Syndepositional Fault Control on Sandbody Distribution at Two Eocene Confluence Deltas in the Dongying Depression, Bohai Bay Basin (Eastern China)

The prediction of sandstone distribution is the main target for hydrocarbon exploration and petroleum reservoir engineering, especially in a rift basin with a complex geological setting. During the Middle Eocene, the Dongying and Yong’an deltas converged in the Dongying depression of the Bohai Bay Basin, eastern China. So far, studies on the control of the existing syndepositional faults on the deltaic sandbodies of the two confluence deltas have been largely neglected. In this contribution, the sedimentary characteristics and spatial distribution of the two deltas, converging in the Dongying depression, were determined. In addition, the morphodynamic controlling factors of the deposits of the two deltas were identified based on core examination, log analysis, and seismic data analysis. During delta progradation, the sandbodies of the initially separated deltas were affected by the development of syndepositional tensional faults, which eventually also influenced the distribution of the sandstone reservoirs. The results of this study can not only be applied to petroleum reservoir engineering but also provide important new information for the studies on delta sandbody all over the world.