Optimizing Polymer Costs and Efficiency in Alkali-Polymer Oilfield Applications.

In this work, we present various evaluations that are key prior field applications. The workflow combines laboratory approaches to optimize the usage of polymers in combination with alkali to improve project economics. We show that the performance of AP floods can be optimized by making use of lower polymer viscosities during injection but increasing polymer viscosities in the reservoir owing to "aging" of the polymers at high pH. Furthermore, AP conditions enable the reduction of polymer retention in the reservoir, decreasing the utility factors (kg polymers injected/incremental bbl. produced). We used aged polymer solutions to mimic the conditions deep in the reservoir and compared the displacement efficiencies and the polymer adsorption of non-aged and aged polymer solutions. The aging experiments showed that polymer hydrolysis increases at high pH, leading to 60% higher viscosity in AP conditions. Micromodel experiments in two-layer chips depicted insights into the displacement, with reproducible recoveries of 80% in the high-permeability zone and 15% in the low-permeability zone. The adsorption for real rock using 8 TH RSB brine was measured to be approximately half of that in the case of Berea: 27 µg/g vs. 48 µg/g, respectively. The IFT values obtained for the AP lead to very low values, reaching 0.006 mN/m, while for the alkali, they reach only 0.44 mN/m. The two-phase experiments confirmed that lower-concentration polymer solutions aged in alkali show the same displacement efficiency as non-aged polymers with higher concentrations. Reducing the polymer concentration leads to a decrease in EqUF by 40%. If alkali-polymer is injected immediately without a prior polymer slug, then the economics are improved by 37% compared with the polymer case. Hence, significant cost savings can be realized capitalizing on the fast aging in the reservoir. Due to the low polymer retention in AP floods, fewer polymers are consumed than in conventional polymer floods, significantly decreasing the utility factor.

Modification of surface wettability through adsorption of partly fluorinated statistical and block polyelectrolytes from aqueous medium.

The wetting properties of electrostatically charged hydrophilic substrates were modified through adsorption of ultrathin layer of amphiphilic block or statistical polyelectrolyte from aqueous medium. The studied polymers were copolymers of 2-(dimethylamino)ethyl methacrylate (DMAEMA) and 2,2,2-trifluoroethyl methacrylate (TFEMA). They were adsorbed on mica from varying pH conditions, either as dissolved unimers or as kinetically trapped aqueous nanoparticles. The structures (by atomic force microscopy) and wetting properties (by dynamic contact angle measurements) of the obtained surface layers were determined. The majority of the surface layers consisted of polymeric nanoparticles with varying surface coverage. Annealing at 150 °C flattened and spread the particles on the surfaces. The surface wettability was found to be significantly influenced by the morphology and chemical composition of the obtained polymeric surface layer. The surfaces with the most homogeneous and smooth polymer layers exhibited the lowest contact angle hysteresis. The advancing/receding contact angles on the most hydrophilic copolymer layer on mica were 47°/<20°, and on the least hydrophilic layer they were 96°/63°. On unmodified mica surface the water contact angle is ∼0°. When those copolymers that provided the highest contact angles on mica were adsorbed on cellulose fiber substrates and annealed at 120 °C, highly hydrophobic surfaces were obtained, with advancing contact angles around 160°.

Glycopolymers via catalytic chain transfer polymerisation (CCTP), Huisgens cycloaddition and thiol-ene double click reactions.

CCTP has been used to give alkyne-functional macromonomers which are subsequently functionalised with sugar azides and thiols, using both CuAAC and thiol-ene Michael addition reactions, to yield end-functionalised glycopolymers in a convenient manner.

Modular modification of xylan with UV-initiated thiol-ene reaction.

Birch xylan was functionalized with various thiols through UV initiated radical thiol-ene reaction under mild conditions. Xylan was allylated through etherification with allyl glycidyl ether under alkaline conditions. The allylated xylan was then reacted with thiols containing varying functional groups: trimethylbenzyl mercaptan, dodecanethiol, thioglycolic acid, L-cysteine and cysteamine hydrochloride. The reactions were conducted under homogeneous conditions at room temperature, either in water (hydrophilic thiols) or in DMF (hydrophobic thiols). The effect of reaction parameters to the functionalization efficiency was studied, including, for example, thiol excess, thiol character, initiator amount and reaction mixture concentration. The reactions were fast and 100% conversion of allyl groups was reached in most cases, sometimes already within 10 min. Water as solvent resulted generally in faster reactions when compared to DMF, and it was possible to conduct the aqueous reaction even without added UV initiator. It was also possible to incorporate two functionalities simultaneously during one reaction into the xylan structure.

Synthesis and characterization of copolyanhydrides of carbohydrate-based galactaric acid and adipic acid.

A series of copolyanhydrides, consisting of 2,3,4,5-tetra-O-acetylgalactaric acid (AGA) and adipic acid (AA) as monomer units, was polymerized. Synthesis of AGA monomer consisted of two steps. First, O-acetylation of galactaric acid secondary hydroxyl groups was performed using acetic anhydride as a reagent. Acetic anhydride was then further used as a reagent in the synthesis of diacetyl mixed anhydride of AGA. Polymerizations were conducted as bulk condensation polymerization at 150 °C. Thermal properties of the copolymers varied depending on monomer composition. Increase in the AGA content had a clear increasing effect on the Tg. A similar increasing effect was observed in Tm. The degree of crystallinity decreased as AGA content increased. There was a slightly lowering tendency in the molecular weights of the obtained polymers when the AGA content in the polymerization mixtures increased. The described synthesis route shows that bio-based aldaric acid monomers are potential candidates for the adjustment of thermal properties of polyanhydrides.