| 摘要: |
| 目的 解决富含钙质胶结物低渗储层采用土酸酸化投产效果不佳、酸化有效期短的问题。方法 利用核磁T2谱、电镜、ICP等测试手段对该储层岩心强酸酸岩反应前后矿物成分、孔喉结构、残酸及返排液离子成分和固相组分进行了测试分析，明确强酸投产效果差的原因及改进措施。结果 强酸主要对碳酸盐岩胶结物进行充分溶蚀，对钾长石、斜长石、黏土矿物进行局部溶蚀，但岩心溶蚀不均匀，存在明显溶蚀区与非溶蚀区界面。强酸酸化后，岩心在1.14~18.38 μm范围的中~粗孔喉频率分布增大1倍以上，小于1.14 μm的细孔喉略微增加或有所下降。酸化后产生了高含量的Ca2+、Fe3+、Si2+、Al3+等，易形成Fe（OH）3、CaF2、Na2SiF6等二次沉淀物，同时，未完全溶蚀的地层微粒易剥落堵塞。在返排阶段，酸化二次沉淀物及溶蚀不完全的微粒造成酸蚀后的中~粗孔喉被分割堵塞，造成酸化后岩心渗透率的降低，降低幅度大于50%。结论 提出强化Fe3+抑制能力、控制酸化解堵后油井产液速度、采用多氢酸体系等改进措施；现场实施后，大幅提高了该类储层的酸化改造效果，首口实施井有效期已超过8个月。 |
| 关键词: 低渗储层 富钙质胶结物 强酸 酸化 二次伤害 |
| DOI：10.3969/j.issn.1007-3426.2025.02.016 |
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| Damage mechanism and improvement measures of strong acid acidification in calcium-rich cement low-permeability reservoirs |
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Yuan NAN1, Shuangzheng MA1, Yaoyuan ZHANG1, Xiaojuan CHEN1, Weihao XIE1, Hongming TANG2
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1.CNOOC Energy Development Company Limited, Engineering Technology Branch, Zhanjiang, Guangdong, China;2.School of Geoscience and Technology, Southwest Petroleum University, Chengdu, Sichuan, China
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| Abstract: |
| Objective In order to solve the problem of poor production effect and short acidification validity period of low-permeability reservoir with calcium-rich cement by using soil acid acidification, the research of the mechanism and improvement measures of strong acid acidification has been carried out. Method The mineral composition, pore throat structure, ionic composition of residual acid and flowback fluid, and solid-phase composition of this reservoir core before and after the strong acid acid rock reaction were tested and analyzed by using NMR T2 spectroscopy, electron microscopy, ICP, and other testing methods, to clarify the reasons for the poor effect of the strong acid put into production and the improvement measures. Result Strong acid is mainly used to fully dissolve carbonate rock cement, and locally dissolve potassium feldspar, plagioclase feldspar and clay minerals, but the core dissolution is not uniform, and there exists obvious interface between dissolved and non-dissolved areas. The frequency distribution of medium-coarse pore throats in the range of 1.14 to 18.38 μm in the core increased by more than one times after strong acid acidification, and the fine pore throats smaller than 1.14 μm slightly increased or decreased. Acidification produces high concentrations of Ca2+, Fe3+, Si2+, Al3+ and so on, which are easy to form secondary precipitates such as Fe(OH)3, CaF2, Na2SiF6. Meanwhile, the incompletely dissolved formation particles are easy to strip off and clog. In the return stage, the acidified secondary precipitates and incompletely dissolved particles cause the medium-coarse pore throat after acid etching to be divided and blocked, resulting in the reduction of permeability of the core after acid etching, and the reduction is more than 50%. Conclusion Improvement measures such as strengthening the inhibition ability of Fe3+, controlling the rate of fluid production in wells after acidizing and unplugging, and adopting a multi-hydrogen acid system are proposed, and the effect of acidizing of this type of reservoir has been greatly improved after the application in field, and the validity period of the first implemented well has been more than 8 months. |
| Key words: low-permeability reservoir calcium-rich cement strong acid acidization secondary injury |
