Fracturability of shale based on rock brittleness and natural fracture tensile reactivation

Exploration and development practices have proved that fracturability evaluation is the primary basis for successful fracturing operations. Current studies mainly rely on using traditional physical parameters to evaluate shale fracturability. However, fracture morphology and the extension of natural fractures during fracturing are also crucial for shale fracturability evaluation. In this study, correlations between factors and rock fracture complexity and the degree of natural fracture opening were analysed using 40 sets of related experiments, and a new method is proposed for shale fracturability evaluation that considers Young's modulus, the shear expansion angle, residual strain, the approach angle and the stress variance coefficient. Finally, taking the shale gas field in the Sichuan Basin as an example, a comprehensive evaluation model of shale fracturability was established using the grey correlation method combined with core experimental data. One well was selected in order to compare and analyse the fracturability profile with the stimulated reservoir volume. The results show that peak strain has the most significant influence on shale fracture complexity, followed by the shear expansion angle and Young's modulus. The approach angle and the stress difference coefficient affect the degree of natural fracture opening at the same time. The model is accurate because the fracturability values match the study block's stimulated reservoir volume data. This new method of shale fracturability evaluation provides important technology for predicting the fracturability of shale gas reservoirs and optimizing operation schemes.