Structural Evolution of Organic Matter in Deep Shales by Spectroscopy (1H & 13C−NMR, XPS, and FTIR) Analysis

Amorphous organic matter in geomaterials also known as kerogen undergoes 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), and Fourier transform infrared (FTIR) techniques. For this study, 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 using programmed pyrolysis. Later, organic matter was extracted from selected aliquots for chemical spectroscopy. 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 quantified by ...