Evaluation model of CBM resources in abandoned coal mine and its application

How to evaluate the CBM resources in abandoned coal mines has become a key issue for development. On the basis of study on the deformation and failure law of overlying strata in coal mining,the authors set up an evaluation model and method for evaluating the CBM resources in abandoned coal mines through theoretical analysis and mathe- matical deduction. In particular,the CBM resources in Jinsheng mine goaf,which belongs to Shanxi Jincheng Anthra- cite Mining Group Ltd. ,China,have been evaluated using the evaluation model. Results show that the deformation and failure of the rock mass in coal seam roof,and the stress redistribution of the surrounding rock mass have been caused by coal mining. The CBM resources in abandoned coal mines are mainly composed of adsorbed and free gas from coal pillar,residual coal and surrounding rock. Based on the deformation and failure characteristics of overburden rock and the relationship between porosity and expand coefficient of fractured rock mass,the pore volume models of caving and fracture zones in goaf are established separately. Considering the distribution characteristics of CBM resources and floo- ded situation in abandoned coal mines,the calculation models of water volume and saturation are also established. Al- so,the e2valuation results show that the abandoned8coa3l mines are abundant of CBM resources,with a coal mine area of 6. 5 km and a total CBM resource of 5. 871 7×10 m in coal seam No. 3 of Shanxi Group,Permian. The volume of ad- sorbed gas is 5. 835 3×108 m3 and free gas is 0. 036 4×108 m3 ,and the resource abundance is 0. 902 0×108 m3 / km2 .