To Boldly Monitor Where No One Has Measured Before

By Robert Stewart, College of Natural Sciences and Mathematics

Robert_Stewart_EFEnergy is fundamental to the great richness of life. The power of a country – literally, its ability to do work over a period of time – is associated with its energy capabilities.

The largest primary energy producers in the world are, in order, the United States, China, Russia, Saudi Arabia, and Canada. Some visionary authors even have ranked civilizations based on their ability to produce energy (the Kardashev Scale). In the United States, oil discovery and the internal combustion engine were critical parts of the development of the automobile and aviation revolutions in the early 1900s. The Lucas well at Spindletop, near Beaumont with its prodigious blowout in 1901, ignited the imaginations of many and led to the foundation of the Texas oil industry.

Blow-outs are less highly regarded now: We depend on new technologies to make energy discovery, production, and consumption as safe, clean, efficient, inexpensive and impact-free as possible.

That’s a long list! And, at very least, the second law of thermodynamics teaches us that there is always waste and untoward consequence in energy’s transformations. While we can’t guarantee waste- and risk-free energy, we can go a long way toward that goal by conscientiously monitoring all steps of its journey. If there is something awry in the process, we can try to catch it and remediate. If there is a problem, the goal is to find and correct it rapidly.

One of the most exciting ways to do this is derived from fiber optics. Lasers have been used for decades to pulse light packets down hair-thin strands of glass to transmit information, lively conversations, and interesting videos. But it turns out that laser light is also reflected back toward the source by small impurities or changes in the fiber. If the fiber is stretched a bit at a location, then the amount of reflected light varies with the stretch (or strain). The lasers can be pulsed very fast, allowing a record to be made of the motion at many points along the fiber. This is called Distributed Acoustic Sensing, or DAS.  A fiber-optic line can be affixed to the pipe (casing) of an oil or gas well, and as the well produces, its flow can be characterized by the vibrations as they are recorded by the DAS system. If there are changes in the recorded vibrations along the well, they can be pinpointed and remediated.

Another remarkable technology is 4D reservoir monitoring. Motion sensors or seismometers (OBS) can be placed on the ocean floor and used to listen to vibrations from a nearby ship, inside the earth or events associated with a well’s production. Most commonly, the sensors record vibrations generated by a vessel on the sea surface and then reflected from deep under the ocean bottom. These subterranean echoes are assembled into a 3D geologic picture. This remarkable representation of the earth’s structure and rock type can be used to identify potential oil and gas deposits. By repeating the survey, small differences in the echoes can be used to infer changes in the saturation of a producing reservoir. Reservoir monitoring with 4D seismic, along with computer simulation of the reservoir and its fluid changes, can help identify inefficiencies and problems in production, then provide ways to solve them.

People produce and consume vast quantities of energy in their quest for happiness and prosperity. Monitoring every stage of this process can help make energy discovery, recovery and use more efficient and safer. Exciting science and engineering make monitoring happen in ways not previously imagined.

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