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Journal of Energy and Power Technology

(ISSN 2690-1692)

Journal of Energy and Power Technology (JEPT) is an international peer-reviewed Open Access journal published quarterly online by LIDSEN Publishing Inc. This periodical is dedicated to providing a unique, peer-reviewed, multi-disciplinary platform for researchers, scientists and engineers in academia, research institutions, government agencies and industry. The journal is also of interest to technology developers, planners, policy makers and technical, economic and policy advisers to present their research results and findings.

Journal of Energy and Power Technology focuses on all aspects of energy and power. It publishes not only original research and review articles, but also various other types of articles from experts in these fields, such as Communication, Opinion, Comment, Conference Report, Technical Note, Book Review, and more, to promote intuitive understanding of the state-of-the-art and technology trends.

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Publication Speed (median values for papers published in 2024): Submission to First Decision: 6.6 weeks; Submission to Acceptance: 11.7 weeks; Acceptance to Publication: 7 days (1-2 days of FREE language polishing included)

Current Issue: 2025  Archive: 2024 2023 2022 2021 2020 2019
Open Access Original Research

High Data Rate MWD Mud Pulse Telemetry – From Mysteries to Discovery

Wilson C. Chin *, Xiaoying Zhuang , Jamie A. Chin

  1. Stratamagnetic Software, LLC, Houston, Texas, USA

* Correspondence: Wilson C. Chin

Academic Editor: Grigorios L. Kyriakopoulos

Received: September 07, 2024 | Accepted: November 26, 2024 | Published: December 06, 2024

Journal of Energy and Power Technology 2024, Volume 6, Issue 4, doi:10.21926/jept.2404023

Recommended citation: Chin WC, Zhuang X, Chin JA. High Data Rate MWD Mud Pulse Telemetry – From Mysteries to Discovery. Journal of Energy and Power Technology 2024; 6(4): 023; doi:10.21926/jept.2404023.

© 2024 by the authors. This is an open access article distributed under the conditions of the Creative Commons by Attribution License, which permits unrestricted use, distribution, and reproduction in any medium or format, provided the original work is correctly cited.

Abstract

Our new approach to MWD mud pulse telemetry offers significant increases over conventional data rates. Using waveguide acoustics, we show that common drilling communications channels support carrier frequencies exceeding several hundred Hertz. Such signals are prone to attenuation over large drill pipe distances. Low power, self-spinning “turbosirens” are designed, providing high torque and rotation rate performance at all flow rates without electric or hydraulic motor drives. The sirens rotate, drawing only on the kinetic energy of the mud, like flapping flags oscillating in wind. Our turbosirens are minimally affected by LCM jamming. Turbine and siren rotor components ride freely along longitudinal trenches built into rotating shafts. Both magically float into the oncoming mud as it slows down, thus, widening all gap spaces and freeing any trapped debris even as both travel opposite to the mud flow. In addition, “turbosirens in series” signal superposition, drawing on constructive wave interference, offers strong pressure signals at high frequencies without mechanical complexity. Rapid modulations are possible, also without motor drive, relying on rapidly acting electro-magneto rheological brakes powered by turbosirens. To take advantage of hardware capabilities, “Intelligent i FSK” telemetry, or Frequency Shift Keying creates clean signals without the ambiguous wave reflections found with PSK and randomized time shifts. Frequency pairs are not selected arbitrarily, but chosen from “neighboring pressure peaks and valleys” in frequency space as determined from bottomhole assembly waveguide Fourier analysis. Finally, surface signal processing and reflection removal are facilitated with time delay and differential equation algorithms. For deep wells where multiple drill pipe reflections are unlikely, analytical solutions for both are obtained assuming single reflections which do not involve windowing challenges and complicated digital filter design. Software and hardware developments patented, published and validated over the years, are integrated, refined and readied for controlled field tests.

Graphical abstract

Click to view original image

Keywords

Carrier frequency; frequency shift keying; measurement while drilling; mud pulse telemetry; negative pulser; positive pulser; turbosiren

1. Introduction: Background, Mysteries and Reconciliation

We will review the development of Measurement While Drilling mud pulse technology over the past four decades, in particular, the reasons for its continuing lack of progress and importantly, physical insights acquired over the past decade offering a credible path toward high data rate MWD telemetry. Reviews are subjective and biased toward a writer’s experience and personal perspectives. Thus, it is important to understand this author’s background so comments can be taken in context.

1.1 Author Background

In 1981, the author joined Schlumberger as MWD Telemetry Manager, chartered to increase siren data rates from 3 bits/sec (or, “bps”) to 12. This was supposedly straightforward, doable by changing carrier frequencies from 12 Hz to 48. This would not be the case, with any type of pulser, for reasons explained later. In the intervening decades, the author would continue his efforts with multiple organizations. This work, with Schlumberger, NL Industries, Halliburton, Gyrodata Schlumberger, GE Oil & Gas, BakerHughes, CNPC and Sinopec, was often separated by years, dependent on funding, industry interest and simply luck. During this time, companies would disappear or merge, personnel would leave the industry or retire, with any accumulated knowledge relegated to passages in forgotten papers never to be shared. This author, however, persevered throughout his journey, and finally, new methods and an integrated perspective on MWD technology have emerged that will define improved approaches to hardware, telemetry and signal processing design.

The author’s early background includes a Ph.D. from the Massachusetts Institute of Technology (MIT) and a M.Sc. from the California Institute of Technology (Caltech), with majors and minors in physics, applied math, aerospace engineering and electromagnetics. His Doctoral Thesis, “Physics of Slowly Varying Wavetrains in Continuum Systems,” sought to unify disparate ideas in wave propagation, waveguide physics, group velocity, energy propagation, and the like. This background should, at least theoretically, prepare him to effectively combine modern communications concepts with downhole acoustics physics and hardware design, but this would not be the case. When individuals make radical changes, for example, transitioning from urban to rural environments, or in his case, high speed aerodynamics to petroleum engineering, fundamental learned principles can lie dormant until that final “Ah ha” moment. This, in fact, has been the case, but all unresolved pieces of the puzzle have now fallen in place. We will discuss both anecdotal stories and true-to-life incidents chronologically.

1.2 Conventional MWD Pulser Types and Principles

In the 1980s literature, and continuing to the present, mud pulsers appear in three categories, negative pulsers, positive pulsers (or “poppet” valves), and mud sirens (or “rotary shear valves”), as shown in Figure 1. Here, cross-hatched or shaded areas represent the drill collars that contain these signal sources. A negative pulser creates disturbance pressure signals by slowly “opening and closing a door” in the collar. When the door opens, drill pipe pressures drop as shown, and when it closes, pressures return to prior hydrostatic levels. Negative pulsers have not proven popular, because resulting fluid jets and high pressures can damage formations.

Click to view original image

Figure 1 Three mud pulse pressure source designs.

Positive pulsers, on the other hand, are very popular. They are easily fabricated, with the number of worldwide manufacturers in the dozens and rapidly increasing. In Measurement While Drilling, they are described as “Frankenstein tools” because numerous designs have evolved dangerously and erratically in “Mom and Pop” shops. As depicted in Figure 1, higher positive pressure signals are created when an upgoing plunger or piston slowly moves against a narrowing passage toward a small orifice, thus increasing drill pipe pressure, as indicated. When the piston or poppet valve is retracted, pressures return to hydrostatic levels. It is clear that directly confronting and stopping oncoming mud flow requires large mechanical power and energy expenditures, so that data rates will be severely limited.

Finally, “mud sirens” and “rotary shear valves” are depicted in Figure 1. “Mud sirens,” for example, those operated by Schlumberger, rotate continuously in one direction, slowing down as required to introduce phase changes. They create classic “water hammer” pressure signals when oncoming mud impacts rotor-stator combinations in closed positions. The term “rotary shear valve” implies fundamental differences in operating principles, but the inherent physical laws used are little different. Like sirens, rotors move transversely relative to the oncoming mud. As before, audible signals are only created upon complete rotor-stator closure. They do not “quickly slice” through the mud as the word “shear” implies, but actually “bang” into it just as sirens do, although now in alternate rotating and counter-rotating directions. However, these actions are neither energy nor time efficient. For every change in direction required, a deceleration to zero velocity is needed, followed by an acceleration from zero that must be made. This process needlessly consumes energy, time and slows bit rate. A mud siren that is able to efficiently reduce phase shift times will easily produce higher data rates than a comparable rotary shear valve. Rotary shear methods, introduced to provide siren competitive alternatives, were originally designed to avoid patent infringement issues.

In our research, we will focus on mud siren and “turbosiren” designs that rotate only in one direction. Again, rotors move relative to stationary stators, and then, transversely against the mud flow. Periodic pressures in time are created with constant rate rotations, and for this reason, siren processes are synonymous with “continuous wave telemetry.” Negative and positive pulsers may execute one or two mechanical closures per second, at best, given the “brute force” nature inherent in direct confrontations with high momentum mud. In contrast, sirens are “see through,” that is, half-opened and half-closed for the duration of a time cycle. Thus, they permit 50% of the oncoming flow to move through temporarily aligned “port” (or “empty”) spaces. As such, they consume much less energy, at the same time supporting higher “open and close” operations per second, taking care not to invoke “bits per second” terminology for now. While these rates are faster, the strengths associated with siren disturbance pressures are much lower than those of positive pulsers due to incomplete closure, falling rapidly as gap distances between rotors and stators increase or as erosion takes hold. This reduces effective bit rates because created signals cannot travel over large drill pipe distances. The simple 1980s introductions above shown in Figure 1 (without our detailed explanations) have not changed over four decades. Prominent oil and gas trade journals, not to mention experienced petroleum engineers and designers, continue to offer such over-simplified descriptions. They are only partially correct and at best misleading, and have resulted in stalled progress in an important engineering endeavor and in continuing low data rate expectations.

1.3 Confusion over “Hydraulic” versus “Acoustic” Signaling

For slow pulser motions, or “hydraulic events,” the overview above just might suffice. In the petroleum literature, Bernoulli’s equation “P + ½ρU2 = constant” (strictly applicable to inviscid flows) and Hagen-Poiseuille’s law “ΔP = 8µLQ/(πR4)” for viscous Newtonian pipe flow only, are indiscriminately used to describe pressures as they react to changes in speed, which in turn result from orifice area changes at moving pulsers. Incorrect usage of these formulas proliferates in numerous company publications. Throughout MWD history, in fact, drilling researchers have rarely described mud pulse events in “acoustic” terms. This semantic barrier has not allowed MWD to benefit from the wealth of scientific information available from a maturing technology. Many MWD applications were and are simply “hydraulic,” as in civil engineering. However, as the technology increased in popularity in the 1980s, relevant but confusing questions arose while the knowledge base grew slowly but surely.

To avoid reader confusion, we will define “hydraulic” and “acoustic” in laymen’s as well as mathematical terms. Imagine Person A communicating with Person B over a given distance. This is possible using “smoke signals,” initiated by native tribes long ago in American history, which are clearly limited in range. On the other hand, A and B can be connected by a long tube through which either physically slowly blows fluid to the other, intermittently blocked by a slowly closing valve to convey information. This “hydraulic” approach involves actual movements of large bodies of fluid, and its efficiency depends on separation distance, frictional loss and fluid density. On the other hand, it is not necessary to move the entire body of fluid. A and B can simply “speak” to each other, through words, grunts and groans, or “0 and 1” clicks of a rapidly acting valve. This is “acoustic,” or “sound” transfer.

Sound travels quickly through a medium at “sound speed,” usually denoted by “c,” about 5,000 ft/sec in water, 3,000 ft/sec in heavy mud, and 1,000 ft/sec in air in acoustic wind tunnels. Like waves propagating along stretched jump ropes, disturbances move throughout the entire length unimpeded, while portions of the rope only move temporarily and locally while the disturbance is passing through it. Thus, acoustic methods are more efficient. Hydraulic motions are governed by the incompressible flow equations, say the constant density Navier-Stokes model for Newtonian fluids – these generally require computational finite difference or finite element methods for analysis, which are plagued by truncation errors and grid dependencies. Acoustic equations solve simpler classical wave equations, for example, “

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