High-quality compression of MWD signals

Measurement-While-Drilling (MWD) services efficiently support drilling decisions and they 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 (WT) 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 the current generation downhole equipment, without major modifications. This can also be achieved exploiting specialized hardware, lowering the computational requirements and synchronization issues of the downhole main controller.