CBM geological characteristics and exploration potential in the Sunan Syncline block, southern north China basin

摘要

The Permian coal-bearing strata in the Sunan Syncline block contains abundant coalbed methane (CBM) resources. However, systematic studies of CBM geological characteristics in the block are still lacking which severely hinders the CBM development. This paper presents a synthetic study of the CBM geological characteristics in the block from the aspects of gas accumulation conditions and geological controls. Results show that the coal seams are dominated by medium-to high-volatile bituminous coals with the coal structure of normal and cataclastic, possessing relatively high fracability and permeability. The total thickness and gas content of the main coal seams are 9-12 m and 2-21 m(3)/t, respectively. The CBM in the shallow and deep parts of the block shows the feature of secondary bacterial gas and thermogenic gas, respectively. The roof lithologies of the coal seams and the structure types in the block provide good gas sealing conditions for CBM. In addition, the groundwater migration from the flanks to the axial region of the Sunan Syncline leads to relatively high gas content in the deep part of the block. Based on the CBM geological characteristics, the CBM exploration potential in the block was evaluated, and 2 zones were selected as favorable targets for CBM exploration.