ANALYSIS OF THE PHYSICAL CHARACTERRISTICS OF No. 15 COAL RESERVOIR IN NORTHEASTERN QINSHUI BASIN

A comprehensive analysis is carried out on No.15 coal reservoir in the Upper Carboniferous Taiyuan Formation in northeastern Qinshui Basin from the aspects of macroscopic view, thin slide, electronic microscopy, mercury intrusion and mechanics. The result shows that the coal facies of such type can form good coal reservoir, with high V/I value, which reaches Grade I standard for reservoir assessment in depth, thickness, effective porosity and structure, favorable for the exploitation of coalbed methane. The cleats in No.15 coalbed are developed, but commonly filled with vein calcite. The pore-throat relation of microporous-micro throat type is also unfavorable factor for coalbed methane development. Comparison of mechanic parameters of the coalbeds in the studied area to those in southern Qinshui Basin shows obvious differences in the roof and floor rocks. Although the pressure-breaks extend to the roof and floor, width and height of the breaks are smaller than those in southern Qinshui Basin. So the pressure-breaks are relatively easy to be controlled in coalbeds.