High-quality compression of MWD signals

Measurement-while-drilling (MWD) services efficiently support drilling decisions and are emerging as a powerful option on well sites. Presently, the main drawbacks of MWD equipment are the low data bandwidth of standard telemetry systems (up to 10 bits/s), and the high cost of storage memory in the downhole tool. Both these limitations can be reduced using data compression. We investigate the application of a lossy compression algorithm based on the wavelet transform to data recorded downhole while drilling. The user can select the maximum level of noise in the reconstructed signal; the compression ratio is adapted automatically. Numerical tests based on real field data achieve compression ratios up to 15:1 without noticeable signal degradation. This allows a significant increase in downhole acquisition time and in real-time information transmission rate through the telemetry system. We present signal-quality indicators to analyze the performance of the compression. The algorithm is simple enough to be embedded in current-generation downhole equipment without major modifications. This implementation can also be achieved using specialized hardware, lowering the computational requirements and synchronization issues of the downhole main controller.