Fractureability evaluation of shale gas reservoirs

There are abundant shale gas resources in the Lower Paleozoic marine organic shale strata of the upper Yangtze region, South China. However, affected by multi-period tectonic activities, leading to poor exploitation of the Lower Paleozoic marine shale gas in the complex tectonic zone. Therefore, this study proposes fracturability index (FI) based on shale brittleness, fracture toughness, and stress decay rate. Therefore, this study combines logging data and rock mechanics experiments to obtain the rock mechanics parameters of the Fenggang block shale reservoir. Based on Young's modulus, fracture toughness and critical strain energy release rate, combined with the analytic hierarchy process, the shale fracturability index is proposed to guide the exploration and development of shale gas. The fracturability index of the Longmaxi Formation shale in the study area is 0.34 similar to 0.72. The fracturability of the middle and lower part of the Longmaxi Formation shale is obviously better than that of the upper part. In general, shale reservoirs with high brittleness index, low fracture toughness, and low critical strain energy release rate have high fracturability.

Automated summary

This study introduces the fracturability index (FI) based on shale brittleness, fracture toughness, and stress decay rate for the exploration and development of shale gas in the lower Paleozoic marine organic shale strata of the upper Yangtze region in South China. The fracturability index of the Longmaxi Formation shale in the study area ranges from 0.34 to 0.72, with the middle and lower parts showing better fracturability than the upper part. Shale reservoirs with high brittleness index, low fracture toughness, and low critical strain energy release rate tend to have high fracturability.