REGIONAL GROUNDWATER FLOW AND ENERGY RESOURCES: NEW CHALLENGES IN CONTINENTAL SHELVES

Deep regional groundwater flow systems influence energy resources through the transport of heat and solutes, water-rock chemical interactions, pressure gradients, and capillary forces. Numerical models have proven to be important tools for data interpretation and hypothesis testing in these deep flow systems. Such models show that hydraulic and density gradients should drive pervasive flow to great depths throughout sedimentary basins, and it is now possible to create calibrated models of deep regional flow and transport in well-studied systems like the Alberta Basin, Canada. The ability of numerical models to estimate flow and transport rates depends heavily on knowledge of the stratigraphy and permeability structures of deep sedimentary basins, however, and this information is typically unavailable for basins that have not already been heavily developed for energy resources. Thus, as we push the frontiers of both energy- and water-resource production, numerical models become increasingly uncertain. Continental shelves represent an important frontier in this respect. Modern continental shelves, slopes and rises hold 80% of the sediments in the world, and fluid flow in these systems is of significant interest for petroleum resources, gas hydrates, CO₂ sequestration and submarine groundwater discharge (SGD). Continental shelves also host an estimated 500,000 km³ of freshwater sequestered in unconventional aquifers offshore, which represents a potential resource for coastal megacities whose only alternative may be desalination of seawater. Over the last decade, models for groundwater flow in continental shelves have focused primarily on specific aspects of large-scale flow systems, rather than the whole. It is critical that we begin to develop more comprehensive models of groundwater flow in offshore settings, where these models can be used to guide future exploration plans and, given better data availability, balance the possible interactions between offshore energy- and water-resource production.