Effect of Salinity on Drag Reduction of Additives and Mixtures under Turbulent Flow

Abstract

The performance of partially hydrolyzed polyacrylamide (HPAM), which is the most commercially used polymer in drag reduction (DR) applications, is affected by several factors. These factors include Reynolds number, polymeric concentration, molecular weight, and, more importantly, salinity conditions, which can dramatically impact the polymeric structure and its behavior. In the current work, a deep analysis is done on the performance of HPAM at salinity levels mimicking industrial conditions by using an industrialscale fluid flow loop and a rotational rheometer. The impact of salinity on DR performance and degradation rates of HPAM was investigated at various molecular weights and a fixed concentration and then fitted with exponential decay models. Then, measurements of DR of the additives alone at different concentrations as well as blends of two saltresisting polymers, i.e., xanthan gum (XG) and poly(ethylene oxide) (PEO), were analyzed in tap water and in brine at different mass ratios. Our results showed that the presence of salts led to the drop of the DR of HPAM to almost half its value in tap water, while PEO was found to have an increase in the DR, and XG maintained nearly the same performance. The HPAM−XG mixtures had higher levels of improvement in both media and a slight improvement in the DR in brine over those of HPAM measurements alone. In the case of the HPAM−PEO mixture, the DR is substantially increased compared to HPAM alone. The results of this work confirm that conventional solutions, represented by the physical mixing of HPAM with inexpensive and environmentally friendly additives, are possible and can lead to a massive reduction in energy and freshwater consumption in industrial applications such as hydraulic fracturing.

Drag Reduction by Polymer Additives: State-of-the-Art Advancements in Experimental and Numerical Approaches

“…Under aqueous conditions, the polymer chains stretch due to favorable solvent–polymer interaction, leading to the developing elastic retractive force in the polymer network that balances the reduction in the entropy associated with the resistance of the polymer to the swelling-induced polymer network. , The degree of macro or micro scale swelling is impacted by the PAM dissolution conditions, such as temperature, pH, and the coexistence of metallic ions. , In fact, the presence of mono and bimetallic ions allows the presence of incomplete swelling due to the electrostatic interactions between the exposed carboxylate groups with alkali and alkaline earth metal, forming aggregates, negatively impacting the polymeric linearity, and reducing their tendency for hydration. To overcome the salinity issue, polymeric structural modifications were usually performed by adding some surfactants or copolymers, such as PEO or XG, to the HPAM backbone to alter the net charge of the existing molecules. ,,,− Recently, our research group has investigated the performance of virgin polymers of HPAM, XG, PEO, and mixtures of HPAM with XG and PEO at different salinity levels mimicking industrial conditions by using an industrial-scale fluid flow loop and a rotational rheometer. The effect of salinity levels on DR performance and degradation rates of virgin and mixture of polymers were studied and discussed.…”