Dolomitization of Fahlian Fm. In Dashtak No.1 brehole and Kuhe Dal sections; implication for role of dolomitization on rescrvoir quality

Fahliyan Formation (Neocomian in age) is a hydrocarbone reservoir in SW Iran (Dezful Embayment). In this research, this Formation were investigated in an outcrop (kuh-e-Dal) and a subsurface section of Dashtak#1 borehole in the Dezful Embayment. Vertical Microfacies changes suggest that Fahliyan Formation was deposited as a transgressive and deepening upward sequence. Based on microfacies analysis, depositional environment of the Fahliyan Formation were interpreted as a shallow ramp with a gentle slope. In this research two types of dolomitization have been recognized in the formation based on petrographic examination of thin sections, that are attributed to Dorag and burial (Saddle dolomites) dolomitization models. The petrographic evidences and the geophysical log interpretations reveal that the saddle dolomites considerably increased intercrystalline porosity of the Fahliyan Formation in the study area