N2泡沫/CO_(2)复合吞吐提高采收率三维物理模拟试验研究

Experimental Study of CO_(2) Huff and Puff Combined with N2 Foam for Enhanced Oil Recovery by Three-Dimensional Physical Models

经CO_(2)多轮吞吐后,华北某稠油油藏增油效果逐年变差,为进一步改善开发效果,采用N_(2)泡沫/CO_(2)复合吞吐提高原油采收率。为明确N_(2)泡沫/CO_(2)复合吞吐提高原油采收率机理,通过泡沫体系动、静态性能评价试验,评价了N_(2)泡沫体系的封堵性能;采用自主研制的三维非均质物理模型开展了N_(2)泡沫/CO_(2)复合吞吐室内物理模拟试验,分析了N_(2)泡沫与CO_(2)复合提高采收率的效果及其相关机理。试验结果表明,质量分数0.3%的α-烯烃磺酸钠(AOS)和质量分数0.3%的聚丙烯酰胺(HPAM)可形成稳定的泡沫体系,其封堵率达到99.57%,可实现对高渗层的有效封堵。三维试验结果表明,N_(2)泡沫/CO_(2)复合吞吐可使采收率提高22.74百分点,吞吐过程中含水率最低可降至2.07%,有效作用期是纯CO_(2)吞吐的2.5~3.0倍。N_(2)泡沫/CO_(2)复合吞吐可有效扩大CO_(2)和后续水的波及体积,为其后续现场应用提供理论支撑。

The oil increment of a heavy oil reservoir in North China decreases gradually year by year after multiple CO_(2) huff and puff operations.In order to improve the developmental effect,CO_(2) huff and puff combined with N_(2) foam was proposed to enhance the oil recovery.Evaluation experiments on dynamic and static performances of foam systems were conducted to clarify the mechanism of CO_(2) huff and puff combined with N_(2) foam in enhancing oil recovery and assess the plugging performance of N_(2) foam systems.Then,a self-designed three-dimensional heterogeneous physical model was used to carry out laboratory physical simulation experiments on CO_(2) huff and puff combined with N_(2) foam,with the effect of which on improving oil recovery and related mechanisms studied.Experimental results showed that a stable foam system could be formed by usingα-olefin sulfonate(AOS)and polyacrylamide(HPAM)both with a mass fraction of 0.3%,and the plugging ratio could reach 99.57%,which thus effectively plugged high permeable layers.The results of three-dimensional experiments showed that CO_(2) huff and puff combined with N_(2) foam could improve the oil recovery by 22.74 percentage points,and the water cut could be reduced to as low as 2.07%during huff and puff operations,with its effective action period lasting 2.5–3.0 times that of pure CO_(2) huff and puff.The CO_(2) huff and puff combined with N_(2) foam can effectively enlarge the swept volumes of CO_(2) and subsequent water,which provides theoretical support for its future field applications.