Fluvial-Aeolian-Evaporitic Interactions in Arid Continental Basins: Implications for Basin-Scale Migration and Reservoir Characterisation

Abstract

The sedimentary fill of arid continental basins may comprise deposits of aeolian, fluvial, and evaporitic environments. While the distribution and preservation of different facies associations within each environment are reasonably constrained from comprehensive past studies, the relationships between deposits of coeval environments, and the temporal evolution of sediment through environments, have received comparatively little attention despite their potential to affect both basin-scale fluid migration and reservoir quality. We present results of studies of sedimentary interactions between arid environments of the Paradox Basin, USA, along with analysis of the allocyclic-controls upon them. The studies are based upon extensive regional fieldwork to examine the sedimentology, and 3D photogrammetry techniques to examine geometries and interactions. Fluvial-aeolian sediments of the Kayenta Formation preserve associations of varied reservoir quality. Relationships between them are spatially predictable, governed by one system's dominance. A dominant aeolian system limits fluvial sediments to interdune corridors and controls localised sediment supply, resulting in flash-flood and debris facies of moderate reservoir quality comprising sediments of aeolian calibre and texture. Dominance of the fluvial system restricts aeolian bedforms and preserves extensive ephemeral fluvial sediments of poor reservoir quality with fluvial textures dominated by extraformational sediment. The temporal evolution between systems preserves unique facies, but a switch in dominant system takes place quickly, severely limiting the vertical extent of interactions and potentially isolating reservoir intervals of basin fill. The margin of the Cedar Mesa erg preserves aeolian-evaporitic sediments. Interactions suggest a dominance of the evaporitic system, even during drier times, with extensive reworking of aeolian sediments into sabkha-related associations of poor reservoir quality. Interactions can be extensive, but sporadic, in space and time, preserving complexly interbedded relationships of clean aeolian and evaporitic strata that can both compartmentalise and provide migration pathways to connect reservoir intervals. Our studies provide evolutionary models that we apply to subsurface data from the arid Permian basins of the North Sea, UK – an active hydrocarbon province – in order to better characterise basin-scale migration and reservoir quality in terms of the evolving basin fill.

AAPG Datapages/Search and Discovery Article #90291 ©2017 AAPG Annual Convention and Exhibition, Houston, Texas, April 2-5, 2017