Effects of Mineral Composition and Microstructure on Stress-sensitivity of Mudrocks
矿物成分和微结构对泥质岩储层应力敏感性的影响

The mudrocks which are rich in clays have the differences of stress sensitivity,because of the complexity of mineral composition,micro-construction and microporous-structure.This paper carried out a study of stress sensitivity evaluation on clay shale and sandstone reservoirs of Yanchang Group in Ordos basin and compared the differences of stress sensitivity.The results showed that: shale has a strong stress sensitivity; silty sandstone has a medium-partial strong stress sensitivity; tight sandstone has a weak stress sensitivity; under the effective stress of 30MPa,the rock presents plastic deformation.Rock deformation is mainly affected by the composition of rock,cementing type and content,micro-fracture system,pore structure parameters,morphology contacting way and distribution of the particles,and clay mineral content and microstructure.The stress sensitivity differences of the three rocks reflect the influence of the composition and microstructure of mineral rock on stress sensitivity.Therefore,for different lithologic reservoirs,reasonable production pressure difference should be adopted to avoid the occurrence of reservoir stress sensitivity damage.