Carbonate Diagenesis in a Sequence Stratigraphic Framework; Case study from Miocene Dam Formation, Eastern Saudi Arabia

The Miocene Dam Formation in the Al-Lidam area of Eastern Saudi Arabia consists of a succession 

of mixed siliciclastic-carbonate sequences that were deposited during Miocene (Burdigalian) 

times. Stratigraphic equivalents of the Dam Formation occur as hydrocarbon reservoir intervals in 

the Arabian Plate. Reservoir quality of carbonate rocks is controlled by a combination of 

depositional setting and post-depositional diagenetic factors. 

In this study, fifteen lithofacies were identified as they were deposited on a low angle dipping 

carbonate ramp, under supratidal, beach, intertidal and shallow subtidal conditions. Carbonate 

diagenesis has been examined using: thin-section petrography, SEM, XRD and 

cathodoluminescence. These analytical tools have shown that the intertidal lithofacies are 

influenced by extensive meteoric dissolution and minor cementation. Marine diagenesis was 

restricted to beach grainstone and subtidal lithofacies, in the form of aragonite and high magnesium 

calcite cement. Shallow burial conditions were inferred by grain contacts represented by point, 

suture and concavo-convex contacts. Mimetic dolomitization for the whole succession was also 

observed. Three fourth - order, shallowing upward sequences were identified in the study area, and 

they are separated by two sequence boundaries. A clear relation between sequence surfaces and 

diagenetic processes was observed; meteoric diagenesis and dolomitization increases upwards in 

each sequence. Porosity and permeability measurements have shown that the highest values are 

associated with the HST of each sequence, followed by the TST and the LST. The results of this 

study can help in understanding of diagenetic processes, and consequently in developing better 

and more accurate predictions of the porosity and permeability distribution within hydrocarbon 

reservoirs.