Basic Research Needs for Geosciences - Energetics Meetings and ...

PRIORITY RESEARCH DIRECTION:DYNAMIC IMAGING OF FLOW AND TRANSPORTFigure 39. (a) Temperature distribution over time (vertically) and space (horizontally). (b) Amount of waterflowing through the stream with the gains from the different sources and the losses as inferred from the temperatureprofiles and the up- and downstream v-notch measurements. (c) Average temperature over time with sunny daysearly on and cloudy days toward the end of the measurement period. From Selker, J., van de Giesen, N., Westhoff,M., Luxemburg, W., and Parlange, M.B. (2006). Fiber optics opens window on stream dynamics. GeophysicalResearch Letters 33, L24401. Copyright © 2006 American Geophysical Union. Reproduced by permission.Smart tracers may be developed to interrogate the biogeochemical reactivity, and physical orbiological properties of formations. Tracer injections are conventionally used in subsurfacescience to track flow paths, and the ideal tracer for this purpose is nonreactive. Solutes withknown reactivity could be used in addition to nonreactive tracers to acquire already upscaledmeasurements of reaction coefficients. Tracers could be designed to characterize small-scalemixing processes, quantify different phases, and measure the chemical and biologicalcharacteristics of formations that control chemical transformations.Development of some smart tracers has already begun. Partitioning tracers that preferentiallydissolve into oil are used to quantify remaining oil saturation in oil-bearing formations, andsurfactants can quantify the interfacial area between phases. Conservative tracers with differentdiffusion coefficients can be used to quantify the role of diffusion and transfer between regionsof high and low fluid velocity. Tracers can potentially be used to enhance the response toprobing geophysical fields.The opportunity now exists to develop new tracers that target the geochemical characteristics ofa formation where chemical transformations and retardation occur. First, simple reactive solutescan be used to quantify the small-scale mixing process that drives complex geochemicalreactions. By using well-understood and easily measured reactants, descriptions of small-scalemixing processes can be derived that are specific to a given formation. These empirically basedmodels of chemical mixing and segregation would greatly improve our ability to model muchmore complex geochemical transformations. Second, reactants can be designed to target126 Basic Research Needs for Geosciences: Facilitating 21 st Century Energy Systems