The geophysical identification, characteristics, and petroliferous significance of sublacustrine fan deposits in the second member of Dongying Formation in Liaozhong Depression, Bohai Bay Basin

Large sublacustrine fan deposits have been identified within the lacustrine successions of the second member of the Palaeogene Dongying Formation in the Liaozhong Depression. In this study, by using comprehensive and detailed analyses of the borehole lithology, limited cores, wireline logs, and seismic facies, 4 types of sublacustrine fan deposits were identified and characterized. Then, an integrated depositional model was established based on the above investigations. The result indicates that the geophysical characteristics of the different sublacustrine fan deposits differed from each other, in terms of their internal configuration and external geometry of seismic reflections, and stacking patterns of wireline logs, and stratigraphic position in the vertical successions. Subsequently, the model was established according to the comprehensive analysis of the geophysical characteristics and stratigraphic position. The discussion of developing conditions and hydrocarbon discoveries within different types of sublacustrine fan deposits provided robust insights regarding how to locate and evaluate reservoirs in such deposits. Furthermore, the results of this study may potentially assist in achieving a new understanding of how to identify sublacustrine fan deposits in similar lacustrine basins and may also assist in making further decisions regarding the terms of hydrocarbon migration and accumulation.