Comprehensive Water–Alternating-Gas (WAG) injection study to evaluate the most effective method based on heavy oil recovery and asphaltene precipitation tests

• Different Water–Alternating-Gas (WAG) injection scenarios are considered.
• Using water and hot water as the liquid phase for WAG processes.
• Using CO2, N2, and associate gas as the gas phase for WAG processes.
• Asphaltene-Precipitation-Envelope (APE) is used as a tool for evaluating the injected gases performance.
• The best scenario has been selected from the asphaltene precipitation and oil recovery points of view.

This research provides a laboratory displacement study of several Enhanced-Oil-Recovery (EOR) scenarios including water, hot water, N2, CO2, associated gas, and four Water–Alternating-Gas (WAG) (CO2/water, N2/water, associated gas/water, and associated gas/hot water) injections to obtain the optimum injection fluid with respect to the ultimate oil recovery and asphaltene precipitation tests. Crude oil °API, viscosity, and asphaltene content are 19.94, 13.11 cp, and 12.773 wt%, respectively. Asphaltene content has been measured during the natural depletion for different planned injection scenarios. Asphaltene precipitation is strengthened during an increase of injected gas mole percent. Our static results demonstrated that associated gas injection resulted in the lowest precipitation among the injection scenarios. The ultimate recoveries and breakthrough times for water, hot water, CO2, N2, and associated gas injections were (52%, 90 min), (63%, 100 min), (64.5%, 60 min), (59.5%, 65 min), and (73%, 175 min), respectively. Regarding the results, due to the higher ultimate oil recovery and later breakthrough time, hot water flooding is much more efficient than water flooding. After, the four different WAG injection tests were done to obtain the best method in terms of oil recovery. The best ultimate recovery was 88.5%, and it was for hot water alternating associated gas; moreover, gas and water breakthrough times were 215 and 255 min, respectively.