ABSTRACT
Features of coal reservoirs with low rank and their coalbed methane storage were studied of the Jurassic continental basins in northwestern China, The results show: (1) the coal reservoirs possess a large pore volume and pore specific surface area, a high free gas storage potential, but a low in-position gas absorbability; (2) the gas storage volume of the deep coal reservoirs is remarkably larger than that of the shallow; and (3) the shallow coal reservoirs store absorption gases, whereas the deep ones store absorption gases, free gases as well as solution gases at the same time. The pool-forming models of coalbed methane in the shallow zone are the steep-slope-basin-rim model, the gentle-slope-basin-rim model, and the inside-basin depression model of continental basins in northwestern China, of which the gentle-slope-basin-rim model is of important significance in practice. However, the structural high-points and traps might influence greatly on coalbed methane pooling in the deep areas, which indicates that the concurrent exploration and development of coalbed methane and natural gas are theoretically feasible.
