Fully Coupled Near-Wellbore Multiphase Poromechanics Simulation for CO2 Storage

ABSTRACT In geological CO2 storage operations, wellbore deformations and leakage pathways formations can occur around injection and abandoned wells subjected to high rates and long-term CO2 injection. To guide engineering design and prevent CO2 leakage risks, a full understanding of the underlying physics and robust numerical models are necessary to evaluate the response of underground formations in the near wellbore region and in the reservoir. In this study, a multi-scale and multi-physics open-source simulator (GEOS) is used to simulate multiphase flow and poromechanical deformations over time in three dimensions. The governing equations for mechanical deformations of the rock body and multiphase compositional fluid flow within the rock matrix are solved with a fully coupled finite element and finite volume approach. Simulation results are validated against multiple analytical solutions for multiphase flow and wellbore problems, thus demonstrating the accuracy of this advanced simulator. This work focuses on short-term processes in the vicinity of injection wells where stress evolutions, rock deformations and multiphase compositional flow and transport are simulated jointly to ensure wellbore stability and prevent damage. This fully coupled geomechanical model can simulate multiphase flow and any associated poromechanical effects within the CO2 storage site and in the surrounding formations. Such a large-scale, long-term, multi-physics simulation model is useful in many ways: it can guide operational decisions for CO2 injection, assess the containment potential and risks of a site, and analyze the wellbore stability and integrity during and after CO2 injection. INTRODUCTION Geological carbon sequestration (GCS) is a method to reduce atmospheric carbon concentration by storing vast amounts of CO2 in underground formations. The mechanical deformation of underground formations around CO2 injectors can lead to operational and geological hazards. If subjected to high rates and long-term CO2 injections, leakage pathways might be formed around abandoned wells and mega-faults (Nogues et al., 2011; Gan et al., 2021). Therefore, during and after CO2 storage operations, wellbore and caprock stability and integrity should not be compromised to mitigate the risk of CO2 leakage (Bachu and Bennion, 2009; Vilarrasa, 2014; Torsæter et al., 2017; Onishi et al., 2019).