Energies, Vol. 11, Pages 3133: Growth Mechanism of Siliceous Cement in Tight Sandstone and Its Influence on Reservoir Physical Properties (Energies)

To investigate the effect of siliceous cementation on the densification of sandstone and the forming process of tight sandstone, based on cathodoluminescence, scanning electron microscopy and thin section analysis, the growth mechanism and characteristics of quartz particles in tight sandstone formations are explored. Meanwhile, combined with conventional core analysis and X-ray diffraction experiments, the factors affecting the crystallization of quartz particles, including the chlorite content, grain size and clay mineral, are analyzed, respectively. The entire siliceous cementation is divided into two processes. The first part is the process in which the weathered and rounded particles in the formation are restored to the hexagonal dipyramid crystal by siliceous cementation. The second part is the process of coaxial growth that the hexagonal dipyramid crystal continues to increase with the form of micro-quartz film. As siliceous cements continue to increase, the petrological characteristics of sandstones are constantly changing. The tight sandstone developed in the study area is composed of lithic sandstone and quartz lithic sandstone. Based on the analysis results, 2D and 3D evolution models are established for densification of two different lithic sandstones. When the content of siliceous cement in the study area is less than 17%, the porosity of tight sandstone increases with the increase of cement. When the content of cement is more than 17%, the porosity of tight sandstone is negatively correlated with the content of cement. When the cement content is greater than 10%, the reservoir permeability is negatively correlated with it. Furthermore, the particle size mainly affects the permeability of reservoir, and the particle size is negatively correlated with the permeability of tight sandstone. The most high-quality tight sandstone reservoir in the study area is in the first cementation stage when siliceous cements are distributed in porphyritic texture with the content of 10–15% and a grain size of 0.2–0.3 mm. In addition, the relatively high-quality reservoir is the one developing clay mineral film with a content of cementation about 5–12%.