Abstract: Taking the tight sandstone reservoir of the Yanchang Formation in the northern Shaanxi as an example, and based on the reservoir characteristics about lithology, pore texture and physical properties, the core flow tests on reservoir sensitivities were conducted. Based on the results, the tight sandstone reservoir of the Yanchang Formation showed medium to strong velocity sensitivity, medium to weak water sensitivity, nil to weak acid sensitivity, weak alkali sensitivity,and strong pressure sensitivity. The results also gave three critical values:the critical velocity of 1.0 mL/min, the critical salinity of 8 500 mg/L, and critical pH of 8.5. Sensitivity is mainly affected by mineral composition and pore structure. The velocity sensitivity is the result of kaolinite in pores; chlorite/montmorillonite interstratified mineral and illite/montmorillonite interstratified mineral are the main factor causing water sensitivity and salt sensitivity; ankerite and iron-containing chlorite make part of the samples weakly acid sensitive; extremely complicated pore structure, easily compressed flake throat and plastic minerals in samples, such as mica and clay are the main controlling factors on the reservoir pressure sensitivity. The results provides theoretical basis for the subsequent development in the studied area.

Key words: sensitivity, tight sandstone, Yanchang Formation, Shanbei area, Ordos basin