Analysis of key geologic factors of fracturing effect of CBM wells for high-rank coal in Southern Qinshui Basin

Geological conditions are key factors which affect the performance of hydraulic fracturing used in CBM (coalbed methane) straight wells. It is vitally important to figure out the influence of geological conditions on the per- formance of hydraulic fracturing in order to improve the adaptation of formation stimulation techniques. Based on the propagation experiments of hydraulic fractures,this paper analyzes the construction curve shape and the artificial crack monitoring data with equal correlation data,and summarizes the law of fracture propagation and discusses the relation- ship between artificial fracture and coal structure,crustal stress and the mechanical parameters of the CBM straight wells and its effect on gas production. The direction and improvement of fracturing process are put forward. The re- search shows that the coal structural effect of length and complexity of artificial main crack;the length and direction of the crack opening are controlled by crustal stress;the degree of difficulty in fracturing construction is mainly deter- mined by mechanical parameters. The differences of these geological conditions mentioned above result in the limita- tions of normal hydraulic fracturing techniques. Therefore,the formation stimulation techniques should be optimized and special formation stimulation measures should be adopted,according to the differences of these geological condi- tions,to improve the performance of hydraulic fracturing techniques. These results will have a guiding significance for improving the hydraulic fracturing techniques of coalbed methane wells in Qinshui Basin.