ALBERT

Description: Temperature is one of the main parameters influencing CO2 properties during storage in saline aquifers, since it controls along with pressure the phase behavior of the CO2/brine mixture. When CO2 replaces brine as a free gas it is known to affect the elastic properties of porous media considerably. In order to track the migration of geologically stored CO2 in a saline aquifer at the Ketzin pilot site (Germany), 3D time-lapse seismic data were acquired by means of a baseline (pre-injection) survey in 2005 and monitor surveys in 2009 and 2012. At Ketzin, CO2 was injected from 2008 to 2013 in a sandstone reservoir at a depth of about 630 - 650 m. In total about 67 kilotons of CO2 were injected. The present study is devoted to the 4D seismic dataset of 2005 - 2009. The temperature in the storage reservoir near the injection well was observed to have increased from 34 °C in 2005 to 38 °C in 2009. This temperature increase led us to investigate the impact of temperature on the seismic response to CO2 injection and on our estimations of spatial CO2 mass distribution in the reservoir based on the Ketzin 4D seismic data. Both temperature scenarios in the reservoir of 2005 and 2009 were studied using multiphase fluid flow modeling. The isothermal simulations carried out for both 34°C and 38°C show that the impact of temperature on the seismic response is minor, but the impact of temperature on the CO2 mass estimations is significant. The multiphase fluid flow simulations show a strong temperature impact on CO2 density stressing the need for temperature monitoring in a CO2 storage reservoir to support quantitative observations in the storage complex.