Wang Jiangtao, Wan Xiaolong, Ren Junsong, Zhu Genggeng, Xu Wei, Hu Yingxue
School of Human Settlements and Civil Engineering, Xi'an Jiaotong University, Xi'an, China.
Oil Production Plant NO.5 of Changqing Oilfield, China National Petroleum Corporation, Xi'an, China.
Front Chem. 2025 Jun 18;13:1621714. doi: 10.3389/fchem.2025.1621714. eCollection 2025.
Low-salinity water flooding is widely recognized as an effective enhanced oil recovery (EOR) method, primarily by altering wettability and reducing interfacial tension. However, chemical incompatibility between injected water and formation water may induce scale deposition, leading to pore blockage and injectivity impairment, thereby posing significant challenges to EOR efficiency. A better understanding of the interplay between chemical incompatibility and pore-scale oil-water interface dynamics is crucial for optimizing waterflooding performance, particularly in low-permeability reservoirs. This study integrates ion characterization, colloidal analysis, solubility product calculations, and microfluidic visualization to systematically evaluate the compatibility of formation and injected waters, while directly observing pore-scale fluid displacement processes. Results reveal that ionic composition analysis reveals significant incompatibility between the sulfate-rich injection water and calcium/barium-containing formation water, creating conditions favorable for mineral scaling. Subsequent examination of scaling dynamics demonstrates that incompatible fluid mixing initiates nanoparticle formation, which progresses through two distinct growth pathways: coalescence-driven crystal enlargement and aggregation-dominated cluster formation, ultimately leading to pore-throat obstruction. Microfluidic visualization shows residual oil persists primarily as interfacial films and pore-center clusters after initial waterflooding, with their spatial arrangement governed by salinity-dependent wettability alteration and capillary forces. The introduction of incompatible water further exacerbates fluid trapping through capillary valve effects-a capillary-driven resistance occurring when interfacial forces oppose fluid advancement at pore-throat junctions-creating stagnant zones that promote particle accumulation. Pressure monitoring during flooding experiments reveals characteristic response patterns: an initial pressure peak during waterflooding, followed by secondary pressure elevation due to scale deposition, and subsequent partial pressure reduction through surfactant-mediated interfacial tension reduction and wettability modification. A self-reinforcing cycle emerges, coupling ion incompatibility, capillary trapping, and precipitate growth, encapsulated in a colloid-capillary coupling framework. To disrupt this cycle, a synergistic chemical strategy combining surfactants and scale inhibitors is proposed, simultaneously enabling interface modification and nucleation suppression to enhance sweep efficiency. This integrated approach provides a mechanistic foundation for optimizing waterflooding in chemically complex reservoirs, achieving a balanced synergy between interfacial control and scale mitigation.
低盐水驱油被广泛认为是一种有效的提高采收率（EOR）方法，主要是通过改变润湿性和降低界面张力来实现。然而，注入水与地层水之间的化学不相容性可能会导致结垢，从而导致孔隙堵塞和注入能力受损，进而对提高采收率的效率构成重大挑战。更好地理解化学不相容性与孔隙尺度油水界面动力学之间的相互作用对于优化注水性能至关重要，特别是在低渗透油藏中。本研究整合了离子表征、胶体分析、溶度积计算和微流控可视化，以系统地评估地层水和注入水的相容性，同时直接观察孔隙尺度的流体驱替过程。结果表明，离子组成分析揭示了富含硫酸盐的注入水与含钙/钡的地层水之间存在显著的不相容性，为矿物结垢创造了有利条件。随后对结垢动力学的研究表明，不相容流体混合引发纳米颗粒形成，其通过两种不同的生长途径进行：聚结驱动的晶体增大和聚集主导的团簇形成，最终导致孔喉堵塞。微流控可视化显示，在初始注水后，残余油主要以界面膜和孔隙中心团簇的形式存在，其空间排列受盐度依赖性润湿性改变和毛细管力控制。引入不相容水会通过毛细管阀效应进一步加剧流体捕集，毛细管阀效应是指当界面力在孔喉交界处阻碍流体推进时产生的毛细管驱动阻力，从而形成促进颗粒聚集的停滞区。注水实验期间的压力监测揭示了特征响应模式：注水期间的初始压力峰值，随后由于结垢导致二次压力升高，以及随后通过表面活性剂介导的界面张力降低和润湿性改变实现的部分压力降低。一个自我强化的循环出现了，它将离子不相容性、毛细管捕集和沉淀物生长耦合在一起，封装在一个胶体-毛细管耦合框架中。为了打破这个循环，提出了一种结合表面活性剂和防垢剂的协同化学策略，同时实现界面改性和成核抑制，以提高波及效率。这种综合方法为优化化学复杂油藏中的注水提供了一个机理基础，在界面控制和结垢缓解之间实现了平衡的协同作用。
