Washington, DC — Researchers participating in the National Energy Technology Laboratory Regional University Alliance (NETL-RUA) are using a familiar piece of medical equipment – a CT scanner – to evaluate cutting-edge improvements to enhanced oil recovery (EOR) techniques. Results from these studies could be used to help increase domestic oil supplies from EOR while helping to reduce the amount of carbon dioxide (CO2) emitted to the atmosphere.
Scientists from the University of Pittsburgh, University of Bristol, Rutherford Appleton Laboratory, URS, and NETL are using the scanner and surfactants (fluids added to injected CO2 that change its flow properties) to optimize CO2 viscosity to make EOR more efficient. NETL is the research laboratory for the Department of Energy’s Office of Fossil Energy.
EOR methods are used to extract oil from reservoirs in which all the "easy" hydrocarbons have already been produced. Injecting CO2 into oil-bearing formations can increase reservoir pressure, pushing more difficult-to-reach oil to the surface. Because CO2 is a greenhouse gas, using it for this purpose also directly avoids emitting carbon dioxide into the atmosphere.
The NETL-RUA research team has evaluated CO2 flows with surfactantsthat can increase the efficiency and efficacy of EOR with CO2. Surfactants produce bubbles, like soap in water, which raise the viscosity of a fluid, in this case CO2. Injected CO2 with a higher viscosity will improve "sweep efficiency;" that is, the surfactant will increase the viscosity of the CO2 so that it pushes through a reservoir more uniformly, thereby sweeping more oil along with it. More resistance and a more stable flow also prevent the CO2 from tunneling through the rock in tiny channels at uneven rates, a phenomenon called "viscous fingering" that reduces sweep efficiency.
Using NETL’s medical computed tomography (CT) scanner at its Morgantown facility, researchers observed flow phenomena within core samples of rock and porous media that indicated a uniform plug of CO2 traversing the length of the core and sweeping along a greater percentage of the in-place fluids. This indicates that adding surfactant will make EOR efforts more successful. NETL’s CT scanning capabilities played a critical role by allowing researchers to visualize how CO2 with surfactant behaves within the rock throughout the core sample; scientists could examine the entire flow path, rather than simply the beginning and end of the core. Using data from the CT scanner, researchers can directly measure fluid flow phenomena, such as fingering or stable/uniform flow. In addition, the scanner’s ancillary equipment allows researchers to conduct experiments at the same pressures as naturally occur in reservoirs, enabling accurate predictions of how the CO2 and surfactant will behave in real-world applications.
NETL-RUA was formed in 2010 as a partnership among NETL, the nation’s leading fossil energy laboratory; a consortium of universities, located in the energy-rich region of the mid-Atlantic, comprising West Virginia University, Carnegie Mellon, Penn State, the University of Pittsburgh, and Virginia Tech; and URS, one of the nation’s largest engineering, design, and construction firms. The NETL-RUA research program assists NETL in conducting basic and applied energy and environmental research that supports DOE’s mission to advance U.S. national, economic, and energy security. Working with the region’s commercial energy sector, NETL-RUA research is aimed at accelerating deployment of new technologies, thereby stimulating regional economic development, spurring high-tech job creation nationwide, and fostering the education of America’s new energy leaders.