Numerical Simulation Study of Fault Reactivation in CO2 Geological Storage

Abstract

In order to reduce global warming and combat climate change CO2 geological storage (CGS) is an effective method to reduce anthropogenic CO2 emissions The CGS method is to inject CO2 into an appropriate geological formation from preventing CO2 releasing to the atmosphere For the safety of the CGS understanding the interaction of the geomechanics and fluid flow is critical If there is a pre-existing fault near the storage reservoir the possibility of the effects of the fluid injection on the faults must be evaluated The safety of the CGS will be affected by the induced seismicity and the fault reactivation The purpose of this study is to use numerical simulation method to evaluate the possibility of the pre-existing fault being reactivated by CO2 storage Based on the compositional simulator CMG-GEM which is coupled reservoir simulation with and geomechanical module the approach of simulating the fault reactivation caused by CO2 geological storage is established in this study The approach allows us to model the behavior of fault slip and to estimate the related induced seismicity The approach combining the generalized plasticity model based on the Mohr–Coulomb yield surface with the jointed rock model is proposed in this study The anisotropic deformation behavior of fault is modeled by the jointed rock model The slip?weakening behavior and the elastic-plastic behavior of fault can be captured by the generalized plasticity with softening friction Moreover the seismic moment magnitude of the induced seismicity caused by fault activation can be calculated from the geomechanical results The results based on a hypothetical site show that fault reactivation occurs along the fault portion intersecting the reservoir when a sufficiently high fluid pressure has been reached Due to the reactivation of the fault portion inside the reservoir the points of fault portion underneath the reservoir become failure gradually The ruptured zone affects the fault portion both inside the reservoir and in the bottom caprock The results of sensitivity analysis show that fault reactivation is sensitive to the fluid flow properties The fault reactivation may occur when the permeability of fault zone is semipermeable When the vertical permeability of the fault zone getting bigger the slip and the rupture width getting large Besides if the distance between injection well and fault getting shorter the maximum fault slip and rupture width getting larger

Date of Award	2019
Original language	English
Supervisor	Bieng-Zih Hsieh (Supervisor)