The effects of opening-mode-fracture and fault systems on subsurface fluid migration depend on the aggregate characteristics of the fractures, including fracture size, openness, connectivity, and spatial arrangement along and across stratigraphy. Such characteristics can vary widely, depending on mechanical properties of the host material, the history of applied stresses, the fluid chemical environment, and the presence of pre-existing fractures or other rock-fabric features during fracture growth. Moreover, characterisation of fractured and faulted reservoirs is hindered by various sources of uncertainty. We seek contributions from all geological and geophysical fields describing fracture populations, modeling how fractures grow and interact to enhance or inhibit subsurface fluid migration, and illustrating how uncertainty in fractured reservoirs can be addressed.