注水井螯合酸复合解堵体系研究与应用

针对海上疏松砂岩油藏使用常规含氟酸液体系酸化易造成岩石骨架疏松和二次伤害的问题，结合海上油田注水井不动管柱酸化和酸化后残酸不返排便直接转正常注水的特点，研制出一套低腐蚀、低沉淀的螯合酸复合解堵体系，并以渤海油田X区块注水井为例，对注水井欠注原因及解堵效果进行分析。结果表明，螯合酸复合解堵体系具有较好的缓速性、缓蚀性和抑垢性，可有效增加酸液作用距离、保障注水管柱安全、避免造成岩石骨架疏松和抑制二次和三次沉淀产生，能高效解除无机物和聚合物伤害；X区块注水井欠注原因主要是水敏、微粒运移、悬浮颗粒、结垢和聚合物等形成的多元复合物堵塞地层；现场应用单井视吸水指数增加幅度大于65.4%，解堵效果显著，可在类似油田推广应用。

Research and Application of Chelating Acid Blocking Removal System for Injection Wells

Aiming at the problem of rock skeleton loosening caused by acidification with conventional fluorinated acid fluid system in offshore unconsolidated sandstone reservoirs, and containing the characteristics of acidification of immobile string in offshore oilfield injection wells and direct conversion of residual acid to normal water injection after acidification, a chelating acid blocking removal system with low corrosion and precipitation under surface conditions is developed. Taking the injection well in Block X of Bohai Oilfield as an example, the causes of poor injection capacity and the effect of plugging removal are analyzed. The results show that the chelating acid blocking removal system has good retardation, corrosion inhibition, scale inhibition, and medium corrosion ability. It can effectively increase the acid action distance, ensure the safety of water injection pipe string, avoid causing rock skeleton loosening and restrain secondary and tertiary precipitation, and effectively relieve the damage of inorganic substances and polymers. The main reasons for poor injection capacity in Block X are the formation plugging by multi-component complex formed by hydration expansion of clay minerals, particle migration, suspended particles, scaling and polymer. The apparent water absorption index of single well increased by more than 65.4% in field application, and the chelating acid blocking removal effect was remarkable, which could be popularized and applied in similar oilfields.