The Effects of Rain Water Percolation through the Fractures on the Petroleum Quality, Hemrin Oilfield, Northern Iraq

The present study suggests that this variation resulted by percolation of rainwater through the fractures present in Hemrin anticline, which lead to the devastation of petroleum quality. For this reason, this study highlights the hydrogeochemistry of tertiary reservoir formation water as a result percolation of surface waters. The formation water under study are mixed origin from meteoric and marine water, associated with open system reservoir, influenced by percolation of surface water and as bad zone for preservation of hydrocarbon accumulations especially in Albufudhul and some parts of Nukhaila domes, but Allas dome recognized as semi-closed system, that a good zone for hydrocarbon accumulations. Formation water differs in the hydrochemical system, chemical composition, and salinity ranging between7430-59118 mg/l. The hydrogeochemical study suggests that the tertiary formation water is Na-SO₄-chloride type changed to Na-Ca-chloride type reflecting the different hydrodynamic system in the field. According to piper classification, formation water samples are fall in the class (g) which represents alkaline water with prevailing sulfate and chloride. The hydrochemical parameters, salinity and their distribution maps were utilized to determine the hydrodynamic zones and  percolation flow path to formation water from Albufudhul dome, toward Allas dome that  differ in properties on other domes.