Numerical forward Modelling of River-dominated Deltas

Abstract

A delta is a type of sedimentary system that is closely related to oil and gas. Shallow-lake delta deposits in the Mesozoic-Cenozoic strata of China are of particular interest. This delta has significant oil and gas reserves that are developed widely. Based on a numerical simulation of the sand body of the shallow-lake delta, this study analyzes the influence of various sediment conditions on the sand-body development. The formation and distribution rules of the sand body are concluded and verified, and the results can effectively guide the exploration and development of oil and gas resources. Unlike traditional flume experiments, this study adopts sediment numerical simulation technology. This approach is borrowed from the advanced achievements of computational fluid dynamics, and Delft3D is used to establish a three-dimensional numerical model of the delta. The calculation field was 20.5 km in length by 10 km in width. With the Mor-Factor set to 60, the simulation time was 45 days. The formation and the avulsion of the mouth bar, as well as the extension, migration and bifurcation of distributary channels, have been observed and studied through analysis of the simulation results. The vertical cross-section shows that the distributary channel was filled multiple times. According to distributary channel evolution characteristics combined with quantitative methods, the terminal distributary channels can be extremely developed under ideal conditions. Due to the cross-cutting and reform effort of distributary channels, sediments were spread widely and continuously. The results show that the numerical model works well in explaining the process of evolution in fluvial-dominated delta distributary channels. This study not only enables us to quantitatively understand the dynamic processes of terminal distributary channels in fluvial-dominated delta systems, but also provides a reference model for numerical simulation of hydrodynamics in sedimentology study.