Impact of Overbank Deposits on Dynamic Connectivity in a High-Sinuosity and Low Net-To-Gross Fluvial System

Abstract

Summary In fluvial reservoirs, connectivity and the heterogeneity of hydraulic properties are closely related to the geometry of geobodies and facies distributions. These systems are extremely difficult to model given the inherently high degree of uncertainty, wide range in geometries and possible geobody distributions. High-sinuosity fluvial depositional systems are composed principally of three sedimentary geobodies: main channels, point bars and crevasse-splays; embedded in floodplain deposits. These geobodies generate the sedimentary heterogeneity at the macro- and mesoscale in equivalent subsurface reservoirs. The degree of their juxtaposition and amalgamation determines the level of connectivity in the reservoir, whereas mud plugs and floodplain deposits serve to increase lateral and vertical reservoir compartmentalisation. Typically, main channel and point bar geobodies are considered as main reservoir geobodies. However, crevasse-splay geobodies also play an important role in reservoir connectivity and should also be considered as important in the evaluation of this reservoir type. To address the importance of crevasse-splay deposits in reservoir connectivity, an outcrop with a high-resolution sedimentological study integrating both outcrop and subsurface data, located in the Triassic Red Beds of Iberian Meseta was selected to create a 3D static model and several connectivity scenarios were simulated through the use of streamlines.