The Effects of Burial Diagenesis on Multiscale Porosity in the St. Peter Sandstone: An Imagine, Small-Angle, and Ultra-Small-Angle Neutron Scattering Analysis

Published

November 4, 2017

Author(s)

Lawrence M. Anovitz, Jared T. Freiburg, Matthew J. Wasbrough, David F. Mildner, Kenneth C. Littrell, Vitaliy Pipich, Jan Ilavsky

Abstract

To examine the effects of burial diagenesis on heirarchical pore structures in sandstone and compare those with the effects of overgrowth formation, we obtained samples of St. Peter Sandstone from drill cores obtained in the Illinois and Michigan Basins. The multiscale pore structure of rocks in sedimentary reservoirs and the mineralogy associated with those pores are critical factors for estimating reservoir properties, including fluid mass in place, permeability, and capillary pressures, as well as geochemical interactions between the rock and the fluid. The combination of small- and ultra-small-angle neutron scattering with backscattered electron or X-ray-computed tomographic imaging, or both, provided a means by which pore structures were quantified at scales ranging from aproximately 1 nm to 1 cm - seven orders of magnitude. Larger scale (>10 υm) porosity showed the expected logarithmic decrease in porosity with depth, although there was significant variation in each sample group. However, small- and ultra-small-angle neutron scattering data showed that the proportion of small-scale porosity increased with depth. Porosity distributions were not continuous, but consisted of a series of a log normal-like distributions at several distinct scales within these rocks. Fractal dimensions at larger scales decreased (surfaces smoothed) with increasing depth, and those at smaller scales increased (roughen) and pores become more isolated (higher lacunarity). Data suggest that changes in pore-size distributions are controlled by both physical (compaction) and chemical effects (precipitation, cementation, dissolution).

Citation

Marine and Petroleum Geology

Volume

92

Pub Type

Journals

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Keywords

backscattered electron images, permeability, pore size distribution, porosity, sedimentary reservoirs, ultra-small-angle neutron scattering

Citation

Anovitz, L. , Freiburg, J. , Wasbrough, M. , Mildner, D. , Littrell, K. , Pipich, V. and Ilavsky, J. (2017), The Effects of Burial Diagenesis on Multiscale Porosity in the St. Peter Sandstone: An Imagine, Small-Angle, and Ultra-Small-Angle Neutron Scattering Analysis, Marine and Petroleum Geology, [online], https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=923248 (Accessed October 9, 2024)