Sandstone act as reservoir rocks because these rocks have sufficient porosity and permeability. Sandstone is formed by the sand-sized particle whose grain size ranges from 62 to 2mm. When it came to sandstone composition, there are no specific requirements; it can be composed of quartz, feldspar, and rock fragments. But all of these grains have the same size (62μm to 2mm).
Sandstone is one of the significant types of sedimentary rocks formed by weathering pre-existing rocks, transported through different transporting agents such as wind, water, or ice, and finally deposited.
A combination of porosity ad permeability that’s makes a sandstone a reservoir rock. One interesting point is that the more sandy a sandstone is (more minor impurity), the more they act as a reservoir rock.
The texture of sandstone also plays a critical role in the sandstone reservoir. For a Good sandstone reservoir, the surface of sandstone should not be dominated by the cement (The material that bonds together grains) and matrix (more acceptable material whose size is less than sand within the pore spaces), which later decrease the porosity and permeability. Another critical point for the excellent sandstone reservoir is that sandstone should be composed of durable and rugged components and should be completely free from those grains formed from deformation or decomposition.
So the quality of sandstone is controlled by the supply/source area, different processes during deposition, and finally, the environment in which deposition occurs.
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