Sedimentary environment, diagenesis, and evolution of reservoir characteristics of the Sarvak Formation in the Sarvestan Oil Field, SE Shiraz

The upper part of the Sarvak formation (Cenomanian–early Turonian) is the main reservoir rock in the Sarvestan oil field. The Sarvak formation showed a shallowing-upward sequence in this field. Detailed petrography on thin sections in two wells (SV#5 and SV#6) suggested that the Sarvak formation is composed of 12 microfacies that can be classified in four facies belts، including inner ramp، mid ramp، outer ramp، and basin. These facies indicated a homoclinal ramp-type carbonate platform at the time of deposition. According to petrographic evidence، the facies were influenced by marine، meteoric (eogenetic and telogenetic)، and burial diagenesis. Meteoric dissolution and fracturing were the most important factors enhancing reservoir quality، while cementation and compaction reduced porosity and permeability. The evaluation of the reservoir development showed that meteoric digenesis during Cenomanian–Turonian and mid-Turonian times has had a significant influence on shoals، patch reefs، and their taluses، which created vuggy and moldic porosity and improved their reservoir quality، especially during the mid-Turonian.