Integrating geochemical and reservoir engineering approach to evaluate reservoir continuity: A case study from Foroozan field, Offshore Iran

Abstract

Foroozan field, with seven different reservoir layers, is one of the complex fields in the Persian Gulf. The purpose of this study was to identify intra-reservoir compartmentalisation using geochemical and reservoir engineering evidences. On the basis of this approach, 11 gaseous samples, which belong to different wells producing from the Burgan reservoir of Foroozan field, were selected. Gas composition, gas isotopes and associated oil bulk properties were tested to determine the reservoir continuity through the Burgan reservoir. In addition, fluid contacts and properties are also used to investigate reservoir continuity. Regarding clear differences in gas composition such as hydrogen sulphide concentrations, at least two separate segments in the north and south of the reservoir were detected. Moreover, the percentages of the different gas components indicated two separate compartments. Other evidences such as $\hbox {C}_{1}$–$\hbox {C}_{4}$ alkane isotopic compositions and sulphur and nitrogen isotopic signatures confirmed the Burgan reservoir compartmentalisation. A number of petroleum bulk properties confirmed gradual variations that provide supplementary evidence on the reservoir-filling direction, signifying that fluids equilibrium had not been extended through the Burgan reservoir, laterally. Initial reservoir condition, different original water–oil contacts, solution gas–oil ratio at original pressure and bubble point pressure are other reservoir engineering evidences that support the Burgan reservoir compartmentalisation.