Chemical evolution of saline water produced from Shanoul gas reservoir in south of Iran

Chemical evolution of saline water produced from Shanoul gas reservoir in south of Iran

The Shanoul gas reservoir is located in the Parsian gas field. This reservoir is composed of Permo-Triassic limestone,dolomite sandstone, anhydrite and shale of Kangan and Dalan formations. The produced water salinity of this reservoir is increased due to the more gas production during the past few years. A previous study showed that the source of the produced saline waters is the evaporated seawater. Chemical evolution of the produced water from Shanoul gas reservoir is the main objective of this study. The major, minor and trace elements concentrations of the fresh water and the produced saline water from this reservoir were measured. The chemical evolution of the produced saline water occurred by three different processes: evaporation of seawater, water–rock and water–gas interactions. Due to the seawater evaporation process, the concentrations of all ions in the produced water have increased up to the saturation levels. In comparison with the evaporated seawater, the higher concentrations of Ca, Li and Sr and lower concentrations of Mg, SO4 and Na and no changes in concentrations of Cl and K ions are observed in the produced saline water from Shanoul gas reservoir. The chemical evolution processes of the saline water include dolomitization, precipitation, ion exchange and recrystallization in water–rock interaction. Bacterial reduction and diagenesis of organic materials in water–gas interaction also occur