Experimental Study of the Porosity and Permeability of Clastic Sediments

Abstract

The purpose of this study is threefold: to experimentally evaluate the factors controlling the porosity and permeability of ideal clastic materials; to determine the modifications produced in natural deposits by variations from the ideal; to apply the principles of permeability to the problem of the distribution and localization of mineral deposits in clastic sediments. The effect on porosity of absolute grain-size, variable grain-size, shape of grain, method of deposition, and compaction are experimentally determined for ideal materials and compared with those of river and beach sands and other clastic sediments. Various equations for permeability are discussed; and the controlling factors of temperature, hydraulic gradient, size and shape of grain, uniformity of grain-size, porosity, and stratification are experimentally evaluated for ideal materials, and the modifications caused by natural materials are delimited and discussed. Field observations on the effects of wave and river depositional processes on porosity and permeability are presented. Comparisons are made of the relative permeability of gravel, sand, clay, loess, till, and unsorted alluvium. Changes produced in the original porosity and permeability of clastic sediments by the metamorphic processes of compaction, cementation, and recrystallization are outlined. Finally, the principles governing the flow of fluids through unconsolidated clastic materials are applied to the flow of hydrothermal solutions through rocks of clastic origin in an attempt to use the principles of permeability to explain and predict the distribution and localization therein of hydrothermal mineral deposits.