They develop better vugs and fractures that are relatively important for flow and storage of fluids. Carbonate reservoirs are also harder and tighter than sandstone reservoirs (Renpu 9). Primary porosity of sandstone reservoirs is exclusively interparticle while that of carbonate reservoirs can either be intraparticle, interparticle, intercrystalline, vuggy, fenestral or cavernous. Porosity-permeability relationships of sandstones are relatively consistent and dependent on particle texture while that of carbonate reservoirs are highly varied and independent of particle size (Ahr 53).
Shale reservoirs differ from sandstone reservoirs in that shale reservoirs can contain organic mudstones which are not present in sandstone reservoirs. They can also have open fractures which are not common in sandstone reservoirs. Conglomerate reservoirs differ from sandstone reservoirs in that conglomerate reservoirs exhibit an extra-high heterogeneity as a result of a complex pore structure. They also display rapid changes in permeability and porosity between their layers which is not the case with sandstone reservoirs (Zou 298).
Advantages of Sandstone Reservoirs
Porosity of sandstone reservoirs is uniform over time since it does not diminish with increasing saturation of the reservoir. Chemical processes do not affect the permeability and porosity of sandstone reservoirs. Effects and of micro and macro organisms do not impede fluid transfer through sandstone reservoirs as can be the case with carbonate reservoirs (Renpu 11). ...