Abstract:

Combined with SEM, EDS, dynamic evaluation of plug formation, microscopic visualization and long core displacement experiments, the damage mechanism of residual acid in polymer injection oilfield to the reservoir was studied. The results show that the damage of residual acid to the reservoir is mainly due to the crosslinking point of the polymer molecular chain with high valence cations such as Al³⁺ and Fe³⁺ in residual acid. The crosslinking network elastic colloid is formed by the coordination between carboxylic acid radicals in the polymer side group and high valence cations, and the degree of crosslinking increases with the increase of ion concentration. The elastic colloid formed blocked at the edge and pit of the pore throat, which makes the pore throat diameter gradually smaller. In the process of flow, it wraps around the formation particles and carbonate sediments, forming a composite blockage micelle, resulting in deep plugging. The long core displacement experiment shows that residual acid can damage the core up to 60%. The research results provide a theoretical basis for the research and development of plugging removal fluid system and optimization of plug removal processes in polymer injection oilfield

Key words: Polymer injection oilfield, Residual acid, Damage mechanism, Organic micelles

摘要：

结合扫描电镜、能谱法以及堵塞物形成动态评价、微观可视化、长岩心驱替等实验，进行了注聚油田残酸对储层伤害机理研究。结果表明，残酸对储层的伤害主要是由于聚合物分子链以残酸中Al³⁺、Fe³⁺ 等高价阳离子为交联点，通过聚合物侧基中的羧酸根和高价阳离子之间的配位作用，形成交联网状弹性胶状物，且交联程度随离子质量浓度的增加而增强；生成的弹性胶状物堵塞孔喉边缘和凹坑部位，使孔喉直径逐渐变小，流动过程中包裹缠绕地层微粒、碳酸盐沉淀物等，形成复合堵塞物胶团，造成深部堵塞。长岩心驱替实验表明，残酸对岩心渗透率伤害率高达60%以上。研究结果可为注聚油田解堵液体系研发和解堵工艺优化提供理论参考。

关键词: 注聚油田, 残酸, 伤害机理, 有机胶团