Degradation of confining pressure effects on elastic wave velocities of rocks, A case study: Sarvak formation

Authors

Geology Department, Ferdowsi University of Mashhad

Abstract

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 that 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 types of cements reduced reservior quality and dissolution, dolomitization and fractures increased reservior quality.Observed porosity in the Kangan Formation is: 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.
 

Keywords

References

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