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

APPENDIX 1: TECHNICAL PERSPECTIVES RESOURCE DOCUMENTand Australia (Allis et al. 2001; Czernichowski-Lauriol et al. 2002; Watson et al. 2004). In theseregions, accumulations have held large volumes of CO 2 for tens of millions of years. Thesesystems show evidence of CO 2 leaks through fault networks, natural CO 2 springs, and evidenceof fossil leakage (e.g., Shipton et al. 2005) but apparent cap-rock fractures have been sealedthrough mineral precipitation and porosity reduction (Wilson and Monea 2004). Ultimately,these are either time-integrated or steady-state systems, and as such, information concerning thephysical and chemical transients related to CO 2 storage can only be inferred from these systems.Large uncertainties remain in the behavior of coal exposed to CO 2 . Many experiments haveproduced coal adsorption isotherms, which underlie estimates of enhanced coal bed methanepotential. However, most experiments have used powdered coals instead of continuous plugs,and have only preliminarily characterized the physical and chemical response to gas exchange.For example, CO 2 adsorption causes coals to swell, which in turn reduces permeability withincleats (coal fractures) and micropores (e.g., Reeves et al. 2003). This in turn affects totalinjectivity, capacity, and economic potential. Some workers also theorize or observe structuralchanges in the coal matrix, plasticization, which reduces transmissivity, and adsorption (e.g.,Larsen 2004). These uncertainties present challenges to operations, prediction, and simulation ofcoal-CO 2 systems.Current evaluations for risk estimation must be based on present understanding of trappingmechanisms through experimentation, analog analysis, and simulation. Specifically, it isestimated that more than 99.9% of injected CO 2 can be reliably stored over 100 years, and it islikely that 99% of CO 2 can be reliably stored for 1000 years (Benson and Cook 2005). Whilethese estimates are predicated on the assumption of careful siting and due diligence beforeinjection, it reflects the view that the crust contains sites that are generally well configured tostore CO 2 effectively.Other potential geological target classes have been proposed and discussed by various workers.These include oil shales, flood basalts, and salt domes (Figure 2). They will require substantialscientific inquiry and verification before commercial deployment because the storagemechanisms are less well tested and understood and there is much less commercial technology orexperience for the tasks of simulation, monitoring, verification, and risk assessment (see below).Monitoring and verification (M&V)Once injection begins, a program for monitoring and verification of CO 2 distributions will berequired. Scientific objectives in the short term will require such monitoring to understandtrapping mechanisms, validate previous simulations and their predictions, and to discover newand important local features, events and processes. Longer term monitoring and verification willserve additional technical, regulatory, and economic needs:• Provide constraints for probabilistic risk assessments• Manage the injection process• Delineate and identify leakage risk and surface escape pathways• Provide early warnings of failure near the wellbore or above the reservoir• Provide assurances to insurers and investors in geological carbon sequestration operations• Verify storage for accounting and creditingAppendix 1 • 12Basic Research Needs for Geosciences: Facilitating 21 st Century Energy Systems