Prevention of Dynamic Sag in Deepwater Invert Emulsion Fluids

Controlling weight material sag in invert muds is difficult in deviated wellbores, where the phenomenon of sag is not completely understood and simultaneous optimization of all hydraulics variables is complex. The fluid must be designed with a specific rheological profile over the entire temperature range encountered in the drillpipe and wellbore. This is particularly difficult for deepwater wells, where temperatures may vary from near freezing to greater than 250 o F. Organophilic clays are especially well suited for this purpose. In this work, a blend of specific organophilic clays was used to provide the rheology necessary to minimize dynamic sag in two deepwater wells in the Mississippi Canyon, Gulf of Mexico. Reduction of the sag potential was accomplished without an increase in the viscosity profile of the mud.