Abstract: To address the problem of poor fluid permeability and reduced production capacity caused by strong stress sensitivity in tight reservoirs, a core from a tight reservoir in the Jidong Oilfield was selected for full-diameter core displacement experiments and in situ CT scanning experiments to study the pore structure and oil-water two-phase permeability characteristics of tight reservoirs under the stress sensitivity. The study shows that with the increase of net stress, the stress sensitivity increased, the throat and larger pores in the core were compressed and deformed, some of the ultra-fine pores were even closed, the falling speed of the relative permeability of the oil phase and the rising speed of the relative permeability of the water phase increased, and the two-phase permeability curve gradually shifted down; the saturation of irreducible water and residual oil increased, the co-permeability point shifted to the right, the two-phase permeability zone gradually became smaller, and the efficiency of water-oil displacement decreased; it indicated that after water breakthrough in the oil well, the water cut increased significantly, the oil-water production period was shorter, the breakthrough of water displacement was rapid, and the efficiency of water-oil displacement decreased.The impact of stress sensitivity on oil-water two-phase seepage law and recovery factor was mainly reduced by supplementing formation energy. The study results have important guidance significance for the development of technical solutions for tight reservoir development.

Key words: Tight reservoir, stress sensitivity, pore structure, oil-water two-phase seepage, relative permeability, oil displacement efficiency, Jidong Oilfield