Palaeogeomorphology of Middle Es3 Formation in Pucheng area of Dongpu depression and its relationship with sedimentary facies

According to the "sag-wide oil-bearing theory" for the hydrocarbon-rich depression, the lithologic reservoir exploration near the sags has currently become the focus in the exploration work in Dongpu depression and other hydrocarbon-rich depressions of Bohai Bay basin. Paleogeomorphologic analysis makes up the foundation for accurate prediction of deep reservoirs,while favorable sedimentary facies with good tectonic background constitute the key to successful exploration. Based on the technology of basin modeling, the authors reconstructed the paleogeomorphology of Middle Es3 Formation in Pucheng area, Dongpu Depression. Through core observation, thin section identification, grain size analysis,sand ratios and seismic attributes research, the sedimentary facies types were established and their relationships with paleogeomorphology were studied in detail. The results show that the sedimentary systems in the study area were fan delta,lacustrine mudstone and beach bar facies, which were controlled by Paleogeomorphology. There were two gullies on the uplifted side of Lanliao fault and two fan deltas on the downthrown side, assuming a gully-fan corresponding relation. In Pucheng anticline belt, two paleo low uplifts were developed during the formation of Middle Es3, which were surrounded by thicker sandstone, with the sedimentary facies being beach bar. The fan delta front and the beach bar between the two fan deltas in the slope area are favorable exploration areas because upward dipping wedge-out reservoirs and lenticular reservoirs are likely to have been formed in these areas.