The Effect of Stress on Brittleness of Synthetic Shale with Different Types of Clay Minerals

Clay minerals are important components in shale, controlling elastic properties and anisotropy of shale. Knowing the elastic properties of shale with different types of clay minerals is therefore imperative to fully understand seismic properties of the reservoir. In this study, three sets of samples with different type of clay minerals were made. Ultrasonic experiments have been conducted to study the effect of stress on brittleness of synthetic shale with different types of clay minerals. The results show that the types of clay minerals have great influence on the brittleness of shale. Structure difference and compositional variations of clay minerals may explain some of the behavior. Dynamic Young’s moduli E and Poisson’s ratios ν increase with applied pressure, but the rate of increase for samples is higher at low pressures (< 20 MPa). Besides, we also find that E11 is always larger than E33 and ν31 is also different from ν12, which indicate that Young’s moduli E and Poisson’s ratio ν of samples have anisotropic behavior. In terms of the birttleness of samples, B11 is always larger than B33, which may be attributed to the layer charge and low-aspect-ratio pores between the clay particles.