INVESTIGATION OF THE EFFECTS OF USING CHEMICALLY ENHANCED WATER DURING WATER ALTERNATING GAS INJECTION ON OIL RECOVERY

The field incremental recovery of immiscible water alternating gas (WAG) process is
about 5-l 0% original oil in place (OOIP). A low recovery of the WAG process is
associated with water blocking, gravity segregation, unfavorable mobility control, and
decreased gas injectivity. To minimize the aforementioned problems a new EOR
technique, named as chemically enhanced water alternating gas (CW AG), which
significantly improves the performance of the WAG process, is proposed. The
CW AG process uses alkaline, surfactant, and polymer as a chemical slug which is
injected during WAG process to reduce the interfacial tension (IFT) and improve the
mobility ratio, simultaneously.
Our objectives were to design an ASP slug which can produce a low IFT aqueous
system and a good mobility control, to demonstrate the EOR potential of the CW AG
process both experimentally and numerically, and to identify important parameters
involved in CWAG process. By screening the available chemicals, the ASP slug was
designed by IFT measurement and microemulsion phase behaviour and its stability
was checked before core floodiLg test. The performance of the CW AG process was
compared with conventional WAG and alkaline-surfactant-polymer (ASP) floodings.
The core flood data were history matched by fitting parameters of the rock and fluid
properties measured in the experiments. History matching of the core flood model
helped to optimize the experiments and was useful to evaluate the criticality of the
parameters in the CW AG process that influence sweep efficiency.