The high telemetry data rates required by state-of-the-art downhole imaging tools have made real-time tool data compression desirable. This increases the effective telemetry data rate and decrease data storage requirements. A variety of lossless and lossy data compression techniques are available for possible logging applications.

Lossless variable-length-coding techniques are applied to different classes of well log data (i.e. dipmeter, density, imaging tools …) to determine the achievable compression ratios and feasibility for real-time processing. Compression ratios of ranging from 1.2:1 to 22:1 are achieved depending on the type of log data.

Lossy image compression techniques developed by the telecommunications industry for the transmission of high definition images over reduced bandwidth channels are adapted to provide real-time compression of imaging logs. The modified image compression algorithms are used to compress log images from a circumferential acoustic scanning tool. Circumferential Acoustic Scanning Tool images compressed by a factor of 20- to-1 were barely distinguishable from the original uncompressed images. Most of the important geologic features are still preserved when the images are compressed at ratios exceeding 80-to-1.

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