东濮凹陷地质特征研究

Discussion on geological features of Dongpu Depression

岩心观察及精细的层序地层对比表明,东濮凹陷北部沙三段的盐岩与暗色泥岩、膏泥岩及砂岩具有共生组合关系,盐岩是低水位期的沉积。在高水位期,盆缘沉积了三角洲和扇三角洲,盆内沉积了深灰色泥岩和少量重力流砂体;在低水位期,湖盆面积缩小,许多地区暴露地表,从湖泊中心向周围沉积物依次为盐岩、膏岩、膏泥岩、碳酸盐岩、灰质泥岩和牵引流砂岩体。高水位和低水位的频繁变化导致深水暗色泥岩和低位盐、低位砂的纵向叠加。通过对高频振荡湖盆的古地理环境以及盐岩与砂体分布、盐岩分布与沉积中心的关系的研究,得出与以前"深水成盐"、"高山深盆"、"浊积成砂"等不同的新概念,对确定盆地油气资源潜力和勘探方向有一定借鉴作用。

The observation result of cores and stratigraphic correlation showed that the salt rocks in the third member of the Shahejie Formation of Dongpu Depression were associated with deep gray mudstone, gypsum mudstone and sandstone,and the salt rocks were deposited during low-level period. In the high-level stage, delta and fan delta were developed on the basin margins ,and deep gray mudstone and a few gravity flow sandbodies were developed in the center of basin. In the low-level stage, the area of lake was exposed on the surface, because of the shrinking of lake, As a result, the sediments were salt rocks, gypsum,gypsum mudstone, carbonate rocks, calcilutite and drag flow sandstone from the center to the margin of the basin. The frequent change of water depth resulted in the frequent alternation of dark mudstones and low-level salt rock and sandstone. The paleogeographic environment of the high-frequency oscillating lake basin and the relationship between distributions of sandstone and salt rock as well as between the distribution of salt rock and the deposition center were studied, A new conclusion different from the theories, such as ＂deep water salts-forming＂,＂high mountain and deep basin＂ and ＂hackberry facies sand＂ , was obtained. The new conclusion will be useful for confirming the resource potential and indicating the exploration target of Dongpu Depression.