渤海湾盆地孤南洼陷沙河街组三段中、下亚段沉积特征

从区域地质资料出发,以岩石学、沉积学及岩相古地理学理论为指导,主要针对岩石颜色、成分、粒度、沉积构造等岩心相标志,对区内10口井的岩心进行了观察,并结合45口井的测井曲线形态特征分析,对孤南洼陷沙河街组三段中、下亚段沉积微相的划分和沉积环境的演化展开了研究,并对其与油气储层的关系进行了探讨.研究表明孤南洼陷沙河街组三段中、下亚段主要发育扇三角洲、三角洲、湖泊共3种类型沉积相,9种沉积亚相,16种沉积微相；并首次发现风暴沉积,认为风暴对油气储集层有一定改良作用；沙河街组三段下亚段沉积时期,洼陷北侧发育小规模三角洲、扇三角洲,南侧发育三角洲,随着湖泊体系的扩展而逐渐萎缩,总体为生油层形成的有利环境；到沙河街组三段中亚段沉积时期,物源区供给增强,洼陷内砂体含量增高,有利于形成良好油气储集层.

Sedimentary characteristics of the middle and lower 3rd member of Shahejie Formation in Gunan Sag,Bohai Bay Basin

Based on the regional geological data and the theory of petrology,sedimentology and lithofacies paleogeography,this paper analyzed sedimentary facies markers of cores from 10 wells including color,composition,granularity,sedimentary structure and etc.The facies makers were integrated with logs of 45 wells to study the division of sedimentary microfacies and sedimentary environment evolution of the middle and lower 3rd member of Shahejie Formation in Gunan Sag,and analyzed their relation to reservoirs..Three main sedimentary facies are identified in the middle and lower 3rd member of Shahejie Formation in Gunan Sag,namely fan delta,delta and lacustrine,which are further divided into nine sub-facies and sixteen microfacies.Tempestite sediments is found for the first time in this sag,which is considered as a positive factor for improving the quality of reservoir.During the depositing of the lower 3rd member of the Shahejie Formation,small-scale delta and fan delta were developed in the north of the sag,whereas delta were developed in the south.These deltas gradually withered along with the expansion of the lake,being favorable for the development of source rock.And during the deposition of the middle 3rd member of the Shahejie Formation,the deposits supply increased and the net-to-gross ratio of the sandbody in the sag enlarged,which were favorable for the quality of reservoir.