The porosity of a reservoir rock is best described by the size, shape, and arrangement of the pores comprising this porosity, rather than in terms of gross per cent. It is as important for a petroleum geologist to be able to predict the probable producing characteristics of a reservoir rock as it is for him to know the precise location of a new reservoir. With this in mind, a textural classification of reservoir rocks has been devised to assist well-site geologists in differentiating producing from non-producing zones in a reservoir body. The classification is based on an empiric association between rock textures as viewed on a polished surface and producing characteristics as determined by capillary pressure, porosity, and permeability measurements.

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