Controls on Reservoir Sand-Body Architecture: Modelling and Fluid Flow Simulation of Modern Analog, East Sudan

The purpose of this study is to describe and model a modern fluvial channel that cut gently dipping alluvial plain (in eastern Sudan) and changes its morphology from upstream to downstream. Ultimately this study explores the spatial variability in geomorphological characters of this channel with the topography of the alluvial plain and how such variability controls channel connectivity and reservoir architecture. The workflow of this study integrates remote sensing, reservoir modeling, and fluid flow simulation. Satellite images (8 panels of a 160-km fluvial channel) provide means to capture channel morphology (width, sinuosity, and amalgamation), and were used to produce realistic two-dimensional (2D) geo-cellular models. Stacked on top of each other from upstream to downstream, the 2D models provide a three-dimensional (3D) geo-cellular model that simulates the horizontal variability in the channel morphology vertically. Within this 3D model, fluvial channels were assigned to clean sandstone facies (relatively higher porosity and permeability), and flood plains were assigned to mudstone facies (relatively lower porosity and permeability). Systematic penetration of the 3D models by 27 pseudo wells shows a low chance of penetrating the channel sandstone by these wells―only 8 out of the 27 pseudo wells (∼ 30%) penetrate the channel sandstones. The opportunity of penetrating channel sandstone increases toward the upstream area (lower zones in the 3D models), where the channel has a wider width and low sinuosity. The penetrated thickness also increases toward the upstream area. These trends affect the oil's flow properties, which is presumed to fill the channel sandstone in the 3D model. Modeling and understanding such horizontal channel variability provide perspectives into the nature and controls on complex architecture patterns of fluvial reservoirs in rift basins.