الملخص

Two hydrogeochemical indices are presented namely: the balance of sulfate (B.S) and the index of aeration (I.A) and may be used as geochemical tools to give important information that indicate the presence of good prospects of oil and native sulphur deposits. The B.S and I.A are calculated from the hydrochemical data of natural waters (formation waters, oil field brines, sulphurous springs, …etc) that are associated with these deposits. For hydrocarbon deposits the B.S values were negative and ranged from few to several thousands, while I.A values were positive and ranged from zero to 10 for excellent prospects to 100 or to 1000 for less important prospects. For native sulphur deposits, both the B.S and I.A values were positive and ranged from few hundreds to thousands. Many examples of oil field waters and sulphurous springs from Iraq were examined and gave results of high positive significance.