Petrophysical and Geomechanical Study of CO2-Enhanced Gas Recovery and CO2 Storage in Shales: A Critical Review

This paper comprehensively reviews the role of geomechanical and petrophysical studies in CO2-enhanced gas recovery and/or CO2 storage following CO2 injection in shale gas reservoirs. In order to achieve CO2-enhanced gas recovery (CO2-EGR) from shale reservoirs and/or CO2 storage in shale reservoirs, numerical models and designs rely on an effective appraisal of the target reservoir. This paper analysed the geomechanical and petrophysical characteristics that were taken into account while constructing models for a successful CO2-EGR, in addition to examining assessments of shale reservoirs undertaken in diverse fields of research. The factors were weighted based on their importance in distinct shale reservoir settings. Natural fracture system, fracture conductivity, hydraulic fracture half-length, unconfined compressive strength (UCS), Young's modulus, Poisson's ratio, and other geo-mechanical and petro-physical parameters are important throughout the entire process, which also includes CO2 injection, residual hydrocarbon mobilisation, variations in stress and strain during hydrocarbon production, and the subsequent impact on fracture network conductivity. This research will also give recommendations on how to improve the previously described geomechanical and petrophysical characteristics in order to achieve effective CO2-enhanced gas recovery and/or CO2 storage in shale gas reservoirs. The energy sector's goal is to continue employing unconventional resources to provide sustainable energy. As a result, this review study will contribute significantly to our understanding of how to reduce subsurface failure in CO2-EGR fracturing and injection, as well as refracturing and CO2 injection in depleted shale gas reservoirs for CO2 storage.