Petrophysical and IPSOM Electrofacies Characterization of the Hartha Formation in Xn Oil Field, Central Iraq

Abstract

Carbonate reservoirs of the Hartha Formation in central Iraq are characterized by significant heterogeneity, which poses challenges for accurate petrophysical evaluation. Traditional interpretation approaches often fail to adequately capture vertical and lateral variability in carbonate systems. The study presents a combination of conventional log interpretation and Interactive Petrophysics Self-organising Maps-based electrofacies classification to improve reservoir characterization and identify productive intervals. Wireline logs from wells EB-4, EB-52, and EBSZ-1 were subjected to quality control through depth matching, core-log calibration, and neutron-density crossplots. Petrophysical parameters were estimated using a carbonate workflow calibrated to core and SCAL data, with water saturation calculated using the Archie equation. Interactive Petrophysics Self-organising Maps electrofacies classification enabled effective reservoir zonation and differentiation between high and low quality intervals. The Hartha Formation shows strong vertical heterogeneity, with Ha-2 representing a low-quality water- bearing unit, while Ha3, particularly Ha3-c, forms the main reservoir unit with better porosity and lower water saturation. Net pay varies across the field, with EB-4 showing the highest values.