Petroleum geochemistry and oil–oil correlation of the Fahliyan and Surmeh reservoirs in the Garangan and Chilingar oilfields, the Dezful embayment (Sw Iran)

The Dezful embayment located in southwest of Iran is one of the most potential areas for exploration and development of hydrocarbon reservoirs in the world. There are several source rock units with different geological ages. In this research, the Fahliyan and Surmeh reservoirs from the Garangan and Chilingar Dezful oilfields were studied using geochemical techniques including gas chromatography and carbon and sulfur stable isotope measurements. Carbon preference index of both reservoir oils was around one, indicating mature oil samples. The collected oil from both the fields was paraffinic in nature. Pr/nC17 and Ph/nC18 sand ratio and the plot of δ13C (arom) versus δ13C (sat), both indicated that a marine reducing environment prevailed during the deposition of their progenitor source rock. The organic matter deposited in this sediment is of kerogen type II (algal). Plot of stable carbon isotope values versus Pr/Ph ratio indicates that both oils originated from the same shaly limestone belonging to Mesozoic. The results of isotopic and geochemical studies show that a single source rock contributed to the oil family found in both fields.