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; (b) obtaining a 3D image of the rock sample; (c) segmenting the 3D image into at least two compositional classes where the regions within each class have similar properties; (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 (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 to reduce mismatch between effective material property values predicted by the model and effective material property values computed numerically from the local properties volume.