7.8.1 Business Purpose
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Well logs have been used in oil and gas operations for more than 100 years. Today, log data is captured digitally. But until about 1980, logs were recorded on paper. Because the life cycle of an oil field is long, “old logs” provide vital data for modern-day operations.
Paper logs are scanned and saved as a raster format (for example, a .TIF file format), which are converted to digital data—or digitized. However, accurate interpretation of the raster format requires additional processing and the resulting data.
A depth registration is performed that provides digital depth references on the raster log image. The results of the calibration are stored in another file, separate from the image, which is commonly known as the depth registration file. The primary role of the depth registration file is to match pixels from the well log image with depth pixels represented in the wellbore. This file acts as a vehicle for the storage, maintenance, and continuity of the raster image and its calibration for future use.
Understanding the data in these logs requires both the image file and the depth registration file. But in the course of business, problems arise and the files get separated (often resulting in someone calibrating the file again), then multiple versions of the file may exist and there is uncertainty on which is the correct version.
Additionally, various vendors offer depth calibration services—but each vendor’s depth calibration file had proprietary and incompatible formats.
For details of the supported use case, see 7.8.4 Use Case: Digitizing Depth-Registered Raster Well Logs