AN INVESTIGATION OF THE KEROGEN-MINERAL INTERACTIONS IN GREEN RIVER OIL SHALE

The richest oil shale deposit in the world is found in the Green River Formation Basin located in the United States with the potential to be a major national resource, yielding significant amounts of oil upon heating. Green River oil shale contains minerals, bitumen, and kerogen, the insoluble organic remains found in sedimentary materials. Current extraction methods are environmentally unfriendly and are very inefficient due to tremendous energy requirements. Thus, the extraction of kerogen is commercially not viable in the United States at this time.

Experimental studies performed at North Dakota State University are aimed at evaluating the molecular interactions in oil shale by studying the in situ chemical composition, mechanical properties, and the physical location of kerogen in Green River oil shale. Research efforts have gone into understanding how the kerogen is “locked” in the surrounding mineral matrix. Fourier Transform Infrared studies have been conducted using the photoacoustic step-scan method to investigate the molecular nature of light and dark-colored areas of the oil shale as well as kerogen-mineral interactions. Results show that light colored oil shale has a higher kerogen content with spectra similar to that of isolated kerogen while dark oil shale contains more mineral components. Kerogen band shifts were observed due to interactions occurring on the molecular scale between kerogen and the surrounding minerals. Scanning Electron Microscope studies were performed in order to obtain information on the size and layout of kerogen in the shale. Energy Dispersive Spectroscopy performed on light and dark colored samples coincided with FTIR results, further indicating that the light colored oil shale contains more kerogen while dark oil shale samples have lesser amounts of kerogen. The SEM images and nanoindentation results indicate the absence of large kerogen regions leading us to conclude that Green River kerogen is on the scale of tens of nanometers. Based on Nano-mechanical testing of in situ Green River kerogen, an elastic modulus of 9 GPa and hardness of 1 GPa was found. The nano-size kerogen regions are in very close proximity to the minerals and previous work from our group suggests a significant influence of the minerals on the properties of in situ kerogen.