The study suggests that the sedimentary facies and sand body types of the middle sub-section of the Es~3 in the Wendong area,Dongpu Sag,are developed neither in shallow water nor in deep water,it should be a sediment developed in the alternate environments between shallow and deep water.

The natural gases in Baimiao area mainly stemmed from the Tertiary Hydrocarbon source rock and Permo-Carboniferous coal-bearing strata in Qianliyuan depression.

Being controlled by Lanliao fault on the margin, Qianliyuan depression continues developing to provide the necessary foundation of the formation of deep basin gas accumulations.

Based on analyzing the sequence interface, studying sequence stratigraphy division and system realm of Sand 3 of Paleogene, Qianliyuan annular sub depression, several sequence stratigraphic patterns were constructed in this paper.