抗垢碱提高稠油采收率机理研究

Study on enhancing heavy oil recovery mechanism of antiscaling alkali

针对胜利油田夏八区块稠油油藏地层水钙镁离子浓度高,使用常规碱剂如氢氧化钠和碳酸钠等进行驱油均会产生结垢问题,开展了具有抗垢作用的驱油用碱研究。选用具有良好耐垢性能的偏硼酸钠(NaBO2)进行了室内研究,并使用填砂管驱替实验评价了其驱油效果。结果表明:虽然NaBO2溶液降低油水界面张力的效果不好,但其驱油效果较好。驱替过程中,在较高的碱溶液浓度下出现了大的压差响应,且提高采收率的幅度随着碱溶液浓度的增加而增大。NaBO2溶液提高稠油采收率的微观机理为:碱溶液易侵入原油中并形成分散液滴,这些液滴随即转变为W/O型乳状液,封堵高渗流通道,抑制黏性指进,从而提高波及系数。

The content of calcium and magnesium ions in the formation water in Xiaba block is relatively high, so scaling problem will occur when use conventional alkali agent such as sodium hydroxide and sodium carbonate. This paper investigated the alkaline which has antiscaling effect, and chose NaBO2 which has strong chelating capacity for calcium and magnesium ions to do indoor research and used sandpacks to evaluate its displacement efficiency. The results show that although the dynamic interfacial tension is high, the displacement efficiency during the sandpaeks tests is good. During the displacement process, a large differential pressure response appeared when the alkali concentration is high, and the incremental oil recovery increased with the increase of alkali concentration. Microscopic mechanism shows that the alkaline solution penetrates into the crude oil to form water drops inside the oil phase, and those water drops turn into W/O emulsions subsequently, which could block the water channel and inhibit the viscous fingering, leading to the improvement of sweep efficiency.