Abstract: In this study, the main purpose is to evaluate porosity, mineral composition, microstructure and mechanical characteristics and their relations for tight gas reservoirs in Da Qing. Therefore, Porosity, XRD, thin section observations and triaxial compress experiments are carried out for 18 specimens. Values of porosity, mineralogical compositions, microstructure (cementation type,contact relation, interstitial fillings, grain size and sorting features), mechanical properties (full stress-strain curve, elasticity modulus, triaxial peak strength, triaxial residual strength, drop amplitude of stress-strain curve, Poisson’s ratio, Peak strain, elasticity strain and fracture diagram) are obtained. The above factors are then analyzed synthetically, it is revealed the relations of mechanical properties and material factors. 1) lower porosity and clay content, larger grain size, higher quartz and calcite content, the elasticity modulus and triaxial comprehensive strength are higher. 2) Poisson’s ratio is increasing obviously with the increase of orthoclase and anorthose content. 3) With the decrease of porosity and increase of grain size and the content of quartz and calcite, the drop amplitude of stress-strain curve (DROP) is increasing obviously. 4) The peak and recoverable strain are both increasing with the increase of porosity, the content of orthose and anorthose. The test results and regularities supply the basis in earth science, well completion and stimulation.
Keywords: Tight gas reservoir, mechanical characteristics, mineral composition, porosity, microstructure, grain size
