石油与天然气地质2025，Vol.46Issue(3)：910-925,16.DOI:10.11743/ogg20250314
中国东海陆架盆地西湖凹陷西部斜坡带古近系宝石组沉积充填特征
Sedimentary filling characteristics of the Paleogene Baoshi Formation in the western slope of Xihu Sag,East China Sea Shelf Basin
摘要
Abstract
Hydrocarbon exploration in the Xihu Sag of the East China Sea Shelf Basin is concentrated primarily in the Eocene Pinghu Formation and the Oligocene Huagang Formation.In recent years,it has shifted to the Baoshi Formation in the western slope of the sag.However,fundamental research on the Baoshi Formation remains limited,leading to an unclear understanding of its sedimentary environment and characteristics.In this study,we investigate the sedimentary filling characteristics of the Baoshi Formation in the Xihu Sag using seismic,borehole,log,and paleontological data,as well as data from elemental geochemical analysis.The results indicate that the Baoshi Formation occurs between the T04 and T08 seismic reflection interfaces.This formation consists of a series of clastic layers,with its top and bottom boundaries characterized by pronounced onlapping seismic reflection and truncation.It has a thickness of up to 2 000 m at the sag center,providing a material basis for the formation of source rocks.The Baoshi Formation is deposited under the control of segmented fault activities,resulting in the formation of multiple independent depocenters.The western slope exhibits varying structural styles from north to south.Specifically,the northern Hangzhou slope zone occurs as a reversely harmonic tectonic ramp,the central Pinghu slope zone consists of a steep slope structure shaped by multi-stage fault superimposition,while the southern Tiantai slope zone represents a normally harmonic tectonic ramp.The Baoshi Formation is formed in a brackish,weakly oxidizing to weakly reducing sedimentary environment,with paleosalinity increasing from north to south.This formation consists of the deposit of the marine-continental transitional facies in shallow water with frequent lake/sea level fluctuations.It exhibits distinct sedimentary systems in its northern and southern portions.Specifically,the northern Hangzhou slope zone is characterized by a braided river delta-bay sedimentary system,whereas the southern Tiantai and Pinghu slope zones(excluding the Pingbei area)are dominated by a tidal flat-tidal delta-littoral neritic sedimentary system in a restricted marine sedimentary environment.The northern and southern sedimentary systems along the western slope are dissected by a low salient in the central Pinghu slope zone,which serves to shelter lagoon and bay sedimentary systems in a restricted setting.The thickly laminated mudstones in these sedimentary systems act as the major source rocks of the Baoshi Formation in the Xihu Sag.关键词
沉积体系/沉积环境/宝石组/西部斜坡带/西湖凹陷/东海陆架盆地Key words
sedimentary system/sedimentary environment/Baoshi Formation/western slope zone/Xihu Sag/East China Sea Shelf Basin分类
能源科技引用本文复制引用
王辉,秦兰芝,徐靖琦,陈永军,张威,代勇,陈贺贺..中国东海陆架盆地西湖凹陷西部斜坡带古近系宝石组沉积充填特征[J].石油与天然气地质,2025,46(3):910-925,16.基金项目
中国海洋石油有限公司重大科技专项(KJZX-2023-0101) （KJZX-2023-0101）
国家自然科学基金项目(42306083) （42306083）
中央高校基本科研业务专项(2-9-2021-006,3-7-9-2024-06). （2-9-2021-006,3-7-9-2024-06）
