鄂尔多斯盆地上三叠统层序地层模式的探讨

Research on Sequence Stratigraphic Modes in Upper Triassic Series in Ordos Basin

鄂尔多斯盆地晚三叠世为克拉通内部坳陷的湖盆沉积演化时期,构造活动稳定,周边水系发育,形成了良好的生油岩和生烃条件,沉积了众多的大型三角洲及水下扇等储集体系。通过钻井资料结合地震层序地层学的研究,将上三叠统(延长组)划分为一个完整的二级层系,以沉积旋回和3次湖泛期(FMS)为准则,划分了4个三级层序,每个三级层序内又进一步划分出了不同的体系域。在此基础上,分析了生储盖组合特征及岩性地层油气藏成藏条件,提出了要充分利用地震资料、进一步开展层序地层学研究和岩性地层圈闭综合评价的建议。

Late Triassic of Ordos Basin is the lake-basin sedimentary evolution period of Craton Interior Depression. It features in stable structural activities and well-developed peripheral drainage network system. It has favorable oil generating conditions and hydrocarbon generation conditions and has deposited a great number of bearing systems, including large deltas and submarine fans. Based on the research on drilling data combined with seismic sequence stratigraphy, this paper classifies the Upper Triassic Series (Yanchang Formation) as a complete secondary series of strata. By taking sedimentary cycles and three lake-flooding periods as the principle, it divides it into four tertiary series of strata, each of which is further divided into various system tracts. Based on this, it analyzes the features of source-reservoir-cap rock assemblages and the conditions for hydrocarbon accumulation in lithologic strata, putting forward some suggestions on making full use of seismic data, conducting sequence stratigraphic research and comprehensive evaluation of litho-stratigraphic traps.