Geochemical characterization and hydraulic interpretation of formation waters in the reservoirs of the North African cratonic basin

This study characterizes formation waters from three fields within a North African hydrocarbon concession to determine their genetic origin, assess hydraulic connectivity, and evaluate implications for hydrocarbon preservation. More than fifty water samples from seven formations, Cambrian to Carboniferous, were analyzed for major ion concentrations and total dissolved solids. Samples were validated using charge-balance and pH-carbonate consistency criteria and statistically anomalous samples were removed using the interquartile range method. Water types were classified using the Sulin genetic scheme, and hydraulic relationships were assessed using Stiff diagram correlation. Full quantitative treatment was applied to the two main reservoir intervals (Formations 1 and 6); the remaining five formations were evaluated using Sulin classification only. Of the 38 reservoir formation samples, 20 were retained after validation. Fields 1 and 2 contained connate chloride-calcium waters with average TDS of 9,665 mg/L and 8,775 mg/L, respectively, and average resistivity of 0.78 and 0.85 Ω·m at 60 °F. Field 3 contains meteoric bicarbonate-sodium water across all formations, with TDS averaging 1,835–2,006 mg/L and resistivity averaging 4.1–4.3 Ω·m. Stiff diagram correlation supports possible hydraulic communication between Fields 1 and 2 and isolation of Field 3. The anomalously low salinity of the connate waters is interpreted as meteoric dilution during Hercynian uplift. This study provides a validated, integrated framework that combines petrophysical parameter calculation, genetic classification and graphical correlation to distinguish connate from meteoric systems and assess reservoir connectivity. The findings demonstrate that produced water geochemistry is a practical diagnostic tool for evaluating hydrodynamic regimes and hydrocarbon preservation potential in cratonic basins.