Geological model of hartha formation in majnoon oilfield, Southern Iraq

Abstract

This study aims to construct a 2D geological model for Hartha Formation in Majnoon oil field based on well logs data from eight wells (Mj-1, Mj-3, Mj-10, Mj-11, Mj-15, Mj-16, Mj-20 and Mj-33), core and cutting samples. Petrophysical properties (effective porosity and water saturation) are derived from CPI interpretation of well logs while facies associations are interpreted through the study of microfacies analysis of thin sections for core and cutting samples. By using RockWorks16 software, 2D facies and petrophysical model are built to estimate the vertical and lateral variation of these properties. The 2D facies models display the dominance of outer ramp facies in the lower part of Hartha Formation, whereas mid-ramp, shoal, and inner ramp facies associations occupy the upper part. The shoal facies has a wide and continuous extent, which is characterized by high effective porosity and low water saturation. Therefore, it represents the most important reservoir of Hartha Formation in Majnoon oilfield. Other facies have less reservoir quality due to low porosity and high water saturation. Besides, their occurrence in deeper structural depths. Based on the output of the 2D effective porosity model, the porosity increased upward the succession of Hartha Formation as a result of the transition from outer ramp to shoal or inner ramp facies. Accordingly, the water saturation model shows low values at upper parts of the anticline structure of Majnoon oil field, which indicates high hydrocarbon saturation at the upper parts of Hartha Formation.