Abstract: Oil-water flow characteristics in different temperature regions are unknown during the thermochemical flooding in ultra-heavy oil reservoirs. The effects of hot water and oil displacement agents on oil displacement efficiency and the change rule of relative permeability at different temperatures were quantitatively investigated, and the impact of hot water and oil displacement agents on the oil flooding and their interaction were analyzed by using microscopic visualization experiments and one-dimensional physical simulation experiments. The experimental results show that the oil phase relative permeability increases in high-temperature oil displacement agent flooding when the temperature is 70 ℃, and the water phase relative permeability changes are negligible when the temperature is 150 ℃, the synergistic effect of hot water and oil displacement agent is more significant, and the relative permeability of the oil phase and water phase increases significantly under high-temperature oil displacement agent flooding after hot water flooding and direct high-temperature oil displacement agent flooding; the role of oil displacement agent weakens at the high-temperature restriction, and the hot water significantly enhances the oil displacement efficiency after the temperature is more than 200 ℃. The oil displacement efficiency of the oil displacement agent increases first and then decreases After the temperature exceeds 200 ℃. Thermochemical flooding can realize the beneficial development of ultra-heavy oil reservoirs through the successive driving and synergistic action of hot water and oil displacement agents in different temperature regions. This study can provide a reference for thermochemical flooding to enhance the recovery of ultra-heavy oil reservoirs.

Key words: ultra-heavy oil, hot water flooding, thermochemical flooding, oil diplacement mechanism, flow characteristics