Method comprising contacting a hydrocarbon-bearing formation with a composition comprising solvent and a fluoropolyether compound. The fluoropolyether compound: is represented by formula Rf—[C(0)—NR1—X′—(Z)m]n; or comprises at least one first divalent unit represented by formula (I) and, at least one of, a second divalent unit comprising a pendant Z group; or a monovalent unit comprising a thioether linkage and at least one terminal Z group. Each Rf is independently a fluoropolyether group. Rf is a monovalent or divalent fluoropolyether group, and each Z group is independently —P(O)(OY)2 or —O—P(O)(OY)2. Hydrocarbon-bearing formations treated according to this method are also disclosed.