Reservoir Architecture and Facies Modelling of a Permian Dryland Fluvial System (Utah, USA)—Ground-Truthed Virtual Outcrop Interpretation for Subsurface Reservoir Modelling

The Permian-aged Slochteren Formation (Dutch Sector, SNS) is comprised of fluvio-aeolian reservoirs that pinch into playa lake associations of the Silverpit Formation. As a proven system for natural gas, many fields of the Rotliegend Group are now at the mature stage of their life cycle. In recent years, this stemmed interest for carbon sequestration, as well as continued exploration for overlooked play concepts.

The Permian-aged Organ Rock Formation (Utah, USA) has been selected as an analogue for the Slochteren Formation. Sourced from the basaltic Uncompahgre Uplift, conglomeratic alluvial facies of the Undifferentiated Cutler pinch downstream into amalgamated channel systems with low sinuosity (e.g., Fisher Towers). Overlying the aeolian-dominated Cedar Mesa Formation, confined multi- and single-storey fluvial channels of the Organ Rock Formation are inter-digitated by overbank sheetfloods, floodplains, and reworked fluvio-aeolian sediment in the medial DFS (e.g., Indian Creek). Sheetflood processes dominate the terminal pinch-out zone, by which aeolian sediment is reworked by unconfined fluvial splays, occasionally engulfed by a laterally traceable dune system (e.g., Farley Canyon).

In this study, detailed field logs were conducted across a depositional transect of the dryland distributive fluvial fan system (DFS). A common facies scheme was used to ground-truth outcrop interpretations, later translated into reservoir models for deterministic simulation using real petrophysical data from the subsurface. The Organ Rock Formation near Indian Creek is overlain by the Triassic-aged Moenkopi Formation, a distal fluvio-lacustrine system considered analogous to the Silverpit Formation. Thus, this locality provides an excellent analogue for the Rotliegend system in vertical section.