Abstract

Recognition of pore types in sandstones is important because primary porosity is indicative of depositional framework, whereas secondary porosity is suggestive of diagenetic framework. A classification of porosity in sandstones is proposed in which two basic types of primary pores (intergranular and intragranular) and four basic types of secondary pores (intergranular, intragranular, grain fracture, and rock fracture; can be differentiated on the basis of (1) position of pores, (2) timing of origin, and (3) processes of origin. The proposed classification is useful in inferring reservoir quality.

As sandstone composition may ultimately be controlled by the dissolution of unstable framework grains such as feldspar, chert, and other rock fragments, it is imperative to estimate the amount of grain dissolution in determining the original composition. Failure to recognize the original composition of sandstones will lead to incorrect interpretation of provenance and paleogeography.