Effects of reservoir temperature and water salinity on the swelling ratio performance of enhanced preformed particle gels

Preparation and Characterization of Preformed Polyelectrolyte and Polyampholyte Gel Particles for Plugging of High-Permeability Porous Media

Excessive reservoir water poses significant challenges in the oil and gas industry by diminishing hydrocarbon recovery efficiency and generating environmental and economic complications. Conventional polymer flooding techniques, although beneficial, often prove inadequate under conditions of elevated temperature and salinity, highlighting the need for more resilient materials. In this research, two types of acrylamide-based preformed particle gels (PPGs) were synthesized, as follows: polyelectrolyte and polyampholyte. These PPGs were engineered to improve plugging efficiency and endure extreme reservoir environments. The polyelectrolyte gels were synthesized using acrylamide (AAm) and sodium acrylate (SA), while the polyampholyte gels incorporated AAm, AMPS, and APTAC, with crosslinking achieved through MBAA. The swelling properties, modulated by temperature, salinity, and pH, were evaluated using the Ritger-Peppas and Yavari-Azizian models. The mechanical characteristics and surface morphology of the gels were analyzed using SEM and BET techniques. In sand pack experiments designed to mimic high-permeability reservoirs, the inclusion of 0.5 wt.% of fine PPGs substantially reduced water permeability, outperforming traditional hydrogels. Notably, the polyampholyte PPGs demonstrated superior resilience and efficacy in plugging. However, the experiments were limited by the low test temperature (25 °C) and brine salinity (26.6 g/L). Future investigations will aim to apply these PPGs in high-temperature, fractured carbonate reservoirs.

Introduction of a novel mathematical model for the prediction of the preformed particle gel's swelling in the presence of monovalent and divalent ions

Excess water production is one of the challenges that can cause several operational and economic problems. In this work, a comprehensive study of the PPG swelling in the presence of monovalent and divalent ions was conducted. Then, a comprehensive and practical mathematical modified fractal grow (MFG) model that can calculate the amount of PPG swelling in different salinities overtime was introduced. The output of the model was compared with the experimental data and showed a matching of about 80%. The viscosity of the PPGs at various shear rates was studied and matched with the cross-viscosity model. To assess the thermal stability of the particle gels. The TGA result represented the 10% of weight loss up to the reservoir temperature. In the following, core flooding tests with different injection scenarios were conducted. The oil recovery for the water and water/PPG/water scenarios were 39.5% and 71.5%, respectively. Eventually, the relative permeability curves were plotted using the Corey approach, and the effect of the PPG injection on the relative permeability curves was shown. The PPG injection increased oil production and reduced the excess water production by reducing water mobility.

Synthesis and physicochemical properties of dual-responsive acrylic acid/butyl acrylate cross-linked nanogel systems

HYPOTHESIS

A cross-linked amphiphilic nanogel containing a high mole% of hydrophilic pH-responsive moiety can provide enhanced functionality regarding stimuli-responsiveness, water-dispersibility, hydrophobic substance loading, and structural stability under harsh environmental conditions. These nanogels could be synthesized using a one-pot procedure for large-scale applications. Moreover, the interplay of various interaction forces in these colloidal systems is being investigated.

EXPERIMENTS

Model nanogels consisting of acrylic acid-butyl acrylate-ethylene glycoldimethacrylate were synthesized using an emulsion copolymerization via a seeded semi-batch process under an acidic condition. The structures were assessed by Fourier transform infrared spectroscopy and potentiometric-conductometric titrations. Zeta potential, field-emission scanning electron microscopy, and transmission electron microscopy were used to evaluate the dispersion stability, size distribution, and structural distribution, respectively. Their stimuli-responsive behavior was studied by combining static and dynamic light scattering and titration analyses.

FINDINGS

Monodisperse nanospheres of approximately 150 nm were successfully prepared by implementing a one-pot practical pathway. These nanogels displayed a dual thermo- and pH-responsive behavior, reflecting the high efficiency of physical cross-linking make it ideal for drug delivery and oil industry applications. Moreover, a novel symmetric pH-activated morphology transformation behavior was revealed. Accordingly, a compositional distribution was proposed and assessed by exploring the polymerization process.