Examining organic carbon in Utica shale - reading density data isn't so black and white

Abstract

Many studies have focused on the micro- and nanometer scale distribution of organic matter is shales. In this research, we are attempting to examine organic matter distribution at a larger ~ 0.1-1 millimeter scale, which would be easier to link to bulk reservoir properties. We investigate samples from Pt. Pleasant Shale (also known as the Utica Shale) from Eastern Ohio, United States, using X-ray computed-tomography (XCT) and Scanning Electron Microscope (SEM). Comparing both sets of data, we hope to find a stronger correlation between the XCT values and the distribution of organic matter and minerals in the shale. We scanned Utica samples (2.5 cm diameter and a few cm in length) on an industrial micro-CT, which results in voxel sixes of ~20 microns. Hounsfield values for targeted “organics” were ~5000 compared to the background shale value ~8000. Areas containing possible organic carbon were identified, and these sections were subsampled and investigated with SEM to determine geochemistry, with special focus on identification of organic matter. Preliminary results show that organic matter distribution is not resolvable at the ~0.1-1 millimeter scale. However, research in this area has just begun this summer, there is still much more CT data to sift through in order to gain more conclusive results.