Feasibility evaluation of commingle fracturing in the integrated development of coal-derived gas resources

The geological characteristics of coal-derived gas resources in Linxing and Shenfu area show a multi-layer system vertically,a superposition and mutual occurrence of lithology,as well as the development of thin interlayers and a low effective rate by monolayer fracturing within these thin interlayers or directly / closely-contact layers. A multilayer fracturing technology for exploring and developing the coal-derived gas resources was introduced in this paper. By nu- merical simulation method,the paper studied the influences of cementation strength and dip angle of interface,stress difference between layers,fracturing operation displacement and other factors on fracture propagation. Also,the fractu- ring operation parameters were optimized,then a suitable reservoir conditions for multilayer fracturing was determined. Based on rock crack criterion and interface fracture criterion,a multilevel evaluation model of multilayer fracturing fea- sibility in coal-derived gas reservoir was finally established,with factors like coal structure,interface mechanics and stress field taken into account. The study has a certain guiding significance to the application of the multilayer fractu- ring technology.