Effects of the Detrital Composition and Early Carbonate Cementation on Porosity Loss in Sandstones: An Integrated Petrographic and Experimental Approach

Abstract

ABSTRACT In general, sands at the time of deposition present initial porosity around 40-55%. This primary porosity is reduced by mechanical compaction and/or cementation with increasing burial. The intensity of the mechanical compaction is a function of detrital mineralogy and grain shape (BENSON, 1981) 1 This paper deals with the relationship among detrital composition, carbonate cement and porosity loss by mechanical compaction. Statistical analysis from petrophysical data, systematic petrography and experimental analysis were done with sandstones, with variable amounts of ductile grains and carbonate cement. This study showed that porosity and permeability reduction were more effective in sandstones which present greater amounts of ductile grains. However, petrographic evidences demostrated that early diagenetic process, such as carbonate cementation, can support the mechanically unstable lithoclasts against increasing overburden, preserving the potential porosity and permeability.