Study on stress sensitivity anisotropy of continental tight reservoirs in China plays an important role in evaluation of reservoir damage during the exploitation of low permeability oilfield.In view of the practical problems

the X

Y and Z columns from three inter-perpendicular orientation of three typical samples from Chang-6 reservoir in Ansai oilfield of Ordos Basin are used to test permeability by changing confining pressure under the in-situ condition and study the relationship between permeability and effective stress.In addition

microscopic mechanism and anisotropy of stress sensitivity in tight oil and gas reservoirs are analyzed through integrating various data including casting thin sections

scanning electron microscopy and XRD

etc.The results demonstrate that stress sensitivities of different rock samples are different and stress sensitivities of the same rock sample are also quite different in different directions.The ranking of stress sensitivity index from strong to weak is fine-grained lithic feldspathic sandstone

feldspar lithic quartz siltstone and medium to fine-grained lithic feldspathic sandstone

and the ranking of anisotropy coefficient from strong to weak is feldspar lithic quartz siltstone

medium to fine-grained lithic feldspathic sandstone and fine-grained lithic feldspathic sandstone.Microscopic experiments indicate that mineral composition

the arrangement and pore structure characteristics of different types of reservoir are key factors to cause reservoir stress sensitivity anisotropy.Therefore

stress sensitivity anisotropies are quite different in different types of tight reservoirs

and the microscopic heterogeneity characteristics of reservoirs are the major factors influencing stress sensitivity and anisotropy.This understanding is of great significance to highly-efficient exploitation of the continental heterogeneous tight reservoirs in Ordos Basin.