Fluids containing surfactants and hydrophobic particles are effective media for cleaning non-aqueous fluids (NAFs) out of a subterranean wellbore. The fibers and surfactants are preferably added to a drilling fluid, a spacer fluid, a chemical wash, a cement slurry or combinations thereof. NAFs, such as an oil-base mud or a water-in-oil emulsion mud, are attracted to the fibers as the treatment fluid circulates in the wellbore.