Sedimentary facies analysis using sequence stratigraphy and seismic sedimentology in the Paleogene Pinghu Formation, Xihu Depression, East China Sea Shelf Basin

Abstract: Based on integrated investigation of seismic multi-attribute, well logs, cores and geological data, the sedimentary facies and lithofacies analysis are conducted in the Paleogene Pinghu Formation of the Xihu Depression, East China Sea. The Pinghu Formation is the main hydrocarbon-bearing strata and source rock interval in the Xihu Depression, and represents a second-order sequence. It can be subdivided into three third-order sequences, (from base to top: SQ1, SQ2, and SQ3), from SQ1 to SQ3 Sequences displayed almost similar depositional patterns, displaying different characteristics of lithology and facies distribution. The fan shaped and lobate proximal tidal-delta facies are deposited at the western edges with relatively strong hydrodynamics, while the lobate and belt shaped scattered tidal-flat facies are deposited at the center of the area with relatively weak hydrodynamics. From SQ1 to SQ3, the distribution of the sand-rich tidal-delta facies evolves from a large range to a small, then larger again, are predominantly influenced by the hydrodynamics, tectonic and topography. This study demonstrates facies analysis using sequence stratigraphy and seismic sedimentology provide useful insight to Paleogene oil and gas exploration in East China Sea Shelf Basin and other similar basins and can also be effectively used in areas which lack well or outcrop data.