Session: Undergraduate Research Posters: Computational Chemistry:

In recent years of fracking, the issue of borehole failures arising from shale instability has been increasing. Shale instability is caused by the intermolecular interactions of polar water-based drilling fluids (DFs) with shale minerals. Therefore, DFs formulated from liquefied petroleum gas (LPG) have been proposed as an alternative to those water-based DFs traditionally used in fracking. LPG is a mixture of propane, butane, isobutane, and other nonpolar substances that can be safely recovered from the borehole. This project aims to solve the issues of shale instability by improving upon this waterless fracking method via polyol alcohol additives, like ethylene glycol and glycerol, which can be incorporated with the LPG to advantageously increase its polarity. Intermolecular interactions between components of LPG-alcohol mixtures and phyllosilicates that create this shale instability were identified and analyzed using computational chemistry methods, such as density function theory (DFT) and fragment molecular orbital theory (FMO). Quantum DFT calculations provided the geometric optimizations for each of the six orientations of the LPG component-phyllosilicate systems in the gas-phase. Following optimization, the FMO investigation employed pair interaction decomposition analysis (PIEDA) to calculate the energy values of non-covalent interactions, which included Coulomb, polarization, dispersion, quantum exchange repulsion, and charge transfer in solvation under the polarizable continuum model (PCM). Essentially, PIEDA was utilized to predict which intermolecular interactions are most prevalent in each of those six orientations of the LPG component-phyllosilicate systems. These intermolecular interactions were studied further by examining the bond length and bond angles between the LPG-component and phyllosilicate in all six configurations. Throughout the entirety of this project, bulk steric factors that influence LPG-phyllosilicate interactions were also taken into consideration. The results obtained reveal that interactions of the nonpolar LPG components with domination of dispersion-driven and weak electrostatic interactions (C–H…O) have little preference to a particular phyllosilicate face, while polar molecules with domination of hydrogen bonding (O–H…O) have higher affinities to faces of the phyllosilicate cluster that represent imperfections or cracks in an ideal crystal.

Dr. Yana Kosenkov

Lecturer, Monmouth University

Appearances