Geomechanical Impacts
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  Sample FLAC3D geomechanical simulation to evaluate induced deformations, stresses, and fault activation risks for the Wilmington Graben Characterization Project located offshore near Long Beach, California. (DE-FE0001968)

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.

Description

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

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Methodology workflow developed by Battelle Memorial Institute that involves gathering laboratory geophysical and petrophysical data in order to generate a reservoir model, perform simulations, and develop/refine a geomechanical Earth model for determining Geomechanical risk factors in the Illinois and Michigan basins. (DE-FE0023330) (click to enlarge)
 

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:

  • By 2020: Integrate geomechanical impacts into models to assess and mitigate risk. Research includes studies of faults, fractures, seismicity, and wellbore damage from pressure changes related to injection and integration of results into basin-scale models.

  • By 2030: Develop new, coupled geomechanical/fluid flow models that reduce costs and uncertainties in model predictions while increasing their accuracy. Use these models to assess and mitigate geomechanical impacts of injection in formations encountered in broad deployment projects.
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GSRA Geomechanical Impacts Research Timeline (click to enlarge)

NETL-Supported Geomechanical Impacts Research

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  Fractures and faulting noted in potential CO2 confining layers at the Crystal Geyser site (University of Texas at Austin DE-FE0023316) (click to enlarge)

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 CO2 storage 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.