Characterization and Numerical Modelling of a ‘Dry’ Aeolian System: Page Sandstone, Arizona

Aeolian sediments are excellent host rocks for subsurface fluids and have excellent potential for CO2 storage. CO2 is more buoyant than hydrocarbons, meaning that interactions with internal reservoir fabrics are more complex, increasing the importance of their characterization. The formation of these bounding surfaces is understood to be allogenically controlled, but the relative effect on formation and preservation is not well understood. This study uses forward numerical modelling to investigate the influence of two of the largest controls (water table and subsidence rate) on the development of aeolian systems and subsurface preservation in ‘wet’ and ‘dry’ climatic scenarios.

The Page sandstone, Arizona, a preserved ‘dry’ aeolian system with low subsidence rate was examined using photogrammetric methods, sedimentological logging, and quantitative data. It shows four major sequences: two small wet sequences enclosed by two larger dry sequences bound by deflationary super-surfaces. The dry sequences preserve only large compound bedforms, while the wet sequences preserve algal mats, small bedforms, and sabkha deposits. Further interpretation provides inputs for numerical modelling, helping to determine the relative effect of controls on accumulation, preservation, and predict spatial variability of bounding surfaces. Numerical modelling shows slowly subsiding, dry aeolian systems lack initial dune building preservation, probably caused by lack of sediment availability.

This study investigates the influence of allogenic controls on aeolian accumulation and preservation. Future work will characterize climatically ‘wet’ aeolian systems, and the effects of subsidence on aeolian strata to better inform spatial variability of bounding surfaces and heterogeneity within aeolian reservoirs.