Abstract: There exist relatively individual formation water chemical systems in five petroliferous structures in Block C of Gobustan, Azerbaijan for reasons of differences in hydrocarbon accumulation and hydrogeologic conditions. The study shows that Solakhay structural reservoir of Bala VII formation is suggested to be a residual reservoir with a gas cap of crude biodegradation origin, according to its formation water chemical characteristic and petroleum geochemical feature. The chloride-calcium type water from Surakhany V-VII sand layers in West Duvanny structural reservoir reflects that it is a constant-volume gas reservoir with good seal conditions. The high-salinity water and chloride-calcium type water from Balakhany VII sand layer in Kyanizadag structural reservoir indicate that it is in good conservation condition. The sodium-bicarbonate type water from Balaknany VII sand layer in Dashgil structural reservoir is formed by crude biodegradation. And the sodium-sulfate type water found in Wellblock Das53 of the south side of Dashgil structural reservoir belongs to mixed genetic water possibly resulted from fluid accumulation and mixing in different periods.

Key words: Azerbaijan, Gobustan area, formation water, water type, petroleum, hydrocarbon accumulation, relationship