Micro-FTIR Mapping of Organic Matter Connectivity in Devonian and Mississippian New Albany Shale (Indiana)

Abstract

High-resolution imaging with micro-FTIR (Fourier Transform Infra-Red Spectroscopy) allows users to distinguish mineralogical compositions as well as different organic matter (OM) types of a micrometer scale in a nondestructive manner. FTIR spectra of a suite of upper Devonian New Albany Shale samples were obtained via reflectance micro-FTIR mapping of 1 × 1 mm regions. For each sample, we analyzed two planes parallel and perpendicular to the bedding to understand the difference in OM and mineral connectivity in various orientations. It was observed that in the samples with high OM content there was a greater connectivity of OM in the plane parallel to bedding than the perpendicular. In samples with a low amount of OM, the OM was more isolated. Clay minerals exhibited 97–100% connectivity, whereas carbonates formed isolated grains. Our results demonstrate that the resolution used in the micro-FTIR mapping allows for accurate representations of the distribution of OM (based on the aliphatic stretching region), clay minerals, and carbonates. This technique, however, can miss very fine-grained particles (less than a few micrometers) that are interspersed throughout the matrix. Therefore, SEM was also employed to better document the distribution of quartz. Preliminary results suggest that distribution and connectivity of minerals and OM influences porosity distribution and permeability, and therefore, the micro-FTIR technique may prove useful for studying the flow of gas and oil through pore networks.

AAPG Datapages/Search and Discovery Article #90218 © 2015 Eastern Section Meeting, Indianapolis, Indiana, September 20-22, 2015