鄂尔多斯盆地晚三叠世湖盆浊积岩发育特征及地质意义

Developmental Characteristics of Turbidite and Its Implication on Petroleum Geology in Late-Triassic Ordos Basin

鄂尔多斯盆地晚三叠世延长组长6、长7期的深湖区域经过钻探发现多套厚薄不等的浊积岩砂体。通过岩心观察描述及岩石结构、构造特征分析研究,得出鄂尔多斯盆地延长组长6、长7期湖盆深湖区域发育的浊积岩属于三角洲前缘滑塌成因;其中西南物源方向的辫状河三角洲前缘的深湖部位主要发育较粗粒滑塌浊积岩;盆地东北物源方向的曲流河三角洲前缘的深湖部位主要发育较细粒滑塌浊积岩。弄清鄂尔多斯盆地晚三叠世湖盆中浊积岩特征及分布规律,不仅对大型陆相湖盆深湖区浊积岩的形成机理与发育特征研究具有重要意义,而且对深湖区浊积岩中油气的成藏机理研究也具有指导作用。

Unequal thickness of turbidite sandbodies are found in the deep-lake area of Triassic Yanchang Formation Ch7 and Ch6 member of Ordos Basin. Based on the integrated study of the sedimentary facies features, rock texture, structural attitude of the Ch6-Ch7 drilling core, the turbidite was caused by the delta-front landsliding. The turbidite is concluded into two types： the coarse grains fluxoturbidite was mainly developed with braid river delta-front which the clastic source was from southwest; the fine grains fluxoturbidite was mainly developed with meandering river deltafront which the clastics source was from northwest. Figuring out the developmental distribution and regular pattern of turbidite in the Ordos Triassic lake-basin not only directs the exploration of the turbidite reservoir in the deep lake, but also benefits the study on hydrocarbon accumulation of the turbidite on the deep-lake facies.