Clay peptization and clay swelling inhibition in the presence of carbonic acid, bicarbonate and carbonate ions and calcium ions

• Published in: Bulletin of the Tomsk Polytechnic University Geo Assets Engineering
• Main Authors: Dmitriy A. Baranov, Sergey F. Vyaznikovtsev, Oksana G. Mamaeva
• Format: Article in Journal/Newspaper
• Language: Russian
• Published: Tomsk Polytechnic University 2024
• Subjects: clay peptization; clay swelling inhibition; carbon dioxide; carbonic acid; bicarbonate ions; carbonate ions; Engineering geology. Rock mechanics. Soil mechanics. Underground construction; TA703-712; Carbonic acid
• Online Access: https://doi.org/10.18799/24131830/2024/2/3783; https://doaj.org/article/692f86462d17446bbca55ddefde85e76

Relevance. The need to ensure the integrity of the wellbore, composed of clay rocks, and the stability of drilling fluid when drilling in conditions of carbon dioxide and bicarbonate aggression. Aim. To determine experimentally the effect of carbonic acid, bicarbonate and carbonate ions on clay depending on the presence of calcium ions in the dispersion medium. Objects. Water contaminated with carbonic acid, bicarbonate and carbonate ions with different equivalent concentrations of calcium ions. Methods. Inhibitory and peptizing properties of the objects of study in relation to the clay rock were studied by the method of clay swelling when it was in the water under study (on the Zhigacha-Yarov device); methods of chemical analysis (complexometric and acid-base titration) and potentiometry were used to control water composition and properties. Results. The peptizing and inhibiting properties of drilling fluid depend significantly on the form of carbonic acid present in the dispersion medium and the equivalent content of calcium ions (Ca2+). It was found that carbonic acid (H2CO3) contributes to clay inhibition (coagulation), bicarbonate ions (HCO3–) and carbonate ions (CO32–) – clay peptization. Calcium ions (Ca2+) do not have an inhibitory effect in the presence of carbonic acid (H2CO3) – hydrogen ions (H+) displace exchangeable cations from the interlayer space of clays and, due to their small diameter, independently inhibit clay swelling. In the presence of bicarbonate ions (HCO3–), calcium ions (Ca2+) also do not have an inhibitory effect – bicarbonate ions (HCO3–), being in a dispersion medium, draw calcium ions (Ca2+) from the clay surface, increasing the thickness of the electrical double layer. In the presence of carbonate ions (CO32–) the calcium ions (Ca2+) precipitate and effectively prevent clay peptization only in the presence of hydroxide ions (OH–). The authors proved experimentally that calcium ions (Ca2+) in the presence of hydroxide ions (OH–) have a better inhibitory ability than hydrogen ions ...