Long-term thermal effects on injectivity evolution during CO2 storage

Abstract

Carbon dioxide (CO 2 ) is likely to reach the bottom of injection wells at a colder temperature than that of the storage formation, causing cooling of the rock. This cooling, together with overpressure, tends to open up fractures, which may enhance injectivity. We investigate cooling effects on injectivity enhancement by modeling the In Salah CO 2 storage site and a theoretical, long-term injection case. We use stress-dependent permeability functions that predict an increase in permeability as the effective stress acting normal to fractures decreases. Normal effective stress can decrease either due to overpressure or cooling. We calibrate our In Salah model, which includes a fracture zone perpendicular to the well, obtaining a good fitting with the injection pressure measured at KB-502 and the rapid CO 2 breakthrough that occurred at the observation well KB-5 located 2 km away from the injection well. CO 2 preferentially advances through the fracture zone, which becomes two orders of magnitude more permeable than the rest of the reservoir. Nevertheless, the effect of cooling on the long-term injectivity enhancement is limited in pressure dominated storage sites, like at In Salah, because most of the permeability enhancement is due to overpressure. However, thermal effects enhance injectivity in cooling dominated storage sites, which may decrease the injection pressure by 20 %, saving a significant amount of compression energy all over the duration of storage projects. Overall, our simulation results show that cooling has the potential to enhance injectivity in fractured reservoirs.

Induced seismicity in geologic carbon storage

“…Geologic carbon storage projects, both at large scale and pilot scale, have not induced any perceivable earthquake to date (White and Foxall, 2016;Vilarrasa et al, 2019). This lack of perceivable seismicity may be due to some favorable aspects of CO 2 storage with respect to water injection that will be explained in this paper.…”

“…The dissolution of CO 2 into the resident brine forms an acidic solution that has the potential of dissolving minerals, which in turn may lead to subsequent precipitation of other minerals (Zhang et al, 2009). The fastest geochemical reactions occur in carbonate rocks and in rocks with carbonate-rich cement (Vilarrasa et al, 2019). Carbonate minerals dissolve when they interact with the acidic CO 2 -rich brine, leading to porosity and permeability increase (Alam et al, 2014).…”

The Influence of Coupled Thermomechanical Processes on the Pressure and Temperature due to Cold Water Injection into Multiple Fracture Zones in Deep Rock Formation

“…This approach has been applied to model stress-induced changes in porosity and permeability in fault zones [17]. In fracture zones, an approach based on the effective normal stress is applied in [8]. The models described above are empirical, and they are developed for sedimentary rocks.…”

“…Due to the limitation of the analytical solutions, the study of the coupled thermo-hydro-mechanical processes induced by cold water injection often requires the development of numerical models. Recent numerical modelling studies consisting of hydromechanical and thermo-hydro-mechanical simulations due to the injection of cold water/CO 2 in hot reservoirs through an injection borehole intersecting preexisting fractures or fault zones have been conducted [7][8][9][10]. To the authors' knowledge, no numerical study of separate coupled thermomechanical, hydromechanical, and thermohydromechanical processes due to injection of cold water in multiple fractures in hot rocks intersected by an injection and production borehole doublet has been done.…”

A Three-Dimensional Analytical Solution for Reservoir Expansion, Surface Uplift and Caprock Stress Due to Pressurized Reservoirs

“…An example of subsurface CO 2 injection and surface uplift is the In Salah storage project, where 3.8 Mt has been injected since its start in 2004, and where a total uplift of roughly 15 mm has been measured around three injection wells (Rutqvist 2012). The uplift measured at In Salah has attracted a considerable amount of scientific interest, and a number of modelling studies have been published (Vasco et al 2008;Rutqvist et al 2010;Rutqvist 2012;Bissell et al 2011;Verdon et al 2011;Zhou et al 2010;Shi et al 2012;Rinaldi and Rutqvist 2013;Rucci et al 2013;White et al 2014;Vilarrasa et al 2015Vilarrasa et al , 2017Rinaldi et al 2017). Similarly, seabed uplift is expected over offshore CO 2 sites, although it is more difficult to measure than land uplift.…”