Present thermal regime of the Paris Basin: A review

The resources of sedimentary basins have been and remain primary targets for exploitation. The occurrence of resources depends on processes and forcings that constrain the thermal regime of basins. Thermal anomalies provide clues to these processes and forcings. The Paris Basin is an interesting area of study in Western Europe. Its history of exploitation for centuries provides a rich source of data, such as geological, hydrogeological and thermal data (temperature profiles, DST (Drill Stem Test), BHT (Bottom Hole Temperature), etc.). We also draw on a diverse body of research spanning several decades. This study reexamines these data, which were obtained using the tools and concepts available at the time. A systematic approach is adopted, considering the basin in its entirety. The anomalies are thus viewed in their context and considered against the models and thermal processes proposed to date. This study highlights the importance of equilibrium temperature profiles which show that the current thermal regime is transient because, for instance, of paleoclimatic forcing. On the basin scale, the thermal regime is affected by advection, with topography-driven flows and also probably convection-driven flows. Moreover, flows via discreet seal bypass systems through formations that are usually described as confining produce pronounced thermal anomalies; this has rarely been observed in the onshore domain. Such seal bypass systems are found in the Paris region where water and geothermal resources are exploited intensively. These anthropic forcings result in perturbations and a transient regime. Flows through faults are also associated with pronounced thermal anomalies of several tens of degrees Celsius. Lastly, recommendations are proposed and orientations for scientific research and sustainable resource management are deduced to assist public agencies after 55 years of experience of geothermal exploitation.