Petrography of carbonate rocks in the Asmari Formation, Zagros Basin, Dezful Embayment and Izeh Zone, SW Iran

摘要

This research aims at studying the Oligo-Miocene Asmari Formation, which is known as one of the best oil reservoirs in Iran. For better understanding and comparing the trend of lithological changes and depositional environment of this formation in a wider area, 5 sections were selected which consist of Lali 20, Karun 3, Masjed Soleyman 186 subsurface, and Asmari anticline surface sections in Dezful Embayment and Gurpi anticline surface section in Izeh Zone. Using polarizing and cathodoluminescence microscopic studies, diagenetic processes affecting the Asmari and their paragenetic sequence in the study areas were interpreted. Index diagenetic processes that have affected the Asmari Formation carbonate rocks include micritization, bioturbation, boring, cementation (such as marine, meteoric, and burial cementation), dissolution (meteoric and burial dissolution), dolomitization (in different phases), pyritization, hematitization, silicification, mechanical and chemical compaction, and fracturing. In general, diagenetic processes such as dissolution and fracturing have increased the reservoir quality, while cementation and compaction have decreased the reservoir potential of this formation. Cathodoluminescence studies indicate three generations of cement of marine, meteoric, and burial based on the color contrast.