Testing the Viability of Supercritical Carbon Dioxide as a Fracking Fluid by Computing its Chemical Interaction with Illite

Open Access
Ajayi, Oluwaseyi Adebola
Graduate Program:
Master of Science
Document Type:
Master Thesis
Date of Defense:
August 25, 2016
Committee Members:
  • Dr. James Kubicki, Thesis Advisor/Co-Advisor
  • Dr. Michael Arthur, Committee Member
  • Dr. Derek Elsworth, Committee Member
  • Dr. Demian Saffer, Committee Member
  • molecular modeling
  • fracking
  • hydraulic fracturing
  • marcellus shale
  • supercritical CO2
  • illite
  • density functional theory
  • molecular dynamics
  • DFT
  • DFT-MD
  • scCO2
  • interfacial tension
  • interfacial energy
  • interaction energy
  • VASP
  • energy minimization
In this study, supercritical CO2 (scCO2) was investigated as a hydraulic fracturing fluid by modeling the interfacial energy of scCO2 versus water with the common shale mineral illite. The interfacial tensions between supercritical CO2 (scCO2) and illite and H2O and illite were measured and compared under conditions relevant to hydraulic fracturing using density functional theory (DFT) methods. Different illite models were used, two with a water monolayer (simulating wet pores) and two with a polymethyl methacrylate (PMMA) monolayer (simulating hydrocarbon-filled pores). Additionally, two of the illite models were charged at the surface with 8 K+ ions and two of the illite models contained no K+ ions. The illite surface with the water monolayer charged with 8K+ ions is most likely to behave as a real illite surface. The calculated interfacial energy between scCO2 and this illite surface was 0.0144 J/m2 and between water and illite was 0.0397 J/m2. The lower interfacial energy between scCO2 and illite suggests that scCO2 would create a better fracturing fluid because it can enter the nanopores of illite-dominated shales more readily than water. The orientations of the scCO2 molecules with respect to the illite also suggest that scCO2 is not influenced by a charged ion surface on the surface of the illite whereas the water is; these surface orientations explain the disparity between the interfacial energies between scCO2 and illite and water and illite.