VEN-LIG™, an oxidized lignite, is a highly efficient, multipurpose mud conditioner. It is used in water based muds to (1) reduce viscosity and gels and to maintain desirable flow properties; (2) improve aging characteristics in high temperature fluids by controlling fluidity, (3)reduce high pressure, high temperature filtrates and provide tough, thin filter cakes; (4) thin and emulsify oil-in-water or liquid lubricant containing fluids; (5) reduce effects of contaminants; and (6) control the equivalent circulating density by maintaining suitable flow properties. VEN-LIG™ is referred to mineralogically as “Leonardite.” It is sufficiently different from lignite-grade coal to warrant a different mineral name.