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 recovered from 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 imaging, provided a means by which pore structures were quantified at scales ranging from approximately 1 nm to 1 cm—seven orders of magnitude. Larger scale (>10 μm) 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 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 (surfaces roughened) 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).
| Original language | English |
|---|---|
| Pages (from-to) | 352-371 |
| Number of pages | 20 |
| Journal | Marine and Petroleum Geology |
| Volume | 92 |
| DOIs | |
| State | Published - Apr 2018 |
Funding
This material is primarily based upon work supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, Chemical Sciences, Geosciences, and Biosciences Division grant number ERKCC72 . Research neutron facilities used in this work were supported by the National Institute of Standards and Technology , Center for Neutron Research, U.S. Department of Commerce , and the High-Flux Isotope Reactor, a DOE user facility operated by the Oak Ridge National Laboratory . This work is also based in part upon experiments performed at the KWS-3 instrument operated by JCNS at the Heinz Maier-Leibnitz Zentrum (MLZ), Garching, Germany. Access to the ultra-small-angle neutron scattering instrument BT5 was provided by the Center for High Resolution Neutron Scattering, a partnership between the National Institute of Standards and Technology and the National Science Foundation under Agreement No. DMR-0944772. Certain commercial equipment, instruments, materials and software are identified in this paper to foster understanding. Such identification does not imply recommendation or endorsement by the National Institute of Standards and Technology, the Department of Energy, or the Oak Ridge National Laboratory, nor does it imply that the materials or equipment identified are necessarily the best available for the purpose. The authors have no pertinent commercial of other relationships that are known to them to create a conflict of interest.