Well completions engineering is very likely the junction point of every other technical discipline in the oil industry. Feed-ins from geosciences and drilling must be balanced with predictions from reservoir engineering and requirements from production to deliver a fit-for-purpose well design. All this must be contained in a package that retains sufficient flexibility to handle life-of-well changes while retaining well integrity beyond the designed life of the well. Expected well life may range from a few years in deep water to more than 70 years in tight gas applications.
Conditions range from the pressure and temperature fluctuations of ultradeep water to those of long horizontals and 20- to 50-multistage-fracture stimulations in shale oil and gas completions. The extremes of pressure and temperature are continually increasing, and environmental requirements are a moving target.
Because of the engineering complexity involved, completions engineering is where a large amount of new technology enters the industry. If you are interested in engineering challenges, then take a closer look at well completions engineering.
Do you pick an engineering field, or does it pick you? Natural engineers such as Leonardo da Vinci have historically risen out of the background in human population to a height of accomplishment that suggests the existence of an embedded genetic skill. Talented engineers, such as Edison, Marconi, Bell, Newton, Fleming, and Tesla, often have not been formally educated as much as they have been compelled into their tasks by curiosity across a wide and complex range of interests.
Engineers of this caliber are often said to be born, not made. Some of the best completions engineers I’ve met are not formally trained as engineers, but they possess two unusual talents: They have the ability to construct a mental image of what is happening downhole, and they can balance influences of several physical and chemical effects with the effects of the fourth dimension, time.
In completions engineering, we are at a distance from our work—usually from 1 to 7 miles away—without most opportunities to see, touch, or hear the final work product (and you sure don’t want to smell or taste it!). What is left? The ability to refine knowledge from a mass of data is the first step, and the skill to assemble the best compromise is the second. That’s right: compromise. Randy Pausch, in his book The Last Lecture, writes that “engineering isn’t about perfect solutions, it’s about doing the best you can with limited resources.”
A solid understanding of technology allows us to dream, but experience with a wide array of sciences allows us to accomplish. Completions engineering, as a juncture of many technologies, is learned on the job, building on a solid foundation of technical knowledge acquired by both formal and literal methods. My first boss, who literally sent me to every challenging job he could find and loaned me to chemists, geologists, and drillers at Amoco, told me “You can’t build a skyscraper on the footings of an outhouse.” Within that tidbit of east Texas lore, there resides more than just a grain of truth. To really handle a system of change, you must understand both the components and how they react as a system.
Effective well completions engineering requires one of the broadest technical backgrounds of any petroleum engineering discipline. Mixed with the formal skill are the literal education needs that make experience such a prized asset. Ultimately, the completions engineer needs to integrate the available technology to overcome what nature presents as obstacles. Completions engineering is defined by managing change. Temperature, pressure, fluid composition, formation stresses, and well-production techniques are continually changing during the life of the well. Change is the only real constant.
What is involved? A completions engineer must know the conditions imposed by the reservoir and the requirements dictated by operations, with particular attention to changes of operations or fluid properties in the formation. Any description of the reservoir-to-well-to-facilities connection is a snapshot of a moment in time.
The system can change in a few minutes and will substantially change over time. Temperature extremes in an Arctic well, for example, can change in a short time from subzero near-surface temperatures to 100°C or more as hot fluids from the reservoir transfer heat through the tubulars. As temperature increases, every component of the well and every fluid in contact with the well is heated, with the potential for creating pressure and stress increases that may challenge collapse, burst, or tensile ratings of the pipe or even the seals created by the cement. This cyclic environment of startup, steady-state production, and shutdown will affect each part and component of the well design.
A well is essentially a pressure vessel composed of miles of pipe, hundreds of connections, and a variety of metal and nonmetal components; and, that’s just the start. If parts of the well tubulars are sealed off without a way to relieve fluid expansion when heated, the temperature-induced pressure rise during startup can create higher pressures than anything the reservoir can produce naturally. Examples of the trapped annular space problem have been seen from the Arctic to deep water. In one case, the addition of gas lift to a well that had been designed for natural flow created an unexpected trapped annulus that was then heated by produced fluids, causing a pressure rise higher than the initial design could take.
These very real problems demonstrate the dynamic nature of well completion design and underscore the need for the services of a completions engineer at every step and change of well operation.
Ignoring future operations and requirements is not feasible for a completions engineer. You can drill wells you cannot complete, and you can complete wells you cannot produce. A perfectly designed well is a failure if it cannot deliver an economic return through production. Even a good well design can be defeated by changes in the well over its life.
Delivering a well that can be produced both safely and economically is the initial product; however, the product will need to evolve to fit changing needs over the life of the well. Producing fluid from a well initiates an array of changes. In addition to temperature and pressure changes, just producing oil, gas, or water removes some of the reservoir fluids, which may be load supporting if the rock strength is insufficient to support the overburden. In cases of weak formations, the potential of subsidence, formation creep, and disaggregation raise their own dynamic challenges to the system.
Well completion design is both reactive to historical failure cases and proactive to the needs newer completions produce. As we learn what is needed in well completions and operations, we often must reach out to the wider completions community. When deepwater wells were rapidly increasing in importance, several of us saw a need for historical and performance-based sand control reliability information that could be used in designs and well life projections. Working across company and country boundaries, a small group of engineers gathered sand control success and failure operations data and reported this back to the industry through SPE (paper SPE 84262). Although we often think of these joint industry data-sharing projects as cumbersome, slow-moving, meetings-inducing events, this particular need was fulfilled using data from 40 companies and without contracts, meetings, or legal agreements. Personal-level networking solved what was a major concern in just 3 months. Never forget that none of us truly works alone.
While the challenges initially presented by the formation pressure and temperature may seem formidable, the changes in fluids, coupled with variability in internal and external natural stresses, require the design to have a high degree of flexibility. The flow mechanism of the well may shift from natural flow to one or more forms of artificial lift and, perhaps, even to secondary or tertiary recovery. Every change of operation changes requirements within the well. Changes to the well are commonplace, and well recompletions to handle changing properties or to access new reservoirs are a fact of life.
As formation and environment requirements push toward limits of materials, completions engineers must learn new materials, construction methods, and application details that were unknown just a few years before. New and adapted technologies are proven drivers to increase recoverable reserves. How good are you at adapting technology to meet a challenge? What is cutting-edge design today may be commonplace in 2 years and outdated in 4. For proof, simply look to the progression of well component metallurgy, well control evolution, subsea wellheads, and Arctic well issues.
So, why, if the challenge is this high, would you want a career in well completions? Simply put, seeing new challenges on a regular basis is a refreshing requirement for many engineers. And then, of course, there is an endless opportunity to learn. Although engineers, like most professionals, are specialists by definition, completions engineering requires you to push the limits of learning and widen the scope of your knowledge and abilities. Is it easy? No. But an easy job isn’t what attracted you to engineering in the first place.
George E. King is a registered professional engineer with more than 40 years of experience since joining Amoco Research Center in 1971. His technical work has provided advances in foam fracturing, production from unstable chalk, underbalanced perforating, sand control reliability, and shale gas completions and complex fracturing. Currently, King is working with new technologies for the oil and gas industry. He holds a BS degree in chemistry from Oklahoma State University, and a BS degree in chemical engineering and an MS degree in petroleum engineering, both from the University of Tulsa, where he also taught completions and workovers for 11 years as an adjunct professor. King has written 65 technical papers, was awarded the 2004 SPE Production Operations Award, and was recognized as the 2012 Engineer of the Year by the Greater Houston Chapter of the Texas Society of Professional Engineers. After 37 years, he retired in 2008 from BP as a distinguished advisor and is currently Apache’s global technical consultant. King lives in Katy, Texas. One of his hobbies is rebuilding vintage Ford Mustangs.