Impact of mineral composition and distribution on the mechanical properties of porous media

¹ Department of Civil Engineering, Auburn University, Auburn, AL, 36849
² Department of Civil, Construction, and Environmental Engineering, San Diego State University, San Diego, CA, 92182

^* Corresponding author: mmiletic@sdsu.edu

Abstract

Geological sequestration of CO₂ in deep saline formations is a promising means of reducing atmospheric CO₂ emissions. Once injected, CO₂ dissolves into formation brine, lowering pH and creating conditions favorable for mineral dissolution. Cations released from dissolving minerals may create conditions favorable for secondary mineral precipitation, which can result in the long-term mineralogical trapping of injected CO₂. These reactions may alter the natural rock mechanical properties, which can affect the safety and efficiency of geological sequestration. This work aims to investigate the impact of mineral composition and distribution on the mechanical properties of porous media. In this study, the mineralogy, mineral distribution, and mechanical properties of samples from Escambia County, AL, are evaluated. The mechanical properties of the rock samples are evaluated using the unconfined compression and indirect tensile tests in the combination with digital image correlation. The mineral composition and distribution are determined through the analysis of scanning electron microscopy backscattered electron and energy dispersive X-ray spectroscopy images of thin sections. These analyses showed that the mechanical properties vary with composition, which may have significant practical consequences for geological sequestration of CO₂.