Fluorous-Based Drilling Fluid for Ultra-High Temperature Wells
Résumé
The growing industry demand to operate in high-pressure/high-temperature (HP/HT) environments (>10,000 psi and >350°F) requires robust drilling fluid performance to facilitate drilling under such harsh conditions. Several water-based and synthetic-based drilling fluids have met these high temperature operational challenges. However, despite the thermal stability of these fluid systems, deeper exploration has prompted the need for new technologies to drill in ultra-high-temperature reservoirs (>450°F). A fluorous-based drilling fluid can help meet these demands because fluorous materials are well-known to function in harsh chemical and thermal environments. Fluorous materials are composed of a carbon framework that is highly saturated with fluorine atoms. The increased electronegativity of fluorine relative to hydrogen provides fluorinated materials unique properties compared to their hydrocarbon counterparts. Fluorous fluids and additives exhibit thermal stabilities upward of 600°F. The properties of fluorinated materials could assist drilling operations by increasing thermal stability, improving lubricity, minimizing corrosion, stabilizing shale, and increasing contamination resistance. However, because of the water- and oil-repellant nature of fluorous materials, conventional drilling fluid additives do not perform. The high inherent density of fluorous liquids allows fluorous drilling fluid to be formulated at high densities (16.0 to 20.0 lb/gal). Only 7% by volume barite loading was necessary to achieve 16.0-lb/gal density with the fluorous fluid, compared to 27% by volume barite loading required to prepare a 16.0-lb/gal water-based mud. A fluorous surfactant provided emulsion stability, and the required concentration was optimized for the fluorous-based fluid. This paper presents the detailed laboratory study of a new fluorous-based drilling fluid that was formulated with 16.0-20.0 lb/gal densities, adequate suspension, and reasonable rheology with some degree of filtration control. Emulsion stability, rheological properties, suspension, and filtration control provided by the new drilling fluid system are also discussed. The fluorous-based drilling fluid potentially provides an ultra-high-temperature stable drilling fluid solution that can readily function in ultra-high-temperature wells.