Fracability Evaluation in Deep Shale Reservoirs Based on a Fuzzy Grey Correlation Analysis Method

Fracability is used to evaluate if it's easy to form complex fracture networks by the volumetric fracturing in shale gas or not. The main parameters of shale gas fracability evaluation methods at home and abroad are analyzed and summarized, combining the characteristics of high temperature, high pressure and strong plasticity in deep shale gas layers, the comprehensive evaluation parameters of deep shale reservoirs fracability based on the geological and engineering factors are optimized. Fully considering the effects of formation confining pressure and rock anisotropy on parameters, the calculation method of fracability evaluation parameters is formed. Using fuzzy grey correlation analysis method, the correlation between the fracability index curve of different weight combinations and the fracture complexity index curve is analyzed. According to the maximum principle of correlation coefficient, the weight combination is optimized, the comprehensive evaluation mathematical model of fracability is established, and the comprehensive evaluation method of deep shale gas fracability is formed. It is of guiding significance to the optimization design of fracturing parameters for deep shale gas to improve fracture complexity.