Imaging and Analysis of Geological Porous Media

Abstract

Geological carbon sequestration (GCS) is a promising technology to remove CO2 from the atmosphere. GCS is the process of capturing CO2 from large point-sources or directly from the atmosphere, transporting the captured CO2 to a storage site, and injecting it underground in geological formations for long-term storage. In this study, a calcareous dolomite sample obtained from Bartow County, Georgia was analyzed as a potential geological carbon sequestration site. Understanding carbonate rich minerals and their complex structures is crucial for predicting the impacts of dissolution and precipitation reactions when carbon dioxide is sequestered during carbon capture and storage. Here, scanning electron microscopy (SEM) imaging is utilized to obtain high resolution backscattered electron (BSE) images and energy dispersive spectroscopy (EDS) images of the sample’s thin section. These images were used to create mineral maps. The mineral maps were then used to evaluate 2D sample characteristics such as porosity, pore connectivity, mineral abundances, and mineral accessibilities. Following mineral map analysis 3D x-ray computed tomography (XCT) images were obtained of the core sample. XCT images were used to extract larger 3D pore networks of the sample; however, XCT imaging cannot account for small-scale surface features. The BSE and EDS images used for analysis were then applied to the XCT images to allow for 2D and 3D image analysis of the core sample. This study aims to evaluate the mineral concentrations present around pore grain interfaces in carbonates by correlating 2D images with 3D images of two regions of a highly heterogeneous carbonate sample. In addition to imaging and analysis of mineral concentrations around pore structures in carbonates, this study also includes the development of an aqueous barium chloride contrast agent for enhanced XCT imaging of core samples. Two sets of XCT images were obtained to assess the viability of the contrast agent: one for a dry Bentheimer sandstone core, and one for the Bentheimer sandstone core saturated with the aqueous barium chloride contrast agent. The captured XCT images were qualitatively processed, compared, and discussed.