Polyacrylamide-based Polymer Research Articles

Molecular Dynamics Simulation of Polyacrylamide Adsorption on Calcite.

In poorly consolidated carbonate rock reservoirs, solids production risk, which can lead to increased environmental waste, can be mitigated by injecting formation-strengthening chemicals. Classical atomistic molecular dynamics (MD) simulation is employed to model the interaction of polyacrylamide-based polymer additives with a calcite structure, which is the main component of carbonate formations. Amongst the possible calcite crystal planes employed as surrogates of reservoir rocks, the (1 0 4) plane is shown to be the most suitable surrogate for assessing the interactions with chemicals due to its stability and more realistic representation of carbonate structure. The molecular conformation and binding energies of pure polyacrylamide (PAM), hydrolysed polyacrylamide in neutral form (HPAM), hydrolysed polyacrylamide with 33% charge density (HPAM 33%) and sulfonated polyacrylamide with 33% charge density (SPAM 33%) are assessed to determine the adsorption characteristics onto calcite surfaces. An adsorption-free energy analysis, using an enhanced umbrella sampling method, is applied to evaluate the chemical adsorption performance. The interaction energy analysis shows that the polyacrylamide-based polymers display favourable interactions with the calcite structure. This is attributed to the electrostatic attraction between the amide and carboxyl functional groups with the calcite. Simulations confirm that HPAM33% has a lower free energy than other polymers, presumably due to the presence of the acrylate monomer in ionised form. The superior chemical adsorption performance of HPAM33% agrees with Atomic Force Microscopy experiments reported herein.

Development of Superabsorbent Polymer (SAP) Seed Coating Technology to Enhance Germination and Stand Establishment in Red Clover Cover Crop

Drought conditions after sowing threaten the seedling establishment of all seeds, including cover crops. Cover crops are commonly broadcast and, thus, are often susceptible to drought stress after sowing. Our hypothesis was that seed coating with superabsorbent polymers (SAPs) would enhance germination in the lab and stand establishment in the field by increasing water availability to single seeds. Red clover (Trifolium pratense L.) seeds were coated with the following selected SAP formulations at 2% of their seed weight: cross-linked potassium polyacrylate (PAL), cross-linked polyacrylamide-based polymer (PAM), PAM with graphite (PAM+G), and Starch-g-2-Propenoic acid (potassium salt) (STR). The water absorbency of each SAP formulation was >200 g water/g of polymer; STR had the greatest absorbency, at 352 g water/g of polymer. A seed coating method was developed, resulting in the uniform application of SAP from seed to seed. All SAP coating treatments increased germination compared to the 0% SAP coating in controlled environment studies in the lab. Three field trials were conducted for each seed coating treatment, providing a range of climatic soil conditions. Within each field trial, the STR with the greatest water absorbency had a higher stand for treatments sown by broadcasting followed by raking to incorporate seeds. The first two trials were conducted under more stressful conditions. PAM+G performed best in the first two trials by broadcasting seeds with no raking. Collectively, the selected SAP seed coating improved field stands compared to the non-treated controls.

Sensitivity analysis of parameters affecting nano-polymer solution for water shutoff in carbonate rocks

Excessive water production impacts the economics of petroleum reservoir and often leads to their premature shut-in. Production of high saline water represents a major corrosion for casing, tubing, flow lines, and production facilities. Polymer solution has been used to control water production and to plug in high-temperature reservoirs. Most of these polymer solutions consist of polyacrylamide-based polymer and an organic or inorganic cross linker. Polyethylene mine has been used as an organic cross-linked for polyacrylamide. Literature reported that polyethylene mine can also form ringing gels with polyacrylamide copolymers in addition to polyacrylamide concentration. In this study, nano-chemical solutions has been prepared and studied in detail for their efficacy at reservoir condition. The compositions of the nano-chemicals mainly consisted of polyacrylamide mixed with nano particles, cement, coated-clay and polyethylene mine as cross-linker. The aim of using nano particles and coated-clay was to control gel performance and strength under the reservoir condition. Moreover, the effect of nano-chemical composition at higher temperature have been studied extensively on the gelation properties, elastic modulus, viscosity, and swelling ratio. Results showed that the elastic modulus and viscosity improve significantly with the increasing nano particle concentration. Coated-clay can control the gelation time as clay swallows and absorbs more formation water in the target zone, when its thin coated film breaks down, lesser water production can be predicted. Cited as: Soka, S., Sidiq, H. Sensitivity analysis of parameters affecting nano-polymer solution for water shutoff in carbonate rocks. Advances in Geo-Energy Research, 2022, 6(3): 230-240. https://doi.org/10.46690/ager.2022.03.06

Image recognition model based on deep learning for remaining oil recognition from visualization experiment

Steam flooding and chemical flooding have been widely proven to be the most promising methods to facilitate the development of heavy oil reservoirs. However, the remaining oil reserves after steam flooding or chemical flooding still account for the vast majority, and it is challenging and necessary to study the occurrence state and formation mechanism of the remaining oil. In this paper, an anionic Gemini surfactant and an amphoteric surfactant are synthesized and combined with a hydrophobic modified polyacrylamide-based polymer to form the surfactant-polymer (SP) flooding system. Then, the development effect of the system is investigated by the visualization experiment, and high-resolution images of the remaining oil are obtained. Finally, Mask R-CNN, an intelligent image recognition technology based on deep learning, is introduced to more accurately and quickly study the microscopic remaining oil occurrence state and macroscopic remaining oil distribution. The results show that the SP system has excellent synergistic oil displacement effect and can increase the oil recovery by 47.2% in visualization experiments. Remaining oil is classified into four categories: flake oil, columnar oil, droplet oil and membranous oil. The algorithm achieves an accuracy of 93.83% on the identification task and an intersection over union (IOU) of 91.5% for the instance segmentation. The oil remaining after steam and chemical flooding is mainly flake oil and dispersed column oil, droplet oil and film oil, respectively. This algorithm lays the foundation for the study of the microscopic occurrence state and macroscopic statistical distribution of remaining oil under different displacement methods.

A comprehensive review ofin situpolymer hydrogels for conformance control of oil reservoirs

In fractured reservoirs, fluids injected Enhanced Oil Recovery (EOR) are channeled through the fracture zones and travel through highly permeable regions, failing to displace part of the oil, and decreasing oil recovery efficiency. To solve these problems, the conformance control technique is now widely used, as it allows the reservoir to be swept totally, similar to the ideal condition. In this context, polyacrylamide-based polymer gel systems can be used to block the high-permeability regions of the rock matrix, formingin situhydrogels that block the rock pores, avoiding the channeling of the fluids, and increasing the oil production. These polyacrylamide-based hydrogels can be crosslinked by inorganic (metal ions) or organic substances, and various systems are used for conformance control. Due to the greater stability of the bond formed between the polymer and the organic crosslinker, these systems are now used in higher temperature reservoirs. In order to produce hydrogels with higher resistance to severe salinity and temperature conditions, nanoparticles are applied to form systems with good mechanical resistance, and high thermal stability. These have presented promising results for conformance control.

Comprehensive methodology for chemicals and nano materials screening for heavy oil recovery using microemulsion characterization

This paper reports laboratory scale screening of different chemicals based on microemulsion generation and the feasibility to be recommended for non-thermal heavy oil recovery applications. The objective of this study is to discover optimal chemicals which can form Winsor type 4 oil in water emulsions with heavy oil. The study was performed through visualization of microemulsions generated using vials and microscopic images. The impact of brine salinity on the emulsification was studied thoroughly in order to identify the synergy between the selected chemicals and the heavy oil. An alcohol propoxy sulfate surfactant from the Alfoterra series, Alfoterra S23-7S-90, a non-commercial surfactant blend HORA-W10, performed best for emulsion formation at low salinity conditions (2.5 wt.%, 3.8 wt.%), whereas Polysorbate-type nonionic surfactant Tween 20 performed best for high salinity conditions (6.35 wt.%, 7.6 wt.%). The observed performance was obtained for an oil with a viscosity of 4.812 mPas and 11.74 °API. Moreover, the results helped creating an initial performance correlation, with dependence on two variables: crude oil composition and synthetic brines. Attempts were also made to stabilize oil-in-water emulsions formed with Alfoterra S23-7S-90, HORA-W10, Tween 20 using nanofluids (metal oxides), sodium carbonate, and an anionic polyacrylamide-based polymer (PolyFlood MAX-165). Emulsions were visualized under the Axiostar plus transmitted-light microscope and their stability was studied in order to screen the most optimal chemical (or chemical combinations) available for low cost heavy oil recovery.

Dramatically shrinking of hydrogels controlled by pillar[5]arene-based synergetic effect of host-guest recognition and electrostatic effect

Polyacrylamide-based polymer networks were constructed as a hydrogel, and the novel and simple method was demonstrated to create dramatically shrinking hydrogels triggered by water-soluble pillar[5]arene (WP5)-based synergetic effect of host-guest recognition and electrostatic effect. The shrinking behavior of hydrogels was studied, which significantly exhibited an equilibrium shrinking percentage of approximately 89.2% in weight. More importantly, the WP5 controlled shrinking behavior of hydrogels was further investigated by the encapsulation and release of two types of small molecular drug models (anionic calcein and cationic rhodamine B), which displayed a much better selective release of anionic calcein than that of cationic rhodamine B, due to the host-guest interaction of WP5 and guest moiety of polymer networks in hydrogel as well as the electrostatic effect of anionic host molecule WP5.

A New Organic Gel System for Water Control: a Computed Tomography Study

Summary Because of their thermal stability, organically cross-linked gels have been used in conformance treatments for high-temperature applications. Most of these gels consist of a polyacrylamide-based polymer and an organic cross-linker. Polyethyleneimine (PEI) has been used as an organic cross-linker for polyacrylamide-based copolymers. Allison and Purkaple (1988) reported that PEI can form aqueous gels with simple polyacrylamide (PAM) at room temperature. In a previous study (Al-Muntasheri et al. 2008), we have shown that PEI can form ringing gels with polyacrylamide homopolymers at temperatures up to 130°C (266°F). In addition, the gelation kinetics of this system was reported up to 140°C (285°F). However, the placement of this system in porous media was not examined. In this study, the displacement of this gel system was visualized with computed tomography (CT) in sandstone cores. A permeability reduction of more than 94% was realized at 23°C for cores shut in at 50°C and 45°C. In addition to CT visualization, this study reports on the bulk testing of this system over a wide range of concentrations of PAM and PEI. Visual observation revealed the formation of stable gels for 3 weeks at 100°C (212°F). These gels were rigid and nonflowing at PAM concentrations of 5, 7, and 9 wt% cross-linked with PEI at concentrations from 0.5 to 3 wt%.

A Study of Polyacrylamide-Based Gels Crosslinked With Polyethyleneimine

Summary Organically crosslinked gels have been used to control water production in high-temperature reservoirs. Most of these gels consist of a polyacrylamide-based polymer and an organic crosslinker. Polyethyleneimine (PEI) has been used as an organic crosslinker for polyacrylamide tertiary butyl acrylate (PAtBA) copolymer. Literature reported that PEI can also form ringing gels with polyacrylamide (PAM) copolymers in addition to simple PAM homopolymers. We report a comparative study of two water-control gel systems (i.e., PAtBA copolymer and PAM crosslinked with PEI). Several techniques were used in the present study, including gas chromatography (GC), carbon 13 nuclear-magnetic-resonance (C13 NMR) spectroscopy, and steady-shear viscometry. The gases produced during the reaction, structural changes, and gelationtime data were all integrated to provide further insights into differences between the two gelling systems. The evolution of isobutene gas was identified at temperatures as low as 60°C during the formation of PAtBA/PEI gels. In addition, GC studies revealed the release of carbon dioxide (CO2) as a product of thermal decomposition of the tBA groups on PAtBA during PAtBA/PEI gelation. Lower initial pH values were found to delay the gelation time of the two systems. Salts were found to increase the gelation time. This paper summarizes these results and investigates the main reaction mechanisms involved. It also discusses how these new findings will affect the application of these gels in the field.

Clay flocculation improved by cationic poly(vinyl alcohol)/anionic polymer dual-component system

The synthesis of cationically modified poly(vinyl alcohol), CPVA, by copolymerization of vinyl acetate and diallyldimethyl ammonium chloride (DADMAC), followed by alkaline hydrolysis was systematically studied. The application of the resulting polymer to the fine clay flocculation was also reported. The charge density and the structure of the resulting CPVA were characterized by polyelectrolyte titration and NMR. A photometric dispersion analyzer was used to conduct the dynamic flocculation experiments. Under fine clay experimental conditions, the CPVA alone contributed little to inducing clay flocculation. However, in conjunction with anionic polyacrylamide-based polymer with high molecular weight and low charge density, significant improvement in the flocculation of fine clay particles was achieved. The influence of factors such as pH and shear force on clay flocculation was also investigated to identify optimum application conditions for clay flocculation. The electrostatic interactions between the clay and CPVA, as well as those between the CPVA pre-treated clay and anionic polymer, were studied to explore the flocculation mechanism.

Enhanced removal of dissolved metal ions in radioactive effluents by flocculation

Decontamination of radioactive effluents of low or intermediate level of radioactivity generated from different nuclear industries is done through the chemical precipitation route. The precipitates thus formed are of very fine sizes thereby requiring flocculation for faster settlement. The presence of polyacrylamide-based polymer not only enhances settling velocity but also increases removal of dissolved non-radioactive as well as radioactive metal ions from the liquid. About 99.5% of Cu 2+ and Fe 3+ ions are removed due to the presence of cationic Rishabh 611. Flocculation by either cationic or anionic flocculant has shown improvement in removal of radioactive strontium while turbidity of the liquid is reduced to a very low value (0.8 NTU). Decontamination factors (DF) of the effluents from different plants are improved by 3–5 times.