稠油油藏尿素泡沫辅助蒸汽驱三维物理模拟实验

Three-dimension physical simulation experiment of urea-foam assisted steam flooding in heavy oil reservoir

稠油油藏蒸汽驱过程中,经常出现蒸汽超覆和窜流等现象,导致蒸汽波及系数小,原油采收率低。为此,利用三维驱替实验系统,分别进行纯蒸汽驱、蒸汽驱转尿素辅助蒸汽驱和蒸汽驱转尿素泡沫辅助蒸汽驱3组实验。结果表明:纯蒸汽驱驱替效果不理想,而蒸汽驱转尿素辅助蒸汽驱和蒸汽驱转尿素泡沫辅助蒸汽驱的驱替效果要好于纯蒸汽驱。蒸汽驱转尿素辅助蒸汽驱和蒸汽驱转尿素泡沫辅助蒸汽驱实验在转驱点后,瞬时油汽比分别提高0.24和0.27,采出程度分别提高9.56%和16.29%,进出口压差最大提高0.18和0.33 MPa,瞬时含水率分别降低15.77%和36.80%;从三维温度场变化可知,尿素辅助蒸汽驱可扩大蒸汽波及区域,但效果不明显,而尿素泡沫辅助蒸汽驱可以有效抑制蒸汽超覆和窜流,提高蒸汽波及系数和原油动用程度。综合对比指标可知,尿素泡沫辅助蒸汽驱的驱替效果最好。

In the processes of steam flooding in heavy oil reservoirs,the steam overlay and channeling often occur,which leads to small sweep efficiency of steam and low recovery efficiency of oil. Aiming at these problems,three experiments were conducted with a three-dimension displacement system,which included steam flooding,steam flooding converting to urea assisted steam flooding and steam flooding converting to urea-foam assisted steam flooding. The results show that the effect of the conventional steam flooding is not satisfactory;however,that of steam flooding converting to urea assisted or to urea-foam assisted steam flooding is better. After the conversion points of these two experiments,the instantaneous oil steam ratio was increased by 0.24 and 0.27 respectively;the recovery efficiency was improved by 9.56% and 16.29% respectively;the pressure difference between inlet and outlet increased by 0.18 and 0.33 MPa respectively and the instantaneous water cut decreased by 15.77% and 36.80% respectively. Variation of three-dimension temperature fields shows that the urea assisted steam flooding can expand the steam swept area but the effect is not obvious,and the urea-foam assisted steam flooding can control the steam overlay and channeling effectively and improve the sweep efficiency of the steam and produced degree of the oil. Comprehensive comparison of the above indexes indicates that the effect of urea-foam assisted steam flooding is the best.