(535f) pH and Salt-Responsive Dynamic Binary Complexes Based on Supramolecular Complexation with Applications in Unconventional Reservoirs

Hydraulic fracturing of reservoirs has seen tremendous growth in recent years, to keep up with the ever-increasing energy demand. The rheological properties of the fracturing fluid used during the process plays a crucial role in determining the result. A key research problem has been being able to design fluids that carry proppants with enough driving force into fissures while keeping costs reasonable. Hence, several efforts have been active towards development of more efficient and improved fracturing fluids while keeping sustainability in check.

Herein, we present a dynamic binary complex (DBC) solution, composed of a facile self-assembly of a supramolecular assembly of oleic acid and diethylenetriamine under alkaline conditions. With lower than 2 wt% constituents dispersed as an aqueous suspension, a gel-like substance that exhibits high viscosities even under application of shear was formed. Important attributes include dual responsiveness of the rheological properties to salinity and pH, as well as a zero-shear viscosity that can be tuned by a factor of ~280. Also, the gel-like nature was more obvious in the presence of salt which was confirmed by observing the morphology under a microscope. Sand settling tests revealed its potential to hold up sand particles (proppant) for extended periods of time.

In conclusion, this DBC suspension system with a simple assembly process has the potential to be utilized as a smart pH-switchable and salt-responsive hydraulic fracturing fluid. Also, the fact that oleic acid is a natural substance derived from olive oil may add to the sustainability and cost-efficacy of this system.