The Influence of Super-critical CO2 Saturation on the Mechanical and Failure Properties of a North Sea Reservoir Sandstone Analogue

Induced-seismicity geomechanics for controlled CO2 storage in the North Sea (IGCCS)

“…This observation could be potentially linked to fluid viscosity (Benson et al, 2014;Clarke et al, 2019) or squirt flow effects, as mentioned previously (Dautriat et al, 2016). Inferred AE source mechanisms are similar between tests and are generally characterized as compressive, with varying amounts of shear depending on test phase (Griffiths et al, 2021). We may conclude for the reactivation phases that there is little difference between fracture source mechanisms due to the stress path to reactivation or the presence of different fluids.…”

“…The geomechanical properties are compiled from extensive laboratory test data, both pre-existing (Grande and Cuisiat, 2008) and newly acquired in IGCCS (Mondol et al, 2018;CLIMIT, 2020;Grande et al, 2020, CLIMIT, 2020Griffiths et al, 2021); the laboratory data is upscaled through correlations with logs for the relevant North Sea lithologies (Horsrud, 2001). The compiled laboratory data includes those produced in IGCCS in order to obtain not only extended geomechanical properties of the North-Sea-specific materials at relevant stress levels and stress paths, but also AE responses and insights.…”

“…In addition, multistage triaxial tests are performed on two caprock lithologies as well: one with shallow (700 m) mudstone from Nordland Group and the other with a deeply-buried (2581 m) shale from the Draupne Formation (CLIMIT, 2020;Grande et al, 2020). Furthermore, two reservoir sandstone analogues, Red Wildmoor and Grès des Vosges, are also tested (Griffiths et al, 2019(Griffiths et al, , 2021, which can be relevant for the intermediate depth Sognefjorden (Smeaheia) and the deeper Johansen Formations (Aurora), respectively. Tables 1-3 summarize, respectively, all the tests performed in IGCCS, the geomechanical parameters extracted from the tests performed on the overburden and reservoir lithologies, and the compiled in-situ stresses for different lithologies and depths.…”

“…4), which may suggest event magnitude can be used as a fluid-type indicator in the shearing phase. Note that Griffiths et al (2021) shows the results for all four test stages of shearing, sliding, pore pressure reactivation and axial loading reactivation. The brine-saturated sample gives the lowest number of AE events in total (Table 4).…”

“…Our focus is particularly on the following fundamental mechanisms: (1) differences in geomechanical response between CO 2 and brine injections; and (2) thermal effects due to cold CO 2 injection. The current paper provides a brief summary of the main findings and learnings from IGCCS, and for more details, refers to the IGCCS-related publications of Bjørnarå et al (2021aBjørnarå et al ( , 2021b, CLI-MIT, 2020, Fawad and Mondol (2019), Grande et al (2020), Griffiths et al (2019Griffiths et al ( , 2021, Mondol et al (2018) and Mondol (2019).…”