This paper was prepared for presentation at the 1999 SPE/IADC Drilling Conference held in Amsterdam, Holland, 9-11 March 1999.

TX 75083-3836, U.S.A., fax 01-972-952-9435. AbstractSynthetic drilling fluids have evolved into the systems of choice for deepwater drilling, particularly in the Gulf of Mexico. As these systems are proportionately more expensive than their traditional counterparts, the loss of even a few barrels can impact well economics significantly. Historically, it has been commonplace to leave hundreds of barrels of synthetic drilling fluid in the wellbore during open-hole displacements. Attempts to retrieve synthetic muds with waterbase systems have proved counter productive. When exposed to water-base muds in open hole, the formation becomes extremely unstable and will literally cave in, resulting in a number of operational problems. This paper describes the development and application of a new displacement procedure and a modified water-base mud that successfully recovered 961 bbl of synthetic fluid on the Manatee project in the deepwater Gulf of Mexico. When compared directly with conventional open-hole completions in the deepwater GOM, the new procedure resulted in savings of $228,718, not including saved rig time. Furthermore, no additional rig time was required to condition the water-base system used in the successful open-hole displacement. More importantly, the wellbore remained stable and no problems were encountered while tripping through the 4,462-ft of open hole exposed to the re-engineered water-base fluid system. _____________________________________ References and illustrations at end of paperThe authors will describe both the new procedure, which included a casing shoe with an extremely high leak-off test and realigned pumps, and the new 15 lb/gal water-base displacement fluid. The modified system was both inhibitive to reactive shales and could also withstand the contamination effects of the calcium employed in synthetic muds.