The Adaptability Research of Steam Flooding Assisted by Nitrogen Foam in Henan Oilfield

Abstract With the further study on foaming agent performance, steam flooding assisted by nitrogen foam has been applied more widely. But the flexibility of this technology in heterogeneous shallow layer heavy oil reservoir has not been fully researched. Through introducing a new dimensionless parameter—foam comprehensive evaluation index (FCEI), we use physical simulation to evaluate foaming agents. Then we make five sand filling tubes modeling permeability contrast in the light of Henan heterogeneous shallow layer heavy oil reservoir. Based on two kinds of foam-injected methods (steam following or not) impact analyses, the applicability of foam to multi-permeability contrast is further discussed. Furthermore, we use numerical simulation to optimize parameters including foam slug size, nitrogen steam ratio, foam injection interval and production-injection ratio, which applied to this type of reservoir. The obtained results show that through foaming coefficient and decay coefficient, FCEI can unify the criteria of foam screening by taking foam volume and half-life into consideration. On even ground, compared with cold foam flooding, the oil production of unit foaming agent of hot foam flooding stays 1.24 % higher. There exists none negative correlation between foam's contributions to each layer's flooding efficiency and permeability. Two methods both indicate that the middle permeability layer, of which the producing degree is similar with lower ones, has great exploitation potential. When injected with cold foam, the start-up pressure of heterogeneous formations increases linearly along with the increase of permeability grade, but for hot foam, this value increases in function of power. And to higher permeability contrast layers, hot foam is better. Finally, under hot foam slug injection condition, the optimum foam slug size is 0.02PV, the optimum nitrogen steam ratio is 20:1, the optimum foam injection interval is 90 days and the best production injection ratio is 1.32:1. Based on the study, this technology has been applied for selected field sites in 2011, and preliminary results have been achieved. The results demonstrate that this research can play an important guiding role in applying steam flooding assisted by nitrogen foam to heterogeneous shallow layer heavy oil reservoir.