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

GRAND CHALLENGE: SIMULATION OF MULTISCALE GEOLOGIC SYSTEMS FOR ULTRA-LONG TIMESCourtesy of Sally Benson and Curt Oldenburg, Lawrence Berkeley National LaboratoryFigure 37. Processes affecting geologic CO 2 storage and monitoring occur over a wide range of length scales, fromsubpore scale to reservoir and basin scale. Aggregated pore-scale processes can give rise to larger-scale emergentphenomena. Well-known examples include the upward rise of CO 2 plumes by buoyancy forces, and residual phasetrapping as water imbibes into a mobile CO 2 plume. The ability to predict emergent processes over the full range oflength and time scales using seamless modeling frameworks remains a fundamental scientific challenge.Processes occurring at interfaces between fluids and between fluids and solids are fundamentalto multiphase flow and reactive transport in geologic systems (Figure 37). While some interfacialphenomena are understood, local couplings of interfacial phenomena with flow are less wellknown. Linkages between interfacial phenomena and flow as scales increase are hard todemonstrate. Consequently, the understanding of how behavior at one scale affects behavior atboth larger and smaller scales remains one of the most difficult challenges.A grand challenge for multiphase flow in the subsurface is a mathematical description ofbehavior that is self-consistent across many length and time scales. A familiar example is theproblem of relating the Navier-Stokes description of flow at the pore scale to the Darcy’s lawdescription at the core-to-reservoir scale. Introducing multiple fluid phases greatly increases thedifficulty because capillary forces must then be accounted for. An indication of the inadequacyof the art is that continuum descriptions still routinely use an empirical modification to Darcy’slaw parameterized only by the volume fraction of the fluid phases. Efforts to place multiphaseflow on a more rigorous foundation have begun, but much work is needed to develop these to thelevel where reliable macroscale predictions can be made. Intensifying the challenge still furtheris the effect of heterogeneous properties across a wide range of length scales. Variation in98 Basic Research Needs for Geosciences: Facilitating 21 st Century Energy Systems