泥岩标志层在海陆过渡沉积环境地层对比中的应用——以珠江口盆地陆丰凹陷A油田古近系为例

Identification of Mudstone Markers and Its Application in Stratigraphic Correlation in Transitional Sediments:A Case of the Paleogene in Oilfield A,Lufeng Sag,Zhujiangkou Basin

珠江口盆地A油田区古近系海陆过渡沉积环境砂体变化快,由此带来砂体追踪对比的困难。基于测井和地震资料,在恩平组和珠海组共识别出5套具有等时意义的泥岩标志层。在泥岩标志层约束下,建立了目的层段的高分辨率层序地层格架:3个长期旋回、8个中期旋回以及21个短期旋回。在等时地层格架内,短期旋回的砂体平面分布特征研究表明,恩平组为北东向物源的辫状河三角洲沉积,珠海组为北东—南西展布的滨岸沉积;单砂体沉积微相及含油性研究表明,恩平组的辫状河三角洲分流河道和珠海组的滨岸砂坝为含油有利相带,这一认识在后续开发中得到了验证。

The rapid change of sand body in the Paleogene transitional sediments makes the sand body tracking and isochronal correlation difficult in the oilfield A, Lufeng sag, Zhujiangkou Basin. According to well log and seismic data, five sets of mudstone markers with isochronal significance are identified in Zhuhai Formation and Enping Formation. Under the constraints of the mudstone marker layers, a high-resolution sequence stratigraphic framework of the target interval is established： 3 long-term cycles, 8 mid-term cycles, and 21 short-term cycles. The result of the distribution of sand bodies in short-term cycles shows that the braided river delta from northeastern source developed in Enping Formation, and the coastal deposition developed in a NE-SW derection in Zhuhai Formation. The study on the microfacies and oil-bearing properties of the single sand body shows that the distributary channels of the braided river delta in Enping Formation and the coastal sand dams in Zhuhai Formation are the favorable phase of oil-bearing zone, which has been verified by fol low-up development.