Measurement-While-Drilling telemetry background ...

High-data-rate MWD mud pulse telemetry, essential to high density logging resolution and drilling safety, remains an elusive goal in modern petroleum engineering. Without data compression, 1-2 bit/sec data rates or less are the rule in deep wells, with no end to the problem in sight.

For three decades, few papers have appeared worthy of scientific publication ... only the usual sermons about positive, negative and siren pulsers, high mud attenuation and generalities about multiple transducer signal processing, even in the patent literature. Discussions are not available on serious topics, e.g., wave reflections, erosion, or turbine and siren torque and power.

The developer, holding a Ph.D. from M.I.T. in wave propagation, served previously as Supervisor, MWD Telemetry, with Schlumberger, and Manager, MWD Fastalk at Halliburton, and earned more than forty patents in downhole tool design. Mr. Chin, who started his career at Boeing as Research Aerodynamicist, was first to pioneer short and long wind tunnel usage for turbine and siren design, and mud pulse telemetry optimization and signal processing, all innovative and exacting methods derived from first principles based on dynamic similarity.

Mr. Chin's patents include Schlumberger's well known unjammable "stable open, rotor downstream" low-torque siren and Halliburton's "signal enhancement by constructive wave interference," which produces additional amplitude without power or erosion penalties. His signal processing methods were first to employ wave-equation-based analysis, avoiding the confusing (and often incorrect) principles taught in recent patents.

Developing ideas into broad bodies of knowledge useful in real world application requires time, commitment, and the willingness of research partners to publish what is normally deemed proprietary. Stratamagnetic Software, LLC is pleased to announce just such an effort ... and we're "giving away" our results to stimulate oil industry development.

We'll share our findings with you right now.

Just what typical "wild and crazy" ideas are new to the industry?

• Pulser characterization. Industry papers describe positve and negative pulsers as "over-pressure" and "under-pressure" sources acting like piston-driven signal generators. Mud sirens, well, are a different beast.

  In practice, antisymmetric pressures are created about positive and siren pulsers, while symmetric ones develop at negative pulsers. Opposing signals propagate uphole and downhole, reflecting at the drillbit and at pipe-collar junctions (among others), introducing acoustic interactions that are important at high data rates or carrier frequencies. Downhole source properties are never discussed, yet they hold the key to viable high-data-rate systems.

• Controlling wave interactions. When phase-shift-keying (PSK) is used, "ghost phase-shifts" can be introduced by downhole reflections that are difficult to distinguish from the real thing at the surface (random phasing will also destroy parts of the signal by destructive interference). No amount of "multiple transducer signal processing" can unwrap the confusion created near the pulser unless, of course, one understood the physical process.

  These interactions can, however, be beneficially used ... we use constructive wave interference (together with a new telemetry scheme) to create additional signal amplitude without incurring power or erosion penalties. And to increase data rate, we locate our siren closer to the drillbit (with the turbine now at the top of the tool string) ... in contrast to (incorrect) conventional thinking that needlessly worries about (non-existent) signal trapping.

• Advanced acoustic models. Service company simulators use, at best, simple "method of characteristics" approaches to model signal propagation for job planning and tool design. Aside from ignoring source properties, almost all fail to treat impedance mismatches properly and all model the drillbit reflector incorrectly. We've introduced a "six segment acoustic waveguide" to model the complete drilling telemetry channel, and use analytical, closed form solutions (devoid of numerical truncation error, which introduce attenuation and phase errors) to guide our telemetry and signal processing designs.

  At the surface, conventional multiple transducer signal processing is based on "plain English recipes" and "gut feeling" addition and subtraction. We employ wave-equation-based descriptions that unambiguously show why several patented methods can't possibly work ... and have developed successful extraction methods that apply to signal-to-noise ratios as low as 5% in the presence of strong mudpump noise and reflection.

  Many long mud flow loops used in petroleum industry for MWD testing are simply that ... long. Almost all are designed with incorrect end boundary conditions, thus complicating signal processing applications and amplitude measurement. Even for "simple" attenuation modeling, true thermodynamic loss is never distinguished from the standing wave patterns, with their frequency-dependent nodes and antinodes, that contaminate data. In this sense, good mathematical models are really better than "real" flow loops.

• Proven test methods. Innovative methods were used by Mr. Chin to design Schlumberger's "stable-open, rotor-downstream" siren, Halliburton's "constructive wave interference signal amplification" method, and its downhole turbine, and so on (refer to Patents available on this site). At China National Petroleum Company (CNPC) in Beijing, we've gone much further and built a state-of-the-art MWD test facility that's arguably the world's best.

• Erosion modeling and analysis. Wind tunnels won't predict metal erosion rates, but for sirens, turbines, strainers, proppant transport tools, and so on, flow visualization using attached threads and soap bubble pattern mapping can identify good and bad trends using fast modeling clay fixes. We've fixed many tools and have movies and photographs to prove it (presentation available on request).

• Your standard out-of-box thinking. Constructive interference by wave phasing at the source, multiple pulsers in series, a new telemetry scheme, siren-turbine position reversal, wave-equation-based multiple transducer methods at the surface, transducers located at the mudpump ... put these together and what do you get? An integrated high-data-rate system you won't believe!

If you're a MWD company interested interested in improving your tool, e.g., reducing erosion or fixing mysterious signal losses at the surface, or a service company with downhole erosion problems, you need to talk to us now.

Research highlights ...

"High-Data-Rate Measurement-While-Drilling System for Very Deep Wells," Paper AADE-11-NTCE-74 recently presented at the 2011 AADE National Technical Conference and Exhibition in Houston during April 12-14 (sponsored by the American Association of Drilling Engineers) describes key elements of a multi-year collaboration between China National Petroleum Corporation (CNPC) in Beijing and Stratamagnetic Software, LLC.

CNPC's research program, in fact, was recently awarded high national honors, and forms part of China's next five year plan.

The photos below show different siren concepts tested in our "short wind tunnel" (for torque, stable-open, erosion and frequency-content analyses) and "long wind tunnel and mud flow loop" (for telemetry and signal processing design). Amazing?

Our "six segment acoustic waveguide" model simulates the drilling telemetry channel accurately, using analytical solutions (without numerical errors that introduce attenuation and phasing inaccuracies) ... we use it for downhole signal optimization through constructive wave interference and surface modeling.

Complementary surface signal processing methods, based on rigorous solutions to the wave equation, are able to extract high-data-rate signals from reflection and mudpump environments with signal-to-noise ratios as low as 5%.

Our paper shows that real data rates (without compression) up to 10 bits/sec are doable when the methods discussed are integrated in a top-down designed system ... not the usual "hardware first" approach.

Curious? Contact Stratamagnetic Software or wilsonchin@aol.com for a complimentary copy of the above paper. Better off, arrange your own in-house presentation today.

More, and it's almost free ...

While the 2011 AADE paper addresses high-data-rate system architecture, new acoustic modeling approaches, short and long wind tunnel test facilities, and the CNPC experimental test program, it does not cover the detailed mathematics developed to examine downhole and uphole signal processing issues.

Downhole wave interactions, and in fact, the complete acoustic wave field within the drilling telemetry channel, plus surface signal processing methods and multiple transducer analysis, are described in Chapters 1-7 in the new book MWD Signal Analysis, Optimization and Design offered by E&P Press (2011).

This monograph develops numerous models, provides theory, equations, solutions and validations ... and is central to a "signal processor breadboard" under present development. Source code access provides corporate clients with cost-effective enhancements and quick fixes to signal detection problems.

We're happy to make this work available to the petroleum industry (note that Chapters 8-10 on experimental test methods are available to clients only).

About the Author, click here. View Table of Contents now.

The definitive book MWD Signal Analysis, Optimization and Design, Chapters 1-7, is yours for $99 USD, plus $16 USD shipping and handling (total of $115 USD). Order directly from E&P Press at epPublishers@aol.com. Bulk discounts available.

Erosion modeling, your key to profitability ...

If you're running MWD or other downhole tools, drilling mud will erode more than metal ... it means losses to your bottom line. We've developed significant expertise in erosion analysis and remediation, correlating wind tunnel test results to actual erosion patterns for sirens, turbines, strainers, fracturing tools, and so on, that are not addressed in publications or in our book ... and, in all cases, we've developed fixes that have significantly increased lifespan.

For an in-house erosion presentation, with real case studies, photos and movies, contact the developer at wilsonchin@aol.com or directly at (832) 483-6899. Learn how you can control the uncontrollable ... it's the best investment you'll ever make.