裂缝性致密砂岩油藏注气提高采收率技术研究

Technical Research of Gas Injection to Enhance Recovery Efficiency for Fractured Tight Sandstone Reservoirs

为了解决裂缝性致密砂岩油藏采收率低的问题,利用驱替实验方法和气相色谱法测定不同岩心组合下注气驱替的驱油效率和气窜时间,分析流动过程中气窜特征,以此分析了裂缝性致密砂岩油藏气窜的机理。结果表明:裂缝尺度越大,见气、初步气窜和彻底气窜越早。由于注入气直接沿裂缝产出,不能很好地对原油进行驱替,使得裂缝尺度越大的岩心原油采出程度及产出油气比也越低,整体驱替效果较差。为了提高原油的采收率,对4种开发方式(纯注气、水气交替注入、泡沫空气驱、冻胶泡沫空气驱)的注气实验进行了对比研究。其中水气交替驱能在一定程度上延缓气窜和提高驱替效果,但整体效果提升有限;泡沫空气驱、冻胶泡沫空气驱相比纯注气的封窜和驱替效果提升较大,尤其冻胶泡沫空气驱的封窜和驱替效果最好,对裂缝性油藏可以实现边注气边封堵,有效抑制气窜的发生,更大程度动用基质中的原油,大幅提高采出程度。

In order to solve the problems of low oil recoveries for the fractured tight sandstone reservoirs,the displacement experiments and gas chromatography were carried out.The oil displacement efficiency and gas channeling time of the gas injection flooding for different core combinations were measured,and the gas channeling characteristics during the flow process were analyzed to study the mechanism of gas channeling for the fractured tight sandstone reservoirs.The results showed that the larger the fracture size,the earlier the appearance of gas,preliminary channeling of gas and absolute channeling of gas at the outlet end of the core.The injected gas was directly produced from the fractures and the crude oil cannot be displaced well,making the larger fracture have a lower oil recovery and oil-gas ratio.Thus,the recovery efficiency of displacement was low.In order to enhance the oil recoveries,the gas injection experiment was studied by four development methods(pure gas injection,water gas alternate injection,foam-air injection,gelatin-foam-air flooding)in this paper.Compared with pure gas injection,the effect of other methods had positive impact on plugging and displacement.Although gas channeling was delayed by water gas alternate injection and the displacement effect was improved,the overall effect had a low improvement.Compared with pure gas injection,the effect of blocking and displacement was greatly improved by foam-air flooding and gelatin-foam-air flooding.Especially,gelatin-foam-air flooding had the greatest influence on blocking and displacement,which realized the blocking while gas injection for fractured reservoirs and inhibited the occurrence of gas channeling.The crude oil in the matrix was developed so that the oil recovery was greatly enhanced.