Laboratory study on the potential for fault reactivation of the Draupne caprock during CO2 injection

Abstract

The successful injection and storage of carbon dioxide into the subsurface relies on an extensive and robust caprock above the storage formation. Even though migration of CO2 through intact caprocks overlying saline aquifers or abandoned hydrocarbon reservoirs is very unlikely, the pore pressure increase accompanying injection can potentially cause reactivation of existing fractures and faults. Consequently, the caprock permeability can increase and provide potential pathways for CO2 migration through the caprock. Specific knowledge about CO2 injection pressures caprocks can undertake without faults or fractures being critically stressed is therefore important. In this study, residual strength of fractured samples of the North Sea Draupne caprock is evaluated from mechanical testing. Samples containing two different types of fractures have been tested in the direct shear box and results are compared with residual strength determinations from undrained triaxial compression tests. The aim is to improve the understanding of how strength of fractured material differs between these two laboratory tests.