Iranian Journal of Oil and Gas Science and Technology

Abstract Excessive water production represents a significant economic and operational burden in the petroleum industry, necessitating sophisticated control measures to mitigate costs associated with water oil separation, scale formation, and equipment corrosion. This investigation characterizes the performance of preformed particle gels (PPG) as a robust chemical water shutoff treatment through comprehensive rheological and swelling kinetics studies. Experimental results demonstrate that PPG viscosity is highly sensitive to concentration; specifically, a twofold increase in concentration (from 2500 to 5500 ppm) results in a tenfold increase in viscosity. The rheological behavior was successfully modeled using the Cross equation, facilitating the derivation of a unified mathematical model that predicts viscosity as a function of concentration and shear rate. Crucially, at a calculated shear rate of 0.14 s⁻¹ based on the assumption that injection velocity is 100 times the reservoir oil movement PPG maintains sufficient viscosity for effective flow diversion. Furthermore, the study explores the influence of agitation and salinity on swelling performance. Stirring was found to accelerate swelling kinetics, shifting the mechanism from Fickian diffusion at zero RPM to a transport dominated mechanism (n ≈ 0.85) due to the simultaneous activation of multiple diffusion pathways. Salinity experiments utilizing KCl and MgCl₂ reveal that divalent cations (Mg²⁺) are significantly more effective at inhibiting swelling than monovalent cations (K⁺) due to charge neutralization of carboxylate groups. Morphological analysis via Scanning Electron Microscopy (SEM) suggests that ions with larger radii obstruct the gel pores, a phenomenon that can be mitigated during synthesis through the introduction of nonionic hydrophilic monomers and pore forming agents such as ethanol or ammonium bicarbonate. Finally, the research identifies diffusion limited aggregation (DLA) as the dominant growth mechanism. Modified DLA models were developed to predict salinity dependent swelling, providing a rigorous framework for optimizing PPG treatments in heterogeneous reservoirs

Abstract In the event of a main source outage, in the gas distribution network, the high-pressure gas stored in pipes, known as linepack, can be used as a short-term reserve to supply gas to consumers. Moreover, during the redesign of the distribution network, it is possible to convert a tree-structured network into a looped network by connecting two or more nodes. In reliability analysis approaches for networks under real conditions, due to the need to examine multiple and complex states and consequences, the computational burden in proposed network structures is very high, and therefore, simulation techniques are often used. In this paper, a novel approach is proposed to evaluate gas supply reliability in both tree-structured and loop-connected networks, considering the effect of linepack. Hydraulic analysis of the network was performed using the GP-NET software, and the overall reliability of gas supply in the pipeline network was determined, taking into account the random occurrence of failures in critical components that lead to network disruptions. The proposed approach was applied to the gas distribution system of a city in Kurdistan Province, Iran, and, through sensitivity analysis, the effect of changes in model parameters on the overall network supply reliability was also analyzed. The results indicate that creating loops and considering the effect of linepack lead to increased supply reliability and enhanced stability in providing services to consumers.

Abstract This study investigated the corrosion inhibition robustness of an eco-friendly garlic corrosion inhibitor (GCI) for X70 carbon steel in simulated sour oilfield water saturated with hydrogen sulfide (H₂S) environment. The functional groups o GCI were identified using a Fourier-transform infrared spectroscopy (FTIR) technique, confirming the presence of alcohols, phenols, amines, carbonyls, and sulfur-containing compounds, which contribute to adsorption and protective layer formation on the steel surface. The inhibition performance was assessed using the WLM technique, potentiodynamic polarization, electrochemical impedance spectroscopy (EIS), scanning electron microscopy (SEM), and energy-dispersive X-ray spectroscopy (EDX). At the optimal GCI concentration of 200 mg L⁻¹, the inhibition efficiencies determined by weight-loss, polarization, and EIS measurements were 73.9%, 93.9%, and 96.3%, respectively. The differences among these values are attributed to the distinct principles of the techniques: WLM analysis represents cumulative material loss during immersion, whereas polarization and EIS characterize the electrochemical response of the steel–solution interface. Increasing the inhibitor concentration to 500 mg L⁻¹ produced only marginal improvements in the electrochemical efficiencies, reaching 94.0% by polarization and 96.4% by EIS. More importantly, the potentiodynamic polarization and EIS analyses revealed a mixed-type inhibition mechanism and the formation of a protective film with high polarization resistance. Surface analyses by the SEM and EDX techniques demonstrated the development of a relatively homogeneous organic layer enriched with nitrogen and sulfur, effectively preventing localized corrosion. On the whole, the acquired outcomes demonstrated that GCI is a promising green corrosion inhibitor for corrosion retardation of metals in sour environments, offering an eco-friendly alternative to conventional chemical inhibitors.

Abstract Most of the productive crude oil and gas basins in the world which includes the Niger Delta is usually characterized by complex geological settings and diverse crude oil signatures. This study evaluates the use of molecular biomarkers particularly hopanes for the geochemical characterization and differentiation of crude oils from four major oil fields: Imo, Nembe, Soku, Bonga, Kwale and Owaza. Crude oil samples were collected directly from production lines and subjected to chromatographic separation and analysis using Gas Chromatography Mass Spectrometry (GC-MS). Diagnostic ratios such as Ts/(Ts+Tm), C29/C30 hopane, oleanane/C30 hopane, C31S/C31R and sterane/hopane (0.16 to 0.87) were computed to assess depositional environment, organic precursor input, thermal maturity, biodegradation status, and inferred age of source rocks. The results revealed that the Imo, Nembe, and Soku oil fields exhibit high oleanane indices (0.68 – 0.84), indicating deltaic depositional environments dominated by terrestrial organic matter and suggesting a Tertiary age for their source rocks. In contrast, the Bonga crude lacked oleanane but contained gammacerane (G/C30 = 0.12), pointing to a stratified marine origin with algal input. Thermal maturity indicators placed all samples within the low to moderate maturity window, with Ts/(Ts+Tm) ratios of 0.53 (Imo), 0.41 (Nembe), 0.42 (Soku), 0.52 (Bonga); 0.51(Kwale) and 0.51 (Owaza). These values are consistent with oils that have not yet reached peak thermal maturity, while biodegradation assessments using norhopane levels revealed different microbial alteration, with Imo and Soku oils being the least degraded. Multivariate statistical analysis was used to identify the genetic relationships among the crude oil samples. The study demonstrates the effectiveness of molecular biomarker analysis in differentiating crude oil sources within a petroleum province. These facts are of significant relevance to petroleum system modeling, reservoir correlation, and optimization of exploration strategy in hydrocarbon - rich basins like the Niger Delta