溱潼凹陷西斜坡阜三段断陷湖盆砂质滩坝沉积特征

Sedimentary characteristics of sandy beach-bar in faulted-lacustrine-basin,Ef_(3) in west slope of Qintong Sag

以溱潼凹陷西斜坡阜三段砂质滩坝为研究对象,通过对钻井岩心、测井、录井以及各类分析化验数据进行综合研究,分析砂质滩坝沉积特征与沉积动力学条件,划分砂质滩坝成因类型并总结沉积主控因素,并在时空条件下讨论砂质滩坝沉积体系与分布特征。研究认为,溱潼凹陷西斜坡砂质滩坝可进一步划分为滩砂与坝砂,两者在岩性、颜色、厚度、粒度、沉积构造等方面存在较大差异。西斜坡带砂质滩坝沉积按照成因可以划分为远源三角洲前缘前端与侧缘再沉积砂质滩坝和近源冲积扇控制下的近岸砂质滩坝两种类型。远源三角洲前缘前端与侧缘再沉积砂质滩坝见于阜三段各砂组中,且在Ef_3~4砂组中分布最为广泛;近源冲积扇控制下的近岸砂质滩坝则仅见于Ef_3~4砂组中,局限于西斜坡东南沿岸呈条带状发育。对陆相断陷湖盆砂质滩坝沉积特征研究,以及湖相薄互层岩性油气的勘探与开发具有一定的理论借鉴。

Taking the sandy beach-bar deposit in the 3rd member of Funing formation(Ef3)in the west slope zone of Qintong sag as the research object,based on core,logging and various analysis test data,the sedimentary characteristics and sedimentary dynamic conditions of the sandy beach-bar are analyzed comprehensively,the genetic types of sandy beach-bar have been divided and the main controlling factors under spatiotemporal conditions have been summarized.The research suggests that the sandy beach-bar deposits can be further divided into beach sand and bar sand,and they have great differences in lithology,color,thickness,particle size and sedimentary structure.According to the analysis of the sedimentary dynamic conditions for the formation of sandy beach-bar,the sedimentary genetic types of sandy beach-bar in the western slope belt can be divided into two types:①the redeposited sandy beach-bar in front or side margin of far source delta,②near-shore sandy beach-bar controlled by near-source alluvial fan.The former is found in each sand group of Ef3,and most widely distributed in Ef34 sand group.The latter is only found in Ef34 sand group,which is restricted to the southeast coast of the west slope and developed in belts.The study of sedimentary characteristics of sandy beach-bar in continental faulted lacustrine basin is of theoretical significance for the exploration and development of lithologic oil and gas reservoirs in thin interbedded lacustrine facies.