Himalayan Geology, Vol. 44 (1), 2023, pp. 12-20, Printed in India
Modeling of Clay mineral distribution and its effect on Chemical Wellbore Stability (Case study: South West of Iran)
HOSSEIN TABATABAEI1*, MOHAMMAD ABDIDEH2
1Department of Petroleum Engineering, Islamic Azad University, Gachsaran Branch, Gachsaran, Iran
2Department of Petroleum Engineering, Islamic Azad University, Omidiyeh Branch, Omidiyeh, Iran
*Email (Corresponding author): Tabatabaei.h@gmail.com; Hossein.Tabatabaei@iau.ac.ir
Abstract: The Pabdeh Formation with shale, marl, and calcareous shale lithology has recorded a lot of Wellbore Stability when using water-based mud drilling. According to the studies, Pabdeh Formation can be divided into several zones. Clay minerals such as montmorillonite, which are always problematic in drilling operations due to their high Cationic Exchange Capacity (CEC), are abundant in the upper part of this formation. Studies show that the distribution of clay minerals in the field is not uniform and is related to fluctuations accompanying it. Overall, the amount of illite has increased to the northwest of the field. Also, studies show that in this formation, with increasing depth, the amount of illite increases, which is related to diagenetic alteration and has enhanced the wellbore stability. During the same process, to the northwest of the field, the weight of drilling mud increased, indicating an increase in the formation pressure, calcareous compounds, and a decrease in clay compounds. The most chemical collapse was due to the presence of montmorillonite in the top part of Pabdeh formation and their chemical reaction with water base mud. The CEC of montmorillonite are 80 to 100. Most of these collapses are seen around wells No. 38 and 48.
Keywords : Chemical Wellbore Stability, CEC, Clay minerals, Pabdeh Formation, Kupal oil field
