Abstract:

Conventional in-situ foams are of poor strength and limited profile control ability, which could not effectively plug the high-permeability layers in highly heterogeneous reservoirs. To solve this problem, in this work, an inorganic gel enhanced in-situ foam system was proposed. The foaming performance and profile control performance of conventional in-situ foam system and inorganic gel enhanced in-situ foam system were both studied by using Waring Blender mixer, electron microscope and double sand-filled tube model. The results showed that, the average particle size of the inorganic gel enhanced in-situ foam system was 200 μm, and the drainage half-life reached 55.2 min, which was smaller and more uniform than that of conventional in-situ foam system and exhibited significantly enhanced stability. Conventional in-situ foam system had good profile control effect for parallel sand-filled tube model with permeability ratio of 5, and the overall recovery factor could be increased from 13% to 30%, but low-permeability layers could hardly be used for permeability ratio≥10. In contrast, the inorganic gel enhanced in-situ foam system had good profile control effect at different permeability levels. When the permeability ratio was≤10, the liquid production rate could be reversed. When the permeability ratio reached 15, the high-permeability layer could still be effectively blocked, and the low-permeability layer could be used. The overall recovery factor could be increased by 21% on the basis of water flooding. This work could provide a reference for conducting in-situ foam profile control in highly heterogeneous reservoirs.

Key words: heterogeneous reservoir, foam strength, in-situ foam, profile control, inorganic gel