Fluid loss control additives for oil-based well-working fluids

摘要

Fluid loss control additives for oil-based well-working fluids comprise a solubilized lignite derivative and an oil-swellable or oil-soluble polymer. The solubilized lignite derivative may be oil-solubilized (e.g. a lignite/amine complex) or water-solubilized (e.g. causticized lignite) and may be incorporated in a polymer matrix or added to a dispersion of a polymer in an aqueous medium.