Depositional setting analysis using seismic sedimentology: Example from the Paleogene Lishagang sequence in the Fushan depression,South China Sea

The Fushan depression is a classic lacustrine rifted sub-basin in the Beibuwan Basin, South China Sea. The Paleogene Liushagang sequence is the main hydrocarbon-bearing stratigraphic unit in the depression.Using three-dimensional(3-D) seismic data and logging data, we analyzed depositional setting of the Liushagang sequence. We use wave impedance inversion to describe progradational directions of provenance and the general distribution of sand body. The seismic facies was analyzed by using the seismic sedimentology approach based on 3-D seismic data, and summed into eight types of seismic facies which could be well related to sedimentary facies. Seismic attributes with six objective sequence boundaries were extracted. Consequently, four provenance system of Liushagang sequence in the study area were confirmed by the corresponding relationship between the geologic information and the warm color and higher value area of seismic attributes:(i) the Hainan uplift provenance area in the south,(ii)the Linggao uplift provenance area in the west,(iii) the Yunlong uplift provenance area in the east and(iv) the northern provenance area. The seismic sedimentology used in this study may provide new insights into a better understanding of depositional setting in continental lacustrine rifted basins.

The Fushan depression is a classic lacustrine rifted sub-basin in the Beibuwan Basin, South China Sea. The Paleogene Liushagang sequence is the main hydrocarbon-bearing stratigraphic unit in the depression. Using three-dimensional （3-D） seismic data and logging data, we analyzed depositional setting of the Liushagang sequence. We use wave impedance inversion to describe progradational directions of provenance and the general distribution of sand body. The seismic facies was analyzed by using the seismic sedimentology approach based on 3-D seismic data, and summed into eight types of seismic facies which could be well related to sedimentary facies. Seismic attributes with six objective sequence boundaries were extracted. Consequently, four provenance system of Liushagang sequence in the study area were confirmed by the corresponding relationship between the geologic information and the warm color and higher value area of seismic attributes： （i） the Hainan uplift provenance area in the south, （ii） the Linggao uplift provenance area in the west, （iii） the Yunlong uplift provenance area in the east and （iv） the northern provenance area. The seismic sedimentology used in this study may provide new in- sizhts into a better understanding of depositional setting in continental lacustrine rifted basins.