A semi-confined turbidite system in the Eocene lacustrine: An example from Niuzhuang Sag, Bohai Bay Basin, Eastern China

Abstract This paper establishes the sedimentary facies distribution model in the middle of the third member of the Shahejie Formation (Es3z), deep-lacustrine and turbidite fans in the Niuzhuang Sag. Lacustrine turbidite systems can form high-quality oil and gas reservoirs and the understanding of these systems is of great significance for lacustrine basins exploration. We identified a series of turbidite fans by comprehensive analyzing core, well log, 3-D seismic data and grain size variations. These fans can be further divided into lobe axis, lobe fringe, and lobe distal fringe settings. The lobes developed in both directions: the vertical fault strike (east-west) direction and parallel fault strike (northeast-southwest) direction. Porosity and permeability data showed that massive sandstone was mainly developed in the middle lobe axis that has better reservoir physical properties. The paleoclimate was determined using geochemical data. The paleoclimate was warm and humid in the highstand system tract (HST), contributing to the development of the turbidite system.