Probing the physicochemical interactions between thermo-thickening polymers and clay fluids for improve rheological performance
The field of thermo-thickening polymer interacting with clay has long been shrouded in mystery and ambiguity. Despite numerous studies and investigations, the complex interactions, underlying mechanism and binding forces remain elusive, imposing further exploration and elucidation. In this study, three thermo-thickening polymers such as poly(acrylamide methylpropane sulfonic acid-co-N-vinylcaprolactam) (PNV), poly(acrylamide methylpropane sulfonic acid-co-N,N-dimethylacrylamide) (PDM), and poly(acrylamide methylpropane sulfonic acid-co-N-isopropylacrylamide) (PNP) with clay fluids (CFs) were investigated to gain deeper understanding of the underlying physicochemical interactions. Techniques such as Fourier transform infrared spectroscopy (FTIR), proton nuclear magnetic resonance ( 1 H NMR), and elemental analysis (EA) elucidated the structural properties, whereas turbidimetry and rheometric analysis elucidated the temperature-induced phase transitions. The interactions between the different polymer side chains and clay double-sheets were investigated through isothermal adsorption testing, probing chemisorption and hydrogen bonding tuned the chemical properties, whereas electrostatic forces (ionic/van der Waals) bind the physical properties as demonstrated by Zeta (ζ) potential, XRD , high-resolution spectroscopy (XPS), and scanning electron microscopy (SEM) imaging. The addition of 0.2–1.5 wt% of the polymers induced significant effect on the rheological properties of CFs, with increase in low shear viscosity and plastic viscosity, attributed to the formation of gel-like structures at high temperatures. PNV/Clay (NVBF)-modified fluid demonstrated exceptional fluid thickening and suspension behaviors compared to linear PDM/Clay (DMBF) and PNP/Clay (NPBF)-modified fluids. In addition, NVBF exhibited significantly higher adsorption energies and basal spacings, along with more crystalline patterns suited to embed clay particles. Overall, the synergistic effect of the different polymer side chains with clay particles provides valuable insights on the mechanistic and enhancement of rheological properties of CFs effective as shale inhibition, viscosifier and wellbore stabilization.
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