Abstract
A large part of the world's oil and gas reserves reside in carbonate reservoirs (Ahr, 2011). Time-lapse reservoir monitoring using seismics has been used since the early 1980s to optimize production, e.g., by identifying bypassed oil (Landrø, 2015). While time lapse seismic monitoring has been a standard method to monitor changes in producing clastic hydrocarbon reservoirs, its application to carbonate reservoirs has been limited due a low sensitivity of seismic parameters towards the substitution of oil by water during production (Landrø, 2015). Other geophysical monitoring methods, such as gravity, EM, or INSAR can provide additional complementary information that may be useful for 4D monitoring of carbonate reservoirs. While these methods may be more sensitive to 4D changes in the reservoir during production, they lack the spatial resolution capabilities of seismic monitoring methods. One solution may be the integration of different monitoring techniques using joint inversion that is able to combine the specific advantages of the different geophysical monitoring techniques with respect to the monitoring target. We present a new multi-method hybrid structural-petrophysical joint inversion method that may be relevant for the application to stiff carbonate reservoirs. The method was originally developed for accurate CO 2 monitoring of large-scale on-shore and off-shore storage applications, but early tests for sub-salt applications also showed promising results in other application areas. We present different applications of the joint inversion for CO 2 monitoring using synthetic and real data from the CaMI Field Research Station (CaMI.FRS), Canada, and the Ketzin CO 2 pilot site, Germany. Ketzin was Europe’s longest operating CO 2 storage facility (Martens et al., 2014) and has finished the complete storage site life cycle after safe injection of 67 000 tons of CO2. Injection at CaMI.FRS is ongoing (Macquet et al., 2018), making it an ideal platform for further development and deployment of advanced monitoring technologies for underground CO2 storage and migration. We describe the workflow of the hybrid joint inversion, present the applications of the joint inversion and compare the effects and contributions of the different joint inversion contributions.
