Cambrian and Ordovician carbonates in Bamianhe area on the southern slope of Dongying depression in Bohai Bay basin have experienced leaching and denudation during the long period of outcropping

resulting in well developed dissolution rugs.Moreover

fractures resulting from tectonic activities communicate with the dissolution vugs lead to the formation of good weathered-crust reservoirs.The brown oil shales and dark-colored mudstones in the 4th and 3rd members of Shahejie Fm in Niuzhuang and Boxing sags have large hydrocarbon-generating potentials

thus they are the major source rocks.The grey and dark-grey mudstones in the 2nd member of Kongdian Fm have relatively good hydrocarbon-generating capacity

thus they are also relatively good source rocks.The hydrocarbons generated from these source rocks might have migrated through the pathways

composed of faults in the southern slope zone

the unconformities between Neogene and Paleogene and between Paleogene and Mesozoic

as well as the sandbodies or cartier beds in Paleogene Kongdian and Shahejie Formations

and upward along the slope.When they migrated into the Cambrian-Ordovician carbonate weathered-crust reservoirs in Bamianhe area

they might have accumulated and become pools

due to the sealing of mudstones in Guantao Fm

the 4th member of Shahejie Fm and Kongdian Fm.