Pores in Marcellus Shale: A Neutron Scattering and FIB-SEM Study
Xin Gu, David R. Cole, Gernot Rother, David F. Mildner, Susan L. Brantley
Recently, the production of natural gas from black shale has increased dramatically due to the development of hydraulic fracturing techniques which significantly increase the porosity and fracture network of shales. Understanding these processes requires better knowledge of the pore structure of shale and how it is related to hydrocarbon storage and gas migration. Here we investigate the porosity of the Union Springs (Shamokin) Member of the Marcellus Formation in five samples from 810 to 910 ft depth from one core in Centre County, PA, focusing on pores ranging in dimension from nanometers to several micrometers by using combined ultra small angle neutron scattering (USANS) and small angle neutron scattering (SANS). These "nano-pores" in Marcellus shale are observed to be randomly distributed when neutrons are scattered from thin sections cut in the plane of bedding, but the scattering pattern is anisotropic when the neutrons pass through sections cut perpendicular to bedding. The total versus connected porosities calculated based on scattering data from the sections in the plane of bedding. Neutron scattering combined with focused ion beam scanning electron microscope (FIB-SEM) reveals that the dominant nano- to micron-sized pores in organic-poor shale samples are connected, sheet-like pores in clay. In contrast, bubble-like, organophilic pores in kerogen dominate organic-rich samples. Better understanding of pore distributions could enable development of more effective hydrofracturing methods as well as better approaches to diminish flowback of brines to the land surface.
focused ion beam electron microscopy, nitrogen gas adsorption, organic-rich black shale, anisotropic porosity, pore structure network, small angle neutron scattering
, Cole, D.
, Rother, G.
, Mildner, D.
and Brantley, S.
Pores in Marcellus Shale: A Neutron Scattering and FIB-SEM Study, Energy & Fuels, [online], https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=915183
(Accessed June 8, 2023)