NETL is working to understand the potential for geomechanical deformation to the injection zone, confining zone, and wellbore as a result of CO2 injection. Such impacts can include induced seismicity, faulting, fracturing, and damage to wellbores.
Geomechanical forces that affect the subsurface are a result of (1) pressure increases due both to the CO2 volume and injection rate, and (2) buoyancy forces from the CO2 itself. Pressure changes in the subsurface can impact effective stress fields and depending on the extent of the pressure increase, mechanical deformations can occur. These can lead to a variety of impacts. For example, elevated pressure in the target formation may lead integrity failure of the confining zone through fracturing.
Ideally injection pressures should be kept low to prevent CO2 release associated with geomechanical impacts. To ensure that this condition is met, research is needed to understand the potential for geomechanical deformation to the reservoir, seal, and wellbore as a result of CO2 injection. Extensive evaluation through laboratory and field studies, as well as modeling and simulation of the mechanical effects on the target formation associated with geologic storage of CO2 is essential to ensure integrity of the confining zone and prevent a breach of CO2.
Research Agenda and Challenges
Geomechanical deformation triggered by increased fluid pressure during injection operations could potentially result in faulting, fracturing, microseismicity, damage to the wellbore, and other types of elastic and inelastic deformation. Ideally, injection pressures should be kept low to prevent CO2 release associated with geomechanical impacts. To ensure that this constraint is met, research is needed to understand the potential for geomechanical deformation to the reservoir, seal, and wellbore as a result of CO2 injection.
Research pathways in this area include:
NETL-Supported Geomechanical Impacts Research
NETL supports projects that are addressing research challenges within the Geomechanical Impacts key technology area. Examples of projects supporting this key technology area include: (1) development of a screening tool for reservoirs to assess geomechanical processes and conditions related to CO2 storage, including faults, fractures, and caprock flaws; (2) development of geomechanical characterization methodologies by combining laboratory rock core testing with downhole tools that determine the strength of rock formations; (3) development of geomechanical models based on chemical/mechanical interactions to evaluate fracture growth at the reservoir-caprock interface and employment of these models to predict top-seal failure via fracture growth under chemically reactive conditions representative of CO2storage reservoirs, and (4) development of tools to identify damaged shale caprock and a method to determine CO2 migration through the damaged caprock.
The GSRA webpage offers links to detailed information on projects performing research in this area.