Diagenetic Effect on Reservoir Quality in the Kangan Formation, Lavan Field, Persian Gulf


1 Department of Geology, Shahid Beheshti University, Tehran

2 Professor, School of Earth Sciences, Shahid Beheshti University, Tehran


The Kangan Formation with Triassic age is the largest gas reservoirs in the Middle East and the world. This formation in Lavan field, consists of 200 meters of carbonate sequences (limestone, dolomitic limestone and dolomite), associated with anhydrite layers, with 164 meters of core samples. Based on microscopic and macroscopic studies, 11 facies in 4 facies belts, tidal flat, lagoon, shoal and open marine have been identified. Based on identified microfacies, the sedimentry environment of this formation can be introduced as a homoclinal carbonate ramp system. Diagenetic processes in the Kangan Formation has  the most influence on reservoir quality are: mechanical and chemical compaction, dissolution, dolomitization, isopachous fiberous cement, equant cement, drusy cement, blocky cement ,vein cement, poikilotopic cement, anhydrite cement and fractures. Compaction processes and different type of cements reduced reservior quality and dissolution, dolomitization and fractures increased reservior quality.Observed porosity in the Kangan Formation are: intergranular , intragranular, moldic, fenestral, intercrystaline, fracture, vuggy and channel porosities. The Kangan Formation in Lavan field is divided into two zones, K1 and K2. K2 is divided into three sub-zones, K2a, K2b and K2c and  K1 is divided into four sub-zones, K1a, K1b, K1c and K1d.  The K1d sub-zone due to granular dolomitic facies (especially ooid grainstone ) and a significant amount of moldic , intergranular, intercrystaline and  fracture porosities has the highest  reservoir quality in this sequence.


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