Investigation of Microfacies, Sedimentary Environment and Diagenesis Processes of Dariyan Reservoir in Salman Oil Field

Dariyan Formation (Aptian-Albian) is one of the main reservoir units in the South West of Iran which is equivalent to Shuaiba Fm،. Since the first step in the evaluation study of reservoir rock is studying the microfacies، depositional environments and diagenesis processes، in this research we have discussed these parameters in Dariyan reservoir in Salman oil field A، B، C، D and E wells. On the basis of petrographic studies classification of carbonate rocks by Dunham’s method and nomination of microfacies by Flugel’s classification was done and 7 basic microfacies have been identified: Mudstone، Mudstone to fossiliferous wackestone، Orbitolinid wackestone to packstone، Bioclast packstone to grainstone with restricted microfauna، Echinoderm wackestone to packstone، Planktonic wackestone to packstone، Mudstone to Planktonic/echinoderm wackestone، that belong to open marine sedimentary environment، shoal and lagoon. The study of vertical and lateral facies changes and comparing them with modern and ancient sedimentary environments show that Dariyan Formation in this area is deposited in a leeward mud dominated carbonate ramp. Due to numerous diagenetic processes observed in the formation، of their direct impact on the quality of the reservoir to the conclusion that micritization، cementation، compaction (mechanical)، neomorphism، and pyritification to block the pores and pore through in the reservoir porosity and permeability decrease while، compaction (chemical)، dolomitization، and fracture caused voids and communication between them. Finally، the porosity and permeability of the reservoir increased and led to higher quality.