莱州湾凹陷南部沙三中亚段层序地层及沉积体系分析

Sequence Stratigraphy and Sedimentary System Analysis of the Middle Es3 Submember in the South of Laizhouwan Depression

摘要: 莱州湾凹陷南部沙三中亚段为重要潜力勘探层系，为明确该段层序地层及沉积体系发育特征，本次研究以经典层序地层学、沉积学、地震沉积学为指导，通过岩心、测井、三维地震资料相结合的方法将莱州湾南部古近系沙三中亚段划为三级层序SQs3m，并识别出两个三级层序界面SBs3M (T62)、SBs3U (T61)及一个最大湖泛面T62-MFS，进而将层序内部细分为低位体系域(LST)、湖侵体系域(TST)、高位体系域(HST)，并建立层序地层格架；层序格架内主要发育外源型三角洲体系和内源型湖泊沉积体系，三角洲相表现为扇三角洲相与辫状河三角洲相，并识别出扇三角洲平原、扇三角洲前缘、辫状河三角洲平原、辫状河三角洲前缘4种亚相，可进一步细分为分流河道、分流间湾、河口坝、席状砂等几种微相，湖相可分为滨浅湖、半深湖–深湖两种亚相；沙三中亚段沉积体系发育主要受控于古地貌形态及物源供给,东部陡坡带主要发育扇三角洲沉积体系，西南缓坡带发育辫状河三角洲沉积体系，湖盆中部平缓地带发育湖泊沉积体系，其物源主要来自于东部走滑带，西部及西南部缓坡带。

Abstract: The middle sub-member of Shahejie Formation in the south of Laizhouwan sag is an important potential exploration layer series, to clarify the sequence stratigraphy and sedimentary system development characteristics of this section. This study is guided by classic sequence stratigraphy, sedimentology and seismic sedimentology. Through the combination of core, logging and 3D seismic data, the middle sub-member of the Paleogene Shahejie Formation in the south of Laizhou Bay is divided into third-order sequence SQs3m, And identified two third-order sequence boundaries SBs3M (T62), SBs3U (T61) and one largest lake flooding surface T62-MFS. Then subdivide the sequence into lowstand system tract (LST), transgressive system tract (TST) and highstand system tract (HST), and establish sequence stratigraphic framework; exogenous delta system and endogenous lake sedimentary system are mainly developed in the sequence framework, The delta facies is represented by fan delta facies and braided river delta facies, And identified four subfacies of fan delta plain, fan delta front, braided river delta plain and braided river delta front. The lake facies can be divided into shore-shallow lake, semi-deep lake and deep lake subfacies. The development of the sedimentary system in the middle sub-member of the Shahejie Formation is mainly controlled by the palaeogeomorphology and the supply of provenance. The eastern steep slope zone mainly develops fan delta depositional system, the southwestern gentle slope zone develops braided river delta depositional system, and the central gentle zone of the lake basin develops lake depositional system. Its provenance mainly comes from the eastern strike-slip zone, the western and southwestern gentle slope zone.