Experimental Investigation of the Effect of Size on the Mechanical Behavior of Shale

China is rich in shale oil resource, which referring to the petroleum accumulation occurred in pure shale （including mudstone and shale） reservoir, namely shale oil. It is expected to become an important alternative energy in the future （Zou et al., 2003）. However, the shale oil production is far from the standard of economic efficiency. So there is a need to carry out effective fracturing treatment in order to increase yield. The mechanical behavior of rocks have an important influence on the fracturing treatment of reservoir, such as crack initiation and propagation during fracturing treatment. Therefore, evaluating the mechanical behavior of shale is an important work.