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 Gas lift is a principal technique used for artificial lifting and Enhanced Oil Recovery (EOR) method, facilitates oil flow in mature fields those in the latter half of their productive life by injecting high-pressure gas into the wellbore to reduce column density. However, the thermodynamics of gas injection in wells requiring high differential pressures introduce severe flow assurance challenges. The intense Joule-Thomson cooling effect across injection chokes is the primary driver of gas hydrate formation. In the studied field (Aghajari), the current hardware-based mitigation strategy employs Thermal Chokes, which utilize the enthalpy of live crude oil to heat the injection gas. Despite this, operational evidence indicates that during cold seasons and for wells with high pressure drops, this system proves inefficient, leading to freezing in injection lines and flow interruption. In the absence of inhibitor injection systems, operators are compelled to resort to reactive measures such as flaring injection gas to induce pressure shocks and clear blockages. This vicious cycle not only results in capital loss but also leads to production deferment and excessive workload for human resources. This research aims to propose a proactive process-based solution by synergizing data mining and computational intelligence. Through the analysis of 5,960 operational records from 101 wells (extracted from the WIMS system), an Artificial Neural Network (ANN) model was developed to serve as a virtual sensor, predicting gas thermodynamic behavior and post-choke temperature with 98.5% accuracy. The core novelty of this study lies in the simulation and validation of a dual-stage pressure reduction strategy. Results demonstrate that splitting the pressure drop profile reduces cooling intensity by up to 60%, maintaining the fluid outside the hydrate stability zone throughout the expansion path. This approach enhances safety and production stability while eliminating the need for costly physical interventions.