Contributions of combination flooding systems to oil recovery in an ultra-low interfacial tension state
SHANG Dansen, HOU Jirui
1 Institute of Enhanced Oil Recovery, China University of Petroleum-Beijing, Beijing 102249, China 2 Basic Theory Laboratory of Enhanced Oil Recovery in Low Permeability Oilfields, Key Laboratory of Tertiary Oil Recovery, PetroChina, Beijing 102249, China 3 PetroChina Research Institute of Petroleum Exploration & Development, Beijing 100083, China
To investigate the contribution of an ultra-low IFT state to oil recovery, a 10 m sand-packed physical model was built with Daqing natural oil sand and studies on the migration of alkaline surfactant polymer (ASP) and surfactant polymer (SP) in stratum were carried out in this model. The results shown that the distribution of remaining oil presented a ladder type change after water flooding, and most of the remaining oil was concentrated after 40% of the model length. The ultra-low interfacial tension state could only be maintained for 25%~35% of the model length, and played a role in the area where remaining oil was comparatively less, and its contribution to oil recovery is 30%~40%. In SP flooding and ASP flooding, contribution of 10-3, 10-2, 10-1 and 100 mN/ m order of magnitude to oil recovery were 33%, 33%, 20%, 14% and 39%, 35%, 18%, 8% respectively. Alkali could prolong the effective action distance of the ultra-low interfacial tension state, increase its contribution to oil recovery, and improve the displacement efficiency of interfacial tension at a 10-2 mN/m order of magnitude. The contribution of interfacial tension state at a 10-2 mN/m magnitude to oil recovery is almost the same as that of the ultra-low interfacial tension state, and the properties of the composite system under non-ultra-low interfacial tension should also be considered. The results could provide an experimental reference for the design and optimization of combination flooding.
