--> Heterogeneities and Facies Architecture in Aeolian Sands Using Core-Calibrated Borehole Image Logs: Deepwater Norphlet

2019 AAPG Annual Convention and Exhibition:

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Heterogeneities and Facies Architecture in Aeolian Sands Using Core-Calibrated Borehole Image Logs: Deepwater Norphlet

Abstract

Theme 1/Siliciclastic systems/continental sedimentary systems dynamics/aeolian system dynamics - what have we learnt in the last 50 years?

Production performance in aeolian reservoirs can be impacted by permeability anisotropy that results from heterogeneity in the primary depositional fabric. Understanding the magnitude of permeability contrast and directional horizontal anisotropy is critical for successful development planning. Despite recognizing the impact of these heterogeneities, however, reservoir characterization in the absence of core has been aggravated by broadly defined facies established from conventional openhole log measurements or inadequate borehole image log interpretations that fail to establish the link between depositional structures and the environmental setting.

Detailed sedimentological description has been achieved using core-calibrated electrical borehole images in which primary depositional fabrics, including wavy-to-planar bedded interdune sands and cross-stratified wind ripple or grain flow sands, have been arranged into discrete facies representing unique dune elements. In both core and images, the fabric-defined dune elements are separated from one another by a hierarchical series of observable bounding surfaces that have been constructed on the basis of variability in foreset orientation and differences in the bed-interface dip magnitude. Together, these associations are used to define dune type and orientation to produce an integrated interpretation of the architecture, variability and spatial extent of the erg.

Electrical borehole images are capable of recognizing bed-scale heterogeneities that can be calibrated to textures and structures observed on core. An understanding built from core-observed fabrics and structures permits an extension of facies and architectural concepts into uncored intervals and uncored wells. Finally, data derived from the dip analysis can be input into process-based models constructed to represent the dune types and dune orientations, and enables the impact of the permeability heterogeneity and spatial anisotropy on reservoir sweep to be tested.