Unraveling Heterogeneous Fluid Pathways in Basaltic Lava Flow Facies: Implications for subsurface CO2 Storage

Abstract

Unlocking the Potential of Subsurface Geological Formations for Sustainable Energy and CO2 Storage necessitates a nuanced understanding of fluid dynamics, notably within diverse volcanic facies. Addressing pivotal challenges entails delving deeper into reactive flow physics and minimizing uncertainties in geological assumptions, particularly pertaining to top seals and vertical reservoir barriers. This study examines the complexities of fluid flow within reactive volcanic porous media, specifically focusing on fractured lava sequences, presenting a promising avenue for future energy storage strategies. Stemming from a comprehensive field study in the Faroe Islands, our research seeks to unravel the reservoir architecture and fluid pathways within fractured lava sequences, with a specific emphasis on two distinct basaltic lava flow facies: the Compound and Tabular lava flows. Leveraging techniques such as drone-based photogrammetry, geological surveys, geochemical and petrophysical data, we seek to construct 3D synthetic reservoir models of these contrasting volcanic facies. The Compound facies at Vidoy showcases lobe-like structures formed from ancient fluid lava tunnels, favoring subsequent fracturing in an alveolar network. In contrast, the Tabular facies at Suduroy, characterized by massive (10m thick) layers, exhibits contrasting microlithic cores with limited porosity and highly porous tops, featuring corded facies networks. This diverse cooling structure engenders partitioned permeability pathways, with predominantly vertical fracturing across the lava flow and horizontal networks at its porous tops. These findings yield crucial insights into the heterogeneous nature of fluid pathways within distinct volcanic facies, establishing the groundwork for refining models crucial for sustainable energy storage strategies. Addressing challenges tied to limited subsurface data and geophysical resolution underscores the need for refined methodologies in evaluating volcanic reservoir properties. This research significantly contributes to upscaling properties in basaltic porous formations, deepening our understanding of their potential as reservoirs or seals for sustainable energy storage solutions.