高邮凹陷始新统统戴南组古环境演化及沉积特征

Paleoenvironment Evolution and Sedimentary Characteristics of Dainan Formation (E2d) in GY Sag

摘要:

苏北盆地高邮凹陷始新统戴南组(E2d)地层中发育丰富的岩性地层油气藏。本文 通过钻井岩心、古生物、微量元素、测井等资料，对戴南组地层沉积环境演化及展布规律进行了详细研究。得出戴南组地层沉积期气候属于温热而湿润的亚热带型气候；戴一段沉积期在吴堡构造运动活动较强背景下，凹陷属于水体处于半咸水—淡水过渡湖相与扇三角洲和近岸水下冲积扇的环境，在凹陷南部断阶带发育了近岸水下冲积扇，北斜坡发育扇三角洲沉积以及湖泊沉积；戴二段沉积期构造活动减弱，凹陷湖泊属于淡水—微咸水水体环境，在凹陷南部断阶带发育扇三角洲，北斜坡带发育三角洲及残余湖泊相沉积。在上述沉积相背景下发育与展布的砂体成为油气聚集的重要储集单元。

Abstract:

Lithologic-stratigraphic oil and gas reservoirs generously developed in Dainan formation of Eocene (E2d) in Gaoyou sag which located in Subei basin. Sedimentary environment and distribution of facies in Dainan formation were researched based on studying of cores, paleontology, trace elements and well-logging data. The weather condition during the depositional period was hot-and-wet subtropic-warm temperate type. Strong tectonic activities which developed during the depositional period of lower Dainan formation generated a sedimentary environment of nearshore subaqueous alluvial fan and fan delta in salty or semi-salty water, southern step-fault zone of Gaoyou sag developed subaqueous alluvial fan deposits while northern part developed delta and lacustrine deposits. Tectonic activities declined during the depositional period of upper Dainan formation, the water in lacustrine was fresh or brackish, fan delta in the south step-fault zone developed while delta and lacustrine deposits developed in the north. The sandbodies developed under that background could form main reservoirs for oil and gas.