渤海湾盆地辽东湾坳陷盆中隆起缓坡带重力流沉积形态及其控制因素

Geomorphology of gravity flow deposits in the gentle slope zone of intra-basinal high in the Liaodong Bay Depression， Bohai Bay Basin and its controlling factors

蒋恕 王浩 郭涛 张如才 杜晓峰 张钰莹 刘恩豪 王华

Shu Jiang Hao Wang Tao Guo Rucai Zhang Xiaofeng Du Yuying Zhang Enhao Liu Hua Wang

随着油气勘探开发的深入，重力流沉积形成的岩性圈闭逐渐成为人们关注的焦点。渤海湾盆地辽东湾坳陷辽西凸起东部斜坡带（辽中凹陷西斜坡）勘探程度低，近期在该盆中隆起缓坡带发现的具高密度浊流性质的重力流扇体表现出良好的岩性地层油气藏勘探前景。建立辽西凸起东斜坡古近系东营组三段高精度层序地层格架，并基于地震、测井及岩心资料对体系域内重力流沉积的形态及其控制因素开展了综合研究。辽西凸起东部缓坡带主要发育4种形态的斜坡扇：舌形扇、花瓣扇、朵叶扇及河道扇。斜坡陡缓程度和重力流物质来源（远源辫状河三角洲前缘）的富砂程度共同控制扇体形态。坡折类型影响湖底扇长宽比：坡折类型越复杂，坡度越陡，湖底扇的长宽比越大，表现为长舌形；坡折类型越简单，坡度越缓，湖底扇的长宽比越小，表现为朵形。物源富砂性决定湖底扇河道化程度及稳定性：砂质含量越高，河道的成型性越差；泥质含量越高，河道越稳定。因此，陡-富砂地质条件易形成舌形扇，缓-富砂地质条件易形成朵叶扇，缓-富泥地质条件易形成河道扇，花瓣扇为过渡型。

Lithologic traps formed by gravity flow deposits have gradually become the focus of hydrocarbon exploration and development. The eastern slope of Liaoxi uplift or the western slope of Liaozhong Sag is still at an early stage of exploration in the Liaodong Bay Depression， Bohai Bay Basin. A gravity flow fan of high-density turbidite nature was drilled recently in the gentle slope zone of the intra-basinal uplift and shows a potential target for future exploration of lithologic-stratigraphic reservoirs in the slope zone. In the study， a high-resolution sequence stratigraphic framework of the 3 member of the Paleogene Dongying Formation in the study area is established at first， followed by a comprehensive study on the geomorphology and its controlling factors of gravity flow deposits within the systems tracts based on an integrated analysis of seismic， logging， and core data. The results show that four types of slope fans are mainly developed in the gentle slope zone to the east of Liaoxi uplift， namely the ligulate fan， petal-shaped fan， lobe-shaped fan and channel-shaped fan， the morphology of which is determined by slope gradient and sand richness of gravity flow sediment sources （the distally-sourced braided river delta front）. Among others， the more complex the slope break and the steeper the slope， the larger the aspect ratio of the sublacustrine fan is， displaying in a long ligulate shape， while the simpler the slope break type and the gentler the slope， the smaller the aspect ratio of the sublacustrine fan is， displaying in a lobe shape. On the other hand， the sand richness of sediment source determines the degree of channelization of sublacustrine fan and its stability. The higher the sand richness， the lower the channel stability is， while the higher the argillaceous sediment content， the higher the channel stability is. Therefore， the steep slope rich in sand is prone to form a ligulate fan， the gentle slope rich in sand is prone to form a lobe-shaped fan， and the gentle slope rich in argillaceous sediment is prone to form a channel-shaped fan； the petal-shaped fan is but of a transitional type.

10.11743/ogg20220407