Mapping Reservoir Pressure from Surface Deformation: An InSAR and Geomechanical Inversion of the In Salah CO₂ Reservoir for Assessing CO₂ Storage Safety

Abstract: The issue of global climate warming is becoming increasingly severe, and geologic CO₂ storage has emerged as a key measure for mitigating climate change, making storage safety particularly critical. In the In Salah region, InSAR technology has been applied to the world’s largest industrial-scale CO₂ storage project to monitor surface deformation induced by CO₂ injection with high precision. In this study, InSAR-observed surface deformation was combined with the surface elastic deformation theory of GEETSMA and Tarantola’s geophysical inversion method to establish a two-dimensional inversion framework linking surface deformation to reservoir pore pressure. Using this framework, we optimized the reservoir’s physical and mechanical parameters, obtained the spatial distribution of pore pressure changes, and evaluated reservoir leakage risk by calculating local mass flux, pressure gradients, and overall mass balance, identifying potential leakage zones and the total possible leaked CO₂, thereby providing a quantitative basis for assessing storage safety. The inverted parameters and pressure distributions can not only support safety assessments but also guide the optimization of injection strategies. Overall, this approach offers a cost-effective method for evaluating the safety of CO₂ sequestration against potential leakage.

Keywords: CO₂ sequestration, InSAR, reservoir pore pressure, geophysical inversion, storage safety