Electro-Responsive Green Gels for Lower Environmental Impact Shale Gas Extraction

Abstract

In this work, carbon black (CB) is added in small amounts (3−10% w/w) to green aqueous dispersions based on sodium oleate, guar gum, sodium hyaluronate, or hydroxypropyl cellulose gels to enhance their stability against mechanical and thermal stresses and to provide electric responsiveness to an external voltage. Rheology, optical microscopy, small angle X-ray scattering, and conductivity measurements are performed to compare the properties of CB-enriched formulations to those of pristine dispersions. Our results demonstrate that even small amounts of CB are able to confer interesting physicochemical properties to these formulations: a remarkable increase in the viscosity of at least 1 order of magnitude is observed for all systems even at high temperature (up to 60 °C) upon CB addition, indicating that carbonaceous particles play a structuring role for the polymeric network. Furthermore, the application of an external voltage of 30 V for 60 min to CB-containing formulations imparts a significant electric responsiveness to the systems, allowing the modification of their rheological behavior. The CB-loaded formulations can be recycled at least three times. All these results suggest that CB can be effectively used as an alternative green additive to enhance the mechanical and thermal stabilities of the formulations and that its addition can be a feasible way to easily tune the properties of viscoelastic materials, thereby avoiding the use of toxic or potentially dangerous chemicals. The possibility of achieving remote control of mechanical and thermal properties of viscoelastic formulations significantly expands the horizon of their potential applications, for example, in the field of shale gas extraction.

Light-Modulated Rheological Properties in Green Innovative Formulations

“…In part 2 we illustrated the specific ion effect induced by the addition of different salts on viscoelastic dispersions of sodium and potassium oleate, and we systematically discussed it in terms of the Hofmeister series [26]. In a previous work we imparted a voltage-dependent responsiveness to an NaOL aqueous dispersion through the addition of carbon black particles [27].…”

Modulation of the Viscosity of Guar-Based Fracking Fluids Using Salts

“…16,17 In the fracking industry, efforts have been made to obtain cross-linked fracking fluids using untreated produced water. 3,18 When reusing produced water, a common approach used in the fracking industry is to increase the concentration of polymers, cross-linkers, and other additives (e.g., scale inhibitors). 14 Strategies have also been proposed to buffer the pH to < 9, to avoid scale precipitation.…”

Viscosity-Reducing Agents (Breakers) for Viscoelastic Surfactant Gels for Well Stimulation

“…Polymers and viscoelastic surfactants (VES) are used to improve well productivity in carbonate and sandstone reservoirs. − These compounds are used in matrix acidizing and hydraulic fracturing. ,− In matrix acidizing, polymers and VES are used as chemical diverters and are known as self-diverting agents. ,− Using diverters ensures that the low viscosity acid pumped into the well goes into the low-permeability zones and not in the high-permeability zones, thus increasing the effectiveness of matrix acidizing. ,− , Diversion by gels replaces mechanical diversion techniques because mechanical diversion methods are not always recommended, especially for long horizontal or extended-reach wells. , In hydraulic fracturing, polymers and VES act as a fracturing fluid and a proppant transporter as a result of their high viscosity. ,,,, They are pumped at or above the formation fracturing pressure to create fractures in the wellbore, thus improving well productivity, especially in low-permeability zones . However, the usefulness of gels is not only based on their diversion or fracturing abilities.…”