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Integrating Early and Late Diagenesis Models for Enhanced Reservoir Quality Prediction in Deeply-Buried Eolian Sandstones

Abstract

Early diagenesis affects the response of sandstone pore systems to burial and therefore strongly influences reservoir quality at depth. Eolian dune sands with excellent depositional porosity and permeability are modified by near-surface diagenesis to create distinctive lithofacies characterized by variable grain dissolution and neo-formed minerals. These early lithofacies evolve during burial to form conventional, tight, or non-productive reservoir at depth. Where depositional and early diagenetic attributes are known, the impact of burial diagenesis on final sandstone porosity and permeability can be calculated using current reservoir-quality forward models. However, where early attributes are not known, or maps for the distribution of reservoir quality in a deeply buried sandstone are required, process models for the early diagenetic overprint on depositional facies models can improve predictions. Process models derived from modern desert studies show that early diagenetic attributes are systematically linked to sand composition, texture, and near-surface paleo-groundwater regimes. Reservoir-quality models incorporating early process models can be used to improve prospect assessment and enhance field development planning.