1. College of Earth Sciences��Jilin University��Changchun 130061��China; 2. Key Laboratory of Oil Shale and Coexistent Energy Minerals of Jilin Province��Changchun 130061��China; 3. Geologic ��esearch Center of G��I��BGP��Zhuozhou 072751��Hebei��China

Lithologic hydrocarbon reservoirs are the main reservoir type in Moliqing fault depression of Yitong Basin��in which Shuangyang Formation is the exploration and development target strata in Moliqing oil field�� Through analyzing drill core��logging and oil testing data��the second member of the Shuangyang Formation can be divided into five sand groups in descent order��which are mainly from subaqueous fan and fan delta sedimentary sand body��and are mainly distributed in Kaoshan depression controlled by contemporaneous faults in the northwest margin�� Meanwhile��thick dark mudstone is well developed in the Moliqing fault depression�� with high organic mat- ter abundance��and has reached the standard of good hydrocarbon source rocks�� All the sand groups are low in po- rosity and low in permeability reservoirs��characterized mainly by “sand wrapped by mud”in the cross section�� Those sand groups are adjacent to hydrocarbon source rocks��which made it easy for the formation of small and rich oil and gas reservoirs with shape of lentoid�� The results indicate that wells with oil production greater than 1 t/d of 80 percent are distributed in the fourth sand group��which is the major hydrocarbon reservoir in the second member of Shuangyang Formation and mainly distributed in the subaqueous sand body near the well areas of Yi ��22 and Yi ��19 in Kaoshan depression in the plane��