The event described here can be limited to specific settings and might not be encountered in every geothermal projects. More details about this topic are presented in a report that can be found on GEOENVI website.
Geothermal development and operation may cause deformation of the ground surface that either lowers or lifts up, generally, in response to pressure and/or temperature changes within the geothermal reservoir. Fluid extraction from the underground can lead to a decrease in both pressure and temperature within the geothermal reservoir, thereby causing ground depression. Conversely, re-injection of geothermal fluids can induce a pressure increase within the geothermal reservoir, resulting in a ground uplift. The latter may be partially counteracted by the rocks and sediments contraction as they cool down due to the temperature decrease. Surface deformation can also occur in case of accidental injection of fluid in non-targeted rock that react with water (anhydrite, rock salts…).
Surface deformation associated with geothermal field utilization is usually in the order of mm/year to cm/year and generally presents low risks.
The table below provides an overview of this topic in term of risk and impact assessment i.e. its causes, consequences, the phases concerned, the influencing contexts or the principals monitoring and mitigation measures that can be adopted.
