Relationship between the distribution of reservoir characterestics of Ilam Formation with sedimentary microfacies and influential diagenetic processes in one of the fields of Abadan plain, southwest Iran

Authors

1 M. Sc., student. Dept., of Petroleum Geology, College of science, kharazmi University, Tehran, Iran

2 Assoc. Prof., Dept., of Geology, faculty of Earth Sciences, kharazmi University, Tehran, Iran

3 National Iranian Oil Company, Tehran, Iran

Abstract

A large part of the hydrocarbons of the Abadan plain region is located in the Bangestan Group, including the Ilam Formation. Ilam Formation of Santonian age is considered as one of the important oil reservoirs of Abadan plain, whose upper boundary is conformable with Gurpi Formation and its lower boundary with Laffan Formation, and it is mainly composed of limestone with regular layering and between thin layers of shale. The purpose of this study is to determine the role of microfacies and influential diagenetic processes in the reservoir part of Ilam Formation. Petrographic studies on the number of 142 thin section samples related to the drilling debris led to the identification of 7 microfacies related to the three belts of lagoon, Shoal and open marine facies. Among the most important diagenetic processes of Ilam Formation, we can mention cementation, micriteization, compaction, dolomitization, Hematization, glauconitization, pyritization, dissolution, and various types of porosity. In general, the results relating the distribution of reservoir characteristics of Ilam Formation with the study of sedimentary microfacies and influential diagenetic processes show that the best reservoir prone microfacies are wackestone to bioclast packstone and wackestone containing planktonic foraminifera. Also, among the effective diagenetic processes in the reservoir section, we can mention the dissolution and resulting porosity (vuggy porosity), porosity resulting from fracture, recrystallization (caused by microscopic porosity) and dolomitization.

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