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

GRAND CHALLENGE: SIMULATION OF MULTISCALE GEOLOGIC SYSTEMS FOR ULTRA-LONG TIMESSIMULATION OF MULTISCALE GEOLOGIC SYSTEMS FOR ULTRA-LONG TIMESABSTRACTOne fundamental gap in the knowledge base for modeling complex processes in the subsurface isaccurate coupling of information across scales, i.e., accurate accounting of small-scale effects onlarger scales, and capturing the effects of fast processes as well as the ultra-slow evolution onvery long time scales. The latter is an unprecedented requirement dictated by the need tosequester materials in the subsurface for hundreds to hundreds of thousands of years—timescales that reach far beyond standard engineering practice. Mathematical and numericalframeworks must capture the stochastic nature of geologic media and the nonlinear dynamicphysical and chemical processes that occur in geologic formations, and must recognize thatsubsurface systems may or may not be in equilibrium. Conceptual model development from thepore scale upward as guided by observations and data from laboratory and field experiments willbe used to define a mathematical framework amenable to computation. Traversing spatial andtemporal scales requires the appropriate mathematical and numerical representations at eachscale and across scales for dynamic processes. Refinement of theoretical and numericalframeworks must also use data integration to calibrate numerical models, validate theorems, andtest multiphysics cross-scale coupling models. Cross-scale modeling of complex, dynamicsubsurface systems requires the development of new computational and numerical methods ofstochastic systems, new multiscale formulations, data integration, improvements in inversetheory, and new methods for optimization. The fundamental importance of heterogeneity on allscales in natural systems suggests that research in this area will have broad scientific impact onsubsurface science. On the technology side, the resulting advanced modeling framework willfind a wide range of applications, from improving the design and optimization of fluid injectionand storage to monitoring programs and risk assessment. The ultimate objective is reliable, longtermpredictions of subsurface processes that span multiple spatial and temporal scales, withsignificant improvement in the quantification of uncertainty.EXECUTIVE SUMMARYSubsurface geologic systems are open systems that participate in the hydrologic, geochemical,biogeochemical and tectonic cycles of the Earth. Storage of anthropogenic waste products,recovery of energy resources, and management of aquifers will perturb these subsurface systems.The anthropogenic perturbations can occur over tens of years, which is a standard time scale forengineering design, prediction, and monitoring. However, regulatory requirements demand thatthe performance of these perturbed systems be predictable for time periods of hundreds of yearsfor CO 2 sequestration, and for up to a million years for nuclear waste isolation. For models toprovide decision-level predictions of such ultra-long-term behavior, an unprecedentedunderstanding is needed of the geologic structure, the processes that occur within the structure,and how the structure and processes evolve over time scales that are very long in comparison tothe relaxation time of normal chemical and hydrological systems.Challenges in modeling geologic systems arise from the large range of scales, both temporal andspatial, that any subsurface site encompasses, and from the coupling of processes on multipleBasic Research Needs for Geosciences: Facilitating 21 st Century Energy Systems 95