Parameters Influencing Porosity in Sandstones: A Model for Sandstone Porosity Prediction: ERRATUM

Abstract

Thirteen parameters were reviewed for their influence on porosity in sandstone core material during compaction. In basins of average geothermal gradients, the first-order parameters are age (time of burial), detrital-quartz content, maximum depth of burial, and sorting. Overpressure may slow the compaction process. Depending on onset of overpressure during burial, approximately 2% primary porosity may be preserved for every 1,000 psi (6.9 MPa) above hydrostatic pressure. Depth-related temperature and median grain size were found to be only second-order parameters. On the basis of 428 cases, function coefficients were calculated for the relationship between porosity and the first-order parameters. This function permits porosity prediction with a high degree of accuracy. Th equation is valid for sandstones older than 3 Ma with little or no cement, no leaching, depth of burial in excess of 500 m, and little or no shear stresses. Secondary porosity is excluded, and estimations will therefore be conservative where leaching occurred. Due to interrelationship of compaction and cementation, the porosity reduction by cement is usually only a small fraction of the total reduction. The function can therefore also be applied to little-cemented sandstones.