Source Rock Evaluation of the Cenomanian Middle Sarvak (Ahmadi) Formation in the Iranian Sector of the Persian Gulf

Abstract

The middle Sarvak formation (Cenomanian) is one of the stratigraphic units of the Bangestan group in the south of Iran. This formation is stratigraphically equivalent to the Ahmadi member of Kuwait and Iraq. There is geochemical evidence that indicates this unit has a high level of organic richness and can be a possible source rock in various locations. This study focuses on the organic geochemistry of the middle Sarvak formation in the Persian Gulf region. Rock Eval pyrolysis, organic petrography, and kerogen elemental analyses were used in order to evaluate the thermal maturity and determine the kerogen type of the middle Sarvak formation. The results of this study show that middle Sarvak formation has entered the oil window in eastern and western parts of the Persian Gulf, but it is immature in the central parts. This regional pattern of organic maturation is probably a consequence of the regional uplift in the Qatar-Fars arch area. The higher maturities in the eastern and western parts are, on the other hand, attributed to its greater depth of burial. The results of the screening analyses by the Rock-Eval pyrolysis in parallel with the results of maceral and elemental analyses show that the kerogen type in the middle Sarvak formation is mainly a mixture of Types II and III.