Characteristics of Structural Controlled Coallbed Methane in East Margin of Ordos Basin

In order to conclude the structural control effect on coalbed methane in East Margin of Ordos Basin, the key elements control coalbed mathane develop ment were analyzed based on tectonic evolution, structural types, gas content and rock mechanic of coal bearing strata in different blocks. Results showed that the coal strata in the study area were subsided into the deepest depth in Triassic, and the heat flow in the south and middle area increased obviously, which resulted in a higher coal rank than the north under a steadily declined heat flow condition; seven types structure favorable for gas accumulation were developed, e. g. gently incline, monocl ine, anticline ( syncline)，nappe tectonics, reverse fault and extruded layer slip, of which the gently incline and monocline developedwere developed largely and the mo st favorable; under the influence of in-situ stresses, the two sets coal seams of the same well showed magnificent difference in gas accumulation; the coal roof develop ed mudstone, sandstone and limestone, with different effects on methane preservation, of which the limestone showed good sealing effect. Based on the analysis of diff erent coal roof combination and structural patterns, the " co-produced sandstone reservoiring" and " water confining gas reservoring" were proposed, and the prolific str uctural area were also plotted.