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

Abstract

The special deepwater and deep well environment in the deepwater area of the ocean puts forward higher requirements 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°C and had good compatibility. The slope of the viscosity-temperature curve of the 4 wt% bentonite mud after aging at 180 °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 effects 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.