"The study of natural fractures can be viewed as a progression from basic qualitative observation, to detailed measurement, to analysis of the collected measurements, to use of the analyses and collected data. Early fracture studies focused on understanding the deformation of rock as recorded by the development of fractures, but since the middle of the 20th century fractures have also been recognized as important controls on fluid flow in fractured media, including hydrocarbon reservoirs. Early fracture data-collection and analyses techniques, developed for structural purposes, were not always applicable to the later purposes of understanding fluid flow"-- |