EVOLUTION OF UNDERSTANDING OF FLUID FLOW IN TECTONIC ENVIRONMENTS; PERSPECTIVES FROM INTEGRATED HYDROGEOLOGIC AND STRUCTURAL STUDIES

Perhaps the highest impact of Craig Forster’s work lay in the field of hydrogeologic analyses of the interaction of fluid flow, faults and fractures. Derived from numerical modeling of flow in mountainous terrain, Forster and students developed an approach that has impacted analyses of groundwater and geothermal resources, ore deposits, oil and gas exploitation, CO₂ sequestration, and understanding tectonic processes. Forster’s scientific success is attributed to four factors that characterize the approach: 1] Scientific rigor and clarity of thought in approaching a problem, 2] willingness to listen to ideas and engage workers from a wide field of interests, 3] willingness and excitement to cross disciplinary boundaries, and 4] a humane approach of supporting others, often at the sacrifice of his own career and time. The fundamental insights into how fluids and fracture zones interact with fluids and heat stem from two concepts: 1] Any structural element is embedded in a fluid flow regime, governed by its fluid and thermal potential field, just as stress potentials drive deformation and 2] We can and should quantify the flow properties of rock at the scale and resolution required by numerical models. Early 2D analyses incorporated realistic fault geometries and fault structure that incorporate the protolith-damage zone-core model, and indicated that large fluid, heat and solute fluxes may occur in the damage zones. These results are borne out by geochemical and structural studies. Recent work that evaluates flow in sedimentary rocks expands these concepts and establishes the importance of determination of the spatial variations and uncertainties of flow properties in rocks. We review a series of studies that examine these concepts as well as consider the next steps for scientists. Given the scale and nature of problems facing society, we consider how to follow on Forster’s efforts to integrate our science with the policy and decision-making realms.