Search for hydrocarbon traps in syncline structures: A case study from the Lishu Depression of Songliao Basin, China

Relatively to petroleum exploration on an anticline or in fault block areas in continental basins, the identification of hydrocarbon traps on a synclinalic structure is a challenging task. In order to locate prospects in synclinal areas of Lishu Depression, this study analyzes the structural development of the Qikeshu syncline, describes the sedimentary facies, the sandbody distribution patterns and localizes potential Lishu Depression traps in the syncline based on seismic and well data. Furthermore, the paper summarizes the hydrocarbon trap spatial distribution and discusses the key points points in identifying hydrocarbon traps in faulted-syncline structures of a continental basin. The obtained results show that the tectonic movements at the end of the Barremian and Maastrichtian Ages bounded each limb of the Qikeshu syncline and reoriented paleo-delta lobes deposited in the syncline area. The modifications of the delta lobe affected the distribution of favorable sandbodies and potential hydrocarbon traps. The development of lithologic traps is correlated with the sandbody vertical stacking patterns in a sedimentary sequence. In faulted and folded structures of this continental basin, the post-depositional tectonic modification of paleo-sedimentary bodies strongly influences hydrocarbon play conditions. The petroleum exploration should thus focus on structural history and sedimentary factors, in order to analyze the lithologic and fault-controlled combination traps.