鄂尔多斯盆地中及上三叠统延长组沉积相与油气勘探的突破

鄂尔多斯盆地位于中国的中西部,跨陕、甘、宁、蒙、晋5省区,盆地本部面积25万km2.中及上三叠统延长组在盆地内广为展布,厚逾千米,发育冲积扇、河流、三角洲、湖泊等沉积相,是该地区重要的油气产层.根据盆地腹地100多口井的钻井资料及盆地周边地区的露头资料,以及长庆油田长时期对延长组的油气勘探经验,编制出了鄂尔多斯盆地中及...

Sedimentary facies of the Middle-Upper Triassic Yanchang Formation in Ordos Basin and breakthrough in petroleum exploration

The Ordos Basin lies across Shaanxi，Gansu，Ningxia，Inner Mongolia and Shanxi Provinces of middle-western China.Its area reaches 2.5×10⁵ km².The Middle-Upper Triassic Yanchang Formation，more than 1000 m thick，is widely developed in the basin.Alluvial fan，fluvial，delta and lacustrine facies developed well during the Middle and Upper Triassic，and formed the key oil- and gas-bearing layers of the basin.According to the data collected from more than 100 drilling wells in the hinterland basin and many outcrops in the surrounding areas，as well as the long-term exploration and research experiences，we compiled 7 sedimentary facies maps of different oil-bearing intervals of the Middle-Upper Triassic Yanchang Formation of the Ordos Basin.The features of sedimentary facies in different depositional periods of the Yanchang Formation，especially the distribution and evolution of the dark mudstone and shale of the deltas and lacustrine facies，as well as the sand body of the various strand-bars and the gravity flow facies，were illustrated in detail.By the theoretical guidance of the sedimentary facies and lithofacies palaeogeography，the oil exploration of the Yanchang Formation has made great breakthrough constantly in the Ordos Basin.Several large oilfields，with the proved reserve more than 1×10⁸t，such as Shanbei，Xifeng，Jiyuan and Huaqing oilfields，have been discovered in recent years.