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Geomechanics

The pressure required to inject supercritical carbon dioxide (scCO2) fluid into a deep geological reservoir must be closely monitored and controlled to avoid any deformation and/or fracturing of the reservoir that could induce seismicity and in turn affect the rock properties (porosity and permeability). An estimate of these critical pressure values is given by numerical simulations of hydraulic and geomechanical processes. Both the feedback between geomechanical response and fluid flow and the potential for damage to the overlying caprock are assessed. The figure below shows the conceptual processes involved in microseismic effects of deep injection of buoyant CO2 fluid.

Schematic diagram of conceptual processes involved in microseismic effects of deep injection of buoyant CO2 fluid (modified from Sminchak et al. 2002 )

PNNL has successfully developed two numerical modeling approaches to look at the geomechanical effects of an injection of CO2 in a deep subsurface reservoir:

  • The Rigid-body Interface Element Method (RIEM) geomechanics code (Fang and Zhu 1998a, 1998b) has been integrated into eSTOMP, the high-performance parallel version of STOMP, to allow the simulation of both linear (elastic) and non-linear (plastic) deformations. The code has been successfully tested against benchmark problems taken from the scientific literature. A similar approach is currently being incorporated into the serial version of STOMP.
  • The other approach consists in coupling ABAQUS (Hibbit et al., 2008) and STOMP. It has been applied to the hydro-geomechanical modeling of fluid flow and rock deformation associated with CO2 injection (Carroll et al., 2008) and to study the effects of fault width and inclination on fault reactivation induced by CO2 injection (NGuyen et al., 2008).

Geological Carbon Storage Research at PNNL

Energy and Environment Directorate