FORELAND BASIN: A FAVORABLE PLACE FOR SHALE GAS ACCUMULATION

A comparative analysis of shale gas deposits in the United States of America shows that the shale gas in the US is mainly distributed in a foreland basin bounded by the Appalachian Thrust Fault Zone, Ouachita Thrust Fault Zone and Laramide Thrust Fault Zone. The lower segment of the foreland basin with thick Crationic sediments is rich in organic matter, which provides source of shale gas; whereas the upper segment of the foreland basin was squeezed by the thrust folding in the late stage. The thermal events caused by thrust folding provide the thermodynamic conditions for the maturity of source rocks and the tectonic fractures provided the space for the accumulation of shale gas. We could find similar cases in China, such as the West Ordos Basin foreland basin in the Ordos. The Upper Triassic Yanchang Formation in the basin is the main source rock, where the thick mudstone and shale in the southwest part of the basin is rich in organic matter highly matured. It is similar to some extent to the Barnett shale in Woodford Basin. Therefore, it is inferred that the West Ordos Basin foreland basin is a favorable location for shale gas accumulation.