In carbonate matrix acidizing, the critical design parameters are interstitial velocity and pore volume to breakthrough for wormhole propagation (vi, opt and PVBT,opt). Hydrochloric acid (HCl), the most commonly used acid in carbonate acidizing, sometimes shows low efficiency because the injection rate needed for optimal wormhole propagation is not attainable, especially for when long completion intervals, low permeability carbonates, or coiled tubing operations are involved. It also raises safety, corrosion, and environmental concerns. When conventional retarded acid systems are used to overcome these challenges, the efficiency of acid stimulation often suffers from low reaction rate. This study presents testing results of a modified acid system that has controlled reaction rate with favourable wormhole propagation characteristics, especially at low interstitial velocities. Due to the increased activation energy barriers utilized in these modified-acid systems, it is possible to control the reaction rate of the hydrogen proton and optimize the wormholing effect based on the completion method and formation specifications. Laboratory linear core flooding experiments and acid jetting experiments were conducted to study the wormhole efficiency with the new acid systems. The experimental results showed clear advantages of the modified acid systems. The modified acids have similar or better wormhole efficiency parameters compared with HCl having comparable dissolving power. When combined with acid jetting, further improvement in wormhole growth in low permeability limestone is achieved. In addition to minimizing the hazardous exposure levels and corrosion rates compared with HCl, the new acid system provides the positive aspects of solubilizing ability, thus improving optimal wormhole conditions.

中文翻译：

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增强碳酸盐基质酸刺激的改良酸系统：一项实验研究

在碳酸盐基质酸化中，关键的设计参数是虫洞传播的间隙速度和孔体积（vi，opt 和 PVBT，opt）。盐酸 (HCl) 是碳酸盐酸化中最常用的酸，有时效率较低，因为无法达到最佳虫孔扩展所需的注入速率，尤其是在涉及长完井间隔、低渗透性碳酸盐或连续油管作业时。它还引起了安全、腐蚀和环境问题。当使用传统的延迟酸系统来克服这些挑战时，酸刺激的效率通常会受到反应速率低的影响。本研究展示了一种改性酸系统的测试结果，该系统具有可控的反应速率和良好的虫洞传播特性，特别是在低间隙速度下。由于在这些改性酸体系中使用了增加的活化能垒，因此可以根据完井方法和地层规范控制氢质子的反应速率并优化虫洞效应。进行了实验室线性岩心驱替实验和酸喷射实验，以研究新酸系统的虫洞效率。实验结果表明改性酸体系具有明显的优势。与溶解能力相当的 HCl 相比，改性酸具有相似或更好的虫洞效率参数。当与酸喷射相结合时，可以进一步改善低渗透性石灰岩中的虫洞生长。与 HCl 相比，除了最大限度地降低危险暴露水平和腐蚀速率外，