NERSC Supercomputers Help Reveal Secrets of Natural Gas Reserves

Supercomputers at the Department of Energy’s National Energy Research Supercomputing Center (NERSC) helped scientists at Oak Ridge National Laboratory (ORNL) study gas and oil deposits in shale and reveal structural information that could lead to more efficient extraction of gas and oil from shale.

It could also enable environmentally benign and efficient energy production from coal and perhaps viable carbon dioxide sequestration technologies, according to Yuri Melnichenko, an instrument scientist at ORNL’s High Flux Isotope Reactor.

A scanning electron microscope image illustrating mineralogy and texture of an unconventional gas reservoir. Image: Oak Ridge National Laboratory

In a paper published in the Journal of Materials Chemistry A, Melnichenko and colleagues from ORNL’s Materials Science and Technology Division Research describe a small-angle neutron scattering technique that, combined with electron microscopy and theory, can be used to examine the function of pore sizes.

Using their technique at the High Flux Isotope Reactor's General Purpose SANS instrument, the scientists showed there is significantly higher local structural order than previously believed in nanoporous carbons. This is important because it allows scientists to develop modeling methods based on local structure of carbon atoms. Researchers also probed distribution of adsorbed gas molecules at unprecedented smaller length scales, allowing them to devise models of the pores.

“We have recently developed efficient approaches to predict the effect of pore size on adsorption,” said James Morris, co-author on the paper and a member of ORNL’s Materials Science and Technology Division. “However, these predictions need verification, and the recent small-angle neutron experiments are ideal for this. The experiments also beg for further calculations, so there is much to be done.”

While traditional methods provide general information about adsorption averaged over an entire sample, they do not provide insight into how pores of different sizes contribute to the total adsorption capacity of a material. This research, in conjunction with previous work, allows scientists to analyze two-dimensional images to understand how local structures can affect the accessibility of shale pores to natural gas.

“Combined with atomic-level calculations, we demonstrated that local defects in the porous structure observed by microscopy provide stronger gas binding and facilitate its condensation into liquid in pores of optimal sub-nanometer size,” Melnichenko said. “Our method provides a reliable tool for probing properties of sub- and super-critical fluids in natural and engineered porous materials with different structural properties. This is a crucial step toward predicting and designing materials with enhanced gas adsorption properties.”

Together, the application of neutron scattering, electron microscopy and theory can lead to new design concepts for building novel nanoporous materials with properties tailored for the environment and energy storage-related technologies, the researchers noted. These include capture and sequestration of man-made greenhouse gases, hydrogen storage, membrane gas separation, environmental remediation, and catalysis.

The research was funded by DOE’s Office of Basic Energy Sciences.

This article was adapted from an ORNL news release.