Carbon dioxide (CO2) capture and sequestration (CCS) can play a significant role in reducing anthropogenic CO2 emissions while allowing society to slowly phase out traditional energy sources. One of the main challenge in CCS is the current absence of a clear revenue model. One idea is to use the sequestered supercritical CO2 as a working fluid for geothermal energy extraction from sedimentary reservoirs (Carbon-dioxide Plume Geothermal or CPG). Due to the large variability in density and mobility of CO2 under different temperatures, reservoir heterogeneities can give a rise to a combination of convective and conductive heat transfer. In this work, qualitative and quantitative descriptions
of the effect of reservoir properties on the performance of CPG in depleted
gas fields are provided using an example realistic depleted gas field. The primary focus is on the behaviour of the CO2 plume with regards to different reservoir properties such as porosity, permeability and thermal properties. The effect of large-scale reservoir structure, such as a presence of an aquifer, net-to-gross ratio and layering is also studied. In order to accurately model these effects, a thermal multi-component multiphase model based on a fugacity-activity Equation of State is built and validated for for pressures from 50-400 bar and temperatures from 35°C to 130°C. The developed thermodynamic model
is implemented into the Delft Advanced Research Terra Simulator. Numerous studies of 2D and 3D ensembles and sensitivity studies are carried out to examine the effects of isolated parameters on CPG performance. Results reveal that increased net-to-gross (N/G) ratio is associated with increased recovery factor. In addition, layering architecture becomes an important factor for the importance of conductive flux only at low N/G. Variations in the required pressure to sustain a production rate is associated with fluctuations
in production temperature and density due to expansive cooling. Varying reservoir properties and state also have a significant effect on brine upconing, which is detrimental to CPG performance. It appears that an increase in injection rate have a positive effect on the performance of CPG, but this should be studied in conjunction with a coupled wellbore and power plant model. Heterogeneous porosity-permeability realizations show a strong decrease in reservoir lifetime compared to their upscaled homogeneous counterparts, which is caused by a combination of preferential flow, reduced conductive flux and lower production BHP associated with the upscaled realizations. It was also found that reducing production rate delays the time of thermal breakthrough due to the combined effect of these factors.