High-resolution Reservoir Architecture Modelling of Crevasse Splay Deposits in Low-net-to-gross Fluvial Stratigraphy

Abstract

Thin-bedded crevasse splays in low-net-to-gross fluvial stratigraphy were previously not considered as potential reservoir targets. This paper focuses on the construction of a high-resolution static reservoir-architecture model of crevasse splay deposits associated with meandering rivers on the low-gradient coastal plain of endorheic basins. Outcrops of the Miocene Huesca fluvial fan (Ebro Basin, Spain) display low-net-to-gross fluvial stratigraphy, bounded by two large sand-prone channel belts. A static model of the study area is constructed following a sequential macro-to-micro approach. The model shows connectivity between the channel belts through crevasse splays. Connections between separate crevasse splays are present through incisions of younger crevasse splays and channels. Without the connectivity between the channel belts, connectivity would still be present in vertical wells through the extensive crevasse splays originating from the channel belts. This makes the model suitable for reservoirs with less connections as well. Ongoing research on process-based modelling of crevasse splays will yield an improved understanding of the grain-size distribution and can be used to populate the static model. The model will be upscaled to allow for fluid flow simulations in which several production mechanisms will be evaluated in order to assess the economic potential of these secondary tough gas reservoirs.