Exploitation of unconventional resources could prolong the gas production in the North Sea. Low-net-to-gross fluvial intervals may have tough-gas reservoir potential in thin-bedded crevasse splays.To assess economic risks associated to the development of these reservoirs, a numerical model can help to predict the sediment distribution. 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 present-day Río Colorado fluvial system in the Altiplano Basin, Bolivia. The grain-size trends of the simulated surface sediments for a single flood event show a trend which is consistent with the validation data. For example, grain-size decreases with increasing distance from the channel, which is in line with the physical concept of decreasing sediment size for decreasing flow energy. This shows that numerical models can be used 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. @en

Floodplain shales are abundant in the distal part of dryland fluvial fans fringing endorheic basins, such as the Río Colorado fluvial system in Bolivia. In a low-gradient coastal plain, lowstand progradation of a fluvial system creates accommodation space. Long periods of low-flow stage only support a single channel, decreasing in capacity downstream. Flooding during short episodes of peak runoff results in massive overbank deposition and aggradation of the floodplain around the active channel. Assuming a constant flow capacity, this is mirrored by an elevation of the channel floor, combining to form an elongated lobe of up to several kilometres in width. Distributary channels within crevasse splays develop reflux phenomena, effectively decreasing the flow capacity of their parent channel. This, combined with the decreased gradient of the active channel profile, causes an upstream increase in avulsion proneness and is a dominant control on the autocyclic switching of channel belts in a process of large-scale compensational stacking. The resulting stratigraphy is heterogeneous and may have tough gas reservoir potential. @en