Evaluation of Electroassisted Carbonated Water Injection (ECWI) in a Tight Reservoir: Outstanding Performance of Enhancing Oil Recovery and CO2 Storage Capacity

Abstract

Summary Traditionally, carbonated water injection (CWI) finds its low injectivity in a tight reservoir with a low efficiency and slow effectiveness. By combining a direct current (DC) electric field with the CWI, i.e., the electroassisted CWI (ECWI), we conducted a series of experiments to evaluate the ECWI performance in a tight reservoir and identify the key underlying recovery mechanisms. Experimental results show that early adopting the ECWI in a tight sandstone reservoir results in the highest oil recovery up to 61.9%, compared to those of 51.2% for the CWI and 41.3% for the conventional waterflooding. During an ECWI process, a voltage of 10 V achieves the highest oil recovery, but that of 15 V has the best water injectivity and CO2 storage capacity. It is found that the underlying recovery mechanisms result from both electroosmosis and enhancement of carbonized water-rock reactions induced by a DC electric field. For a tight reservoir, the ECWI has the advantages of significantly increasing water injectivity, oil production rate, and CO2 storage capacity. By introducing two new indicators to respectively evaluate the water injection performance and energy consumption, the ECWI is found to perform moderately well at a low voltage in an energy-saving and financially viable manner.