砾岩油藏复合驱协作增效聚-表二元体系的构建及微观驱油机理

Owing to the lower sweep volume and rapid water cuts of water flooding in conglomerate reservoirs, a large amount of unrecovered oil left as remaining oil or residual oil, which is the significant target for chemical combination flooding technique because it enables to increase the sweep volume and the sweep efficiency. However, the polymer-surfactant binary combination system hardly achieves the synergistic viscosification and ultralow oil-water interfacial tension, which hinders the industrial application of the polymer-surfactant binary combination flooding. Based on free-radical polymerization mechanism and supramolecular theory, a novel of core-shell like associative polyacrylamide (HBPAM) will be synthesized, and the interaction characteristics of HBPAM and nonionic surfactant alkanolamide (LMEA) will be investigated. The effect of the LMEA on the HBPAM solution properties, such as viscosification, rheology, shearing resistance, viscoelasticity and long-term stability will be studied. Meanwhile, the effect of the HBPAM on the LMEA solution properties, such as interfacial tension and interfacial viscoelasticity will be elaborated. A super synergistic HBPAM-LMEA binary combination system with robust thickening efficiency and ultralow oil-water interfacial tension will be established according to the relationship between the microstructures and macroscopic properties of HBPAM-LMEA binary combination systems. Moreover, the pore structure, pore-throat distribution, seepage system, and state and distribution of the micro-remaining oil and the micro-residual oil will be elucidated using low-field nuclear magnetic resonance, X-ray CT scanning, and visual conglomerate lamination model. Subsequently, a series of core flooding tests of HBPAM-LMEA binary combination flooding will be designed and performed. Finally, based on these experiments, the relationship between maximum reserves utilization and enhanced oil recovery factors, and capillary numbers on the pore space scale will be mathematically correlated to elucidate the microscopic displacement mechanism of the HBPAM-LMEA binary combination flooding in complex porous media. The results of this research will not only enrich and perfect basic theory of chemical combination flooding, but provide the technical support for high-efficiency development of the conglomerate reservoirs.

砾岩油藏水驱采出程度低，产量递减快，复合驱是驱动其稳产的重要技术；然而，聚合物与工业表面活性剂难实现增黏和降低油-水界面张力的协同，聚-表二元复合驱面临瓶颈制约。本项目基于自由基聚合机理和超分子理论，拟制备核-壳型缔合聚合物（HBPAM），研究HBPAM与市售N-羟基烷基酰胺（LMEA）相互作用机制，构建强增黏和超低油-水界面张力协作的HBPAM-LMEA二元体系；借助核磁共振成像、X-射线CT扫描及可视化砾岩薄片模型剖析砾岩的孔隙结构与孔-喉分布、渗流系统及水驱油后微观剩余（残余）油的赋存状态和分布，结合二元复合驱的物理模拟，建立孔隙尺度下的动用界限、驱油效率与毛管数的数学模型，揭示二元体系的微观驱油机理。研究成果不仅为砾岩油藏二元复合驱的高效开发提供技术支撑，同时也能够丰富和完善复合驱的基础理论。

聚-表二元复合驱是高含水砾岩油藏提高水驱波及系数和驱油效率的关键技术，针对聚合物与工业表面活性剂难以实现增黏和降低油-水界面张力的协同问题，本项目基于自由基聚合机理和超分子理论，制备了核-壳型缔合聚合物（SHPAM），分析表征结合分子模拟研究了SHPAM与市售N-羟基烷基酰胺（LMEA）相互作用形成“巨型”表面活性剂的强增黏和协作降低油-水界面张力的微观机制：SHPAM呈现“桥梁”特征，SHPAM的疏水链插入LEMA形成的球形胶束中形成新的巨型“亲水基团”，SHPAM另一部分亲水链与LEMA缔合，将大部分的LEMA分子疏水（亲油）链暴露在外围，组装为新的巨型“疏水基团”；“巨型”表面活性剂显著增强SHPAM的水动力学尺度，受两亲结构控制，SHPAM在油水界面定向分布，亲水内核完全和油-水界面的LEMA亲水基团结合形成强界面膜，稳定和强化LEMA在油-水界面的排列，从而协同降低油-水界面张力。基于核磁共振成像及可视化砾岩薄片模型剖析砾岩的孔隙结构与孔-喉分布、渗流系统及水驱油后微观剩余（残余）油的赋存状态和分布，结合二元复合驱的物理模拟，建立了孔隙尺度下的动用界限、驱油效率与毛管数的关系模型，提取了二元体系驱的相渗曲线，在含水饱和度范围聚-表二元驱的毛管数均为水驱的上千倍，残余油饱和度降低18%以上。研究成果不仅为砾岩油藏的高效开发提供了技术支撑，同时丰富和完善了复合驱的基础理论。