多孔介质的润湿性对聚驱稠油微宏观效率的影响

Effects of Porous Media Wettability on Microscopic and Macroscopic Displacement Efficiency of Polymer Flooding

岩石表面的润湿性影响聚合物微观和宏观驱油效率。采用可视化微观模型和微观照相技术研究了强水湿和油湿多孔介质下聚合物微观驱油效率和驱替机理。分析了束缚水与稠油分别在两种润湿介质下的微观形态和分布对聚合物的吸附、滞留,连续性和非连续性流动,驱替前缘以及洗油效率的影响。微观模型实验结果表明,在水湿环境,地层水趋向分布于岩石骨架表面并在孔壁附近形成较厚的水膜,聚合物趋于附着在孔壁处,在这些区域聚合物的洗油效率较高;在油湿环境,束缚水主要以非连续相分布在孔隙介质中,聚合物溶液发生咬断效应,原油吸附在孔喉处,聚合物只能部分扫除原油,乳液的形成能辅助聚合物溶液驱替油相。聚合物在水湿介质的微观驱油效率明显高于油湿介质。岩心流动实验结果与微观模型分析一致,相同浓度的聚合物溶液在强水湿岩心前缘突破所需的时间长于油湿岩心,突破前缘更规整,水湿岩心和油湿岩心的水驱采出程度分别为21.5%OOIP和15%OOIP。聚合物在油湿岩心的"门槛"黏度较大。聚合物黏度为500mPa·s时,水驱后水湿岩心和油湿岩心的原油采收率增幅分别为23%OOIP和17%OOIP。

The wettability of a porous medium had significant effects on microscopic and macroscopic displacement efficiency. Visual microscopic model and image processing technique were conducted to investigate displacement efficiency and displacement mechanism of polymer flooding. The effect of micro aspect and distribution of bound water and heavy oil on polymer solution adsorption, trapping, continuous and discontinuous flowing, displacement frontier and pore to pore sweep oil had been analyzed under strongly oil-wet and water-wet medium. The results conducted by microscopic model indicated that in water-wet medium, the formation water tended to distribute in the surface of rock skeleton and form thick water film near the wall of hole. Also, polymer tended to adhere to the wall of pore hole which had higher sweep efficiency. On the contrary, in oil-wet medium, bound water mainly distributed to the porous medium in continuous phase and crude oil absorbed on the pore throat. Snap-off effect of polymer solution resulted in a small part of sweep oil, and emulsion formed by oil and polymer solution assisted to polymer flooding. Microscopic displacement efficiency of polymer flooding in water-wet medium was apparently higher than that in oil-wet medium. The experiment results of core flooding accorded with that of microscopic model. On the one hand, longer frontier breakthrough time was observed in strong water-wet cores and the breakthrough leading edge was more uniform with 21.5%OOIP oil recovery for water flooding, compared with oil-wet ones （15%OOIP）. On the other hand, in oil-wet medium, the threshold of polymer viscosity was higher than that in water-wet medium. After water flooding, 23%OOIP and 17%OOIP oil recovery of water-wet and oil-wet cores was improved by 500 mPa. s polymer flooding respectively.