Petrographic and diagenetic studies of thick transition zone of a middle-east carbonate reservoir

This work aims to characterize petrographically some of the transition zone plug samples in order to understand the impact of diagenetic processes on the transition zone rock quality. Three carbonate samples were collected from the same well which cuts through a thick transition zone of a heterogeneous cyclic carbonate reservoir of Abu Dhabi with respect to depth. The petrographic analysis was conducted by the thin sections study and scanning electron microscope (SEM) imaging in order to interpret the main depositional facies, diagenetic features and how the poro-perm characteristics were affected by them. SEM analysis is utilized in order to observe and recognize in detail the diagenetic relationships between different mineral phases or cement types and to help in identifying the pore geometry. Diagenesis in the transition zone is very extensive especially affected by micritization and cementation. The diagenetic features are increasing with depth as the zone is having higher water saturations. The importance of this analysis is to better understand the rock fabric heterogeneity and capillary pressure behavior as a function of depth of thick carbonate transition zones.