Abstract: The 1^st and 2^nd Member of Shahejie Formation reservoir in Shijiutuo uplift of Bohai Bay Basin are complex in vertical lithology because of the nature of mixed clastics and carbonates.The reservoirs feature in low porosity and super-low permeability,large thickness but underdeveloped barriers and baffles with quick lateral variance,and strong internal heterogeneity.As there are limited appraisal wells available in offshore oilfield during the exploration and evaluation stage,it is difficult to understand the reservoirs.In order to finely describe these reservoirs,element capture spectroscopy logging was used to identify the complex reservoir lithology in single well,and nuclear magnetic resonance logging technique was used to optimize permeability interpretation of different lithologies. Then the reservoir lithofacies were divided according to the identified lithologies and petrophysics.By combining seismic attribute slice analysis with lithology distribution of wells,we identified different sedimentation stages of fan deltas and established a stratigraphic framework.By taking the stratigraphic framework as units,we predicted spatial extent of sandbody through seismic multi-attribute analysis and finished the lithofacies model with multilevel constraints by integrating deterministic modeling with stochastic simulation.Finally,we established the reservoir physical parameter modeling by using the lithofacies model as constraint.The modeling method adequately simulated the Paleogene reservoir heterogeneity in Shijiutuo uplift.In addition to ensuring isochronisms,the model with stratigraphic framework can realize fine subdivision of the reservoirs,and accurately map the high quality reservoir distribution,thus improve the prediction accuracy of the deep Paleogene reservoir withcomplex lithology in exploration and evaluation stages.

Key words: multilevel constraint, complex lithology recognition, stratal slice, geological modeling, Paleogene, Shijiutuo Uplift, Bohai Bay Basin