1. A method of evaluating fracture abundance in a subsurface formation, the method comprising: defining a fracture network within a plurality of cells of a three-dimensional model of the subsurface formation using a plurality of geometric primitives; determining an area of the plurality of geometric primitives within at least a subset of the plurality of cells by summing areas of individual geometric primitives within each of the subset of cells; and determining a fracture abundance parameter for the fracture network from the determined area of the plurality of geometric primitives.