MESOZOIC-CENOZOIC BASIN SUPERIMPOSITION AND UPPER PALEOZOIC HYDROCARBON GENERATION DISCIPLINE IN THE MIDDLE AND SOUTH OF BOHAI BAY BASIN

The Upper Paleozoic coal bearing formation in the Bohai Bay Basin is favorable for gas generation.It has undergone complex basin superimposition,resulting in differences of hydrocarbon generation history among different areas.Triassic,Jurassic-Cretaceous and Cenozoic are the 3 periods of hydrocarbon generation of the Upper Paleozoic source rock.Time,style and imbalance of Mesozoic-Cenozoic basin superimposition control hydrocarbon generation amounts and ratio in different periods and transference of hydrocarbon generation centers,which control hydrocarbon potential and distribution of the Upper Paleozoic.Imbalance of basin becomes stronger in the late period.Hydrocarbon generation intensity of the Upper Paleozoic source rocks in the early period is relatively stable;however,strong hydrocarbon generation may also exist in some regions during the late period.With fewer basin superimposition stages,fewer overlying strata,shallower imbedding depth in Mesozoic and deeper imbedding depth in Cenozoic,the Upper Paleozoic source rocks have greater generation potential in the late period.Based on geological model of secondary hydrocarbon generation and numerical simulation,hydrocarbon generation potential of the Upper Paleozoic in different sags is evaluated.