1. A method of evaluating fracture abundance in a subsurface formation, the method comprising, using one or more hardware-based processors: 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, wherein determining the area of the plurality of geometric primitives within the subset of the plurality of cells further includes: organizing the plurality of geometric primitives within a spatially-organized data structure; and accessing the spatially-organized data structure when summing areas of individual geometric primitives within each of the subset of cells to determine which of the plurality of geometric primitives are at least partially 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.