Understanding of brittleness and the relative brittleness index construction

As hydraulic fracturing becomes a routine practice to enhance or enable the recovery of hydrocarbon in tight formation, it is important to estimate the fracturability of subsurface rock formation. The brittleness is the key parameter for rock fracturing evaluation. Since the brittleness of rock is related to mineralogy and mechanical properties, researchers proposed various methods to evaluate brittleness considering the mineral composition and elastic properties. Based on the understanding of brittle and ductile definition, this article proposed two methods to calculate the relative brittleness index. One method uses the mineral composition to construct relative brittleness with the view that different minerals have different brittleness, another one utilizes elastic properties to construct the relative brittleness indexes which are more sensitive than other brittleness indexes presented in the previous study. The evaluation result in a well of Jiannan area in Southern China proves the appropriation of the methods.