Supramolecular dynamic binary complexes with pH and salt-responsive properties for use in unconventional reservoirs

Abstract

Hydraulic fracturing of unconventional reservoirs has seen a boom in the last century, as a means to fulfill the growing energy demand in the world. The fracturing fluid used in the process plays a substantial role in determining the results. Hence, several research and development efforts have been geared towards developing more sustainable, efficient, and improved fracturing fluids. Herein, we present a dynamic binary complex (DBC) solution, with potential to be useful in the hydraulic fracturing domain. It has a supramolecular structure formed by the self-assembly of low molecular weight viscosifiers (LMWVs) oleic acid and diethylenetriamine into an elongated entangled network under alkaline conditions. With less than 2 wt% constituents dispersed in aqueous solution, a viscous gel that exhibits high viscosities even under shear was formed. Key features include responsiveness to pH and salinity, and a zero-shear viscosity that could be tuned by a factor of ~280 by changing the pH. Furthermore, its viscous properties were more pronounced in the presence of salt. Sand settling tests revealed its potential to hold up sand particles for extended periods of time. In conclusion, this DBC solution system has potential to be utilized as a smart salt-responsive, pH-switchable hydraulic fracturing fluid.

Rheological dynamics and structural characteristics of supramolecular assemblies of β-cyclodextrin and sulfonic surfactants

“…The overall procedure in place for the rheological studies is comparable to that of previous studies. 18,35,36 Viscosity versus shear rate was measured in each case using a rheometer (Haake RS 1, Thermo Fisher Scientific, Waltham, MA, USA) equipped with a 60 mm diameter parallel plate (PP60 Ti). The shear rate was increased logarithmically and stepwise (15 steps) from 0.003 s À1 to 100 s À1 , while setting the gap between the plates constant at 1 mm.…”

SAXS-guided unbiased coarse-grained Monte Carlo simulation for identification of self-assembly nanostructures and dimensions

“…Therefore, the development of novel nanostructures of the supramolecular self-assemblies has been widely studied to attain the desired rheological properties. 6 Recently, a complex self-assembly called the dynamic binary complex (DBC) has been synthesized by Liu et al 7 via the complexation between zwitterionic amphiphiles like octadecylamidopropyl betaine (OAPB) and diethylenetriamine (DTA) ions. Specifically, DBCs have unique viscoelastic properties which show sensitivity to the solution conditions like pH.…”

“…Specifically, DBCs have unique viscoelastic properties which show sensitivity to the solution conditions like pH. In recent studies, 6,7 it was observed that DBCs consist of tubular nanostructures, and the viscoelastic properties of DBCs are determined by the entanglement process of these tubular nanostructures whose cross-sectional dimensions are almost an order of magnitude larger than those of the conventional tubular wormlike micelles (WLMs). It is difficult to rely on the existing imaging techniques like transmission electron microscopy (TEM) to image microgels such as DBCs.…”

“…Therefore, the development of novel nanostructures of the supramolecular self-assemblies has been widely studied to attain the desired rheological properties. 6…”