矿床地球化学国家重点实验室知识库

The investigation of pore structures in coal is supposed to be a primary approach to ascertain coal structure's influence mechanism on CBM storage and migration. In this study, pore structures in multiscale have been comprehensively and systematically explored for high-rank primary coal and granulated-mylonitized coal (tectonically disturbed coal with high deformation degree), two main typical kinds of coal structures in southeastern Qinshui Basin, by a series of pore-detecting experiments. Based on pore structure differences between two coals, the influences of tectonic stress on pore structures were discussed and the control mechanisms of pore structures on gas adsorption and seepage were further analyzed. It turns out that, (1) adsorption pores (< 100 nm) are more well-developed for disturbed coal than for primary coal, which determines stronger gas adsorption and reservoir capacities in disturbed coal; (2) micron-level seepage pores (0.1μm-0.1 mm) could be clearly divided into two ranges, namely seepage major-pores and seepage minor-pores. It could be deduced that the main seepage pore/fracture system generally consists of macroscopic cleats/fractures and seepage majorpores. The system is less developed in disturbed coal than in primary coal, which is the essential reason for the low permeability in disturbed coal; (3) strong dynamic metamorphism and ductile deformation induced by intense tectonic compression/shear stress, facilitate further generation of adsorption pores, and also result in the destruction of the main seepage pore/fracture structure. That's the control mechanism of tectonic stress for strong gas bearing potential and poor seepage capability in granulated-mylonitized coal reservoir. This research is of an important enlightening significance in CBM production aiming at high-rank disturbed coal reservoir with high deformation intensity in the study area.