Experimental investigation of the coupling impacts of new gaseous phase formation and wettability alteration on improved oil recovery by CWI

The results of pore scale observations revealed the rapid formation and growth of the new phase as CW comes in contact with ''live'' oil. However, this phenomenon was not observed for the dead oil system. Furthermore, the results of coreflood tests for both water-wet and mixed-wet systems revealed the good potential of CWI compared to waterflood. However, secondary CWI in the mixed-wet system resulted in higher and earlier additional oil recovery than shown in the water-wet system. For the water-wet system, secondary CWI led to 6.2% ultimate additional oil recovery. This incremental oil recovery took place after the breakthrough with the main recovery mechanism being nucleation and growth of the new phase. However, for the mixed-wet system, secondary CWI led to 4.6% additional oil recovery at time of breakthrough and 11% ultimate additional oil recovery. The main recovery mechanisms were wettability alteration and formation and growth of the new phase. Based on the results, the formation and growth of the new phase play a more dominant role on additional oil recovery by CWI.