In the global search for renewable and low-emission energies, there is a strong emphasis on geothermal potential and the accurate characterization of known resources. High-resolution numerical modelling has proven to be a robust tool to successfully resolve sub-surface structure, fractures, and lateral lithofacies variations which control subsurface fluid circulation.
As an integral part of SIG’s strategic Geothermie 2020 work programme, AdTerra Energy conducted a pilot study using a high-resolution geological model to simulate the prolific Mesozoic interval of the Geneva Basin. The study showed that digital 3D subsurface modelling is an effective and efficient approach to quantitively describe and assess subsurface resource potential. By integrating large-scale basin architecture with key geological features, our understanding of subsurface water circulation systems is greatly improved. As such, high-resolution 3D geomodelling has proven itself to be a valuable project management tool by delivering the best possible evaluation of the geothermal target resource, providing a high degree of confidence in decisions on items such as drilling locations, target interval descriptions, and well depth prognosis. Equally, it allows for the best possible well engineering and operations planning, including cost estimation input to the development of future heat networks within the canton.
Systematic Data Management and Integration
Comprehensive seismic data acquisition, quality control, reprocessing, and reliable interpretation are essential for building accurate geological models. Equally important is the accurate identification and management of uncertainties inherent in the data, including adequate consideration of aliasing and boundary effects.
For the Cretaceous interval, all available 2D seismic data was carefully reviewed and so-called “confidence maps” were established for all major seismic markers. This allowed for the identification of areas where the data quality might impact the robustness of the geo-cellular model. A similar uncertainty analysis was performed for all relevant well data, along with a systematic review of corresponding petrophysical log interpretations, core measurements, and mechanical rock properties.
The integration and cross-validation of well and seismic information, merged with the regional geological evolution of the Geneva Basin, provides a solid basis for a viable structural and sedimentological conceptual model. This model captures all critical elements characterizing the deposition, deformation, and preservation of the target interval.
Integration From Well to Basin Scale
In the specific case of the Geneva Cretaceous pilot study, the task was to provide a high-resolution model (25m lateral resolution; 1m vertical resolution) in the vicinity of the recently drilled GEo-01 geothermal exploration well (2018). The objective included capturing and integrating large-scale geological and structural features with lateral resolution of 5km-20km.
The resulting high-resolution 3D model is an essential decision-making tool for geothermal exploration, development operators, and the associated project management teams. Through a hybrid workflow, we are able to analyze and manage uncertainty at both the local and the regional scales.
This pilot study provides a basis for a more comprehensive regional and systematic review of the geothermal potential and resources available in the Geneva Basin.