Process-based Modelling of Sediment Distribution in Fluvial Crevasse Splays

Abstract

Exploitation of unconventional resources could prolong the gas production in the North Sea. Low-net-togross fluvial intervals have tough-gas reservoir potential in thin-bedded crevasse splays. To assess economic risks associated to the development of these reservoirs, a reliable grain-size distribution model is required. Sparse areal data availability for reservoir models commonly results in the use of stochastic interpolation. Numerical models offer the possibility to support these methods with proven physical concepts.To this end, simulations were conducted with Delft3D process-based modelling software. Input parameters and the validation data sets for these models are derived from outcrop studies in the presentday Río Colorado fluvial system in the Altiplano Basin, Bolivia. The grain-size trends of the simulated surface sediments for a single flood event are consistent with the validation data. These trends were used to populate individual crevasses splays within a static model. This shows that process-based models are able to support sediment trends and depositional mechanisms of a crevasse splay. The combination of numerical models and discrete field data provides a solid case for sediment distribution predications. However, simulations still have a limited accuracy.