Hyeonseok Lee

Date of Award

January 2020

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Petroleum Engineering

First Advisor

Hui Pu

Abstract

A series of studies have investigated the applicability of kerogen, which is an amorphous and insoluble organic matter abundant in unconventional shale formations. This geo−materials are known to have undergone significant alteration in chemical structure during thermal maturation which is characterized using a combination of solid−state 1H & 13C−NMR, X−ray photoelectron spectroscopy (XPS), Fourier transform infrared (FTIR), Matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF-MS) techniques. For these studies, four kerogen samples (type−II) from the Bakken Formation were selected based on the differences in their thermal maturity, as well as representing the pre−oil and oil window stages as measured through organic petrology and bulk geochemical screening of the samples. Results documented a systematic structural change in these four samples where the ratio of CH3/CH2 increased when the maturity increases, along with the presence of shorter aliphatic chain length. Furthermore, the aromatic carbon structure becomes more abundant in higher maturities and oil window stages. It concluded that, the structural and chemical changes that occurs in the organic matter involves defunctionalization of heteroatom functional groups, coupled with an increase in cross−linked carbon in the residual remaining kerogen. Also molecular weight distribution variations in kerogen samples revealed the rate of change in molecular mass populations as a function of thermal maturity.

The studies using computational simulation techniques investigated the applicability of kerogen for separation of the mixture of gases (CO2 and CH4) in dry and wet (brine) conditions for an effective storage and injection operation. Here, through grand canonical Monte Carlo (GCMC)/molecular dynamics (MD) simulations, the studies of thermodynamics and kinetics investigated the CO2 transportation and adsorption behavior on three-dimensional (3D) kerogen molecular models from the Bakken, which contains non-periodically arrayed functional groups. The stronger interaction of CO2 molecules with the model leads to the penetration of CO2 molecules to the sub-surface levels. And, the concentration of brine shows a positive effect for CO2/CH4 selectivity that supports our goals of sequestration and enhanced production. These results suggest the important role of kerogen in the separation and transport of gas in organic−rich shale plays that are the target for sequestration of CO2 and/or enhanced oil recovery (EOR).

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