Three-dimensional visualization of the alkaline flooding process with in-situ emulsification for oil recovery in porous media
Three-dimensional visualization of the alkaline flooding process with in-situ emulsification for oil recovery in porous media
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DOI：
10.1016/j.petrol.2021.108519
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发表时间：
2021-07
影响因子：
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通讯作者：
Yun She;M. Mahardika;Yingxue Hu;Anindityo Patmonoaji;Shintaro Matsushita;T. Suekane;Y. Nagatsu
中科院分区：
文献类型：
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作者：
Yun She;M. Mahardika;Yingxue Hu;Anindityo Patmonoaji;Shintaro Matsushita;T. Suekane;Y. Nagatsu
碱性驱是通过原位形成水包油乳状体来提高采收率的一种很有前途的应用。然而，随着原油总酸值（TAN）的变化，提高扫油效率的乳化行为仍不明确，特别是在高酸性油填充的多孔介质中。本研究首先进行了三维（3D）驱油实验，利用x射线计算机断层扫描技术研究TAN和注入流量对采收率的影响。从驱油模式、分形维数、碱性溶液切片平均浓度和采收率曲线多角度分析，证实了随着酸浓度的增加，采收率增加。通过不同系列的流量实验，确定最佳注射流量为360 ml/h。同时，观察了指法结构在非混相流体-流体驱替过程中的演化。非线性手指-手指相互作用，如尖端分裂、屏蔽和聚并，也在三维多孔介质中得到证实。随后，进行了二维孔隙尺度微模型实验，验证了三维多孔介质中可能发生的驱油机制。随着酸浓度的增加，在碱驱过程中乳化能力增强，形成的平均乳滴尺寸为156.1 ~ 78.8 μm，由部分乳化向完全乳化转变。部分乳化主要发生在断裂、分裂和分裂过程中，形成了许多大于孔隙（128 μm）和喉道（39 μm）的油节和/或油滴。充分乳化的特点是在剪切作用下形成适当大小的油滴。更小的油滴被有效地夹带在水相中，并作为连续相通过孔隙和喉道，从而产生最有利的驱油效果。研究结果表明，只有在乳状液滴大小与孔喉结构相匹配的条件下，才能实现高采收率。最后，提出在工程应用中，碱性驱由于具有充分乳化作用，在高酸性油藏中具有最大的提高采收率的潜力。
Alkaline flooding is a promising application for enhanced oil recovery through the in-situ formation of oil-in-water emulsions. However, the emulsification behavior for the improved oil sweeping efficiency varying from the total acid number (TAN) of crude oil is still vague, especially in porous media filled with high acidic oil. This study initially performs three-dimensional (3D) oil displacement experiments to investigate the effects of the TAN and the injected flow rate on the oil recovery performance using X-ray computed tomography. Consequently, the oil recoveries are confirmed to increase with the increasing acid concentration from multi-angle of the oil displacement patterns, fractal dimension, slice average concentration of the alkaline solution, and oil recovery curves. The optimum injected flow rate is confirmed to be 360 ml/h based on different series of flow rate experiments. Meanwhile, the fingering structure evolution is observed with respect to the immiscible fluid–fluid displacement. Nonlinear finger–finger interactions, such as tip-splitting, shielding, and coalescence, are also confirmed in the 3D porous media. Subsequently, two-dimensional pore-scale micromodel experiments are performed to verify the oil displacement mechanism that may occur in 3D porous media. With an increase in the acid concentration, the emulsification ability becomes stronger in the form of an emulsified transition from partial to full emulsification during the alkaline flooding process as a result of formed average emulsion droplet size ranging 156.1–78.8 μm. Partial emulsification is predominated by the snap-off, splitting, and division processes, leading to many oil ganglia and/or oil droplets formation that are bigger than pores (128 μm) and throats (39 μm). Full emulsification is characterized by the proper size of oil droplet formation by the shearing action mechanism. Far smaller oil droplets are effectively entrained in the aqueous phase and passed through the pores and throats as a continuous phase, resulting in the most favorable oil displacement. The study results suggest that high oil recovery could only be achieved under the condition of the proper sizes of emulsion droplets matched with the pore–throat structure. Finally, we propose herein that in engineering application, alkaline flooding has the highest potential of improving oil recovery in high-acidity oil reservoirs because of full emulsification.