Structural Analysis and Comparative Analysis of Fault Depression Basin between Songnan New Area and Changling Sag as well as the Favorable Exploration Direction

In early Cretaceous, both Songnan New Area and Changling Sag were influenced by the approximately latitudinal backarc extensional tectonic setting, with the characteristics of fault depression superposed on the depression. The generation mechanism for the fault depression have been studied in the previous studies, and the fault depression interval in Songliao Basin is divided into three zones, namely, East, West and Middle faulted depression zone. The structural analysis and comparative analysis of fault depression basin between Songnan New Area and Changling Sag shows that there is signifcant difference in the formation mechanism. However, the common point is that the basement faults in these two study area all are in the form of segments. The breakthrough of hydrocarbon exploration from Longfengshan area of Changling Sag demonstrates that the segmented basement faults controlled the distribution of sag, sedimentation, source rock and reservoir. Guided by the experience in Changling, the authors suggest that the exploration in Songnan New Area should focus on the area near segmented basement faults for the source rocks, on the area with maximum fault throw for the depocenters. The authors also believe that the following exploration thinking will beneft the discovery of new reservoirs, i.e. the major faults for source rocks, the front facies for reservoir rocks, the stable deposition for cap rocks, the paleostructure for accumulations, and the tectonic evolutions for reservoirs.