River mouth jet plume related deposition in lacustrine shoal-water deltas: Implications for reservoir characterization in lacustrine basins

Abstract

Shoal water deltaic sand bodies are widely deposited in lacustrine basins and serve as essential hydrocarbon reservoirs. The complex distribution patterns of such sand bodies present a challenge in the characterization and exploration of hydrocarbon reservoirs. Improving the understanding of jet plume deposits in ancient shoal water deltas could give new implication for reservoir characterization. Sedimentary facies of shoal water deltas were interpreted using high-resolution aerial photographs of the modern Ganjiang River delta and the ancient shoal water deltaic deposits in the Lower Cretaceous Quantou Formation, Songliao Basin. There are three jet plume-related sand bars between the multi-order distributary channel network in the Ganjiang River Delta. They are referred to as triangular-shaped bars, V-shaped bars, and diamond-shaped bars in this study. The V-shaped bar and diamond-shaped bar were also interpreted in the ancient deltaic deposits of the Songliao Basin. The jet plume related deposits experienced a river mouth stage under fully turbulent and expanding flow, followed by a fluvial-dominated stage during the progradation of the topset-dominated shoal-water deltas in geological history. The jet plume related sand bars in the lower delta plain were initially generated from the mouth bars in the delta front and were then incised by the fluvial processes during the delta progradation. Overall, knowledge of geometry and internal architecture of these jet plume related sand bars could provide new implication for characterization and prediction of ancient shoal-water deltaic reservoirs.