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spud mud

1. n. [Drilling Fluids]
Mud used to drill a well from surface to a shallow depth. Guar gum or salt gel are commonly used offshore as spud mud. Onshore spud mud is usually a water-base mud containing bentonite clay that is flocculated with lime. In a large-diameter surface hole, a flocculated clay-based mud can remove large gravel cuttings encountered at shallow depths and is simple and inexpensive.