Abstract: Induced and triggered seismicity has become a major hazard in geo-energy projects in the deep subsurface – inclusive of the recovery of deep geothermal energy and hydrocarbons from unconventional reservoirs and in the safe subsurface disposal of wastewater and CO2. In particular, where fluids are to be recovered from low permeability reservoirs, it is important to find a Goldilocks zone…. where brittle rupture must occur to generate permeable fluid pathways but must not be too large to result in project-terminating seismicity. We discuss controls on seismicity-permeability in this context.