Bentonite-free water-based drilling fluids at HP/HT condition: a rheometric analysis

The bentonite-free water-based drilling fluid aids in reducing formation damage in offshore operations in ultra-deep wells. In this scenario, the material experiences high-pressure and high-temperature conditions. The material's rheological behavior may be affected not only by the temperature but also by the pressure. Knowing the influence of these variables on the drilling fluid's rheological characteristics is essential for successfully planning and executing the drilling process. This paper investigates the effect of pressure, temperature, and thermal aging in the liquid-like and solid-like regimes of a bentonite-free water-based drilling fluid. The main viscosifier in the fluid is xanthan gum. The experiments were carried out in a pressure cell coupled to a rotational rheometer. The results show a more relevant impact of temperature than pressure on the rheological behavior of the drilling fluid. The experiments also exhibit a critical aging temperature that induces irreversible fluid degradation. Lastly, these findings bring relevant information over an efficient range of bentonite-free water-based drilling fluids employed in the offshore drilling process.