莺歌海盆地东方区中新统黄流组一段高精度层序地层特征与隐蔽油气藏预测

High resolution sequence stratigraphy and prediction of subtle reservoir in the first section of Miocene Huangliu Formation,Dongfang area of Yinggehai Basin,South China Sea

莺歌海盆地东方区中深层高温高压领域是近年来油气勘探的热点,并在黄流组一段取得了领域性突破,但对其高精度层序地层特征、储层沉积微相与演化、圈闭特征尚有待系统查明。综合利用岩心、钻井、测井以及三维地震数据,构建了东方区黄流组一段高精度层序地层格架,查明了各高频层序单元内沉积微相类型、特征及时空配置,揭示了有利储层特征、隐蔽圈闭类型及分布,探讨了该区油气勘探方向。黄流组一段层序可细分为5个准层序组单元,从下到上依次为Ps1、Ps2、Ps3、Ps4和Ps5;其中Ps1、Ps2和Ps3位于低位体系域,Ps4和Ps5分别对应海侵体系域和高位体系域。低位体系域主要发育浅海浊积扇和浅海相,其中浅海浊积扇系低位扇,由中扇和外扇亚相构成,并以中扇为主体,包括浊积水道、水道间漫溢沉积和天然堤3种微相;海侵体系域与高位体系域均以浅海砂坝和陆架泥为主。浊积水道砂岩为该区最主要的储集体类型,低位体系域为最重要的勘探层位。在底辟构造带内主要发育构造岩性复合油气藏,在底辟构造带翼部发育砂岩上倾尖灭型岩性油气藏,在东方区西侧非底辟构造带则以砂岩透镜体岩性油气藏为主。

Mid-deep strata with high temperature and overpressure of Dongfang area in Yinggehai Basin has become the focus of oil and gas exploration in recent years, and significant exploration breakthrough was made in the first section of Huangliu Formation.However,characteristics of high resolution sequence stratigraphy,reservoir sedimentary microfacies and evolution and subtle trap in it need to be revealed.Based on substantial cores, drilling, well logging and 3-D seismic data, high resolution sequence stratigraphy framework of the first section in Huangliu Formation of Dongfang area was constructed,and the types, sedimentary characteristics and evolution of sedimentary microfacies in different sequence units were investigated. In addition, characteristics and distribution of the favorable reservoir as well as subtle traps were revealed. And finally,the exploration direction of subtle reservoir in this area was discussed.The results show that the first section of Huangliu Formation can be divided into five parasequence sets,they are Psl,Ps2,Ps3, Ps4 and Ps5 from bottom to top in the order.Psl,Ps2 and Ps3 all belong to lowstand system tract, while Ps4 and Ps5 correspond to transgressive system tract and highstand system tract, respectively. There are neritic turbidite fan and neritic facies in the lowstand system tract.The neritic turhidite fan consists of two kinds of subfacies-middle fan and outer fan, and the former is predominant which includes three kinds of microfacies-turbidite channel,inter channel deposition and natural levee, while in both of transgressive system tract and highstand system tract shelf mud and neritic sand bar developed.Turbidite channel sandstone is the primary reservoir in Huangliu Formation of Dongfang area, and the lowstand system tract is the most important exploration strata.There are mainly structural-lithologic composite reservoirs in the diapiric structure zone, and updip pinchout lithologic reservoirs in the wings of diapiric structure zone,and lenticular sandstone lithologic reservoirs in western Dongfang area which is non-diapiric structure zone.