Delaware University scientists have developed a new non-invasive method to measure the variation of surface properties deep inside porous materials.
The team, which consists of researchers from NIST and Aramco Services Company, made use of neutron scattering or X-ray scattering to analyse the materials’ properties.
More than 30 states in the U.S. have shale formations that harbor natural gas underground, according to the Energy Information Administration. But how much fuel lies inside is anybody’s guess.
This is due to the fact that natural gas and other hydrocarbons lie inside nano-scale, difficult-to-measure pores in shale rocks, which have properties that are not yet understood.
The Delaware method could thus help natural gas experts better understand shale samples by examining the compositional distribution on porous surfaces inside the shales that directly influences the storage and transport of hydrocarbons.
This would eventually help them decide whether to invest time and resources to extract gas from the formation the samples came from.
The researchers contend that it’s not just the size of pores that matters, but the surface structure and surface chemistry, since natural gas interacts with the outer edges of each tiny pore in the rock.
According to the researcher, the properties of the pores also determine how gas will flow out of the formation.
To understand these pores, the team started with samples of isolated shale kerogen, an organic matter that stores the majority of hydrocarbons such as natural gas in shales.
To peer inside the kerogen, they used small-angle neutron scattering – which, unlike electron microscopy, is non-destructive – shooting a beam of subatomic neutrons through a substance and collecting information on the neutrons’ behavior to determine the properties of the pores.
Next the group measured the change of neutron scattering signals with gas sorption at different pressures. The change of neutron intensity reflects the compositional distribution on the surfaces inside a sample.
The researchers further contend that the new method reveals more advanced information that other methods do not, such as surface heterogeneity.
Image and content: University of Delaware