Risk analysis of injection-induced seismicity associated with geological
CO2 storage through enhanced oil recovery
Abstract
CO2 enhanced oil recovery (EOR) is being increasingly deployed for the
exploitation of depleted conventional oil and gas fields, due to the
twofold benefit of improved recovery efficiency and reduction in carbon
dioxide emissions. Geomechanics starts playing an increasingly important
role with the injection of CO2 in the subsurface and the subsequent pore
pressure buildup. However, the release of pressure through oil
production enables a higher amount of CO2 to be introduced into the
ground without causing undesirable effects. Understanding the stress
perturbation due to fluid injection and withdrawal aids in comprehending
the fault activation mechanism and the risks of induced seismicity. The
current study evaluates the geomechanical influence of CO2 injection for
enhanced oil recovery in a depleted oil field, and assesses the risk of
injection and production induced seismicity as a constraint in geologic
containment of CO2. The Ankleshwar field in Cambay basin in India is
chosen for the study. The field is a potential CO2 EOR site due to its
excellent permeability and recovery efficiency. Coupled multiphase fluid
flow modeling and geomechanical analysis were carried out to study the
hydro-mechanical characteristics of CO2 injection and fluid production.
The rise in pore pressure near the injection site induces stress changes
even far away from the site of injection due to poroelastic coupling in
rocks. The risk of induced seismicity was then analyzed through
simulation of fault slip potential in the field. FSP analysis suggests
orientation of faults along with proximity to injection site are key
parameters influencing fault stability in the Ankleshwar field.