A sketch-based REV library for tidal lithofacies

Tidal reservoirs exhibit complex sedimentary architectures that remain a major challenge to capture in subsurface geological models. In particular, predicting the influence of sedimentary heterogeneities on fluid-flow behavior across multiple spatial scales still remains a major challenge. Simplified or generic modeling approaches often fail to represent the multiscale elements that are characteristic to tidal deposits, resulting in uncertainty in flow predictions and reservoir performance. This limitation is especially critical for geo-energy applications, where reliable forecasts are required to design efficient injection, storage, or drainage strategies.

This study adopts a scale-aware approach based on the concept of the Representative Elementary Volume (REV), defined as the minimum volume over which a heterogeneous property, such as permeability, can be considered effectively homogeneous. Identification of the REV at relevant modelling scales enables consistent upscaling of petrophysical properties and reduces uncertainty in geological models and flow simulations. As such, REV-based approaches are essential for building robust geo-models that capture key geological heterogeneities and support reliable performance forecasting for subsurface energy applications.

The methodology is demonstrated using reservoir rocks from the Viking Graben (Norway), comprising the Middle Jurassic Brent Group, where the reservoir interval represents a highly heterogeneous tidal depositional system. Detailed sedimentological core logging of selected intervals with pronounced heterogeneity is used to identify the principal lithofacies within the reservoir. For each lithofacies, sketch-based geological models are constructed to capture characteristic heterogeneity, such as key architectural elements, facies proportions, and spatial relationships. This sketch-based approach enables transparent and concept-driven representation of the geological complexity for each lithofacies. For each lithofacies model, the REV is systematically calculated for single-phase flow, resulting in a lithofacies-specific REV. Together, these models form a REV library in which each lithofacies is associated with a representative scale that captures its characteristic heterogeneity. This library provides a transferable framework that can be applied to similar reservoirs worldwide, supporting improved upscaling and flow modeling in data-limited subsurface energy applications.