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8. WBM and drilling fluid performance
WBM systems have been the traditional drilling fluids since the early days of the oil industry. Deeper, hotter wells, more deviated and with increasing well path tortuosity have brought the WBM systems to their limits of economic applicability. Continued efforts in the development of WBM systems have allowed the industry to use systems ranging from the classic Water-Bentonite suspension via the highly dispersive Lignosulphonate drilling fluids to the KCl-Polyglycol drilling fluid presently known as the most inhibitive WBM to-date.