Study On Sequence Stratigraphy And Sedimentary System Of Upper S₁to Dongying Formation In East Zhaohuangzhuang Area, Raoyang Depression

Previous studies suggest that upper S₁to Dongying formation of EastZhaohuangzhuang area in Raoyang depression had developed rich channel sands andfavorable geological conditions, therefore, has advantage for formingstructural-lithologic reservoirs. However, since entering the structural-lithologicexploration stage in the90s of last century, petroleum exploration process in this areaslows down. There are3key aspects affecting the petroleum exploration of lithologicreservoirs in this area:①Due to the violent impacts of lateral changes of fluvialreservoirs, stratigraphic unit in previous studies are in large-scale. The lack ofsedimentary dynamic conditions, structure types, stacking patterns and distributionpatterns in short-term cycles, is not conducive to rational division and isochronouscorrelation of fluvial sand;②The scope of lithologic reservoirs are difficult todetermine, distribution law of Ed, Es1reservoirs are unclear on the plane. Especially,distribution and pinch out line position of sand bodies units in sand groups aredifficult to determine③The lack of systematic and fine studies on depositionalsystems and reservoir distribution of Es1-Ed, particularly the studies on thedistribution of depositional systems and reservoir prediction based on isochronousstratigraphic framework limited the exploration of subtle reservoirs in the area. Forthe above questions, from the practical problems that affecting the lithologic reservoirexploration in this area, this paper applies high resolution sequence stratigraphytheory to build isochronous stratigraphic framework and to subdivide and comparestratigraphic units; Seismic reservoir theory and technology are carried out on thisbasis to research and explore these questions. First, this paper developed studies on sequence boundary types, base-levelcycles, sequence division, sand body geometry, stacking pattern and relationshipbetween structure and sequence of S₁to Dongying Formation in EastZhaohuangzhuang; Then, comprehensive studies on types and models of sedimentaryfacies, characteristics and distribution of reservoirs of the target layer are proceed on;At last, this paper summarizes the effects of sequence and structure on reservoirdistribution in the area and proposes a favorable exploration area of lithologicreservoirs based on structural conditions and reservoir distribution.Based on the research above, there are4long-term （LSC7^LSC10）,8medium-term （MSC1^MSC8） and dozens of short-term cyclic sequence in S₁toDongying formation of East Zhaohuangzhuang area. Third order base-level cycle ofS₁completely developed while it of Dongying formation basically developed therising half circle without the decline half. The top of S₁has hiatus by erosion and thebottom of D₃was filled by deposition which is common in most of the area ofRaoyang depression. Sedimentary facies study shows that the area is mainly deltaplains branch channel deposition during the D₃and upper S₁period, and delta frontdeposition during lower S₁period. In general, S₁deposition is formed underregression that the facies transformed from delta front to delta plain deposition. Therelationship between deposition and hydrocarbon suggests that underwater branchchannel, distributary river course and delta front sheet sand are favorable oil-bearingfacies belts.In conclusion, vertically, geologic conditions of hydrocarbon accumulation ofupper S₁^D₃of Dawangzhuang structure matched well in time and space;horizontally, the south flank of Dawangzhuang structure followed by west flank hasthe most favorable prospective in froming lithologic reservoirs.