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. ... Read more

Displacement-distance diagrams are valuable for studying fault interactions and growth. Examples of displacement patterns for faults that underwent multiple reactivation events are limited. This study presents along-strike and along-dip displacement-distance diagrams for nine basin-scale faults from the West Netherlands Basin, which has experienced multiple phases of displacement. The diagrams were derived from 3D seismic reflection data, covering 2300 km 2 and 6 km in depth. Due to the dataset size, we developed a semi-automated workflow to map faults, reduce noise, and generate displacement-distance diagrams. To determine the effects of both multiphase rifting and transpressive basin inversion on fault growth, we studied four faults only recording extensional events and five faults that also experienced inversion. We observed distinctive along-dip displacement patterns, characterized by piecewise curves, identifying pre-, syn-, and post-rift phases of fault growth, as well for a later inversion event. The shape of lateral displacement patterns suggests quasi-fixed lateral fault tips throughout the fault’s history and faults developing their lateral lengths early, with later reactivation mainly increasing their vertical extent while accumulating displacement. In addition to improving our understanding of how faults grow through multiple reactivations, these results may provide insights into the growth-history of faults in other inverted rift basins world-wide. ... Read more

The West Netherlands Basin, which has a long history in exploration as a former prosperous hydrocarbon province, is currently a geothermal hotspot. Being exploited since the 1950’s, most of its oil and gas fields are now in their final phase of production. In the past decade, interest shifted to sustainable energy sources. The geothermal industry in the area is developing quickly, helped by the legacy of the hydrocarbon industry: a wealth of publicly available seismic and well data. Currently, the area has 14 realized, and at least 3 projects in the development phase, with the Late Jurassic Nieuwerkerk Formation being the main target.

Conversely to petroleum systems, in which anticlines are the preferential target for hydrocarbon exploration, synclines are the most suitable sites for geothermal exploration. They offer higher temperatures with respect to the limbs and anticlines, and possible remaining hydrocarbons are not expected to be located inside the central portions of the synclines.

The West Netherlands Basin is a former rift basin that developed during the Mesozoic in the framework of the North Sea rift, and subsequently inverted during the Late Cretaceous. The Nieuwerkerk Formation was deposited during the last major rifting phase. Thus, the thickest packages of its fluvial-deltaic deposits are fault-controlled and commonly located in the synclines. The heterogeneity of fluvial reservoirs causes lateral and vertical quality variations in porosity, permeability and net-to-gross ratios. With the hydrocarbon industry focussing on the stratigraphic highs, there is only limited well data available for the central portions of the synclines.

With reprocessed 3D seismic data, our study uses an image processing approach, coupling traditional amplitude mapping with seismic attributes. This will help to reconstruct the evolution of the fluvial architecture of the Nieuwerkerk Formation over time. By tying the seismic with well data, a better prediction of the quality of the sandy bodies per location can be made. These results can be implemented in de-risking geothermal well planning across fluvial reservoirs in inverted rift basins. ... Read more

Aiming to contribute to the energy transition, this study provides an integrated picture of the geothermal system hosted in the West Netherlands Basin and shows how the reconstruction of the basin's geological history can contribute to the correct exploration and exploitation of its geothermal resources. In the West Netherlands Basin, the main geothermal targets are found in the Cretaceous and Jurassic strata that were deposited during the rifting and post-rifting stages and were deformed during the subsequent basin inversion. Despite multiple studies on the tectonic setting, the timing and tectono-stratigraphic architecture of the rift system and its overall control on the development and evolution of geothermal systems are still to be fully deciphered. In this study, a detailed seismo-stratigraphic interpretation of the syn- and post-rift intervals in the West Netherlands Basin will be given within the framework of geothermal exploration. A recently released and reprocessed 3D seismic cube is used, covering a large portion of the onshore section of the basin. We identified two major Jurassic rifting episodes and a Late Cretaceous inversion event. During the Jurassic rifting phases, the compartmentalization of the basin and the creation of accommodation space led to the deposition of the Late Jurassic Nieuwerkerk Formation, which is the main regional geothermal producing target. Within this formation, we individuate growth synclines located in the central portions of the Jurassic half-grabens as sites that show good potential for geothermal exploration. ... Read more

In rift basins, the spatial arrangement of extensional faults can influence the facies and the thickness distribution of the syn- and post-sedimentary infill, which can harbour good potential for geothermal systems. In this framework, unravelling the tectono-stratigraphic evolution of a rift basin is decisive, as it can influence one of the key parameters for planning geothermal doublets: aquifer thickness.

In our study, the West Netherlands Basin, located in one of the Netherlands most densely populated areas, is used as a case study. Up to 2022, 14 geothermal doublets were realized in the area, with the main target being the syn-rift deposits of the Late Jurassic Nieuwerkerk Formation. As a NW-SE oriented transtensional basin, the West Netherlands Basin developed as consequence of Mesozoic extensional tectonics, after which it became inverted during the Late Cretaceous and Cenozoic. Using publicly available seismic 3D and well data, our renewed interpretation of the study area shows two important rift events. The first one during the Early-Mid Jurassic and the second one, partly controlled by structures of the former, during the Late Jurassic, coinciding with the deposition of the Nieuwerkerk Formation.

Our study adds to the understanding of a multiple stage rifting history in the West Netherlands Basin. This is important, as the process influences reservoir thicknesses and with that, the amount of MW that can be extracted from geothermal aquifers. Therefore, this study forms a bridge between providing an integrated picture of the West Netherlands Basin and how the basins geological history affects its geothermal resources. ... Read more