Lithological types and characteristics of carbonate open platform in pre-Caspian basin

The Carboniferous KT-II carbonate formation in N Oilfield at the eastern edge of pre-Caspian Basin has been developed in open marine carbonate platform. The present work aims to make an evaluation on the physical properties of limestone reservoirs, in order to identify the causes for strong heterogeneity. In the study area, limestone rocks are dominant and diverse that can be divided into fifteen types based on the grain contents: algal limestone, foraminifera limestone, fusulinid limestone, bioclast limestone, algal skeletal limestone, and oolitic limestone, etc. The oolitic limestone, algal limestone and algal skeleton limestone have the best physical properties and constitute the most favourable reservoirs in KT-II formation.