Geomechanical Models for Clastic Grain Packing

Abstract

This study proposes a classification of sphere models for grain packing types of coarse grained clastic soft and hard rocks with special emphasis on Permocarboniferous red-beds. The classification covers the range of principal packing types and different cements. Random sphere packing models are derived from ideal symmetric packing models. The study comprises both homogeneous models with equal single grain properties and heterogeneous models with different single grain properties. For each packing type geomechanically relevant parameters like the packing density or coordination numbers are calculated and discussed. The models are correlated with results of image analysing and standard rock engineering experiments that were carried out on a variety of grain mixtures and sedimentary rocks of Permocarboniferous age. The discussion is concerned with the principles of grain packing models and the particular effects of distinct packing types on the petrophysical rock properties and the geomechanical behaviour of the examples presented.