歧口凹陷滨海地区沙一段远岸湖底扇沉积特征及形成机制

Sedimentary characteristics and formation mechanism of sublacustrine fan on the far shore of member 1 of Shahejie Formation in coastal area of Qikou Sag

歧口凹陷滨海地区沙一段时期主要发育重力流沉积,为厘清其沉积特征及有利砂体展布规律,通过岩心观察、粒度分析等方法对重力流沉积进行研究,认为研究区发育的重力流沉积主要为滑塌型远岸湖底扇,在港西凸起带上砾岩或砂砾岩指示了补给水道的存在,多条顺向发育的断裂所形成的多级断阶古沉积环境是导致远岸湖底扇多级发育的主要形成机制,其物源供给是远岸湖底扇发育的物质基础。基于此构建了歧口凹陷滨海地区沙河街组沙一段远岸湖底扇的沉积模式,明确了远岸湖底扇有利砂体的空间展布规律。该研究对进一步明确沙一段远岸湖底扇砂体有利储层微相类型和预测有利储层分布具有积极意义,为该区下步油气勘探提供了沉积学支撑。

Gravity flow deposits mainly developed in member 1 of Shahejie Formation in the coastal area of Qikou Sag.In order to clarify the sedimentary characteristics and the distribution of favorable sand bodies,this paper studies the gravity flow sediments by means of core observation and grain size analysis.It is considered that the gravity flow sediments developed in the study area are mainly slump-type far-shore sublacustrine fans,conglomerate or glutenite indicates the existence of recharge channels in the west uplift zone of Gangxi,and the multi-stage fault-step paleosedimentary environment formed by several forward-developing faults is the main formation mechanism of the multi-stage development of far-shore sublacustrine fans,and the material supply is the material basis for the development of far-shore sublacustrine fans.Based on this,the sedimentary model of the far shore sublacustrine fan of member 1 of Shahejie Formation in the coastal area of Qikou Sag is established,and the spatial distribution law of favorable sand bodies of the far shore sublacustrine fan is defined.This study is of positive significance for further clarifying the favorable reservoir microfacies types and predicting the favorable reservoir distribution of the far shore sublacustrine fan sand body of member 1 of Shahejie Formation,thus providing sedimentological support for the next oil and gas exploration in this area.