新型低伤害络合酸体系评价实验

Evaluation experiment of low-damage complex acid system

华北油田砂岩油藏具有低孔低渗、敏感性矿物含量高、储层温度高的特征。为了解决常规酸液体系存在与储层反应速度快、有效穿透距离短、二次沉淀显著等问题,采用实验研究方法对新型络合酸体系的分子结构和性能进行分析评价。研究包括络合酸的核磁共振碳谱和核磁共振氢谱、缓速性能、对金属离子的螯合能力、缓蚀性能以及从岩心流动实验和润湿性测定两方面表征酸化效果。实验结果表明:新型络合酸体系的酸岩反应速度低于常规土酸体系酸岩反应速度的40%;对Ca^(2+)、Fe^(3+)、Mg^(2+)金属离子的螯合值分别是272 mg/g、455 mg/g、167 mg/g;对钢片的腐蚀速率是2.873 g/(m^2·h),远远低于行业一级标准(10~20 g/(m^2·h));地层岩心酸液流动实验渗透率增加倍数大于2;酸化后岩心的润湿性均偏水湿。研究一种具有缓速、抑垢、深穿透的新型络合酸体系,对于华北油田砂岩油藏低渗透储层的酸化增产,提高油气采收率具有重要意义。

The sandstone oil reservoirs in Huabei Oilfeld are characterized by low porosity, low permeability, high content of sensitive minerals and high reservoir temperature. And the conventional acid system is suffered from the problems of fast reaction with reservoirs, short effective penetration distance and obvious secondary precipitation. To solve these problems, the molecular structure and performance of a new complex acid system were analyzed and evaluated by means of experimental researches, including NMR carbon spectrum and NMR hydrogen spectrum of complex acid, retard performance, chelation capacity to metallic ion, corrosion inhibition performance and acidizing effect characterization from two aspects of core fow test and wettability measurement. It is indicated that acid-rock reaction speed of the new complex acid system is lower than 40% of that of conventional earth acid system. The chelation value of metallic ion Ca2＋, Fe3＋ and Mg2＋ is 272 mg/g, 455 mg/g and 167 mg/g, respectively. The steel corrosion rate is 2.873 g/（m2·h）, which is much lower than the primary industrial standard （10-20 g/（m2·h））. In the acid fow test on the formation core, the permeability is increased by over 200%. The core after the acidizing is water wettability prone. This new complex acid system with the advantages of retard, scale inhibition and deep penetration is of great signifcance to the low-permeability reservoir acidizing stimulation and hydrocar-bon recovery improvement of sandstone oil accumulations in Huabei Oilfeld.