Some microorganisms isolated from drill sludge (Bacillus circulans NSh, B. firmus OBR 1.1, B. firmus OBR 3.1, Solibacillus silvestris OBR 3.2, B. circulans OBR 3.3, Halomonas sp. OBR 1, and Erwinia rhapontici OBR 4.1) have been shown to be capable of degrading crude oil, mineral oil, and diesel fuel. It has been established that the B. circulans NSh and B. firmus OBR 1.1 bacteria degrade 62 and 32% of crude oil, respectively, in an alkaline medium (pH 9) for 14 days and degrade 42 and 22%, respectively, in a saline medium (10% NaCl).