Zhang Liyuan, Abbaspourrad Alireza, Parsa Shima, Tang Jizhou, Cassiola Flavia, Zhang Meng, Tian Shouceng, Dai Caili, Xiao Lizhi, Weitz David A
School of Engineering and Applied Sciences, Harvard University, Cambridge, Massachusetts 02138, United States.
Shell International Exploration and Production Inc., Shell Technology Center Houston, Houston, Texas 77082, United States.
ACS Appl Mater Interfaces. 2020 Jul 29;12(30):34217-34225. doi: 10.1021/acsami.0c09958. Epub 2020 Jul 15.
Conformance control during waterflooding in an oil reservoir is utilized to redistribute water and increase the sweep efficiency and hence oil production. Using preformed gel particles can effectively redirect the flow by blocking the high-permeability zones and forcing water into low-permeability zones where the oil is trapped. However, the size of such gel particles can limit their applications deeper within the reservoir and can result in shear-induced degradation near the well bore. Here, we fabricate core-shell nanohydrogels with delayed swelling behavior; their volume increases by a factor of 200 after about 30 days in brine under reservoir conditions. We study their effect on the flow behavior in a three-dimensional porous medium micromodel consisting of randomly packed glass beads. Using confocal microscopy, we directly visualize the spatial variations of flow in the micromodel before and after nanohydrogel injection and swelling. The swollen nanohydrogels block some pores reducing the permeability of the micromodel and diverting the water into low-permeability regions. A core flood experiment further confirms that the nanohydrogels can significantly reduce the permeability of a reservoir sample and divert the fluid flow. Our results demonstrate that these core-shell nanohydrogels might be useful for flow control in porous media and can be used as a conformance control agent.
油藏水驱过程中的一致性控制用于重新分配水，提高波及效率，从而增加石油产量。使用预制凝胶颗粒可以通过封堵高渗透区并迫使水进入捕集油的低渗透区来有效地改变水流方向。然而，这种凝胶颗粒的尺寸可能会限制它们在油藏更深层的应用，并可能导致井筒附近的剪切诱导降解。在此，我们制备了具有延迟溶胀行为的核壳纳米水凝胶；在油藏条件下的盐水中放置约30天后，它们的体积增大了200倍。我们研究了它们对由随机填充玻璃珠组成的三维多孔介质微观模型中流动行为的影响。使用共聚焦显微镜，我们直接观察了纳米水凝胶注入和溶胀前后微观模型中流动的空间变化。溶胀后的纳米水凝胶堵塞了一些孔隙，降低了微观模型的渗透率，并将水转移到低渗透区域。岩心驱替实验进一步证实，纳米水凝胶可以显著降低油藏样品的渗透率并改变流体流动方向。我们的结果表明，这些核壳纳米水凝胶可能对多孔介质中的流动控制有用，并可作为一种一致性控制剂。
