Architectures and responses of physical properties of the unconformity in the uppermost part of the Palaeogene strata in the Yongbei region, Dongying depression

The architectures and responses of physical properties of the unconformity are discussed according to the 3-D seismic data, thin section examination, well logs and physical properties of the unconformity at the uppermost part of the Palaeogene strata in the Yongbei region, Dongying depression. The three-layer architectures are discriminated for the unconformity, including the transgressive sand layer with high porosity, weathered clay layer with higher mud contents and lower porosity, and semi-weathered leached layer with developed secondary opening solutions and higher porosity. There occur two types of stratigraphic traps such as the block-tilting and basin-margin types developed in the upper part of the third member of the Shahejie Formation in the Yongbei region. The blocktilting model is controlled by the unconformity and second-order or lower-order faults, and thus displays relatively small scales of traps. The basin-margin model often appears on the highly-uplifted basin margins constrained by the faults, and thus display relatively larger scales of traps.