Contemporary methods of energy conversion that reduce carbon intensity and address the energy transition draw heavily on fluids in the subsurface. This includes sequestering CO2, fuel switching to lower-carbon sources, such as from abundant gas shales, recovering deep geothermal energy via EGS, and diurnal and inter-seasonal storage of heat, H2 and energized fluids (CAES). In all of these endeavors, either maintaining the low permeability and integrity of caprocks or controlling the growth of permeability in initially very-low-permeability shales or geothermal reservoirs represent key desires. Injected volumes are necessarily enormous, anticipated overpressures large and the potential for hazardous triggered seismicity significant. We explore conditions controlling the linked evolution of seismicity and permeability in particular with respect to the (i) scaling of seismicity, (ii) controls on permeability evolution and the (iii) potential to recover permeability evolution from physics-based models of microearthquakes linked to permeability evolution.