Study on Emulsification of Heavy Oil in Porous Media

Abstract

The existence of an emulsion can greatly improve the oil displacement efficiency, which has important practical significance for the development of heavy oil reservoirs. However, the description of the emulsification phenomenon is basically based on the observation of produced fluid and the monitoring of pressure points along the way. The actual emulsification in the porous media cannot be observed. In this paper, the emulsification phenomenon of heavy oil in porous media was studied by D–T₂ two-dimensional spectrum. In this study, the D–T₂ two-dimensional spectral characteristics of free water, water-in-oil (W/O) emulsions, and oil-in-water (O/W) emulsions were first studied. Second, the D–T₂ two-dimensional spectrum characteristics of emulsions at different temperatures in nonporous media were studied. Finally, the D–T₂ two-dimensional spectrum characteristics of emulsions at different temperatures in porous media were studied. The results showed that at the reservoir temperature, the oil peak and water peak on the D–T₂ two-dimensional spectrum were on both sides of the boundary of the diffusion coefficient of 8 × 10^–10 m²/s, and the diffusion coefficient of oil was much smaller than 8 × 10^–10 m²/s, while the diffusion coefficient of water was still much larger than 8 × 10^–10 m²/s even if it was affected by confined diffusion in the core. In the D–T₂ 2D spectrum, the water signal of free water fell on the free water line; the water signal of W/O emulsion fell below the free water line. The water signal of O/W emulsion was not far from the free water line. The lower the temperature, the apparent diffusion coefficient of water for W/O emulsion was smaller. On the contrary, the higher the temperature, the apparent diffusion coefficient of water for O/W emulsions was smaller. The D–T₂ two-dimensional spectrum characteristics of emulsions in porous media and nonporous media at different temperatures were similar, but the presence of porous *media further reduced the apparent diffusion coefficient of water. The results of this study can more accurately predict and guide the quality and efficiency improvement of heavy oil reservoirs.