Abstract: Molecular deposition film flooding(NMDFF) has become a new method of enhanced oil recovery(EOR). In order to deepen the knowledge of the oil displacement mechanism, two samples of NMDFF agent have been discussed. The type of NMD-100 configuration is an organic poly quaternary ammonium salt, which positive degree is 100% and the branch chain contains the hydrophilic group. The type of NMD-200 configuration is also an organic poly quaternary ammonium salt, which positive degree is 24% and the offshoot chain contains the hydrophilic group. It is shown that the two samples of NMDFF agent have no surface activity and are not surfactant. They can change surface wettability. When the hydrophilic sandstone is respectively dipped in the NMD-100 and NMD-200 liquid (800 mg/L), the contact angle changes from 48.25°to 39.167°and 42.833°; When the hydrophobic sandstone is respectively dipped in the NMD-100 and NMD-200 liquid (800 mg/L),the contact angle changes from 99.583°to 36.333°and 49°.The contact angle decreased greatly when adding NaCl into the NMD liquid that benefits for changing the surface wettability. It is concluded that the strong adsorption of NMDFF agent changes the properties of sandstone surfaces and is propitious to enhance oil recovery. After NMD-100 is pumped, the water driving oil recovery increases from 38.6% to 48.1% (near to 10%). While NMD-200 is pumped, the oil recovery enhances from 31.4% to 38.6%.

Key words: molecular deposition film flooding, wettability, oil recovery