The seismic sedimentology of syn-rift fluvial geothermal reservoirs: Insights from the West Netherlands Basin

Fluvial sandstone reservoirs are among the most promising targets for geothermal exploration projects, making them essential in the energy transition. The heterogeneity of these reservoirs, particularly when syn-tectonic, can pose significant challenges for reservoir characterisation and, consequently, for planning of geothermal exploitation. A detailed understanding of their evolution, architecture, and spatial distribution, especially in relation to major tectonic structures, is therefore essential for effective risk mitigation. In this sense, image processing is essential for improving interpretative tools that detect heterogeneities in seismic data, which is crucial for accurately characterising sandstone reservoirs and reducing associated uncertainties. The comprehensive subsurface data available for the West Netherlands Basin, along with its growing geothermal industrial sector, makes it an excellent area to study fluvial sandstones deposited in a rift setting. Using available 3D seismic reflection data, seven distinct seismic facies were identified within the basins’ main syn-rift Late Jurassic to Early Cretaceous geothermal reservoir, allowing a detailed interpretation of its heterogeneous depositional environment, further aided by the Root-Mean-Square (RMS) amplitude extraction technique. High-connectivity stacked channel intervals, found in both high-energy multi-channel river and delta-plain deposits, show the highest geothermal potential. In contrast, isolated sand bodies formed in a lower-energy meandering system exhibit reduced connectivity and lower reservoir potential. Key controls were the interplay of tectonic activity and sea-level fluctuations that influenced the sediment distribution, channel migration, and stratigraphic architecture of this complex fluvial reservoir. The syn-rift Late Jurassic to Early Cretaceous clastic reservoir rocks of the West Netherlands Basin thus serve as a showcase example for subsurface fluvial reservoirs deposited in rift basins worldwide, emphasising the critical influence of tectonic and climatic factors on the distribution of reservoir heterogeneities and providing essential insights to identify sweet spots for successful geothermal exploration.