Enhanced oil recovery by carbonated (Co2-enriched) water injection

Different enhanced oil recovery (EOR) scenarios have been developed to recover the residual oil remain in the reservoirs after waterflooding. Carbonated (CO2-enriched) water injection (CWI) is one of the currently emerging EOR scenarios which was thoroughly investigated in this study. The main objectives of this thesis are to: (1) quantify the level of additional oil recovery by CWI, and (2) identify the underlying mechanisms by which the additional oil is recovered. The above objectives are investigated via a series of integrated experimental studies. The results of high-pressure high-temperature micromodel experiments revealed a novel oil recovery mechanism by CWI. CO2 partitioning between carbonated water (CW) and ‘’live’’ oil leads to rapid formation and growth of a gaseous new phase inside the oil which would hugely boost the performance of CWI and represents a game-changer for this EOR technique. Furthermore, the results of contact angle measurements revealed carbonated water has a significant impact on the rock wettability state. Next, a series of coreflood experiments were performed to study the potential of CWI for improving oil recovery at core scale. The results of coreflood experiments revealed the promising potential of CWI for improving oil recovery either as a secondary or tertiary injection scenario. A series of high-pressure imbibition experiments were performed in this thesis, to investigate the potential of CW on spontaneous imbibition. Results revealed that CW has a significant potential for increasing the amount of imbibed water and consequently oil recovery. Finally, a series of multiple-contact (PVT) experiments were performed to study the phase behaviour of the crude oil, when contacts with the injected CW. The results of these experiments revealed that the new phase forms immediately, when ‘’live’’ oil contacts with the CW with further growth at subsequent contacts. The new phase is composed of a multi-component hydrocarbon mixture starting with CH4 and CO2 in earlier stages and becoming richer towards the latter contacts. Furthermore, the performance of CWI in a long porous medium was studied to investigate the effectiveness of CWI and its displacement front propagations away from the injection point. The outcomes of this integrated investigation would help us in better understanding the oil recovery mechanisms of CWI and its true potential under realistic reservoir conditions. This would enable us to identify and target suitable oil reservoirs for this EOR technique