Although unconventional resources contributed almost no production in the early 1970s, they now provide almost 30% of US domestic natural gas supply. Unconventional reservoirs have a complex lithology with heterogeneous porosity, complex fluids, or both. Ultimate recovery is typically lower than from conventional reservoirs, so effective exploitation requires more wells to drain the resource effectively. Excluding product price, capital expenditures are a critical factor in the economics and have driven a development culture focused on cost, in the absence of technology that provides a clear cost benefit to increased production and/or recovery. However, the exponential growth of production from unconventional reservoirs has not been accompanied by comparable growth in the knowledge and understanding of the rock properties and completion parameters controlling production.