珠江口盆地珠三坳陷文昌8-3油田珠海组一段潮坪沉积特征

Tidal Flat Facies Characteristics of the 1st Member of the Zhuhai Formation in the Wenchang 8-3 Oilfield, Zhusan Depression, Pearl River Delta Basin

文昌8-3油田珠海组一段岩性以砂泥岩薄互层为主,沉积相和储层展布横向特征变化较快,由于对其沉积相类型、展布和演化认识不清,因而严重制约了油气勘探开发进展。为弄清其沉积展布与演化,通过岩心观察和测井相分析,结合地震反射剖面分析,对珠一段沉积层序、沉积相类型及其垂向上变化特征进行了深入探讨。研究认为,研究区珠一段主要为潮坪相,可分为潮下带和潮间带两个亚相,以潮间带沉积为主,并主要发育潮道、沙坪、混合坪、泥坪等沉积微相;珠海组沉积时期海水从北东向侵入,因此平面上潮道大致由东向西延伸,沿潮道周围发育沙坪微相,可作为油气重点勘探区域;垂向上受海平面升降作用影响珠海组一段下部发育潮道沉积向中部过渡为沙、泥坪微相,而顶部以沙坪、潮道沉积为主。这一研究成果可为文昌8-3油田储层精细预测及油气田开发方案设计提供地质依据。

The deposition of the First Member of the Zhuhai Formation in the Wenchang 8-3 Oilfield is mainly tidal flat one.It is mainly composed of thin interbedded sand and mudstone.The sedimentary facies and reservoir distribution change rapidly laterally,and the unclear sedimentary evolution seriously restricts the progress of exploration and development.In order to clarify its sedimentary distribution and evolution,this paper has a discussion on sedimentary sequence and sedimentary facies and their vertical change of the First Member of Zhuhai Formation based on core and logging data combined with seismic data.The study indicates that the First Member of the Zhuhai Formation may be divided into two sub-facies:subtidal zone and intertidal zone.The intertidal zone is dominant and characterized by development of tidal channel,sand flat,mixed flat,mud flat sedimentary microfacies.During the deposition of the Zhuhai Formation,seawater invaded from northeast to west,so the tidal channel on the plane generally extended from east to west,and sand flat microfacies developed along the tidal channel may be a key oil and gas exploration area.