Bashkirian reservoir is a heavy oil fractured carbonate reservoir. It has a low temperature (23 ℃) and an ultra-high salinity (217.5 g/L). The low injectivity is the main problem that limits the efficient development of this reservoir. Hot water injection has been tried to solve this problem, but it did not work. The purpose of this work is to find an effective surfactant system for high salinity condition to increase the injectivity during water flooding. This paper presents the whole process from laboratory screening and numerical simulation to pilot test. In laboratory, ten surfactants were evaluated by measuring interfacial tension (IFT) and wettability change. For each surfactant, three concentrations were studied to obtain the optimal surfactant formulation. The optimal surfactants were used for filtration experiments to evaluate the effect of surfactant on the injectivity and oil displacement efficiency. The effect of the best surfactant was assessed by reservoir numerical simulation at the field scale. Eventually, the pilot test was implemented to test the effectiveness of surfactant injection. According to the ability to reduce IFT and change the wettability, oil displacement efficiency, the capacity of reducing injectivity, and production performance, as well as considering the cost and accessibility of surfactant, one nonionic surfactant was eventually chosen for pilot test in the oilfield. The pilot test results show that this nonionic surfactant shows a very good effect on improving water injectivity. After the injection of surfactant, the wellhead pressure and downhole pressure were reduced from 40 at and 171.5 at to 24 at and 153.4 at), respectively. Surfactant injection increased additional oil production of about 1094 tones. The good effect of this nonionic surfactant showed in pilot test makes it a good candidate for wide application under high salinity condition to improve well injectivity as well as oil displacement efficiency in the case of complex heavy oil carbonate deposits.

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