Emulsification behavior on steam-front: Effects on heat transfer and recovery

The injection of gas and chemical agents during steam flooding is beneficial for enhancing the thermal recovery of heavy oil. However, the complex emulsification and flow mechanism resulting from the interaction between gas, chemical agent, oil and water at the steam front remain unclear. This significantly affected the movement of the steam front and the expansion of the steam chamber. Therefore, in this paper, through microscopic and twodimensional visualization experiments, the emulsification phenomena at steam front and the steam chamber expansion during composite thermal flooding were investigated from both the mechanism and phenomenon aspects. The research results indicated the presence of gas-water and oil-water emulsification at steam front during composite thermal flooding. Under the effects of emulsification, the viscoelastic liquid film was adsorbed, the surface charge density was increased, the oil viscosity was reduced, and the residual oil saturation was reduced by 15.47%, particularly in low-permeability channel. In addition, the medium temperature area was expanded by the composite thermal flooding, the problem of uneven heating was solved and the deep heat transfer was achieved. When the gas-liquid injection ratio was 2:1, the thermal sweep area expansion was optimized, increasing the deep temperature of the two-dimensional visualization model by 5.74-18.24 degrees C. The finding provided theoretical guidance for minimizing the impact of emulsification on steam front and for expanding the thermal sweep range of steam flooding.