2. n. [Drilling Fluids]
A nonspecific type of shale that becomes sticky when wet and adheres aggressively to surfaces. It forms mud rings and balls that can plug the annulus, the flowline and shale-shaker screens. Gumbo is likely to contain appreciable amounts of Ca+2 smectite clays. It is dispersed in a water mud, causing rapid accumulations of colloidal solids.