Iranian Journal of Oil and Gas Science and Technology

Abstract Municipal and industrial wastewater pose significant environmental hazards if discharged without adequate treatment. Consequently, appropriate treatment processes must be implemented prior to discharge into receiving water bodies, land application, or reuse. Ensuring access to clean water remains a critical global priority. This study aims to contribute to the development of an efficient wastewater treatment plant. The application of process simulation and modeling plays a crucial role in the design, construction, and prediction of operational requirements for wastewater treatment facilities. Simulating a project before full-scale implementation can reduce capital and operational expenditures while enabling comprehensive technical evaluation from multiple perspectives. This study proposes the implementation of a combined nitrifying trickling filter/activated sludge (NTF/AS) process to upgrade a municipal wastewater treatment plant (MWWTP). The performance of the MWWTP was analyzed and compared for two configurations: a combined rotating biological contactor/activated sludge (RBC/AS) process and a combined NTF/AS process. Two treatment scenarios were developed and technically evaluated using operational data from the Ekbatan wastewater treatment plant in Tehran. In these simulations, GPS-X software was employed to investigate the effects of variations in influent characteristics within their minimum and maximum ranges on effluent quality. Considering the variability in influent conditions resulted in more accurate and reliable predictions. Under the fixed-flow scenario, the RBC/AS configuration achieved removal efficiencies of 90.51%, 89.70%, 95.14%, 14.80%, and 76.41% for chemical oxygen demand, total suspended solids, biochemical oxygen demand BOD5, total phosphorus, and ammonia, respectively.

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.

Abstract In this study, nanostructured homogeneous and functionally graded (FG) Ni-Co/SiC coatings were fabricated on aluminum substrates via electrodeposition using a square pulse current. The FG coating was produced by continuously varying the concentration of SiC particles (0–40 g/L) in the electrolyte, resulting in a graded particle distribution across the coating thickness. The microstructure and morphology of the coatings were characterized by scanning electron microscopy (SEM) and X-ray diffraction (XRD). Mechanical and electrochemical properties were evaluated through microhardness testing, T-peel adhesion testing, pin-on-disk wear testing, erosion testing, and potentiodynamic polarization and impedance spectroscopy. The results revealed that the SiC content in the FG coating gradually increased from 0 wt.% at the substrate interface to 6 wt.% at the surface. Compared to the homogeneous Ni-Co/SiC coatings, the FG coating demonstrated 40% higher adhesion strength and twice the wear resistance. Additionally, the FG coating exhibited improved corrosion resistance and overall mechanical performance, highlighting its potential for demanding industrial applications.

Abstract In this study, acid oil, which is a by-product of oil refinery waste was used for acid-catalyzed esterification to produce biodiesel. The reaction variables were methanol: acid oil molar ratio (1:1, 5:1, and 10:1), catalyst concentration (1%, 2%, and 3%), and reaction time (5, 30, and 60 min). Conversion yield, mass yield, free fatty acid (FFA) content, and physical properties (viscosity, density, refractive index, color attributes) of all the biodiesel samples were investigated. With increasing the methanol: acid oil molar ratio, catalyst concentration, and time, conversion yield and density increased, while free fatty acid content, viscosity and refractive index decreased, displaying an asymptotic trend toward equilibrium. At methanol: acid oil molar ratio of 10:1, catalyst concentration of 3%, and reaction time of 60 min, a near-maximum conversion yield of 95.3% was achieved. These conditions were considered optimum practical conditions, balancing biodiesel yield with operational and economic feasibility. Final yield of produced biodiesel at the practical optimum condition was 84.25%, which confirms that acid oil is a suitable feedstock for biodiesel production.

Abstract Understanding gas hydrate formation conditions is crucial for designing natural gas transmission pipelines. These compounds are studied from both thermodynamic and kinetic perspectives. Despite significant advances in the thermodynamic aspect of hydrates, kinetic investigations still demand further research. Accordingly, in order to determine the equilibrium conditions of natural gas hydrate formation, six independent experiments were conducted using natural gas samples from the NF unit of the Bandar Imam Petrochemical Complex. The tests were carried out in a fixed-volume reactor at temperatures of 278.3, 278.6, 284.8, 290.3, 279.3, and 280.6 K, and pressures of 37.8, 19.3, 28.4, 52.2, 32.7, and 16.2 bar, respectively. The experimental results showed that the mass transfer coefficients were 0.343, 0.236, 0.200, 0.314, 0.297, and 0.166 m/s, while the molecular diffusion coefficients were 2.5968 ×10^(-9), 6.2866×10^(-9), 3.3931×10^(-9), 1.49×10^(-9), 4.28×10^(-9), and 7.42×10^(-9) m²/s, respectively. These findings indicate that an increase in reactor temperature leads to a decrease in mass transfer coefficient and an increase in molecular diffusion coefficient, whereas an increase in pressure results in a rise in mass transfer coefficient and a decrease in molecular diffusion coefficient. These trends are consistent with established empirical correlations

Abstract Electrical Submersible Pumps (ESPs) are widely used to sustain oil production in mature and challenging reservoirs; however, their frequent failures often lead to production deferment, costly workovers, and reduced operational efficiency. This study presents a comparative evaluation of predictive maintenance (PM) and reactive maintenance for ESP systems using 50 case studies from diverse reservoirs and operating conditions. Reliability performance was assessed using mean time between failures (MTBF), mean time to failure (MTTF), failure rate, Kaplan–Meier survival analysis, and Weibull probability modeling. The economic impact of maintenance strategy was also evaluated through failure-related costs and deferred production losses.

The results indicate that PM consistently enhances ESP reliability by extending operational run life and reducing failure occurrence. Median survival increased from approximately 400 days before PM implementation to about 750 days after PM adoption, while Weibull analysis showed a shift from early random failures toward more predictable wear-out behavior. Economic evaluation further demonstrated that PM reduces workover frequency and production-loss exposure, yielding estimated cost savings of approximately 30–40% across the analyzed cases, even after accounting for monitoring and diagnostic investments.

This study contributes to the ESP reliability literature by providing an integrated comparison of predictive and reactive maintenance using survival analysis, Weibull modeling, and economic assessment within a unified framework across multiple field cases. The findings confirm that predictive maintenance is both technically effective and economically justified, and they highlight the value of combining advanced monitoring, reliability analytics, and data-driven maintenance planning to improve ESP performance and reduce life-cycle costs in oilfield operations.