Many oil reservoirs are at high temperatures and contain brines of high salinity and hardness. The focus of this work is to develop robust foams stabilized by a mixture of nanoparticles and surfactants for such reservoirs. Two types of silica nanoparticles (Si-NP1, Si-NP2) with different grafted low molecular weight ligands/polymers were used. First, aqueous stability analysis of these nanoparticle dispersions were conducted at high-temperature (80 °C) and high-salinity conditions (API Brine; 8 wt% NaCl and 2 wt% CaCl 2 ). The screened nanoparticles were used in combination with an anionic surfactant. Second, bulk foam and emulsion stability tests were performed to investigate their performance in stabilizing the air–water and oil–water interface, respectively. Third, foam flow experiments in the absence of oil were performed to characterize the foam rheology. Finally, oil displacement experiments were conducted in an in-house, custom-built 2D sand pack with flow visualization. The sand pack had two layers of different mesh size silica sand which yielded a permeability contrast of 6:1. Brine floods followed by foam floods (80% quality) were conducted, and foam flow dynamics were monitored. The grafting of low molecular weight polymers/ligands on silica nanoparticle surfaces resulted in steric stabilization under high-temperature and high-salinity conditions. Foam flow experiments revealed a synergy between Si-NP2 and surfactant in stabilizing foam in the absence of crude oil. In the oil displacement experiments in the layered sand packs, the waterflood recoveries were low (~ 33% original oil in place) due to channeling in the top high-permeability zone, leaving the bottom low-permeability zone completely unswept. Foam flooding with just the surfactant leads to a drastic improvement in sweep efficiency. It resulted in an incremental oil recovery as high as 43.3% OOIP. Different cross-flow behaviors were observed during foam flooding. Significant cross-flow of oil from low-permeability zone to high-permeability zone was observed for the case of surfactant. Conversely, the Si-NP2-surfactant blend resulted in no cross-flow from the low-permeability region with complete blocking of the high-permeability region due to the formation of in situ emulsion. Such selective plugging of high-perm zones using nanoparticles with tailored surface coating and concentration has significant potential in recovering oil from heterogeneous reservoirs.

中文翻译：

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恶劣水库条件下纳米颗粒稳定泡沫的研究

许多油藏处于高温下并且含有高盐度和硬度的卤水。这项工作的重点是为此类储层开发由纳米颗粒和表面活性剂混合物稳定的坚固泡沫。使用了两种具有不同接枝低分子量配体/聚合物的二氧化硅纳米粒子（Si-NP1、Si-NP2）。首先，在高温 (80 °C) 和高盐度条件（API 盐水；8 wt% NaCl 和 2 wt% CaCl 2 ）下对这些纳米颗粒分散体进行水性稳定性分析。筛选出的纳米颗粒与阴离子表面活性剂结合使用。其次，进行了大量泡沫和乳液稳定性测试，以分别研究它们在稳定空气-水和油-水界面方面的性能。第三，在没有油的情况下进行泡沫流动实验以表征泡沫流变学。最后，在内部定制的具有流动可视化功能的 2D 砂层中进行了驱油实验。砂包有两层不同网眼尺寸的硅砂，其渗透率对比为 6:1。进行盐水驱替和泡沫驱替（80% 质量），并监测泡沫流动动力学。在二氧化硅纳米颗粒表面接枝低分子量聚合物/配体导致高温和高盐度条件下的空间稳定。泡沫流动实验表明，在没有原油的情况下，Si-NP2 和表面活性剂在稳定泡沫方面具有协同作用。在层状砂岩驱油实验中，由于顶部高渗透区的窜流，水驱采收率低（约 33% 的原始石油），而底部的低渗透区完全未波及。仅使用表面活性剂进行泡沫驱油可显着提高波及效率。它导致增加的石油采收率高达 43.3% OOIP。在泡沫驱期间观察到不同的错流行为。对于表面活性剂，观察到油从低渗透区到高渗透区的明显错流。相反，由于原位乳液的形成，Si-NP2-表面活性剂共混物导致低渗透区没有错流，高渗透区完全阻塞。