Sequence stratigraphy and sedimentary system of the Paleogene Shahejie Formation in the Raoyang subbasin

The sequence stratigraphy and sedimentary system of the Paleogene Shahejie Formation of the Raoyang subbasin have been studied by employing seismic, well log and drilling core data. On the basis of the identification and correlation of sequence stratigraphic units, the Shahejie Formation has been divided into six third-order sequences and 14 system tracts. The paper analyzes the main cause of formation of each sequence in detail and sums up different characteristics of various sequences. In addition, the sedimentary characteristics and sedimentary systems in each sequence are analyzed and the controlling effects of sequence development on the sedimentary systems are pointed out. During the study, the authors also studied the types of oil-gas reservoirs and characteristics of oil-gas accumulation in different system tracts of a sequence, and on that basis, they indicate the most favorable oil-gas reservoir types possibly developed in various system tracts.