Nano-to-Micrometer Size Pores in Marcellus Shale Matrix: A Neutron Scattering Study

Gu, Xin; Brantley, Susan

Currently, 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. As a result, the pore structure of black shale is an active area of study as it is highly relevant to hydrocarbon storage and the gas pathway through the rock formations. In this study, we focus on the microstructures of the black shale ranging from approximately 0.7 nm to several micrometers in dimension: fractal dimensions, internal specific surface area, porosity, and pore size distribution in the silicate matrix by using combined Ultra Small Angle Neutron Scattering (USANS) and Small Angle Neutron Scattering (SANS). Deep core samples were collected from the economically important Union Springs member of the Marcellus formation from a drillcore in Howard, PA. We find the nano-pores probed in Marcellus shale are isotropic when neutrons are scattered from thin sections cut in the plane of bedding but anisotropic from sections cut from other planes. In addition, the smaller, more anisotropic pores are connected. The porosities in the sections cut perpendicular to bedding are much higher than those in the plane of bedding. Neutron scattering reveals the complex structure of the matrix porosity at scales that are hard to interrogate using other techniques.

AAPG Search and Discovery Article #90163©2013AAPG 2013 Annual Convention and Exhibition, Pittsburgh, Pennsylvania, May 19-22, 2013