Stress sensitivity mechanism of low-rank coal and its influence on gas production:A case study from Erlian Basin

In order to study the stress sensitivity mechanism of low-rank coal,the dual media stress sensitivity model and gas production forecast model were established. Based on the stress sensitivity experiment and numerical simula- tion,the influence of stress sensitivity on the gas production of high and low rank coal were discussed. This research show that:The stress sensitivity is related to the microstructure,mechanical parameters and compression property. The smaller the elastic modulus and the greater the fracture compressibility coefficient,the greater the stress sensitivity. The stress sensitivity of coal with fracture is greater than that of coal without fracture. Multiple increase and decrease of pressure would irreversibly reduce permeability. Discontinuous drainage would cause pressure fluctuation. The gas pro- duction is lower than that when the drainage is continuous,the greater the stress sensitive,the greater effect on gas pro- duction. The effect of stress sensitive on gas production in Huolinhe area is greater than that in Fan Zhuang area. Due to the characteristic of thick coal and strong stress sensitive,the multistaged indirect fracturing technique and staged fracturing in type “L” horizontal well in roof could be applied to reduce stress sensitivity and improve permeability and gas production.