Geochemical signatures and their spatial variations in groundwater adjoining major Kuwait oil fields

Kuwait depends on two major aquifers for the groundwater resources, the younger Kuwait aquifer and the older Dammam formation. The groundwater is brackish to saline in Kuwait aquifers with a probability of contamination adjoining the oil field region. In this context, groundwater samples were collected from three major oil fields in Kuwait (North, Southeast, and West). Sulfate and nitrate were dominant in all three regions. The geochemical signatures indicate the predominance of Na-Cl-SO₄ water type in the North (NK), Na-Ca-Cl in the Southeast (SEK) and Na-Ca-Mg-Cl-SO₄ type in the West (WK). The dolomite and gypsum saturation index dominated the sulfate and carbonate minerals, irrespective of the regions. The log pCO₂ of the groundwater samples ranged from - 1.8 to - 6.2, reflecting the mineral dissolution and microbial process, which mainly contained lower values and governed the carbonate mineral saturation. The common ion effect of Ca has influenced the saturation of carbonate and sulfate minerals. Correlation between EC, pH, and a few major ions was identified, while CH₄ and C₂H₆ were correlated with these parameters only in NK. The principal component analysis indicates that the dissolution of ions from the aquifer matrix leads to brackish groundwater, followed by silicate weathering in NK and hydrogenation in SEK and WK. Further, the study also identified the dissolution of carbonate minerals and fluoride in the NK, sulfate minerals in the SEK, and silicate minerals in the WK. Hence, the study infers that geochemical variation is due to lithology, groundwater salinity, and the physicochemical conditions prevailing in the aquifer.