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

<p>The Miocene Dam Formation in the Al-Lidam area of Eastern Saudi Arabia consists of a succession&#160;</p><p>of mixed siliciclastic-carbonate sequences that were deposited during Miocene (Burdigalian)&#160;</p><p>times. Stratigraphic equivalents of the Dam Formation occur as hydrocarbon reservoir intervals in&#160;</p><p>the Arabian Plate. Reservoir quality of carbonate rocks is controlled by a combination of&#160;</p><p>depositional setting and post-depositional diagenetic factors.&#160;</p><p>In this study, fifteen lithofacies were identified as they were deposited on a low angle dipping&#160;</p><p>carbonate ramp, under supratidal, beach, intertidal and shallow subtidal conditions. Carbonate&#160;</p><p>diagenesis has been examined using: thin-section petrography, SEM, XRD and&#160;</p><p>cathodoluminescence. These analytical tools have shown that the intertidal lithofacies are&#160;</p><p>influenced by extensive meteoric dissolution and minor cementation. Marine diagenesis was&#160;</p><p>restricted to beach grainstone and subtidal lithofacies, in the form of aragonite and high magnesium&#160;</p><p>calcite cement. Shallow burial conditions were inferred by grain contacts represented by point,&#160;</p><p>suture and concavo-convex contacts. Mimetic dolomitization for the whole succession was also&#160;</p><p>observed. Three fourth - order, shallowing upward sequences were identified in the study area, and&#160;</p><p>they are separated by two sequence boundaries. A clear relation between sequence surfaces and&#160;</p><p>diagenetic processes was observed; meteoric diagenesis and dolomitization increases upwards in&#160;</p><p>each sequence. Porosity and permeability measurements have shown that the highest values are&#160;</p><p>associated with the HST of each sequence, followed by the TST and the LST. The results of this&#160;</p><p>study can help in understanding of diagenetic processes, and consequently in developing better&#160;</p><p>and more accurate predictions of the porosity and permeability distribution within hydrocarbon&#160;</p><p>reservoirs.</p><p>&#160;</p>