1. A method for developing a model for hydrocarbon exploration of at least one effective material property of a subsurface reservoir as a function of the reservoir's rock composition and structure, comprising: (a) obtaining a rock sample characteristic of compositional classes existing in the reservoir rock, wherein the rock sample is a core plug or other sample of size equal to or less than a 1 inch diameter by 2 inches long cylinder; (b) obtaining a 3D image of the rock sample; (c) segmenting the 3D image into at least two compositional classes where regions within each class have similar properties, and wherein the compositional classes are classes of inclusions and voids; (d) creating for the rock sample a local properties data volume partitioning the sample into discrete cells, and specifying a value of a selected material property at each cell; (e) choosing a mathematical form of a model relating effective, or bulk, value of the selected material property to volume fractions of the compositional classes; and (f) determining all unknown parameters of the model by adjusting them, using a computer, to reduce mismatch between effective material property values predicted by the model and effective material property values computed numerically from the local properties volume.