https://ijogst.put.ac.ir/ Iranian Journal of Oil and Gas Science and Technology en daily 1 Wed, 01 Oct 2025 00:00:00 +0330 Wed, 01 Oct 2025 00:00:00 +0330 https://ijogst.put.ac.ir/article_247093.html 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 https://ijogst.put.ac.ir/article_250963.html Drilling fluids require effective shale inhibition while maintaining rheology and fluid-loss control, especially in polymer-based water-based drilling fluids (WBMs). Alum (KAl(SO₄)₂·12H₂O) is an eco-oriented chemical widely used in water treatment, yet its concentration-dependent performance in active WBMs remains poorly quantified. This study systematically evaluated alum (0–10 lb/bbl) using a component-based approach and a field-representative polymer WBM, focusing on pH evolution, rheology, filtration, and volumetric swelling in both bentonite and grey marl (calcareous shale). Alum caused strong acidification in all systems, driving the initial pH of the field WBM down from 10.1 to 4.6 at a concentration of 6 lb/bbl. In the field-representative mud, alum progressively improved rheological profiles up to a critical concentration of 6 lb/bbl, where plastic viscosity and yield point reached their peak performance zone due to temporary polymer–Al³⁺ interactions. Beyond these 6 lb/bbl thresholds, severe pH reduction below 4.0 promoted acid-catalyzed polymer degradation, causing rheological collapse and sharply increasing API fluid loss from 1.1 ml to 2.4 ml. Swelling tests showed a monotonic reduction in sodium bentonite swelling, stabilizing at 22.77% expansion at 6 lb/bbl. Conversely, grey marl exhibited a non-linear response; swelling was initially minimized to 17.56% at 7 lb/bbl but experienced a distinct swelling reversal at higher dosages, rising back to 23.78% at 10 lb/bbl due to acid–carbonate reactions that undermined mechanical matrix integrity. These quantitative results define a narrow operational window for alum in polymer-rich WBMs (≤ 6 lb/bbl) and demonstrate that carbonate-bearing shales suffer severe chemo-mechanical instability at elevated dosages, bounding alum's practical applicability in active drilling environments. https://ijogst.put.ac.ir/article_252522.html Accurate detection of marine oil spills in Synthetic Aperture Radar (SAR) imagery remains a major challenge. Mineral oil and naturally occurring biogenic slicks often produce nearly identical signatures in SAR imagery, despite their fundamentally different environmental implications. This review critically evaluates the physical processes governing SAR-based oil spill detection and asks whether secondary dielectric and polarimetric effects can overcome the inherent limitations of single-channel intensity data. The analysis reveals two key findings. First, while wave damping ensures high contrast under optimal wind conditions (3–10 m/s), secondary dielectric effects only emerge in thick emulsions (>0.4 mm). These conditions are rarely encountered in operational scenarios. Second, instrument noise floors (NESZ) severely compromise polarimetric retrievals, limiting their reliability. Together, these findings provide a practical framework for interpreting SAR imagery. They also guide the integration of AI-driven classification with multi-sensor fusion (X-, C-, and L-band) to reduce false alarm rates in operational monitoring systems. https://ijogst.put.ac.ir/article_252524.html 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.