Shear rheological properties of composite fluids and stability of particle suspensions: Potential implications for fracturing and environmental fluids

Abstract

Composite fluids are comprised of particles and polymers and are used for fracking and the in‐situ treatment of subsurface contaminants. This study investigates the correlation between the shear viscoelasticity of guar aqueous solutions and their effectiveness in suspending sand, which is a common fracking proppant. In the absence of a crosslinker, the shear viscous modulus (G”) of 5 g/L guar solutions was greater than the shear elastic modulus (G’). When the crosslinker borax was added, the guar solutions behaved as yield stress fluids (G’ > G”). Sand was well‐suspended in the crosslinked guar solutions but settled in non‐crosslinked fluids. Similar results were obtained with fenugreek gum. This study also investigates the correlation between particle settling and the effect of particle addition on the rheology of the fluids. Granulated activated carbon (GAC) particles are utilized to remediate polluted sites and were used as model particles. Guar and xanthan effectively suspended the GAC. Anionic polyacrylamide effectively suspended the GAC but not after soaking in sodium dodecyl sulphate. Zetag 8167 did not effectively suspend the GAC. The addition of 10 g/L of GAC did not affect the shear rheology of the fluids that suspended them, but decreased the shear viscoelastic moduli of the polymeric fluids that could not suspend them.

Effect of rheology and humic acids on the transport of environmental fluids: Potential implications for soil remediation revealed through microfluidics

“…[25][26][27] Polymeric fluids can be used to transport reactive particles in the subsurface, such as nanoscale zero-valent iron particles. 17 These findings are in agreement with other studies, which showed that when the loss tangent δ (δ = G 00 /G 0 ) is high, fluids behave like liquids and settling is promoted, whereas when δ is low, fluids behave like gels and settling is impeded. 17 These findings are in agreement with other studies, which showed that when the loss tangent δ (δ = G 00 /G 0 ) is high, fluids behave like liquids and settling is promoted, whereas when δ is low, fluids behave like gels and settling is impeded.…”

“…[1][2][3][4] Previous research showed that colloidal particle settling is markedly different in fluids with identical shear viscous moduli but different shear elastic moduli, with high shear elastic moduli leading to negligible particle settling. 17 These findings are in agreement with other studies, which showed that when the loss tangent δ (δ = G 00 /G 0 ) is high, fluids behave like liquids and settling is promoted, whereas when δ is low, fluids behave like gels and settling is impeded. 28 Therefore, high shear elasticity is desirable to ensure that particles remain suspended in aqueous solution.…”

“…A previous study was however conducted with high concentrations of guar and borax, namely, with 5 g/L guar and with 5 g/L guar and 2.5 g/L borax. 17 This previous study showed that the two systems has identical viscous moduli (G 0 ≈ 2 Pa in the linear regime), whereas G 0 was much higher for (G 0 ≈ 40 Pa in the linear regime) guar with borax than with guar alone (G 0 ≈ 2 Pa in the linear regime). Borax alone flowed from cylinders of approximately 1 cm in diameter, whereas guar with borax did not flow.…”

“…Significant efforts have been made in understanding the subsurface transport of reactive particles injected in porous media using polymeric carrier fluids. 17 This study showed that fluids with significant shear elastic moduli are effective in suspending particles. 2,14,15 Previous studies also analyzed the effect of carrier fluids on the aggregation of particles used for the in situ treatment of contaminants and correlated it to particle transport through sand columns, used to mimic sandy aquifers.…”

“…16 Finally, research has been conducted to explore the correlation between the rheology of polymer fluids and their effectiveness in suspending activated carbon micron-sized particles, because particles must be effectively suspended to flow through porous media. 17 This study showed that fluids with significant shear elastic moduli are effective in suspending particles. Although fluids with high shear elastic moduli can effectively suspend reactive particles, they may not effectively flow in the subsurface and may hence fail in delivering the reactive particles to target polluted areas.…”