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

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.