SEDIMENTARY FACIES AND EVOLUTION OF HUAGANG FORMATION IN XIHU DEPRESSION, EAST CHINA SEA SHELF BASIN

Based on the theory of sequence stratigraphy and seismic sedimentology, the well logging data, cores and seismic data, were comprehensive used to analyze the sequence division of the area, the sedimentary facies and evolution are conducted in the Paleogene Huagang Formation of the central part in Xihu Depression, East China Sea. It can be subdivided into three third-order sequences, (from base to top: SQ1, SQ2, and SQ3), SQ1 and SQ2 Sequences shows almost similar depositional, both developing braided river-braided river delta, but the SQ3 displayed different sedimentary facies, developing shallow-water delta. The main factors leading to the transformation of sedimentary facies are structural action and sea level changes. This study not only improves the sequence division and sedimentary facies correlation of Huagang Formation, but also provides a theoretical basis for oil and gas exploration in the central part of Xihu Depression.