Nanometer-Scale Deformations of Berea Sandstone under Moisture Content Variations

TL;DR

This study introduces a real-time method to measure nanometer-scale deformations in Berea sandstone caused by moisture variations, revealing complex shrinkage and extension behaviors with implications for geological storage stability.

Contribution

It presents a novel high-resolution technique to observe and analyze moisture-induced deformations in sandstone at nanometer scale, combining nano-positioning and wave interferometry methods.

Findings

Hydrated Berea sandstone exhibits ~10^(-4) relative deformation.

Moisture increase causes extension; decrease causes shrinkage.

Initial water exposure causes temporary shrinkage before extension.

Abstract

Sandstone mechanical stability is of key concern in projects involving injections of CO2 in sandstone geological reservoirs, for the purpose of long-term storage. We developed a method to measure nanometer-scale deformations of sandstones in real time. We demonstrate that Berea sandstone, when hydrated, changes dimensions with a relative deformation of the order of 10^(-4). If the moisture content increases, sandstone samples exhibit an extension and if the moisture content decreases then the samples shrink. We also discover that, immediately after exposure to water, the sandstone temporarily shrinks, just for a few seconds, after which a slow extension begins, and continues until about half of the fluid evaporates. Such shrinkage followed by an extension has been observed also when the sample was exposed to acetone, Mineral Spirits or Vacuum Oil. The results are obtained using a high-resolution nano-positioner technique and, in independent experiments, confirmed using the technique of coda wave interferometry.