Measurement While Drilling

Signal Analysis, Optimization and Design

Wilson C. Chin

• Publisher: Wiley-Scrivener
• Year: 2018
• Print ISBN: 9781119479154
• eBook ISBN: 9781119479321
• Edition: 2
• Topic: Physical Sciences
• Subtopic: Energy

Trade magazines and review articles describe MWD in casual terms, e.g., positive versus negative pulsers, continuous wave systems, drilling channel noise and attenuation, in very simple terms absent of technical rigor. However, few truly scientific discussions are available on existing methods, let alone the advances necessary for high-data-rate telemetry. Without a strong foundation building on solid acoustic principles, rigorous mathematics, and of course, fast, inexpensive and efficient testing of mechanical designs, low data rates will impose unacceptable quality issues to real-time formation evaluation for years to come.

This all-new revised second edition of an instant classic promises to change all of this. The lead author and M.I.T.-educated scientist, Wilson Chin, has written the only book available that develops mud pulse telemetry from first principles, adapting sound acoustic principles to rigorous signal processing and efficient wind tunnel testing. In fact, the methods and telemetry principles developed in the book were recently adopted by one of the world's largest industrial corporations in its mission to redefine the face of MWD.

The entire engineering history for continuous wave telemetry is covered: anecdotal stories and their fallacies, original hardware problems and their solutions, different noise mechanisms and their signal processing solutions, apparent paradoxes encountered in field tests and simple explanations to complicated questions, and so on, are discussed in complete "tell all" detail for students, research professors and professional engineers alike. These include signal processing algorithms, signal enhancement methods, and highly efficient "short" and "long wind tunnel" test methods, whose results can be dynamically re-scaled to real muds flowing at any speed. A must read for all petroleum engineering professionals!

Chapter 1
Stories from the Field, Fundamental Questions and Solutions

This chapter might aptly be entitled “Confessions of a confused, high-tech engineer.” And here’s why. In my previous reincarnation, I was Manager, Turbomachinery Design, at Pratt & Whitney Aircraft, United Technologies Corporation, the company that supplied the great majority of the world’s commercial jet engines. Prior to that, I had served as Research Aerodynamicist at Boeing, working with pioneers in computational fluid dynamics and advanced wing design. What qualified me for these enviable positions was a Ph.D. from the Massachusetts Institute of Technology in acoustic wave propagation – and I had joined a stodgy M.I.T. from its even stodgier cross-town rival, the California Institute of Technology. These credentials in acoustics and fluid mechanics design made me eminently qualified to advance the state-of-the-art in Measurement-While-Drilling (also known as, “MWD”) telemetry – or so I, and other companies, unknowingly thought. At this juncture in my life, a tumultuous journey through the Oil Patch begins.

1.1 Mysteries, Clues and Possibilities.

As a young man, I had dreaded the idea of forever making incremental improvements to aircraft systems, merely as a mainstay to the art of survival and paying the mortgage, sitting at the same desk, in the same building, for decades on end. That possibility, I believed, was a fate worse than death. Thus, in that defining year, I would answer a Schlumberger employment advertisement in The New York Times for scientists eager to change the world – the petroleum world, anyway. But unconvinced that any normal company would hire an inexperienced aerospace engineer, and of all things, for a position chartered with high-tech underground endeavors, I was unwilling to give up one of my ten valuable, hard-earned vacation days for a job interview doomed to fail. Still, the company was stubborn in its pursuit and, for better or worse, kindly accommodated my needs.

Carl Buchholz, the division president at the time, interviewed me that one fateful Saturday. “What do you know about oil?” he bluntly asked, giving me that honest Texan look in the eye. To be truthful, I did not know anything, zilch. “Nothing, but I’ve watched Jed Clampett shoot it out of the ground,” I confessed (Clampett was the hillbilly in the television sitcom who blasted his rifle into the ground, struck oil and moved to Los Angeles to settle in his new mansion in “The Beverly Hillbillies”). Buchholz broke out in uncontrolled laughter. That type of honesty he appreciated. I got the job. And with that, I became Schlumberger’s Supervisor, MWD Telemetry, for 2^nd generation mud siren and turbine design.

The company’s Analysts division, at the time responsible for an ambitious next-generation, high-data-rate MWD design program, had built ultra-modern office and flow loop facilities in southwest Houston. The metal pipe test section was housed in an air-conditioned room where engineers could work in a clean and comfortable environment away from the pulsations of the indoor mudpump that supplied our flow. A small section of the flow loop was accessible in this laboratory with the main plumbing carefully hidden behind a wall – details no self-respecting, white-collar Ph.D. cared for nor admitted an interest to.

My charter was simple. We were transmitting at 3 bits/sec in holes shallow by today’s standards with a 12 Hz carrier frequency. Our objective was N bits/sec, where N >> 3 (the value of N is proprietary). The solution seemed straightforward, as company managers and university experts would have it. Simply “crank up the carrier to (N/3) × 12 Hz and run.” I did that. But my transducers would measure only confusion, with new pressure oscillations randomly adding to old ones and results depending on mud type, pump speed and time of day. What happened “behind the wall” controlled what we observed but we were too naïve to know. Anecdotal stories told by different field hands about new prototypes were confusing and contradictory. One simply did not know what to believe. Thirty years later, the data rate is still comparable, a bit better under ideal conditions, as it was then. Clearly, there were physical principles that we did not, or perhaps were never meant to, fully comprehend.

Fast-forward to 1992 at Halliburton Energy Services, an eternity later, where I had been hired as Manager, FasTalk MWD. Again, mass confusion prevailed. Some field engineers had reported excellent telemetry results in certain holes, while others had reported poor performance under seemingly identical conditions. The company had acquired several small companies during that reign of corporate acquisitions in the oil service industry. It would turn out that “good versus bad” depended, with all other variables constant, on whether the signal valve was a “positive” or a “negative” pulser. No one really distinguished between the two: because the MWD valve was simply viewed as a piston located at the end of the drillpipe, exciting the drilling fluid column residing immediately above, it didn’t matter if it was pushing or pulling.

Sirens were a different animal; no one, except Schlumberger, it seemed, understood them. But nobody really did. Additional dependencies on drilling conditions only added to the confusion. Industry consensus at the time held that MWD telemetry characteristics depended on drillbit type and nozzle size and, perhaps, rock properties, to some extent. It also appeared that whether or not the drillbit was off-bottom mattered. Very often, common sense dictated that the drillbit acted as a solid reflector, since nozzle cross-sectional areas were “pretty small” compared to pipe dimensions. Yet, this line of reasoning was contradictory and had its flaws; strong MWD signals by then had been routinely detected in the borehole annulus, where their existence or lack of was used to infer gas influx. It became clear that what the human eye visually perceived as small may not be small from a propagating wave’s perspective.

Lack of controlled experiments also pervaded the industry and still does. Whenever any service company design team was lucky enough to find a test well, courtesy of obliging operating company customers, engineering “control” usually meant installing the same pressure transducer in the same position on the standpipe. New tools that were tested in one field situation would perform completely differently in others: standpipe measurements had lives of their own, it seemed, except at very low data rates of 1 bit/sec or less, barring mechanical tool failure, which was often. Details related to surface plumbing, bottomhole assembly, bit-box geometry, drilling motor details and annular dimensions, were not recorded and were routinely ignored. The simple “piston at the end of pipe model” didn’t care – and neither did most engineers and design teams.

By the mid-1990s, the fact that higher data rate signaling just might depend on wave propagation dawned upon industry practitioners. This revelation arose in part from wave-equation-based seismics – new then, not quite understood, but successful. I began to view my confusion as a source of inspiration. The changing patterns of crests and troughs I had measured had to represent waves – waves whose properties had to depend on mud sound speed and flow loop geometry. At Halliburton, I would obtain patents teaching how to optimize signals by taking advantage of wave propagation, e.g., signal strength increase by downhole constructive wave interference (without incurring erosion and power penalties), multiple transducer array signal processing to filter unwanted signals based on direction and not frequency, and others.

Still, the future of mud pulse telemetry was uncertain, confronting an unknowing fate – a technology held hostage by still more uncontrolled experiments and their ...

Table of contents

• Cover
• Title page
• Copyright page
• Preface
• Acknowledgements
• Chapter 1: Stories from the Field, Fundamental Questions and Solutions
• Chapter 2: Harmonic Analysis: Six-Segment Downhole Acoustic Waveguide
• Chapter 3: Harmonic Analysis: Elementary Pipe and Collar Models
• Chapter 4: Transient Constant Area Surface and Downhole Wave Models
• Chapter 5: Transient Variable Area Downhole Inverse Models
• Chapter 6: Signal Processor Design and Additional Noise Models
• Chapter 7: Mud Siren Torque and Erosion Analysis
• Chapter 8: Downhole Turbine Design and Short Wind Tunnel Testing
• Chapter 9: Siren Design and Evaluation in Mud Flow Loops and Wind Tunnels
• Chapter 10: Advanced System Summary and Modern MWD Developments
• Chapter 11: MWD Signal Processing in China
• Chapter 12: Sensor Developments in China
• Chapter 13: Sinopec MWD Research
• Chapter 14: Gyrodata MWD Research
• Chapter 15: GE Oil & Gas MWD Developments (BakerHughes, a GE Company)
• Chapter 16: MWD Turbosiren – Principles, Design and Development
• Chapter 17: Design of Miniature Sirens
• Chapter 18: Wave-Based Directional Filtering
• Cumulative References
• Index
• About the Author
• Wiley End User License Agreement