Features - April 2015

I’ll Believe It When I See It: CT Imaging at NETL

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With thermal imaging, warm or hot objects are distinct against cooler backgrounds. Warm-blooded animals, like humans, become easily visible.

We rely on our eyes; vision helps inform our understanding of the world around us. What we witness feels tangible, concrete, and believable.

But have you ever wanted to look inside things—to see the whirling gears of a clock, the beating of a heart, or the subtle shifts of rock moving deep underground?

Our vision is limited, but through science, we’ve developed different ways to enhance it. Microscopes allow us to view things so small they’re undetectable by the naked eye—even capturing images of a single atom. Thermal imaging enables us to view the infrared radiation caused by heat, illuminating the blood flow in the human form.

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Doctor’s use X-ray technology to peer beneath your skin.

Science has even developed ways to peer into things. X-ray technology uses electromagnetic radiation to capture images of things opaque to the human eye. On its most basic level, X-ray technology works similarly to a camera—yet, instead of using visible light, X-rays expose film via electromagnetic waves.

Electromagnetic waves penetrate into objects but, depending on the material, they’re absorbed at different levels. Have you ever broken a bone? If so, the doctor probably took an X-ray of your body. The bone, fat, and muscle that make up your body all appeared visually distinct on the resulting picture, letting the doctor develop an accurate picture of what’s beneath your skin. But traditional X-ray images are only two dimensional—scientists have discovered a way to build a three dimensional model of what lies beneath a surface.

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Computerized tomography (CT) scanning produces a composite, 3-D image of an object by combining multiple X-ray images that have been taken from different angles. These images are fed into a computer to create a 3-D digital reconstruction of an object. While this technology was originally developed for medical applications in the 1970s, it quickly became apparent how useful it could be in other fields—including research into petroleum and other geo-imaging applications.

The National Energy Technology Laboratory (NETL) relies on CT scanning to observe the inner structures of geographical formations, a crucial component in several of its carbon storage research programs. NETL has a scanner laboratory that provides imaging data that can be used for computer simulations, economic evaluations, and site characterizations. Coal, rock, and other geological samples are imaged in the laboratory to measure how liquids, gases, and solids flow through them—this allows scientists to understand how CO2 is adsorbed or absorbed in coal cores. These measurements provide critical information to researchers on the actual distribution of minerals and fluids inside samples, rather than providing merely average measurements.

The CT scanner laboratory at NETL hosts three CT X-ray scanners, each providing different advantages and benefits:

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  • The medical CT scanner allows scientists to analyze variations in the composition and density of materials. In other words, researchers are able to determine what elements are inside of an X-rayed sample and how they’re moving. This scanner is the fastest in the laboratory, analyzing samples in mere seconds to allow experiments to simulate, in real time, the way fluids (like petroleum) can move through rocks. This gives geo-scientists the critical data they need to understand the physics behind fluid-flow in underground rock formations.
  • The micro-CT scanner offers the highest-resolution images in the laboratory. This scanner is used to take a look at microscopic structures, scanning samples as large as a Rubik’s cube to as small as a pencil eraser. The images produced through this analysis provide resolution at the single micron scale, or one millionth of a meter! Scientists use this highly detailed scanner to yield precise information on porosity and mineral composition—important data for understanding the structure of geographical formations. However, images this detailed take time to produce, a process that can take days.
  • The industrial CT scanner is the bridge between the other scanners, offering researchers a more detailed image than the medical scanner at a fraction of the time needed by the micro-CT scanner. This scanner is primarily used to understand the pore and fracture networks inside of geomaterials like sandstone, limestone, and shale. Researchers are able to image a sample before and during experiments to gain data on the physical and chemical changes that take place.
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NETL’s CT scanning laboratory is a vital resource. The imaging technologies it holds offer researchers world-class, comprehensive testing and evaluation opportunities to gain necessary data. The non-invasive CT imaging process enables the experimental examination of many complex processes being researched via NETL programs—enhanced oil recovery, carbon sequestration, sealing formation integrity, wellbore safety, geothermal energy production, hydrate formation, and shale gas development.

Many of these real-world applications rely on CT scanning to analyze actual core samples and fluids from specific target formations in conditions that simulate real-world situations. The resulting data are integral to advancing research, allowing scientists to develop technology that can improve oil recovery techniques, address safety concerns in the oil and gas industry, help secure American energy independence, provide insight into the technical and economic feasibility of CO2 storage, and help inform energy policy to provide the necessary regulations to promote a future of safe, clean, and efficient energy generation.