Experimental Research On Mechanism Of Thermal-chemical Flooding For Enhancing Heavy Oil Recovery

Thermal-chemical flooding is one of effective methods to enhance heavy oil recovery. In order to research the mechanism of thermal-chemical flooding for heavy oil reservoir, firstly, the interfacial tension(IFT) and emulsifying power of different displacing agents were measured and several kinds of oil-displacement systems were constructed in this thesis. Secondly, 48-group displacement experiments were done to get the displacement efficiency of each system and the produced fluids were measured by microscope. At last, the mechanism of thermal-chemical flooding for heavy oil reservoir was summarized according to the results.The IFT between heavy oil and water was got by rotational method initially, results shows that the IFT can be reduced to 10^-3 mN·m^-1 under S-5 and Na₂CO₃ actions and can be reduced to 10^-1 mN·m^-1 under FCY action. Then, the emulsifying power of different agents was studied and the photos of emulsions were got by microscope. Research shows that in experimental concentration range, the emulsifying power of S-5 can be improved as concentration increasing; the emulsion viscosity reduction rate can be to 95% under Na₂CO₃ action while the emulsion of FCY was unstable. Microscope photos shows that the emulsions formed under agents action were oil in water, the diameter of emulsion decreased as agents concentration increasing. Core displacement experiments were done respectively at 60.0℃and 90.0℃to research how systems with different IFT and emulsifying power affect the displacement efficiency at last, results shows: The displacement efficiency was increased as the temperature increasing; the highest displacement efficiency was got when IFT was 10^-2 mN·m^-1 and emulsion viscosity reduction rate was 50.47%. When emulsion viscosity reduction rate was 95%, the efficiency initially increased then decreased with IFT changed from 10-1 to 10^-3 mN·m^-1.The mechanism we got from experiments was that the viscosity of heavy oil can be reduced because of thermal action so that it would change the mobility ratio between oil and water. In addition, the agents can diffused into dead oil area because of thermal action; IFT is the major factor to affect the oil recovery while the emulsion is the necessary factor. The mechanism of reducing IFT was can make the residual oil peel from rock and can make the oil migration more easily; The mechanism of emulsion to enhance oil recovery was reducing the oil viscosity and mobility ratio between oil and water, blocking the water channel and improving swept volume.In this paper, we got the mechanism of thermal-chemical flooding for heavy oil reservoir and the results provide a reference for follow-up studies.