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

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.