Abstract: One of the most important Palaeogene reservoirs in Bohai Bay Basin is of the hybrid lacustrine carbonates and clastics,with frequent facies changes and strong heterogeneities.In order to gain a good insight into the distribution of such reservoirs,Q oilfield in Shijiutuo uplift,Bozhong depression,had been analyzed as an example.Based on core,logging and geophysical data,combined with the analysis on the regional tectonic setting,sediment supply,paleogeomorphological and paleoclimatic data,we studied the petrologic characteristics,sedimentary facies as well as the depositional models of the 2^nd member of Shahejie Formation in Q oilfield.According to this study,the bulk of the 2^nd member of Shahejie Fm of Q oilfield was developed in a depositional setting favorable for the accumulation of hybrid lacustrine carbonate-clastic deposits.Two depositional models,namely the hybrid-deposit model and the skirt-rim model,were proposed.Uncertainty and risk of reservoir connectivity exist in both models,thus corresponding measures should be taken to lower risk during oilfield development.Hybrid-deposition played a positive role in improving the quality of the middle-deep clasitic reservoir.

Key words: hybrid clastic-carbonate deposit, depositional pattern, lacustrine carbonate rock, Shijiutuo Uplift, Bozhong Depression, Bohai Bay Basin