1. n. [Drilling]
A generic term for soft, sticky, swelling clay formations that are frequently encountered in surface holes offshore or in sedimentary basins onshore near seas. This clay fouls drilling tools and plugs piping, both severe problems for drilling crews.
See: native clay
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.
See: colloidal solids, drilling detergent, montmorillonite, shale shaker, smectite clay, water mud