渤中坳陷上第三系三角洲的发现、沉积特征及其油气勘探意义

长期以来,受勘探程度的影响,渤海湾盆地渤海海域上第三系一直都被认为是河流相沉积,缺乏良好的盖层,勘探风险较大,这一认识束缚了渤海海域上第三系的油气勘探。随着近年来勘探程度的增强,认识到渤海海域渤中坳陷是渤海湾盆地晚第三纪的主要汇水区之一,在渤中坳陷上第三系发现了湖相沉积及湖泊内的重要储集体-三角洲沉积。本文从构造演化、微体古生物、沉积构造、地球物理等方面阐述了渤中坳陷湖相沉积及三角洲沉积存在的地质证据,并将该区上第三系的三角洲划分为两种类型即湖泊正常三角洲和辫状三角洲,并对其沉积特征进行了精细描述,总结了其形成条件和分布规律。渤中坳陷三角洲的发现具有重要的油气勘探意义,上第三系三角洲发育区将是本区今后上第三系勘探的主战场

Discovery and Sedimentary Characteristics of the Neogene Delta in Bozhong Depression and Its Significance for Oil and Gas Exploration

The sedimentary facies of Neogene in Bohai sea area used to be considered as fluvial facies over a long time because of the limitation of the exploration degree. Therefore, the risks of the seal rock in the Neogene exploration were believed to be great. The standpoint has restrained the Neogene exploration in Bohai sea area. With the increasing of the exploration degree, it is recognized that Bozhong depression of Bohai sea area is one of the main catchment area for Bohai bay basin in Neogene. The lacustrine and deltaic depositional systems were discovered in Neogene in Bozhong depression in the recent years. This paper focuses on elaborating the evidences of the existence of the lacustrine and deltaic depositional systems and the characteristic of the delta depositional system(including normal lacustrine delta and braided delta).The discovery of lacustrine and deltaic depositional systems in Bozhong depression have a very important significance in the oil and gas exploration. The development area of the deltaic systems will be the major field of the exploration in Bohai sea area in the future.