Method for volumetric grid generation in a domain with heterogeneous material properties

Method for generating a 3D grid, and for defining a material property model on the grid, to use, for example, in a reservoir simulator. A mapping is defined (61, 71) to a design space in which the material property is described as a piecewise smooth implicit or explicit function in three dimensions. Grid geometry is constructed only in the physical space of the model (62-65, 73-76), and no grid is required in the design space. The material property, for example permeability, is sampled in the design space (66, 77) to populate the cells in the grid constructed in the physical domain. Prismatic grid cells may be truncated based on faults and horizons (65), or maybe conformed to fault surfaces using a 3D parameterization of the model (76). Only forward mapping, i.e. from the physical domain to the design space, is required.