柴达木盆地北缘西段不整合发育特征及其油气地质意义

Unconformity Characteristics of West Segment of Northern Margin in Qaidam Basin and Its Significance in Petroleum Exploration

不整合在油气成藏过程中起着非常重要的作用,它既可以是一种油气侧向运移的输导体,同时又可以遮挡形成不整合油气藏。对柴达木盆地北缘西段中、新生代不整合从上下地层接触关系、岩性配置关系以及不整合面之上底砾岩的厚度及分布特征3个方面进行了统计分析;识别出不整合面上下7种地层接触关系、5种岩性配置关系,并分析了不同配置关系对油气成藏的影响;总结了不整合对于该区油气成藏的控制作用,首先它是该区油气从"源"到"藏"侧向长距离运移的主要输导体,同时不整合的形成及存在直接影响该区的油气聚集成藏。根据不整合发育特征,结合其他成藏条件,提出赛什腾凹陷潜伏地区和冷湖七号地区为柴达木盆地北缘有利的勘探地区。

Unconformity plays an important role in petroleum accumulation.It could be a kind of conductor for lateral petroleum migration and could also obstruct petroleum migration to form unconformity reservoirs.This paper analyzes the unconformity between Mesozoic and Cenozoic of west segment of northern margin in Qaidam Basin from the aspects of stratigraphic contact relationship,lithologic allocation relationship,basal conglomerate distribution and thickness,identifying seven kinds of stratigraphic contact relationship and five types of lithologic allocation relationship,and analyzing the effect of different allocation relationship on petroleum accumulation.It summarizes the role of unconformity in petroleum accumulation.First of all,unconformity is the most important lateral and longdistance conductor from source to reservoir.Secondly,existence and formation of unconformity directly affects the petroleum accumulation and distribution.According to the characteristics of unconformity development,considering other accumulation conditions,this paper puts forward that the buried area and Lenghu No.7 area of Saishiteng sag are favorable for exploration.