Rheological Study of Salted Water-Based Drilling Fluid Formulations Developed Using a Novel Amphoteric Terpolymer
Abstract
This research presents a comparative study of the rheological properties of amphoteric terpolymer (ATP-I) and high-viscosity polyanionic cellulose (PAC-HV) as rheology modifiers across various salinity levels. Thermogravimetric analysis shows ATP-I has better high-temperature resistance than PAC-HV. The viscosity of ATP-I doubles from 0.02 to 0.04 Pa·s at 100 s-1 as salinity increases from 23.2 to 25%. At concentrations between 0.5 and 2.0 wt.%, ATP-I, and PAC-HV have similar viscosities, both polymers demonstrating high salinity tolerance. Although, in a 35 wt.% NaCl solution, the viscosity of 2.0 wt.% ATP-I is 44% higher than that of 2.0 wt.% PAC-HV. The viscoelastic properties of ATP-I improve with increasing salinity from 1 to 35 wt.% NaCl: shear stress rises from 0.6 to 1.34 Pa and from 38.5 to 90 Pa with increasing shear rates from 1 to 1000 s-1, respectively. PAC-HV shows lower shear stress under similar conditions, indicating lower viscoelasticity. Polymer formulations with bentonite (BT) exhibit decreased viscosity, gel strength, and flow behavior at low salinity. However, when NaCl concentration exceeds 15 wt.%, the ATP-I/BT formulation shows improved properties. These findings highlight the significant differences in the rheological behavior of these polymer formulations for use in drilling fluids across a wide salinity range.