Measurement While Drilling, 2nd Edition

Chapter 10Advanced System Summary and Modern MWD Developments

In this summary chapter on Measurement-While-Drilling analysis and design, we recapitulate the basic elements of a hypothetical high-data-rate MWD system which embodies the ideas in this book and the author’s field and modeling experiences. Our exposition applies key telemetry and acoustics concepts which are also useful in other possible prototypes and highlights the pitfalls and fallacies behind commonly accepted engineering design rules-of-thumb. The remainder of this book reviews practical advances that have been made by different groups of industry researchers.

At the present time, several MWD service companies provide mud pulse logging worldwide. Three largely operate in the 1 bit/sec (or less) range, one operates siren tools at 3-6 bits/sec (bps), possibly faster, and the last, in recent product literature related to siren-like pulsers, claims extraordinarily data rates. The exact specifications in all cases are not well documented, that is, technical details related to mud type, borehole depth and environment are not available, but the high data rate at least points to mechanical capabilities which we believe, importantly, are nowhere near present technology limits.

Can we do better? Yes. And just what is required to send and receive signals over large distances successfully at high rates? Three key factors apply: strong amplitudes, high frequencies and low torque. First, the acoustic signal should be large ...