Field-scale reservoir zonation of the Albian–Turonian Sarvak Formation within the regional-scale geologic framework: A case from the Dezful Embayment, SW Iran

Abstract

The Albian–Turonian Sarvak Formation is the second most important reservoir of Iran. In this study, an integrated field-scale reservoir zonation is applied to the Sarvak reservoir in one oil field of the Dezful Embayment, SW Iran to understand the distribution of speed, barrier, and baffle zones. The geologic controls of depositional and post-depositional factors on the suggested reservoir zonation are also discussed here. Based on the results, the studied reservoir is composed of seven zones with different reservoir qualities. The best reservoir zones show considerable amount of dissolution pores, and are developed beneath regional-scale paleo-exposure surfaces that are also recognizable in coeval strata on the Arabian Plate. These surfaces represent recurring subaerial exposure episodes during the development of the Sarvak Formation through which meteoric diagenesis highly affected the rock record leading to the development of paleo-karst profiles with noticeable dissolution pores in the strata beneath the paleo-exposure surfaces. However, the long-lasting emergence time of the mid-Turonian exposure (mT-ES; the interface between the Sarvak Formation and overlying Ilam Formation) caused the over-maturation of the related paleo-karst profile and the deterioration of the created reservoir quality. The results of this study reveal the effects of regional-scale geologic controls on the reservoir characteristics of the Sarvak Formation and may be also applicable to the reservoir characterization of other time-equivalent strata in the Arabian Plate.