Effect of thermal maturity on elastic properties of kerogen

Abstract

We have performed spatially continuous nanodynamic mechanical analysis on four organic-rich shale samples with different thermal maturities to extract the elastic modulus of the kerogen particles. Aliquots were rigorously prepared, and three scans were acquired from each aliquot. Subcritical nitrogen adsorption pore characterization was performed to determine the abundance of kerogen-hosted porosity. To fully characterize the pore system of samples from the oil window, toluene and then chloroform extraction were performed to remove the pore-filling hydrocarbons prior to nitrogen adsorption. The statistical distribution of the measured modulus values was analyzed to extract the properties of the shale particles. In mature samples from the peak oil generation or gas window, the kerogen porosity was the dominant pore morphology. We found that significant lowering of the kerogen particle modulus resulted from intraparticle kerogen porosity. The kerogen particle modulus in mature samples was measured as being lower (7–12 GPa) than the immature sample (15–20 GPa) due to gas- or bitumen-filled pores.