Improved Calculation of Petrophysical Parameters Utilizing Nuclear Magnetic Resonance (NMR) and Conventional Well Logs in One of the Southwest Fields of Iran

Yamini Soltan, Ahmad; Akbari, Majid; Moradi, Siyamak; Bagheri, Hassan; Hamed Mahvelati, Elahe

doi:10.22050/ijogst.2025.403259.1685

Improved Calculation of Petrophysical Parameters Utilizing Nuclear Magnetic Resonance (NMR) and Conventional Well Logs in One of the Southwest Fields of Iran

Document Type : Research Paper

Authors

Ahmad Yamini Soltan ¹

Majid Akbari ²

Siyamak Moradi ²

Hassan Bagheri ³

Elahe Hamed Mahvelati ⁴

¹ MS Student, Department of Petroleum Engineering, Petroleum University of Technology, Abadan, Iran

² Associate Professor, Department of Petroleum Engineering, Petroleum University of Technology, Abadan, Iran

³ Senior Petrophysicist, National Iranian Drilling Company, Ahvaz, Iran

⁴ Associate Professor, Department of Basic Sciences, Petroleum University of Technology, Abadan, Iran

https://doi.org/10.22050/ijogst.2025.403259.1685

Abstract

This study presents an advanced petrophysical evaluation of the Sarvak Formation in one of the major supergiant oil fields in Southwest Iran, achieved by integrating Nuclear Magnetic Resonance (NMR) log data with conventional well logs. NMR measurements from Well-A were analysed to extract critical reservoir properties—including total and effective porosity, and volumes of bound and free water—which significantly enhanced the accuracy of the petrophysical model. A multi-resolution graph-based clustering (MRGC) algorithm was developed to estimate NMR-derived parameters from conventional logs for the adjacent Well-B, where NMR data were unavailable. The MRGC model utilised gamma-ray, acoustic, density, neutron, and photoelectric logs to predict total and effective porosity, clay-bound water, irreducible water saturation, and other NMR-related parameters. The model was calibrated using data from Well-A and subsequently applied to Well-B, enabling NMR-informed petrophysical characterisation in the absence of direct measurements. The optimised petrophysical model demonstrated consistent reservoir characteristics across both wells. Average total porosity was 10.7% in Well-A and 12.2% in Well-B; effective porosity averaged 10.2% and 11.8%, respectively; clay volume was approximately 3.2% in Well-A and 3.6% in Well-B; and water saturation was 85% and 84%, respectively. Based on cutoff thresholds of 5% porosity, 15% clay volume, and 50% water saturation, net pay intervals were delineated, yielding approximately 31 m of productive zone out of 411 m in Well-A, and 30 m out of 380 m in Well-B. The NMR-augmented analysis provided more precise differentiation of hydrocarbon-bearing zones and proved more cost-effective than traditional log-based methods. This refined petrophysical workflow significantly improves reservoir characterisation, enhances the accuracy of hydrocarbon volume estimation, and supports more informed field development planning.

Highlights

· Petrophysical evaluation of Sarvak reservoirs was conducted with conventional reservoir diagrams and NMR.

· Petrophysical parameters such as free fluid volume and total porosity were investigated.

· The MRGC clustering method was used to estimate the NMR output.

· NMR diagram output was interpreted using conventional reservoir diagrams (RHOB, NPHI).

· A cross diagram was drawn for two parameters: irreducible water saturation (SWir) log and reservoir porosity.

Keywords

Petrophysical evaluation

well log

NMR log

Sarvak Formation

MRGC

Subjects

Petroleum Engineering

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