Modelling Facies Distributions and Heterogeneity in Eolian Reservoir Successions

Romain, Hollie G.; Mountney, Nigel

A series of semi-quantitative sedimentological models have been developed for use as a predictive tool with which to account for the 3-D distribution of facies and architectural elements present in a variety of eolian successions. These models serve to characterize and predict the expected distribution of lithological bodies at a range of scales that are representative of both net and non-net reservoir. Developed models have been constrained using data derived from outcropping successions, subsurface well-logs, core, and studies of modern dune systems. Models describe stratigraphic architectures expected for eolian dune and interdune successions arising from the migration and accumulation of a variety of bedform types. They provide quantitative estimates of likely 3-D sand-body geometries and styles of juxtaposition of neighbouring architectural elements; the approach therefore serves as both a predictive tool and for the development of reservoir models.

The style of migration, accumulation and preservation of dunes and interdunes is simulated by mapping the migration of bedforms over a series of time steps and by applying rules to determine how older strata are truncated by younger strata. All commonly-occurring morphological eolian-bedform types can be simulated and the effects of changing bedform morphology, migration speed, migration direction and rate of accumulation can be assessed. Interpretations of sedimentary architectures known from a variety of outcropping eolian successions have been used as input to model the expected 3-D distribution of dune and interdune elements and their bounding surfaces generated by the migration and climb of a series of bedforms. Specific eolian facies are then mapped onto the preserved set architectures based on distributions known from field-based studies of a variety of outcrop successions. This procedure is in part guided by an understanding of how eolian facies types are distributed in modern dunes whose morphologies are inferred to be similar to those represented by the studied ancient successions. The geometry, scale and degree of inter-connectedness of the various architectural elements and the internal arrangement of the facies that they contain can be used as input to constrain reservoir models.

Results from a range of models are presented, each of which assesses the significance of various configurations of bedform morphology and style of migratory behaviour with regard to preserved stratigraphic architecture.

AAPG Search and Discovery Article #90163©2013AAPG 2013 Annual Convention and Exhibition, Pittsburgh, Pennsylvania, May 19-22, 2013