Safe and Efficient CO2 Injection

CO2 injection must be safe assuring the integrity of seal-reservoir pair for long-term gas trapping, and it must be also efficient as commercial activity that seeks business profit. Injection in tight reservoirs, as fractured carbonates, usually needs high pressure values to reach proper injectivity ranges, what means the geological complex integrity could be put at risk due to rock fracturing or fault-slip that may generate leakage pathways. The study case of OXYCFB300 Project is addressed in this chapter, analyzing how the CO2 injection in dense state is conducted in the naturally fractured reservoir of Hontomin pilot. Inputs from hydraulic characterization tests developed on site, addressed on Chapter “ On-Site Hydraulic Characterization Tests”, are briefly analyzed, tackling how the injection strategies were designed under mentioned safety and efficiency criteria. Spanish Patent “Industrial process for CO2 injection in dense state from pipeline transport condition to permanent geological trapping” is analyzed in the chapter. Particularly, the innovative process with alternative injection of CO2 and brine, as well as, the necessary mitigation tools to preserve the operation safety. Both measures to control the bottom pressure build up and the effect of impurities existing on CO2 stream are analyzed. Finally, the conditions necessary to become a patent in operation are described, as future works planned in the project.