THE RELEVANT DOMINANCE OF ALLO-CONTROLS AND LOCAL-SCALE SEDIMENTARY PROCESSES UPON PRESERVED SUCCESSIONS OF ARID CONTINENTAL MARGINS: IMPLICATIONS FOR RESERVOIR CHARACTERIZATION

Aeolian sediments often produce the most homogenous and efficient reservoirs in the depositional record. The sedimentology of erg-centre environments is well-constrained, however the quality of the reservoir changes dramatically upon interaction with contemporaneous non-aeolian environments. Erg-margin relationships are poorly understood and under-represented by case studies. Competing fluvial, lacustrine, coastal and marine settings along with associated sedimentary interactions introduce complex heterogeneities at varying scales affecting reservoir performance and quality.

This work uses detailed sedimentary logging, spectral Gamma Ray (SGR) and UAV photogrammetry data to investigate variations in spatial and temporal interactions of an aeolian dune field with increasing proximity to a coastal marine margin, and the associated effects on reservoir potential, by using the Upper Jurassic Moab Member of the Curtis Formation, Utah as a case study.

Results identify a significant change in the sedimentology and geometry of the erg system with increasing distance from the marine margin. At its most proximal extent, the Moab Member displays five dune packages separated by key time surfaces identified in both the sedimentary logs and the SGR data. Towards the marine margin, these dune packages display a uniform decrease in size and number. In addition, dune packages themselves decrease in thickness and the cross-bedding becomes increasingly shallow. Although this is expected with increasing proximity to a water-source it does raise important questions about how exactly the sediment supply became shut off so quickly. Furthermore, thickness changes across the basin show complex on-lapping relationships and detail the introduction of fine-grained material into the aeolian system.

This work can be applied to hydrocarbon exploration and carbon capture and storage projects as it provides a detailed sequence-stratigraphical framework of aeolian/marine marginal successions. This project also details and predicts the way in which ‘baffles’ impact the flow of intrastratal fluids through the rocks. Although baffles may decrease the efficiency of a hydrocarbon reservoir, they may aid in CO₂ sequestration attempts as mudstones provide an optimal pathway for fluids whilst also limiting upwards movement.