(n.) Shale Gas, Geology. A crack or surface of breakage within rock not related to foliation or cleavage in metamorphic rock along which there has been no movement. A fracturealong which there has been displacement is a fault. When walls of a fracture have moved only normal to each other, the fracture is called a joint. Fractures can enhance permeability of rocks greatly by connecting pores together, and for that reason, fractures are induced mechanically in some reservoirs in order to boost hydrocarbon flow. Fractures may also be referred to as natural fractures to distinguish them from fractures induced as part of a reservoir stimulation or drilling operation. In some shalereservoirs, natural fractures improve production by enhancing effective permeability. In other cases, natural fractures can complicate reservoir stimulation. See: Competent, Dilatancy, En Echelon, Fracture Gradient, Halite, Incompetent, Permeability, Pore, S-Wave, Strain, Structure.