Comprehensive Experimental Study of Steam Flooding for Offshore Heavy Oil Recovery After Water Flooding

The objective of this study is to investigate the feasibility of steam flooding (SF) as an alternative method for offshore heavy oil reservoirs after water flooding (WF). A series of experiments was performed by using specially designed one-dimensional (1-D) and three-dimensional (3-D) experimental systems to prove the feasibility of SF and to study the effects of the timing of SF, the steam injection rate, and the addition of chemical agents (the nitrogen foams and displacing agents) on the performance of SF after WF. The results showed that, for offshore heavy oil reservoirs after WF processes, the SF process is a viable enhanced oil recovery method, which should start as early as possible if the economic conditions permit. It is extremely important to choose an appropriate steam injection rate for SF after the WF process. Compared with the pure SF process, the final oil recovery of the SF process with the addition of the nitrogen foam or the displacing agent increased by 12.83% and 7.58% in the 1-D experiments, respectively. The nitrogen foam and displacing agent have synergistic effects on the performance of the SF after WF processes. The final oil recovery of the SF process with the addition of the two chemical agents at the steam injection rate of 10 mL/min was 37.64%, which was 5.47% higher than that of the pure SF process in the 3-D experiments.