Bacillus velezensis H2O-1 surfactin efficiently maintains its interfacial properties in extreme conditions found in post-salt and pre-salt oil reservoirs.

Biosurfactants are molecules with surfactant properties produced by microorganisms, and can be used in various industrial sectors, e.g., the oil industry. These molecules can be used in enhanced oil recovery (EOR) in the pre-salt and post-salt reservoirs, where conditions of temperature, pressure, and salinity are quite varied, requiring a study of the stability of these molecules under these conditions. Bacillus velezensis H2O-1 produces five different surfactin homologs with a fatty-acid chain ranging from C11 to C16 and with a high capacity to reduce surface (24.8 mN.m) and interfacial tensions (1.5 and 0.8 8 mN.m using light, medium oil and n-hexadecane, respectively). The critical micellar concentration (CMC) was 38.7 mg.L. Inversion wettability tests were carried out under the salinity conditions found in the post-salt (35 g.L) and pre-salt (70 g.L) reservoirs, in which it was observed that the surfactin reversed 100 % of the wettability of the calcite impregnated with light and medium oil. Using a central composite rotatable design, we demonstrated that surfactin maintained its interfacial properties when subjected simultaneously to extreme conditions of pressure, temperature and salinity commonly found in the post-salt (70 °C, 70 g.L and 27.58 MPa) and pre-salt (100 °C, 150 g.L and 48.2 MPa) layers. The results presented here highlight the efficiency and stability of H2O-1 surfactin in environmental conditions found in pre-salt and post-salt oil reservoirs.