Experiments on foam texture under high pressure in porous media

• We developed an experimental real-time and dynamic image acquisition device.
• We established the image processing and statistic analysis methods.
• The pressure difference between the two ends of the core increased gradually.
• The bubble distribution became homogeneous and stabilized during foam flooding.
• We investigated some of the factors affecting the foam texture.

Foam flooding has become one of the most effective methods to improve oil recovery in high water-cut oilfields. In order to obtain images of the texture of foam in the cores under high pressure, this paper developed an experimental real-time image acquisition device for detecting the foam's texture as the bubbles flowed in the porous media. Image processing and statistic analysis methods for describing the foam's texture were also established. Experimental results showed that the bubble distribution became homogeneous and stabilized, and the pressure difference between two ends of the core increased gradually during the process of foam flooding. In the initial stage, the bubbles presented a flake-like distribution. The liquid phase flowed continuously, as did the gas phase. As the displacement continued, the volume of a single bubble lessened, while the number of bubbles increased. When the bubbles reached a steady state, the pressure difference between the two ends of the core was stable, and the bubbles presented a uniform distribution. A larger injection rate, a higher core permeability and a larger gas–liquid ratio all can cause a larger-than-average bubble diameter, poor stability and a decreased degree of homogeneity.