Controls on porosity heterogeneity in carbonate lithofacies of the Miocene Dam formation outcrop, eastern Saudi Arabia

Conventional subsurface models carry a lot of limitations concerning its ability to detect the small scale resolution of the real geologic setting in the inter-well spacing. The uncertainty of these coarse models can be supported by information from fine models in order to get more realistic three dimensional insight of subsurface geologic characteristics. These models were then used as basis for further investigation of reservoir properties and the controls behind its heterogeneity. Such fine models can be obtained using outcrop studies. In this study, a Miocene outcrop of Dam Formation was used to investigate the influencing factors that control porosity variation of carbonate lithofacies. This purpose is attained through high-resolution porosity model for selected lithofacies out of the overall succession. The detailed sedimentology revealed three lithofacies for this purpose, those are, quartz fossiliferous packstone, burrowed wackestone, and stromatolite grainstone. Further laboratory investigations were applied on these lithofacies using detailed petrography and SEM images to explore the controls on porosity variations. The study showed that different depositional and post-depositional factors can influence porosity even in small scale within same lithofacies. This study indicated the importance of small-scale outcrop models as prediction tool to reduce the uncertainty associated with subsurface models.