层序地层学在泌阳凹陷隐蔽油藏预测中的应用

APPLICATION OF SEQUENCE STRATIGRAPHY TO THE PREDICTON OF SUBTLE RESERVOIRS IN THE BIYANG DEPRESSION

层序地层学原理为从成因的角度分析地层及地层中分布的隐蔽油藏提供了行之有效的理论和方法,沉积层序(三级)的各级层序界面(层序边界、初泛面、最大湖泛面)与油气关系密切。其中初泛面对隐蔽油藏的成藏起着重要的控制作用,初泛面泥岩对油气的有效封堵范围控制着低位域中隐蔽油气藏的分布。该文总结出层序地层学用于隐蔽油藏预测的"四定一综合"的方法,并在泌阳凹陷的勘探实践中概括出该区5种隐蔽油藏的成藏规律。其中,"断层切香肠"成藏、初泛面泥岩封盖成藏均发生于低位域中,除前者受下切谷形态及其受断层走向影响外,二者均受初泛面的直接控制。超覆型和不整合遮挡型地层油藏分别发育于湖侵域和高位域中,均与层序边界关系密切。岩性油气藏则可发育于各种体系域中。

Sequence stratigraphy provides an effective theory and method for studying subtle reservoirs e xisting in strata. The distribution of oil and gas is mainly controlled by surfaces of sequence, i.e. sequence boundary (SB), first flooding surface (FFS) and maximum flooding surface (MFS). The FFS is the most important control factor, and the range of the distribution of subtle reservoirs in the lowstand system tract (LST) is greatly controlled by the range of effective enclosing of the first flooding mudstones for oil and gas. A method for forecasting subtle reservoirs,'four confirmations and one integration', is put forward on the basis of sequence stratigraphy and sedimentation, and five subtle reservoirs are summarized in the end. Among the five types, the reservoir formed by the'faults cutting sausage'and sealed by FFS mudstone is always occurred in LST and is strictly controlled by FFS, and the onlap reservoir and the unconformity reservouir are developed in transgressive system tract (TST) and highstand system tract (HST) respectively and both have close relationship with SB. The lithologic reservoirs are developed in various different system tracts.