Star-Like Branched Polyacrylamides by RAFT polymerization, Part II:Performance Evaluation in Enhanced Oil Recovery (EOR)

In the present study the performance of a series of star-like branched polyacrylamides (SB-PAMs) has been I investigated in oil recovery experiments to ultimately determine their suitability as novel thickening agent for enhanced oil recovery (EOR) applications. Hereby, SB-PAMs were compared with conventional linear PAM. The effect of a branched molecular architecture on rheology, and consequently on oil recovery was discussed. Rheological measurements identified unique properties for the SB-PAMs, as those showed higher robustness under shear and higher salt tolerance than their linear analogues. EOR performance was evaluated by simulating oil recovery in two-dimensional flow-cell measurements, showing that SB-PAMs perform approximately 3-5 times better than their linear analogues with similar molecular weight. The salinity did not influence the solution viscosity of the SB-PAM, contrarily to what happens for partially hydrolyzed polyacrylamide (HPAM). Therefore, SB-PAMs are more resilient under harsh reservoir conditions, which can make them attractive for EOR applications

Starlike Branched Polyacrylamides by RAFT Polymerization-Part I:Synthesis and Characterization

Starlike branched polyacrylamides (SB-PAMs) were synthesized using reversible addition-fragmentation chain transfer copolymerization of acrylamide (AM) and N, N'-methylenebis(acrylamide) (BisAM) in the presence of 3-(((benzylthio) carbonothioyl)thio)propanoic acid as a chain transfer agent, followed by chain extension with AM. The amount of incorporated BisAM in the core and the amount of AM during chain extension have been systematically varied. Core structures were achieved by incorporation of total monomer ratios [BisAM]/[AM] ranging from 0.010 to 0.143. The obtained macromolecular chain transfer agents had weight average molecular weights in the range of (2.2-7.8) x 10(3) Da and polydispersity indices between 1.2 and 15.1. Kinetic experiments were performed to investigate the extent of control of polymerization. Finally, the expansion of the core structures by chain-extension polymerization resulted in the successful preparation of high molecular weight SB-PAMs with apparent molecular weights ranging from 19 to 1250 kDa

Triblock copolymers of styrene and sodium methacrylate as smart materials:synthesis and rheological characterization

Well-defined amphiphilic triblock poly(sodium methacrylate)-polystyrene-poly(sodium methacrylate) (PMAA-b-PS-b-PMAA) copolymers characterized by a different length of either the hydrophilic or the hydrophobic block have been synthesized by ATRP. In solution the micelle-like aggregates consist of a collapsed PS core surrounded by stretched charged PMAA chains. The micelles are kinetically 'frozen' and as a consequence the triblock copolymers do not show a significant surface activity. The hydrophilic block length has a major influence on the rheology, the shortest PMAA blocks yielding the strongest gels (at the same total weight concentration). The hydrophobic block length has only a minor influence until a certain threshold, below which the hydrophobic interactions are too weak resulting in weak gels. A mathematical model is used to describe the micelle radius and the results were in good agreement with the experimentally found radius in transmission electron microscopy. The influences of the ionic strength, pH and temperature on the rheology has also been investigated, showing the potential of these polymers as smart hydrogels. The change in conformation of the hydrophilic corona from the collapsed state to the stretched state by changing the pH was quantified with zeta-potential measurements. To the best of our knowledge, this is the first systematic investigation of this kind of triblock copolymers in terms of their rheological behavior in water.</p

Synthesis of novel branched polymers for enhanced oil recovery

De energievraag neemt de komende jaren toe en hoewel het relatieve aandeel olie licht zal afnemen, neemt de absolute vraag met 24% toe tussen 2010 en 2030. Om in de vraag te voorzien, worden aanvullende maatregelen getroffen, zoals de injectie van materialen die van nature niet aanwezig zijn in olievelden, ook wel verbeterde oliewinning (EOR) genaamd. De injectie van waterige polymeeroplossingen is een belangrijke techniek. Hiervoor worden lineaire polymeren bestaande uit acrylamide (AM) gebruikt. Nadelen van dit soort commerciële polymeren zijn de gevoeligheid voor zouten, hardheid en afschuifspanningen. In de literatuur is de introductie van vertakkingen in de structuur van polymeren geïdentificeerd als manier om de tekortkomingen te overkomen. Hiervoor is het nodig om het polymerisatieproces te beheersen, wat kan worden bereikt door toepassing van een gecontroleerd radicaal polymerisatie (CRP) systeem. In dit werk is de CRP methode reversibele additie-fragmentatie ketenoverdracht (RAFT) polymerisatie onderzocht, waarbij een RAFT-agent wordt gebruikt om de polymerisatie te beheersen. Het beschreven werk legt de fundering voor de gecontroleerde polymerisatie van AM tot een hoog molecuulgewicht. Door vertakkingen te introduceren in de polymeren, werd een hogere oplossingsviscositeit behaald dan voor lineaire equivalenten, zelfs wanneer de vertakte polymeren een kleiner hydrodynamisch volume hadden. Om hogere molecuulgewichten te behalen werd een nieuwe tweestaps synthese ontwikkeld. Een vertakte kern werd in een tweede stap uitgebreid met armen van verschillende lengtes. Het effect van de mate van vertakking en ook de lengte van de armen was duidelijk zichtbaar, met name in de elasticiteit en de oliewinning uit een tweedimensionale stroom-cel. Dergelijke vertakte polymeren (SB-PAMs) werden vergeleken met lineaire PAMs en commerciële lineaire gehydrolyseerde polyacrylamides (HPAMs). De SB-PAMs lieten een hogere viscositeit van de oplossingen zien in vergelijking met de lineaire polymeren. Verder waren lagere polymeerconcentraties nodig voor de vertakte polymeren in de tweedimensionale stroom-cel experimenten, terwijl een hogere olieproductie werd bereikte. Deze SB-PAMs zijn bestand tegen zouten en afschuifspanningen van ten minste 1750 s-1. Uiteindelijke evaluaties van deze polymeren zijn uitgevoerd in oliewinning experimenten uit zandsteen kernen, waarbij de vertakte polymeren de hoogste mate van oliewinning lieten zien. Thermische viscositeit verhogende polymeren, als alternatief voor conventionele polymeren met een extreme hoog molecuulgewicht, werden geprepareerd met de CRP methode atoom transfer radicaal polymerisatie (ATRP). De kamvormige polymeren met gemiddeld 17 armen van N,N -dimethylacrylamide (DMA) en N -isopropylacrylamide (NIPAM) beschikten over een thermische verdikkingsfase (voornamelijk bij lage afschuifspanningen en afhankelijk van de samenstelling van de armen). Deze eigenschap maakt zulke polymeren relevant, aangezien de polymeren met lage energieconsumptie in een olieveld kunnen worden geïnjecteerd, terwijl ze een hoge viscositeit genereren in het olieveld

Viability of Biopolymers for Enhanced Oil Recovery

Xanthan gum and scleroglucan are assessed as environmentally friendly enhanced oil recovery (EOR) agents. Viscometric and interfacial tension measurements show that the polysaccharides exhibit favorable viscosifying performance, robust shear tolerance, electrolyte tolerance, and moderate interactions with surfactants. Non-ionic surfactants and anionic surfactants bind to xanthan gum and transform the backbone conformation from a strong helix to a more flexible structure, reducing the viscosifying efficacy of xanthan. In contrast, non-ionic surfactants and anionic surfactants bind to scleroglucan and increase the viscosifying efficacy by non-electrostatic interactions or imparted electrostatic effects. The two polysaccharides are technically viable as viscosifying agents in typical EOR injection fluid formulations

Copper-mediated homogeneous living radical polymerization of acrylamide with waxy potato starch-based macroinitiator

Cu0-mediated living radical polymerization (Cu0-mediated LRP) was employed in this research for the synthesis of starch-g-polyacrylamide (St-g-PAM). The use of a controlled radical grafting technique is necessary, as compared to the traditional free-radical polymerization methods, in order to obtain a well-defined structure of the final product. This is in turn essential for studying the relationship between such structure and the end-properties. Waxy potato starch-based water-soluble macroinitiator was first synthesized by esterification with 2-bromopropionyl bromide in the mixture of dimethylacetamide and lithium chloride. With the obtained macroinitiator, St-g-PAM was homogeneously synthesized by aqueous Cu0-mediated LRP using CuBr/hexamethylated tris(2-aminoethyl)amine (Me6Tren) as catalyst. The successful synthesis of the macroinitiator and St-g-PAM was proved by NMR, FT-IR, SEM, XRD and TGA analysis. The molecular weight and polydispersity of PAM chains were analyzed by gel permeation chromatography (GPC) after hydrolyzing the starch backbone. Monomer conversion was monitored by gas chromatography (GC), on the basis of which the kinetics were determined. A preliminarily rheological study was performed on aqueous solutions of the prepared materials