High Data Rate Measurement-While-Drilling (MWD) Telemetry

Wilson Chin, President and Founder, Stratamagnetic Software, LLC

In early vertical well drilling, high-data-rate logging was achieved using wireline instruments lowered into the hole.  Accurate math simulations facilitated operations, e.g., concentric rheology models supported borehole cleaning while axisymmetric resistivity, sonic and pressure transient analyses provided detailed formation evaluation information.  Modern wells, however, are long and horizontal, with highly eccentric annular geometries.  Because wireline logging is no longer possible, MWD “mud pulse telemetry” is used to transmit real-time drilling and well log data via acoustic pulses through the mud column to the surface.  Unfortunately, because of very low data rates near 1 bit/sec, economic and drilling safety risks are the rule, problems which are compounded by well log interpretation and hole cleaning uncertainties.

This talk reviews MWD state-of-the-art, presents new hardware and telemetry design architectures, plus innovative “short and long wind tunnel” test methodologies, aimed at increasing data rates ten-fold in deep hostile wells while reducing severe tool erosion.  The research, partly supported by China National Petroleum Corporation (CNPC), addresses both new signal processing and downhole tool design approaches.  Key physical concepts, hardware prototypes and experimental facilities are introduced and described in detail.  Comprehensive (wave equation based) signal processing methods, due to time constraints, are not covered but are briefly described, although they are available in detail in book form.  Further MWD and related well logging and drilling researches, suitable at both undergraduate and graduate levels, are suggested, based on the speaker’s assessment of the petroleum industry’s immediate needs and long-term interests.