Quantification of Organic Porosity and Water Accessibility in Marcellus Shale using Neutron Scattering

Published

June 16, 2016

Author(s)

Xin Gu, David F. Mildner, David R. Cole, Gernot Rother, Rudy Slingerland, Susan L. Brantley

Abstract

Pores within organic matter (OM) in gas shales a significant component of the pore system. These pores contribute most of the storage capacity and effective nanopore network in gas shales. Here we present a novel approach to characterize the OM naopore structure (including the porosity, specific surface are, pore size distribution, and water accessibility) in Marcellus shale. By using ultra-small and small-angle neutron scattering, and by exploiting the contrast matching of the shale matrix with suitable mixtures of deuterated and protonated water, both total and water-accessible porosity were measured on cm-size samples from two boreholes from the nanometer to micrometer scale with good statistical coverage. Samples were also measured after combustion at 450 °C. Analysis of scattering data from these procedures allows quantification of OM porosity and water accessibility. Om hosts 24-47% of the total porosity for both organic-rich and -poor samples. This porosity occupies as much as 29% of the OM volume. In contrast to the current paradigm in the literature that OM porosity is organophilic and therefore not likely to contain water, our results demonstrate that OM pores with widths > 20 nm exhibit the characteristics of water-accessible porosity. Our approach reveals the complex structure and wetting behavior of the OM porosity at scales that are hard to interrogate using other techniques.

Citation

Energy & Fuels

Volume

30

Issue

6

Pub Type

Journals

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Keywords

scattering length density contrast, shale pore size distribution, small-angle neutron scattering, organic matter in shale, water accessibility in pore

Citation

Gu, X. , Mildner, D. , Cole, D. , Rother, G. , Slingerland, R. and Brantley, S. (2016), Quantification of Organic Porosity and Water Accessibility in Marcellus Shale using Neutron Scattering, Energy & Fuels, [online], https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=919977 (Accessed May 18, 2024)