Siren Design and Evaluation in Mud Flow Loops and Wind Tunnels - Measurement While Drilling Signal Analysis, Optimization and Design - page 272

9.5.6 The way forward.
We have addressed important issues related, first, to mud siren hardware
design, and second, to telemetry optimization and evaluation. These issues
draw, respectively, on the constant density and compressible flow properties of
fluids, which are in turn studied using short and much longer wind tunnels.
Throughout this topic, we have justified new methods using physical arguments
and first principles, and then, extended our capabilities using mathematical and
numerical models where possible. In the next and final chapter, we integrate
many of the ideas introduced earlier to create a “technology roadmap” to 10
bits/sec for very deep wells. Comprehensive mud siren signal strength testing at
the China National Petroleum Corporation, e.g., see Figures 9.2a to 9.2h, point
to an unfortunate reality: pressure signals produced by conventional, single-siren
MWD tools have reached their technological limits because 'p's cannot be
significantly increased. Thus, every means must be employed to increase the
signal traveling up the drillpipe: constructive wave interference based on
reflection from the bit and also by employing sirens-in-series, use of lower
attenuation muds and larger diameter pipe if possible, introduction of highly
accurate multiple transducer echo cancellation and pump noise removal
schemes, novel transducer placement methods at the surface, application of
piezoelectric transducers, and so on. The mud pulse telemetry tool of the future
must be designed as a system where all components work together, reinforcing
strengths and eliminating weaknesses. The discussion presented next, of course,
represents a first (and not final) attempt at this challenging endeavor.