Abstract

The need for understanding the fluid-rock interaction processes in the subsurface has significantly increased with advances in sustainable (geothermal) geo-resources and subsurface storage (carbon capture and storage – CCS, hydrogen, energy) exploitation. This need has become important because all related technologies require injection of fluids with temperatures and compositions that affect the strength of the rock and reactivity of fluids, resulting in mineral dissolution or precipitation. Thereby, the stability, composition, and properties of the host rocks are modified, significantly affecting the performance and economic viability of subsurface exploitation.

The flow properties of reservoir rocks are controlled by inter-related factors including the depositional facies (original textures and mineralogy), fluid-rock interactions (diagenesis) and fracturing. These often result in complex, multiple pore systems that are variously interconnected and difficult to predict. The practical challenge is to quantify the distribution of flow properties across the reservoir, usually with scarce subsurface data, that, if available, are only representative of very small mm- to cm-scales (core-samples). I developed a unique research and innovation program dedicated to build, apply, and validate new workflows for multi-scale quantification of the subsurface flow properties (from the basin- to reservoir- and rock core-scales). It is based on a combination of observational, experimental, and numerical methodologies, covering the conventional reservoir types (e.g., carbonates, sandstones) and the non-conventional aquifers (e.g., igneous, metamorphic). The long-term impact of this R&I program is to improve the utilization and the sustainability of the subsurface and its resources.

The integrated quantitative characterization and modeling approach deals with three overlapping scales:

1) Basin (large scale) - Integration of global geological processes in numerical models is essential to quantify the impacts of fluid-rock interactions and geo-resources evaluation at the larger basin scale. The Multi-scale Integrative Modeling workflow integrates process-based stratigraphic and burial/thermal models as well as (geochemical) transport reactive simulations together with reservoir-scale models. This allows for modeling the cross-scale, inter-related factors that control the subsurface heterogeneities, such as subsidence, thermal structure, pore fluid pressure evolution, source-sink sedimentary transfers, and diagenesis processes. Natural laboratories provide the means to validate conceptual and numerical models.

2) Outcrop (intermediate scale) - Representative surface exposed geologic objects (outcrops) are invaluable as they provide access to the vertical and lateral continuity of heterogenous reservoir facies at the intermediate, subseismic scale. The concept of Digital Field Models (DFM) consists of using such outcrops to build static and dynamic models that allow for 3D mapping of the sedimentary architecture, structural elements, and flow properties, as well as for capturing the dynamics of fluid flow and fluid-rock interactions in time. First, a photogrammetric model is achieved to capture the 3D image of the outcrop and to geo-reference the field in-situ observations and sampling. The interpretation of such models leads, in a second step, to the construction of static geo-models that can be proposed as analogues to their subsurface equivalent reservoirs. Hydrogeological and thermal well tracer tests applied on the outcrops and integrated in the DFMs will allow for constrained dynamic 4D models. The produced models, which bridge the gap between the core and reservoir scales, could be used as predictive digital tools for testing scenarios and for eLearning education.

3) Rock core (small scale) - At the scale of the rock core, the Coupled Experimental/Numerical Approach aims to twin the fluid-rock interactions laboratory experiments (e.g., X-Ray monitored reactive core-flooding) with (geochemical) transport reactive models. Rock samples taken from representative geo-referenced outcrops and/or well cores are analyzed through a tailor-made multi-scale multi-physics (MsMp) approach, including geological (petrography, mineralogy), geophysical (petro-accoustics) and petrophysical (pore space, flow) quantitative characterization. Dynamic reactive core-flooding (e.g., dissolution, mineral precipitation) is then applied on representative samples (mm- to cm-scale) to analyze specific fluid-rock interaction processes and quantify their impacts on the reservoirs at different scales. This is coupled with (geochemical) reactive transport simulations that are perfectly constrained by the experiments. Henceforth, the numerical solution can be used instead of the experimental one and can be scaled up to the dimensions of the reservoir cells. Guided numerical modelling follows based on precise, up-scalable reservoir characteristics.

The scale-dedicated workflows (basin, outcrop, rock core) overlap and provide feedback loops allowing an overall multi-scale approach that addresses the pressing challenges of the reservoir complexity, as well as the fluid-flow and fluid-rock interactions dynamics. The validated models can be used as tools to assess several applications of the subsurface exploitation (e.g., Geothermal Energy, CCS, Hydrogen), and to quantify their impacts and associated risks.

These workflows will be demonstrated with examples from Europe (e.g., Paris Basin, Germanic Basin, Basque-Cantabrian Basin), the Middle East (e.g., Eastern Mediterranean Basin, Arabian Platform), and rift-related Southeast Asian basins.

Bio

Fadi Henri NADER is currently a Chair Professor of “Multiscale Fluid-Rock Interactions” in the Department of Earth Sciences at Utrecht University (the Netherlands), and a research project leader, senior geosciences expert at IFP Energies nouvelles (France). He leads a multi-disciplinary research project on reservoir characterization and modelling.

Prof. NADER has more than 20 years of experience in fundamental and applied Earth sciences research (more than 100 publications). He is expert in sedimentology, characterization and modelling of sedimentary basins and reservoirs/aquifers (clastics and carbonate rocks, fluid flow, diagenesis), integrated stratigraphy, seismic interpretation, structural geology and geochemistry as well as karst and speleothems studies. He graduated from the American University of Beirut (Lebanon) in Geology (BSc., MSc. -1994/2000), got his PhD at the KU Leuven University (Belgium, 2003), and HDR (Habilitation de Direction de la Recherche) at the Paris-Sorbonne University France (2015), appointed professor at Utrecht University in 2019. He has supervised more than 14 PhD students, 4 post-doctoral young researchers and 40 MSc students.