Figure 6

An illustration of a two-dimensional fracture network model with fractures that intersect in a pattern of fractal-style recursion to generate a pitchfork fracture network. Random fluid injection/extraction wells are located at the red dots. The color bar represents permeability on a logarithmic scale. \({\textbf{b}}\) encodes Neumann boundary conditions (sparse nonzero entries) for a \(64 \times 64\) grid with \(2^{n_b}=4096\) cells \(\Rightarrow {n_b}=12\). Nonzero entries in \({\textbf{b}}\) correspond to well sites.