Presented at SPE Americas E&P Health, Safety, Security and Environmental Conference held, 21–23 March, 2011, Houston, Texas.
Permeability Change during CO2 Injection in Carbonate Formations: Experimental Study
Chemical interactions between CO2/brine/rock can cause formation damage during CO2 injection. These interactions can affect injectivity during EOR operations, as well as affect storage capacity and seal integrity, which are primary concerns during CO2 sequestration. These interactions and the degree of impact are affected by several parameters, including pressure, temperature, brine salinity, CO2 injection rate, and rock characteristics. Carbonic acid generated from dissolution of CO2 in the formation brine can dissolve carbonate rock. Concurrently, calcium concentration increases in the brine may cause calcium carbonate to reprecipitate. This paper addresses the effects of the formation temperature, and CO2 injection rate on the precipitation and the relative impact of dissolution and precipitation on well performance. A core flood study was conducted using carbonate rock under various temperatures and injection rates. Core effluent samples were collected and the concentration of calcium was measured as the primary indicator of reactivity. Results showed that CO2 injection increased core permeability at high temperature and injection rate. And the permeability of the inlet part of the core always increases, while the permeability of the rest of the core always decreases.