A Rock Physics Model for the Characterization of Kerogen Content and Maturity Level in Shales

Abstract

Exploration and exploitation of shale gas need better understanding of rock physics relations between reservoir parameters and elastic properties. Kerogen content plays a significant role in elastic properties due to its low density, and hydrocarbon-filled pores in organic matter generated during different maturity levels will enhance the effect of kerogen in shales. In this study, we develop a shale rock physics model by incorporating Kuster and Toksöz theory and the self-consistent approximation method to quantify the effects of such factors on elastic properties in shales. Modeling results show that both kerogen content and kerogen-related porosity decrease velocities and density of shales, but kerogen content tends to affect elastic properties more profoundly, and the effect of kerogen-related porosity on the elastic properties only becomes more obvious as kerogen content goes up beyond about 0.1. We also find that the increase in kerogen content increases Poisson's ratio, while the variation in kerogen-related porosity has little effect on Poisson's ratio. Finally, for the reflector model designed in this study, the variations in kerogen content and kerogen-related porosity result in significant and predictable variations in AVO intercept and gradient.