琼东南盆地陵水凹陷渐新统陵水组沉积特征及烃源岩发育模式

Sedimentary characteristics and source rock development model of the Oligocene Lingshui Formation in Lingshui Sag,Qiongdongnan Basin

琼东南盆地陵水凹陷深层渐新统陵水组烃源岩的沉积成因机制和发育分布规律,成为制约现阶段深水区油气勘探的关键问题。综合应用二维地震资料和钻井资料,将陵水组地层划分为3个三级层序。在层序地层格架内,共识别出丘状、楔状前积、斜交前积、席状、下切充填、波状等典型地震相类型。依据地震沉积学理论进行了沉积相解释,识别出滨岸平原、浅海、半深海、海底扇、扇三角洲等5种沉积相类型,并分层序分析了受分隔性古隆起影响的滨浅海沉积体系的平面展布特征。结合地球化学资料,建立了滨岸平原含煤系烃源岩和陆源海相烃源岩的沉积发育模式:腐殖型含煤系烃源岩主要分布于陵水凹陷东侧松南低凸起和南侧陵南低凸起边缘的滨岸平原相带内,有机质来源为陆生高等植物;陆源海相烃源岩主要发育于扇三角洲体系与浅海相、半深海相的过渡带,有机质来源为陆生高等植物与水生生物的混合。

It is very important to systemically study the sedimentary mechanism and distribution of source rock of the Oligocene Lingshui Formation in Lingshui Sag for the successive petroleum exploration in deep water area of Qiongdongnan Basin. Based on 2 D seismic data and drilling data, the Lingshui Formation is subdivided into three thirdorder sequences. Within the sequence stratigraphic framework, six types of seismic facies such as mound, wedge,oblique, sheet, filling, and wave are identified. According to the theory of seismic sedimentology, five types of sedimentary facies such as coastal plain, shallow sea, bathyal sea, submarine fan, and fan delta are identified. The sedimentary characteristic of each sequence is analyzed, especially of the coastal plain and shallow sea affected by the separated paleo-uplifts. By integrated analysis of geochemical data and sedimentary facies, the source rock development model of Lingshui Formation is setup in Lingshui Sag. The coal-bearing rocks mainly developed in the coastal plain along Lingnan low uplift and Songnan low uplift to the east of sag, with sufficient input of terrestrial organic matter.The marine source rocks with terrestrial input mainly developed in the shallow sea and bathyal facies along those fan delta systems, in which terrestrial organisms is predominant and aquatic organisms is minor.