Fault zone hydrogeology: introduction to the special issue

The impacts of fault zones on fluid flow within the Earth’s crust are notoriously difficult to characterize. Over the last several decades, structural geologists, petroleum engineers and hydrogeologists have investigated fault zones with the
objective of understanding what factors and processes control fault zone hydraulic properties. Often these groups of researchers do not work together. One goal of this thematic issue is to highlight different investigation techniques
(e.g. Bense et al. 2013) developed in one field that could be transferred into another discipline potentially shedding new light on long-standing research questions. This becomes especially significant when considering multiphase
flow processes in faults such as in the context of CO2 storage or hydrocarbon production. A synergistic approach to fault zone hydrology research should narrow the gap in approaches and perceptions that exist across various
research disciplines involved in the study of fault zone hydraulic properties. This special issue of Geofluids highlights ongoing work that jointly considers geological and hydrogeological aspects of fault zone properties.