渤海湾盆地埕北凹陷古近系沉积特征与油气圈闭

DEPOSITIONAL CHARACTERISTICS AND HYDROCARBON TRAPS OF THE PALAEOGENE IN CHENGBEI SAG,BOHAI BAY BASIN

为了研究渤海湾盆地埕北凹陷的勘探前景和油气成藏规律,基于埕北凹陷古近系隐蔽油气藏的勘探实践,探讨了埕北凹陷的沉积特点、沉积体系以及油气圈闭特征。对勘探地质资料的研究表明:埕北凹陷古近系主要沉积了沙河街组和东营组,其中沙河街组以沙三段为主,东营组地层较全;埕北凹陷古近系沉积具有多旋回性,具有多期次的沉积间断,凹陷南北沉积差异较大;埕北凹陷古近系主要发育了近岸水下扇、扇三角洲—滑塌浊积扇、远岸浊积扇、辫状河三角洲、低弯度河—泛滥平原、湖底扇等沉积体系,并对应形成了各类油气圈闭。这些圈闭都是油气成藏的有利储集体。以上结论表明,埕北凹陷古近系沉积特征有利于油气成藏。

In order to explore the hydrocarbon accumulation mechanisms for successful exploration of Palaeogene subtle reservoirs,sequence stratigraphy,depositional characteristics and types of sedeiments as well as depositional systems of the Paleogene in the Chengbei sag of the Bohai Bay Basin are studied in this paper.The Paleogene in the sag,which consists of the 3rd Member of the Shahejie Formation and the relatively complete Dongying Formation,is a kind of multi-cyclic deposits with breaks.Difference of depositional features is obvious between the north and the south of the sag.The Paleogene consists of six types of depositional systems,i.e.the nearshore subaqueous fan,fan delta,deepwater turbidite fan,braided stream delta,low-sinuosity channel,and lacustrine subottom fan,and all are good reservoirs for hydrocarbon.