Flume simulation of response of deltaic sedimentary process to Paleogene flexural gentle slope belt in Baiyun Sag, Pearl River Mouth Basin, northern South China Sea

Abstract

Hundreds of millions of tons of oil and gas geological reserves have been discovered through exploration in the deep-water area of the northern continental margin of the South China Sea, and the distribution of large-scale effective reservoirs during the Paleogene rifting period is the key for continuous discovery in deep-water zone. Large braided fluvio-delta can be observed on seismic data from the Wenchang to Enping formations in the rifting period of the flexural gentle slope belt in the deep-water zone. Due to the absence of wells or few wells, for further understanding of the composition and evolution of large braided fluvio-deltaic sedimentary units in the process of tectonic subsidence in this region, a simulation experiment on the response of the deltaic sedimentation process in the flexural gentle slope zone to flume was carried out. Three phases of tectonic subsidence were designed for the simulation experiment, corresponding to the three phases of Paleogene regional tectonic-sedimentary evolution including balanced rifting period, detached rifting period, and faulted depression rifting period. The hydrodynamic mechanism of tractive flow was simulated by means of flood, flat water, and dry water. Simulation results showed that during the three stages of tectonic subsidence, the flexural gentle slope zone deve-loped distributary channels, natural dikes, floodplains, underwater distributary channels, estuaries, inter-tributary bays and other delta sedimentary microfacies units. The braided river delta was dominated by lateral proliferation, supplemented by vertical accretion, and the sedimentary center gradually migrated to the center of the depression, with almost no degeneration. The delta shape and sand body distribution in the flexural gentle slope zone during the rifting period were mainly controlled by factors such as structural geomorphology, river discharge amount into lake, lake level changes, and water depth.

Keywords

• rifting period
• flume simulation
• deep-water continental margin
• flexural gentle slope zone
• baiyun sag
• pearl river mouth basi