陆相湖盆大型重力流发育的成因机制及其优质储层特征研究：以歧口凹陷沙河街组一段为例
Large Gravity Flow Deposits in the Member 1 of Paleogene Shahejie Formation,Qikou Sag, Bohai Bay Basin

陆相重力流沉积是现今油气勘探领域的研究热点.发育在歧口凹陷滨海斜坡古近系沙河街组一段的大型重力流沉积体(沉积范围达到1 700 km2)具有多物源供给、长距离搬运、多级断坡传输、沿路沉积的发育过程与沉积机理特征.以渤海湾盆地富烃凹陷-歧口凹陷的大型重力流为研究对象，在构造-高精度层序地层格架下，以“源-渠-汇”的整体过程为思路，(1)研究多物源的形成、持续供给及匹配关系；(2)分析古地貌(断控陡坡带+多级断阶坡折带)的演化，及其对沉积物搬运、堆积、发育过程的控制作用；(3)针对该重力流具有大规模、多期次的沉积特征，解剖其平面展布及空间分布、沉积模式、时空演化规律；(4)综合探讨陆相重力流沉积体的成因机制、控制因素.综上可知：(1)歧口凹陷大型陆相重力流沉积体发育受多个物源体系的影响与控制，湖盆中心的重力流沉积体与供给物源之间有明确的匹配关系.在古近系沙一段沉积时期，滨海斜坡沉积区主要受北部燕山物源区的大神堂物源、茶淀物源以及西部沧县隆起物源区的葛沽物源和小站物源4个物源共同供给，持续的物源供给使得在歧口凹陷的陆相湖盆中，发育了大规模的重力流沉积体.(2)沙一段同沉积期，歧口凹陷滨海斜坡周缘整个古地貌格局主要表现为断控陡坡带与多级断阶坡折带复合体，断控陡坡带主要发育于滨海斜坡北部，多级断阶带主要呈近东西向发育于斜坡西部.这些断坡带既是物源水下搬运通道又是沉积物堆积的可容纳空间分布区，再加上这些断坡带差异性的持续沉降，对砂分散体系和相带展布具有关键的控制作用.(3)歧口凹陷沙一段重力流沉积过程机制主要表现为重力滑塌沉积、砂质碎屑流、泥质碎屑流、浊流等多种成因，具有横向连片，纵向叠置的沉积样式.
Continental gravity flow deposition is a research hotspot in the field of oil and gas exploration.The large scale gravity flow deposits (up to 1 700 km2) that developed in the Member 1 of Shahejie Formation (Paleogene) in the Binhai slope area in the Qikou Sag shows the sedimentary characters of multiple sediment sources, long distance and multi-fault transport, and preservation along the transfer path during the sedimentary processes. This study focus on the gravity flow deposits in the oil-rich Qikou Sag in Bohai Bay Basin. Under the sequence stratigraphy framework, the sourcetransport path-sink processes has been discussed. The aim of this study is to ① illuminate the formation of the multiple sources, the configuration relationship between different sources, and the origin of continuous sediment supply. ② analyze the controlling and evolution of the paleogeomorphology (faultcontrolling steep slope and multi-step fault slope), sediment transport, the sedimentary develop mechanism in processes. ③ focus on the distributions, sedimentary patterns and space evolution of the large scale multistages gravity flow deposits. ④ discuss the formation mechanism and controlling factors of the gravity flow in Qikou Sag. The conclusions include: ① the gravity flow was controlled by multiple sources. During the Member 1 of Shahejie Formation, the Binhai slope was supplied by sources from four different areas that include: Dashentang source from northern Yanshan Mountain, Chadian sources, Gegu and Xiaozhan sources from western Cangxian Uplift. The continuous sediment supply allows the large scale gravity flow to be formed in the lacustrine basin. ② the paleogeomorphology of the Member 1 of Shahejie Formation in the Qikou Sag is the complex of fault-controlling steep slope and multi-step fault slope. The faultcontrolling steep slope is developed in the northern