Research Of The Mechanism Of Surfactant Flooding For Heavy Oil Reservoir

The chemical flooding is an effect way to enhance oil recovery for heavy oil reservoir. The systems with different IFT and emulsifying power were setup to research the mechanism for enhancing heavy oil recovery. The IFT for anionic surfactant with propylene oxide and betaine were studied. The IFT for anionic surfactant with propylene oxide increase before decrease with the increase of the salinity, and decrease with the increase of the number of PO and carbon chain. The IFT for tetradecyl betaine and hexadecyl betaine increases with the increase of surfactant concentration. The increase for salinity is favor for decrease the IFT. The IFT of octadecyl betaine increase before decrease with the increase of the surfactant concentration and salinity. In surfactant and Na2CO3 system, it could reach the ultra-low IFT with low surfactant concentration if the Na2CO3 is more than 0.35%. The emulsifying power for surfactant is evaluated by the minimum emulsify rotate speed. The emulsifying power of 9AS-n-0 and 13AS-n-0 change with salinity as paracurve, but it has no relation with the IFT. The emulsifying power of betaine is better than 9AS and 13AS and it is enhanced by the increase of the surfactant concentration and salinity. The method to evaluate the oil film shrink velocity is built. The oil film shrink velocity in surfactant and Na2CO3 solution were researched. It shows that the surfactant could decrease the W/S and O/W IFT which is good for oil film shrink. The in-situ surfactant that comes from the reaction of Na2CO3 and oil acid could adsorb on the oil and solid surface to reduce the oil and solid surface interfacial tension which is bad for oil film shrink. The 17 kinds of systems with different ITF and emulsification ability were chosen. Thirty-six experiments were done. It shows that the displacement system with good emulsification ability is the necessary condition to get higher recovery. The recovery for heavy oil reservoir has no relation with IFT. It indicates that the system with low IFT and high emulsification ability and high oil film shrink velocity is good for enhancing separated oil recovery, and the system with low oil film shrink velocity could enhance recovery for the area with higher oil saturation. The sodium carbonate could keep the solid oil-wet and reduce the O-W IFT to prevent the water from penetrating between the oil and solid. It makes the displacement agent flow through the oil, and enhances the displacement pressure and sweep efficiency. The results are helpful to the chemical flooding for the heavy oil reservoir.