Experimental investigation of CO2–rock–brine interaction for injection of CO2 in an Iranian oil reservoir as an EOR method

In this study, possibility of geological storage of CO2 into an Iranian hydrocarbon reservoir is investigated as a method of enhanced oil recovery (EOR). For this purpose, a stainless steel sand packed model, containing rock and brine, was used to simulate the reservoir condition and CO2 injection. Subsequently, CO2–rock–brine interactions (dissolution and deposition of minerals) due to CO2 injection, under reservoir pressure and temperature condition (136 bar and 80 °C), was studied with ion chromatography and pH measurement at time intervals of 7, 14 and 30 days. In addition, the rock structure was identified by X-ray diffraction analysis. Results showed that up to 14 days, pH and the concentration of cations (sodium, calcium, magnesium, and potassium) and anions (chloride and sulfate) were progressively increased. However, in 30 days, assays, both pH and concentration, were decreased compared to those of 14 days of test results. Consequently, the dissolution process was observed to be the dominant phenomenon in the early days; then, the deposition of secondary minerals became the main process during the performed test. Finally, in the case of selecting the right place for CO2 injection, to avoid the porosity and permeability decrease near the well, this method can be used as a safe technique for CO2 geological storage at specific time intervals in the studied oil reservoir.