Characterization of the CO2-Fluid-Shale Interface Via Feature Relocation Using Field-Emission Scanning Electron Microscopy, in Situ Infrared Spectroscopy, and Pore Size Analysis

Abstract

Fundamental research targeting the interactions of CO2 and fluids with unconventional shale systems is limited from the perspective of using carbon dioxide 1) as an alternative fracturing fluid, 2) as an agent to enhance hydrocarbon production, and 3) as an injection agent into the shale formation for storage purposes to avert emissions to the atmosphere. In this work, we apply in-situ infrared spectroscopy (FT-IR), scanning electron microscopy coupled with energy dispersive spectroscopy (SEM-EDS), and Brunauer-Emmett-Teller (BET) surface area and density functional theory (DFT) pore size analysis to examine the effects of CO2 and fluid on the Marcellus and Utica Shales. Results show changes to the shale at both the micron and nanometer scale after reaction with CO2 and water. These alterations could potentially alter overall permeability and fracture networks that may cause issues for future EOR activities, CO2 storage, and/or the practice of using CO2 as a hydraulic fracturing material.