The Chang-6 reservoir is characterized by low porosity, ultra-low permeability and low Deliverability. At present, water injection pilot only occupied 3.6% of the whole reservoir area. Most of wells will been flooded rapidly once water injection was conducted. How to enhance the oil well production and crude oil recovery is of great strategic significance for guaranteeing the sustained and sTab.le development of YanChang oil field In this paper, a series of empirical formula was compared and oil recovery of Chang-6 reservoir was determined at 13.9%. The starting pressure gradient and stresssensitive experiments were carried out. The result suggested that the influence of stress-sensitive cannot be ignored. Based on infiltrating fluid experiments and considering the stress sensitivity, a comprehensive research of numerical simulation for the injection zone was conducted to determine the residual oil saturation and demonstrate the feasibility of cyclic water injection, continuous water injection and surfactant injection for EOR. In addition, a suit of clean-fracturing fluid of surfactant acting agent was invented and a foam fluid system was optimized for Chang6 low-permeability reservoir. This study and pilot show that invented clean-fracturing fluid and optimized foam fluid system was effective for ultra-low permeability reservoir.

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