摘要:
对美国在采页岩气赋存场所的对比分析发现,页岩气主要分布在由阿巴拉契亚逆冲断裂带、沃希托(Ouachita) 逆冲断裂带、拉腊米逆冲断裂带所围的前陆盆地中。究其原因,前陆盆地下部地层通常为厚度较大的富含有机质的克拉通时期的沉积,它为页岩气的形成提供了充足的物质基础;而前陆盆地的上部地层通常受后期冲断褶皱的挤压,由此引发的构造热事件为下部烃源岩的成熟和页岩层天然裂缝的产生提供了热力学条件。鄂尔多斯西缘前陆盆地的上三叠统延长组为主要烃源岩,其中,西南部泥页岩具有厚度大、有机质丰富、成熟度高等特点,与福特沃斯前陆盆地Barnett页岩相似,因此,推测鄂西前陆盆地西南部为页岩气赋存的有利场所,具有较好的页岩气勘探前景。
Abstract:
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.
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