carry out the processing, mostly using Schlumberger GeoQuest’s "GeoFrame" software package. Conventional log data (natural gamma radioactivity, resistivity, density, porosity, sonic velocity, magnetic susceptibility logs) are transmitted via satellite from the ship, processed, and returned to the ship, usually within a week of logging. Processing of other log data (FMS images, GHMT magnetic polarities, etc.) is done after the cruise, either because the file sizes are too large to transmit via satellite, and/or the processing time is longer.
For details on the various types of processing, click on the appropriate link:
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