Evaluation of the coal reservoir permeability using well logging data and its application in the Weibei coalbed methane field, southeast Ordos basin, China

Permeability is one of the most critical reservoir evaluation parameters in coalbed methane (CBM) exploration and development. In this study, an improved collection of sheets model was proposed for evaluation of reservoir permeability of the no. 5 coal seam in the Weibei CBM field, southeast Ordos basin, China. The evaluation model is expressed by k = 8.50 × 10− 4nw2ϕf in which the fracture width (w), fracture density (n), and porosity (φf) can be obtained by analysis of the deep lateral resistivity logging and micro-sphere focusing logging data. The calculated permeability values are ranging from 0.005 to 2.327 mD across the Weibei coalfield. The regional distribution of permeability is mainly controlled by the factors of burial depth and tectonics stress. The permeability is high in the shallow area and the zone of normal faults, but it is low in the anticline area and the upthrust side of thrust faults. The results show that the calculation method developed in this study is reliable, providing a better understanding of the coal reservoir for CBM exploration in the study area.