渤海湾盆地沾化凹陷下第三系高精度层序地层学研究

以钻井、三维地震等资料为基础,运用高精度层序地层学理论及方法,建立了沾化凹陷层序地层格架,划分出1个一级层序、4个二级层序、17个三级层序、51个体系域、70个准层序组和109个准层序。根据地震反射终止结构特征、准层序组叠加方式的转换和岩性剖面,识别出层序边界、首次洪泛面和最大洪泛面等关键界面。根据准层序组的叠加型式及地震相区分沉积体系类型,恢复了沉积体系。在层序地层格架内,低位体系域沉积体系类型丰富,以三阶坡折控制的冲积扇-扇三角洲(三角洲)-低位楔-低位扇为特征;水进体系域和高位体系域的沉积体系具有继承性。每个体系域的沉积体系组合具有成因上的连续性。强烈断陷期发育的沉积体系与不整合面、断层面相配置的地区是油气勘探的有利区带。

High accuracy sequence stratigraphy of Lower Tertiary in Zhanhua depression, Bohai bay basin

Based on 3-D seismic,drilling data and other data,and by using the theories and methods of high-accuracy sequence stratigraphy,sequence stratigraphic framework has been established in Zhanhua depression,which consists of 1 first-order sequence,4 second-order sequences,17 third-order sequences,51 system tracts,70 parasequence sets and 109 parasequences.Critical surfaces,such as sequence boundary,initial flooding surface and maximum flooding surface,have been defined on seismic profiles,according to the termination patterns of reflection configuration,transformation of stacking patterns of parasequence sets and lithologic profile.Sedimentary systems are categorized and restored based on the stacking pattern of parasequence sets and seismic phases.In the sequence stratigraphic framework,lowstand system tract (LST) consists of many types of sedimentary systems,which are characterized by alluvial fan-fan delta (delta)-lowstand wedge-lowstand fan under control of the third-order slope break.The sedimentary systems in transgression system tract and high stand system tract have inheritance.Combinations of sedimentary systems in each system tract have genetic continuity.Areas where sedimentary systems developed during strong fault subsidence and allocated with unconformities and fault planes are the favorable exploration play.