College of Earth Sciences, Northeast Petroleum University, Daqing 163318, Heilongjiang, China

A case study on reservoir sensitivity from Chang 6 ultra-low permeability sandstone reservoir in the Jiyuan oilfield in Ordos Basin is carried out, in combination with SEM analysis, core sample studies, X-ray diffraction analysis, conventional mercury pressure test and other methods. The sensitivity types, degree of injury and influence factors of reservoir were analyzed. Research results show that the clay minerals of Jiyuan Oilfield in Ordos Basin are mainly consist of chlorite, kaolinite, illite and mixed-layer montmorillonite-illite, and the main factors causing reservoir sensitivity are chlorite, kaolinite and illite. The reservoir is characterized by weak-medium water sensitivity, weak velocity sensitivity, weak-medium acid sensitivity,weak alkali sensitivity and weak-medium salt sensitivity.The reservoir shows weak sensibility generally. The sensitivity of the reservoir in the Jiyuan area is also related to the pore structure and physical properties of reservoir. The reservoir pore structure has direct influence on reservoir water sensitivity. The results of velocity sensitivity experiment shows strong sensibility in poor pore structure, tiny throat and poorly sorted reservoir, in which the throat of reservoir is easy to be blocked.