Comparison of Reservoir properties and pore network characterization of limestone and dolomite units: A case study from Kangan and Dalan gas reservoirs at South Pars field

South Pars gas field which is the host of largest gas reserves in the world is located on Iran- Qatar border line in Persian Gulf waters. Main reservoir rocks of this field are the Permo-Triassic Upper Dalan member and Kangan formation. Lithology of this succession is predominantly carbonate and composed of limestone and dolomite. Dolomitization is one of the most important diagenetic features. In addition to, dolomitization has mainly affected this succession and changed reservoir parameters and pore network characterizations. In this study, some reservoir properties and pore network parameters; such as, porosity, permeability, pore size and pore throat size of limestone and dolomite units have been evaluated and compared. The results show that Dolomite units, despite of lower porosity and smaller pores have higher permeability and subsequently better reservoir quality than limestone units. This is due to larger pore throats in dolomites and then the pores are connected together with larger pore throats.