层序地层构成与层序控砂、控藏的自相似特征——以三角洲-浊积扇体系为例

受不同级次基准面旋回控制,沉积盆地地层具有明显的旋回性和旋回的多级次性。不同级次的沉积旋回具有自相似性特征。陆相盆地大型三角洲-浊积体系层序地层划分与构成分析表明,沉积旋回的自相似性导致不同级次层序的沉积相构成与储层分布规律的自相似特征。与三角洲大规模进积作用伴生的浊积成因的"低位扇"通常紧邻长期基准面旋回(三级层序)底界面分布;在长期旋回内部,具有一定规模的浊积扇体同样出现在中期基准面旋回上升早期,沿中期旋回(四级层序)底界面分布。层序地层构成的自相似性特征导致与大型三角洲沉积体系伴生的浊积成因砂体乃至岩性圈闭油藏分布的自相似性。

Self-similarity of constitution of sequence stratigraphy and distribution of sandbodies and lithologic reservoirs:taking delta-turbidite fan system as an example

Strata in sedimentary basins are characterized by remarkable multistage cyclicity,due to the control of multistage base-level cycles.Sedimentary cycles in different stages have certain self-similarities.Sequence stratigraphic analysis of large delta-turbidite systems in terrestrial basins indicates that self-similarity of sedimentary cycles would result in the self-similarity of sedimentary facies and reservoir distribution of sequences in different stages.Low-level fan of turbidity genesis,formed in the lowstand system tract and associated with large-scale progradation of delta,are generally adjacent to the lower boundary of long-term base-level cycle (third-order sequence).Within the long-term cycle,turbidite fans of certain scale also occur during the early rising of medium-term base-level cycle,and are distributed along the lower boundary of medium-term cycle (fourth-order sequence).The self-similarity of sequence stratigraphy leads to the self-similarity of distribution of turbidity sand bodies and lithologic reservoirs that are associated with large scale delta sedimentary systems.