When I first joined the petroleum industry more than two decades ago, my exposure to field operations, or just about anything "oily," was minimal or next to nothing. My supervisor at Schlumberger, Larry Leising, would preach incessantly about the need for "hole cleaning," something that I, an M.I.T. Ph.D. firmly grounded in applied math, should focus on. Something important. Something that those new-fangled horizontal wells on the horizon died for. But no, that was impossible. My parents, who’d never made in past elementary school in China, I said, "paid good money" to send me to college. So explaining why I’m sitting next to a "rathole" or "dog house" on a drilling rig in the middle of nowhere cleaning holes would not go well with them. Or with my worthy ancestors. And so, annular flow and drilling safety would have to wait.

Some years later, I’d hear more "dirty stuff" about dirty stuff. Why mudcake was "bad" and responsible for differential sticking. Stuck drillstrings. Lost tools. Fishing jobs. Unimpressive things responsible for impressive hundreds of millions in damage each year. As for hole cleaning and cuttings transport, mudcake catastrophes were likewise "solved" by empirical "common sense" methods seemingly pulled from thin air. No one understood why they worked. Or why they probably didn’t. War stories proliferated in trade journals and at conferences. And then there were well logging folks running "formation testers." Petrophysicists who curiously wanted good thick mudcakes. Cakes that would seal their pads well and enable the extraction of clean fluid samples. Thick ones that reduced invasion at the sandface so that pore pressure measurements actually measured formation (and not high borehole) values.

Like hole cleaning, what worked was anyone’s guess. No one really knew why mudcakes grew "like Öt." They just did, it seemed. But they really didn’t. Many drillers believed that formation type didn’t matter. But log analysts argued that formation permeabilities did. In fact, at really low mobilities, they could control the physics and dangerously reduce cake thickness. Along with pore pressure, of course. And pore pressure? In tight zones, such as those encountered in today’s unconventional applications, you couldn’t even measure pore pressure without waiting hours! So, one might ask, now what? What are our alternatives? What can we really solve as a hard-pressed industry?

Those who have read the author’s books over the years will appreciate that substantial personal efforts have been directed at annular flow modeling, cuttings transport, hole cleaning and pressure control. And that mudcake dynamics, and pore pressure and permeability prediction in tight formations, have also been the focus of extensive work in formation testing and real-time formation evaluation. And similarly with multiphase reservoir flow and mixing near to the wellbore. We’ve worked hard at many disciplines. A brief narrative of chronological developments appears in Chapter 1 in support of Chapters 2-8.

But it was not until the aftermath of the Deepwater Horizon incident that the underlying ideas for the present book developed. The author, at the time, served as Expert Witness in the Macondo litigation – an eye-opening event clearly highlighting the necessity for credible models of physical phenomena in support of operational safety. And it was during these activities that one key realization developed: that basic elements involving annular flow and pressure control, mudcake growth and dynamic coupling to the formation, and finally, permeability and pore pressure prediction in the reservoir, can be combined to provide an integrated software system for realistic well planning. One dictating how borehole flows are affected by mudcake and reservoir events, how annular flows can be manipulated, how mudcake growth can be controlled, and finally, how (once) elusive properties like permeability and pore pressure in tight reservoirs can be measured rapidly, economically and safely.

This objective forms the basis for the present book, appropriately entitled Modern Borehole Analytics for Annular Flow, Hole Cleaning and Pressure Control. But unlike the author’s previous works which emphasized mathematics, algorithms and physical validations, this volume builds upon prior work and focuses on applications and software models that are available for immediate industry use. Very few equations this time, just the facts. And so, the journey comes full circle . . . from utter initial confusion to, hopefully, something practical, useful and significant.

Wilson C. Chin, Ph.D., M.I.T.

Houston, Texas and Beijing, China Email:

Phone: (832) 483-6899


    1. Acknowledgements

This book is dedicated to Larry. Larry Leising, that is, fellow M.I.T. graduate and Schlumberger colleague who talked me into parting from a glamorous aerospace industry for petroleum endeavors unknown. His early insights on hole cleaning, horizontal wells and MWD telemetry, combined with practical experiences that he shared, made a significant difference in my research interests and modeling approaches over the years. Larry was forever helpful. At the time, I recall, "mud sirens" in MWD always jammed and downhole debris was blamed. I suggested simpler wind tunnel test methods to explore some "wild and crazy" ideas. Maybe jamming was a purely hydrodynamic effect. Maybe. Being the theoretician that I was then, I didn’t know the difference between a squirrel cage blower and a ceiling fan. Larry was instrumental in building our wind tunnel, in developing our test methods, and in the important discovery of the "downstream rotor, stable open" mud sirens now in routine use – a game-changing invention he rightfully shares but never took credit for.

As usual, the author is indebted to Phil Carmical, Acquisitions Editor and Publisher, for his support and encouragement in disseminating his highly technical research monographs, together with equations, cryptic Greek symbols, formal algorithms and more. Our fruitful collaboration goes back some twenty years, first with annular flow modeling, then with reservoir engineering, horizontal drilling, formation testing, Measurement While Drilling and other disciplines. Phil and I share one common goal – we approach real world problems with the best scientific tools available and turn over each and every stone. In times of uncertainty, such as the economic turmoil now facing all of us, it is even more important to "solve problems right" and work more productively. What our industry needs is more math and not less, more questioning and less acceptance, and it is through this latest volume that we hope to stimulate thought and continuing research in engineering endeavors central to the modern exploration for oil and gas.