Diagenetic controls on reservoir quality in the Asmari carbonate reservoir in Gachsaran Field, SW Iran

determing the reservoir quality based on depositional facies and diagenetic texture studies , deduced from macroscopic and microscopic descriptions of cores and thin sections , and qualitative interpretaion of petrophysical data . The aim of this study is to define the diagenetic evolugion of the asmari formation. a core - to - log matching study has been carreid out. development of reservoir quality appears to be entirely controlled by depositional facies and more effectively by diagenesis. the core description and thin section study indicate major sedimentary environments mainly intertidal , lagoonal , shoal and open marine consisting several different microfacies. the comparison study of porosities between the depositional facies showed thay the lagoon facies have had the highest prosity ranges 4-25% . the asmari porosity ranges in whole interval in this field from 0.1 to 25.0% , whereas permeability is between 0.01 and 62.0 md. microscopic investigations reveal the observation of diagenetic factors such as compaction, dolomitization , anhydrite and calcite cementation and dissolution parameter and thereby their effects on porosity. anhydrite cementation significantly reduced both the secondary as well as the primary porosity. however this effect was improved by lated dissolution and leaching processes. the effect of dolomitization causes the enhancement in the original porosity of depositional textures and protracted delomitization therby created intercrystalline porosity.

Keywords:

diagenetis process , dolomitization , porosity , asmari formation , iran