Water-based drilling fluids for high-temperature applications and water-sensitive and dispersible shale formations

This study examines the effectiveness of sodium erythorbate, potassium formate, and polyethylene glycol for the formulation of high-performance water-based drilling fluids. High-performance water-based drilling fluids are environmentally-friendly, remain stable when exposed to high temperatures, and retard problems associated with reactive shale. A biopolymer, diutan gum, is used as drilling fluid viscosifiers in the preparation of drilling fluid formulations. The viscosities of the drilling fluid formulations with pH 8-10 were measured using Model 1100 viscometer before and after aging dynamically in a roller oven for sixteen hours. Shale rock samples were characterised using scanning electron microscope photos while X-ray diffraction analysis was used to identify the mineral contents of the shale samples. Shale dispersion tests were carried out by aging shale cuttings in an inhibitive drilling fluid formulation and in freshwater dynamically in a roller oven for 16 h at 120 degrees C. The percentage recovery of shale rocks after dynamic aging was determined. Experimental data indicated that the diutan gum stability temperature in bentonite water-suspension after aging for 16 h was 115 degrees C. Experimental data also indicated that the mud formulations with the additives - sodium erythorbate, potassium formate, and polyethylene glycol - retained their viscosities up to 232 degrees C. The additives, therefore, significantly retarded the degradation of the biopolymer and other mud additives up to 232 degrees C. The result from the shale dispersion test showed that the shale cuttings recovered from freshwater was 78%; with drilling fluids formulated with the additives, the shale cuttings recovered were 100%. This new fluid system which is stable at high temperatures and inhibits shale dispersion can meet high temperature and shale formation drilling requirements.