Abstract: Crushability evaluation on shale reservoir is to evaluate the difficult degree of generating fracture network; in other words, is to demonstrate the SRV(stimulated reservoir volume) can whether or not be effectively implemented. It is a key of the whole fracturing work. At present, there is no unified reference standard and evaluation method at home and abroad. A new evaluation method is developed in this paper. For 10 kinds of cores, their rock mechanical parameters are tested firstly; and the commonly used three kinds of shale brittle evaluation methods are comparatively analysed. The fracture is characterized quantitatively by using fractal dimension of trace of fracture structure surface and areal density; and the caving clastic mass after fracturing is analysed. The results show that the accuracy of Young’s modulus and Poisson’s ratio discriminance and plastic coefficient discriminance used to evaluate shale brittleness, are higher. The characteristics of high Young’s modulus, or(and) low Poisson’s ratio are usually presented for the brittle rock; but there is no corresponding relation between brittleness and uniaxial compressive strength, tensile strength and indentation hardness. Fracture distribution after fracturing has fractal structure with statistical sense of self-similar. The fractal dimension can be used for quantitative evaluation of fracture network complexity. The higher the rock hardness, the smaller the fracture density after fracturing. The stronger the brittleness, the larger the fracture density after fracturing. The new method is the integrated embodiment of characteristics of rock hardness, brittleness and natural fractures system(and sedimentary structure). It is not only visual and reliable, but also simple and effective to evaluate the ability of forming fracture network after fracturing on shale reservoir; and as a result, it illustrates a good prospect of application and extension in oilfield. This work is very significant for evaluation and development of shale reservoir.

Key words: shale, crushability, brittleness, indentation hardness, fracture density, fractal dimension