Emerging Issues in Fractured-Rock Flow and Transport Investigations: Introduction and Overview

Field, laboratory, and modeling studies of fractured rock have generated great interest from both fundamental and applied perspectives. Many practical applications of these studies are crucial for the exploitation of petroleum and geothermal reservoirs, the safe environmental management of groundwater, the isolation of radioactive waste in under­ ground repositories, cleanup technologies for other sorts of toxic waste, and site characterization and monitoring. Fluid flow through rock fractures is also important in studying numerous geological processes and geotechnical applica­ tions [Aydin, 2000; Menand and Tait, 2001], as well as hydrocarbon [Nelson, 2001] and geothermal reservoirs [O 'Sullivan et al, 2001]. Most of the sites tentatively chosen for underground radioactive waste repositories are located in fractured rock [Bodvarsson etal, 1999; Witherspoon, 2004]. Over the last three to four decades, a great deal of research in fractured rock hydrogeology has been carried out [Bear et al., 1993; National Research Council, 1996; Faybishenko et al. 2000b; Evans et al, 2001]. A comprehensive review of recent trends in quantifying flow and transport through frac­ tured rock has recently been given by de Marsily [2000] and Neuman [2005]. Despite a number of field studies [Nativ et al, 1995; Faybishenko et al, 2000a] and laboratory studies [Nicholl et al, 1993; Glass et al, 2001] concerning the spatial and temporal instabilities of flow in unsaturated media, the physics explaining these phenomena is not completely known. It is also unclear how to optimize related laboratoryand field-scale investigations, or how to explain some paradoxes