Analysis of the Pirallahi deposit for lithofacies of the lower productive series

This paper investigates the genesis of the Productive Series sediments within the uplift zone of Pirallahi Island, focusing on the distribution conditions and lithofacies characteristics of different origins. For this purpose, the lithofacies characteristics and conditions of the Lower Pliocene Productive Series sediments in the Pirallahi Island structure have been analyzed, particularly based on geophysical well logging (GWL) data. Using a significant number of well logging diagrams, the distribution of sand and shale lithologies for the productive horizons were determined, systematically classified, and correlation schemes were established. The research includes a detailed analysis of the sedimentary environments to interpret depositional patterns, integrating GWL data with lithological core analyses where available. The facies analysis on Pirallahi Island has included nearly all the boreholes drilled in the field, with the distribution of facies considered from top to bottom across the study area. In addition, the study includes a quantitative assessment of porosity, permeability and clay content to comprehensively evaluate the reservoir potential. Well log analysis allowed interpretation of the effective porosity of the rocks and their shale content, providing a clearer understanding of reservoir heterogeneity. The main objective of the study reported in this paper is to demonstrate lithofacies variability in both horizontal and vertical directions using cross section and lithofacies modeling techniques. The developed facies model is thus demonstrated on a number of surfaces, providing a predictive framework for identifying favorable reservoir zones. The resulting regularities are discussed, highlighting the implications of facies variability for hydrocarbon exploration and production strategies. Keywords: oil; gas; Pirallahi field; lithofacies feature; facies composition; facies model; correlation.