Study On The Sequence Stratigraphy And Hydrocarbon Accumulation In Chengdong-Feiyantan Area

Chengdong-Feiyantan area is located at the northeast part of Jiyang depression, which belongs to the Bohai Bay Basin.Integration of analysis of seismic explorations, well loggings, cores and paleontology allowed us to suggest that the upper part of the Guantao Formation was composed of a third-order sequence with three systems tracts, ten parasequence sets and twenty-three parasequences. Five sedimentary facies including fluvial facies, lacustrine facies, braided delta, anastomosed delta and storm deposits had been identified on the basis of the types and colors of the rocks, fossils, sedimentary structures and the geometry of the sand bodies. Besides fluvial facies, the lacustrine and delta facies ware first identified in upper part of the Guantao Formation, During the sedimentary period of upper Guantao Formation, paleoclimate was the dominant controlling factor in the development of sequence because of the weak effect of paleotopography and tectonic movements, the relationships between paleoclimate change and the spatial distributions of sediments ware also discussed, and the sedimentary evolution processes of the upper Guantao Formation are analysised, It was suggested that the fluvial and delta facies dominated during the period of Lowstand System Tract (LST), which is characterized by arid environment with high temperature, shore facies dominated during the period of Transgressive System Tract (TST);delta-flooding plain dominated during the period of Highstand System Tract (HST). According to the shape and formation mechanism of the traps, the reservoirs could be divided into four types: stratigraphic reservoirs, structural reservoirs, lithological reservoirs and composite reservoirs, the distribution of sedimentary systems and the characteristics of reservoirs in three important reservoir sections had been analyzed .Through the study of the factors which control the development of the sequence, effect of the sequence boundary ,max flooding surface, first flooding surface and parasequence on hydrocarbon distribution had been demonstrated. These factors played important roles in the different stage of petroleum exploration and development.