鄂尔多斯盆地延长组开阔浅水湖泊风暴沉积

 通过岩心观察，发现鄂尔多斯盆地延长组长8油层组具有典型的风暴沉积特征，主要包括底面侵蚀构造、丘状交错层理、特征异地煤、滞积层、生物逃逸迹等，是风暴流作用于湖岸线附近的三角洲沉积，是沉积物经再搬运和再沉积的产物。其理想的垂向序列由A-G7段构成，向湖盆中心方向，强能量风暴流形成的滞积层和块状砂岩减少，低-弱能量的丘状交错层理和波状纹层段明显增加。鄂尔多斯盆地延长组发育独具特色的开阔浅水湖泊风暴沉积，垂向上表现为多期叠置，平面上表现为对浅水三角洲沉积物的全面改造，总体上呈现出“满盆砂”，成为一种新型储集层，可形成大规模分布的岩性油气藏。

Storm deposits in wide and shallow lacustrine environment in Yanchang Formation,Ordos Basin

Through the core observations, storm deposits are found in Chang 8 of Yanchang Formation, Ordos Basin, with features including the etching structure, the hummocky cross stratification, the ailochthonous coal, the storm lag deposit, and the Fugichnia. The deposits are developed by the tempestuous currents retransporting and redepositing the delta sediment near the lacustrine shoreline. Their vertical sedimentary sequence consists of seven lithofacies units from A to G. Toward the lacustrine centre, the storm lag deposits and the massive sandstones gradually decrease and correspondingly, the hummocky cross stratification and ripples increase. It is shown that the distinctive storm deposits are developed in the wide and shallow lacustrine environment. The multi-stage deposits are overlain in the vertical section and the fully reconstructed shallow delta sediment is in the horizontal section, with rich sandstones being raised in the whole basin to provide a new reservoir. This study is conducive to the formation of the large lithologic reservoirs and to a new field for the petroleum exploration in Ordos Basin.