Abstract: For matrix acidification in carbonate reservoirs, the use of chelating agents can avoid the problems associated with conventional acids, such as excessive acid-rock reaction and extreme corrosion on a well tubular. L-glutamic acid, N, N-diacetic acid (GLDA) has been used as a chelating agent for carbonate reservoir stimulation owing to its high water solubility, effective dissolution effect on carbonate, lower corrosion to metals than conventional acid, and high biodegradability. In this study, the dissolution and acidification effect of GLDA on Baota limestone, as well as its corrosion effect on a well tubular and iron control capabilities, were evaluated. Meanwhile, the mechanism of GLDA on Baota limestone was studied by inductively coupled plasma optical emission spectrometer (ICP-OES), zeta potential, and core flooding experiments at low pH, which was adjusted using a conventional acid. The results indicated that 5% GLDA with the pH adjusted by acetic acid (pH = 4, HAC) exhibited the most significant acidification effect on the Baota limestone. Its dissolution rates were 75.2 and 94.4% at 25 and 80 °C, respectively, after 16 h. The surface of the Baota limestone was mainly positively charged in the aqueous solution; thus, the negatively charged GLDA was easily absorbed and chelated. In terms of iron control and corrosion inhibition, 5% GLDA (pH = 4, HAC) performed better than 5% GLDA, 5% HAC, and 5% HCl. The corrosion rate of 5% GLDA (pH = 4, HAC) on P110 metal test pieces were only 0.74 and 14.43 g/(m2·h) at 25 and 80 °C, respectively, for 24 h, which showed more noticeable corrosion inhibition effects than 5% HCl (2.08 and 56.10 g/(m2·h) at 25 and 80 °C, respectively). Based on the core flooding experiment and computed tomography (CT) scanning, it was determined that 3% GLDA (pH = 4, HAC) had the most significant acidification effect on the Baota limestone at an injection rate of 1 mL/min. The permeability and porosity of the Baota limestone increased from 0.12 to 5.8 mD (approximately 48x) and from 0.44 to 2.22%, respectively. The findings of this study may provide an effective reference guide for matrix acidification design of carbonate reservoirs.

中文翻译：

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L-谷氨酸、N,N-二乙酸螯合剂对酸性环境下碳酸盐岩储层酸化的影响

摘要：在碳酸盐岩储层基质酸化中，螯合剂的使用可以避免常规酸存在的酸岩反应过度、井管腐蚀严重等问题。L-谷氨酸，N，N-二乙酸（GLDA）由于其水溶性高、对碳酸盐具有有效溶解作用、对金属的腐蚀比常规酸低以及高生物降解性，已被用作碳酸盐储层增产的螯合剂。本研究评估了 GLDA 对宝塔灰岩的溶解和酸化作用，以及对井筒和铁的控制能力的腐蚀作用。同时，通过电感耦合等离子体发射光谱仪(ICP-OES)、zeta电位、和在低 pH 值下进行岩心驱油实验，该 pH 值使用常规酸进行调节。结果表明，5% GLDA 和乙酸调节 pH 值（pH = 4，HAC）对宝塔石灰石的酸化作用最显着。16 小时后，其在 25 和 80 °C 下的溶解率分别为 75.2% 和 94.4%。宝塔灰岩表面主要在水溶液中带正电；因此，带负电荷的 GLDA 很容易被吸收和螯合。在铁控制和腐蚀抑制方面，5% GLDA（pH = 4，HAC）的性能优于 5% GLDA、5% HAC 和 5% HCl。5% GLDA（pH = 4，HAC）对P110金属试件的腐蚀速率在25°C和80°C下24 h分别仅为0.74和14.43 g/(m2·h)，显示出更明显的缓蚀效果5% HCl 的影响（2.08 和 56. 10 g/(m2·h)，分别为 25 和 80 °C)。基于岩心驱替实验和计算机断层扫描 (CT) 扫描，确定 3% GLDA（pH = 4，HAC）在 1 mL/min 注入速率下对宝塔灰岩的酸化作用最显着。宝塔灰岩的渗透率和孔隙度分别从 0.12 增加到 5.8 mD（约 48 倍）和从 0.44 增加到 2.22%。本研究结果可为碳酸盐岩储层基质酸化设计提供有效的参考指导。分别为 12 至 5.8 mD（约 48 倍）和 0.44 至 2.22%。本研究结果可为碳酸盐岩储层基质酸化设计提供有效的参考指导。分别为 12 至 5.8 mD（约 48 倍）和 0.44 至 2.22%。本研究结果可为碳酸盐岩储层基质酸化设计提供有效的参考指导。