STRUCTURAL EVOLUTION AND MODEL OF HYDROCARBON ACCUMULATION IN BURIED HILLS IN THE CENTRAL LIAOHE BASIN

The construction and quantitative restoration of regional balanced cross-sections in the central Liaohe Basin have revealed four tectonic evolution stages: the late Mesozoic initial rifting,the Paleocene-Eocene intensive rifting,the Oligocene dextral transtension and the depression since the Miocene.The amounts,ratios and rates of crustal extension were estimated,providing detailed constraints to each evolutional stage.The characteristics of fractures on the buried hills at the southern central uplift of Liaohe Basin were suggested that they were probably secondary shear fractures induced by the sinistral strike-slip of Tanlu fault during the late Mesozoic.These fractures,however,were altered to be competent for hydrocarbon migration and reservation during the Cenozoic rifting stage.Dextral strike-slip was taken place on the Tanlu fault during the Oligocene and new EW fractures were produced,which controlled the hydrocarbon distribution in this region.In terms of petroleum geology we suggested that the local highs on the unconformity surface and the fault terminations,inflexions or intersections in the buried hills were the potential targets of hydrocarbon exploration.