A Novel Workflow for Geothermal Reservoir Characterization: Understanding the Impact of Geological Heterogeneity on Geothermal Energy Production from Hot Sedimentary Aquifers (HSA)

Geothermal energy is critical for the low-carbon energy transition to mitigate the effects of climate change and improve energy security. Hot sedimentary Aquifers (HSAs), characterized by their widespread availability and inherent permeability, present significant potential for geothermal energy production. However, traditional reservoir modelling workflows, largely adapted from the petroleum sector, struggle to address the complexities of multi-scale heterogeneity, subsurface parameters, and lack of data inherent in HSAs. This often leads to over-simplified characterizations of the subsurface and increased uncertainty in energy forecasts. This work introduces a novel workflow for HSA characterization, emphasizing the integration of geological realism and computational efficiency. Utilizing Rapid Reservoir Modelling (RRM) software, flow diagnostics, and numerical simulations, the workflow efficiently prescreens geological scenarios, identifies key fluid-flow pathways, and prioritizes influential uncertainties for further detailed analysis. By focusing on the dynamic interaction between fluid movement and geological features, this method significantly reduces the computational burden while preserving critical geological details. Through conceptual models, case studies, and experimental design, the research systematically evaluates the impacts of heterogeneity on geothermal energy production. Results for these studies reveal the importance of understanding the large-scale structural features that control fluid-flow first, prior to zoning in on the smaller-scale petrophysical variations present. These findings highlight the importance of prioritizing key geological features early in reservoir assessment and creating an array of geological models that are fit-for-purpose in that they are built to answer a specific question. This therein provides an alternative solution to the commonly used single, full-field scale model that is continually developed upon throughout the modelling process. The proposed workflow demonstrates its applicability in reducing risk, optimizing reservoir performance, and supporting informed decision-making for geothermal energy projects. Therein, this work provides a practical tool for industry applications and advances the understanding of geological uncertainty's role in geothermal reservoir modelling and characterization, contributing to more efficient and reliable energy production from HSAs.