A temperature-sensitive polymer with thinner effect as a rheology modifier in deepwater water-based drilling fluids

The special deepwater and deep well environment in the deepwater area of the ocean puts forward higher re-quirements on the temperature resistance and flat rheology performance of water-based drilling fluid. In this study, the flat rheology performance of water-based drilling fluids was improved by synthesizing a temperature-sensitive polymer with thinner effect as a rheology modifier (PVNA). PVNA was characterized by infrared spectroscopy, thermogravimetric, nuclear magnetic resonance hydrogen spectroscopy, X-ray photoelectron spectroscopy and liquid gel chromatography. The results of the evaluation experiments showed that PVNA in 4 wt% bentonite mud resisted temperature up to 180 degrees C and had good compatibility. The slope of the viscosity-temperature curve of the 4 wt% bentonite mud after aging at 180 degrees C/16 h was reduced from 0.84 to 0.17 after the addition of PVNA, indicating that PVNA can substantially improve the flat rheology performance of the 4 wt% bentonite mud. Turbidity analysis, particle size analysis, thixotropy analysis and transmission electron microscopy analysized the temperature-sensitive effect of PVNA. Specifically, PVNA weakens the hydration layer on the surface of bentonite through its hydrophobic properties, reducing the low-temperature aggregation effect of bentonite, and avoiding low-temperature thickening of bentonite mud to a certain extent. At the same time, the temperature-sensitive effect of PVNA after warming brings stronger intermolecular binding, which improves the internal three-dimensional network strength of the bentonite dispersion system after warming. The two ef-fects synergistically improved the flat rheology performance of the dispersion system. PVNA has good application prospects and can be used as a good reference for developing other rheology modifiers.