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

APPENDIX 1: TECHNICAL PERSPECTIVES RESOURCE DOCUMENTdegrees. Even small volumes (~1%) of these co-contaminant gases have the potential to alter thechemical response of a gas-brine-rock system (e.g., Knauss et al. 2005a). Understanding purityrequirements will save capital and operating expenses. A focused study of laboratory reactivechemistry and numerical simulations is needed to provide insight into how these gases mightaffect storage effectiveness and additional types of site characterization.M&V design and integrationGiven the natural variation in storage site geology and the uncertain regulatory requirements apriori today, it is difficult to predict the requirements for standard monitoring and verificationsystems. Many geophysical and geochemical methods are sufficiently well understood for themto be used to make reasonable performance predictions at candidate storage sites (e.g., Benson etal. 2004). Testing which of these approaches will be the most valuable for a given geologicalenvironment remains to be determined. It will require that multiple approaches to testing becompared robustly in terms of performance and cost, and validated in the field.Multivariate hydrogeologic and geophysical integration and inversion provides one approach tothis problem. Unfortunately, there are very few examples from industry or CO 2 storageexperiments where multiple data sets have been integrated robustly. Often these techniquesinvolve geostatistical characterization (e.g., Goovaerts 1997; Pawar et al. 2003) that can requirelarge data volumes and produce mixed results. Multivariate inversion is a more difficult problem,with very few successful demonstrations (e.g., Hoversten et al. 2003; Ramirez et al. 2006).Ultimately, addressing this technical need will require that many comparable data sets arecollected simultaneously and inverted in a common platform or framework.Risk assessment methodology and quantitative basisSeveral frameworks have been proposed for geological carbon sequestration risk assessment(e.g., Stenhouse et al. 2006; Saripalli et al. 2003). The most comprehensive published riskassessment work to date comes from Weyburn (Wilson and Monea 2004), which used acombination of long-term simulation with analysis of features, events and processes. A5000 year interval was selected, and the risk metric was CO 2 returned to the biosphere over thattime interval. This choice of risk end state and metric was ultimately not technically based.While simulations and studies generally show that risk should decrease post injection (Figure 6),there is little quantification of what the magnitude, rate, or trajectory of risk reduction is.Ultimately, such a characterization will evolve from probabilistic risk assessments methodologyand a larger empirical data base. Until then, a scientific basis is needed to choose risk end states,select metrics for risk assessment, and develop methodologies that can be regularly applied toconventional data sets.Wellbore integrityThe many wells penetrating oil reservoirs represent a risk of both gradual and catastrophicleakage of CO 2 to the atmosphere (e.g., Gasda et al. 2004; Celia et al. 2006). For reservoirs olderthan 30 or 40 years, locations of old capped wells are a major concern. Incorrectly constructed orabandoned wells increase potential for substantial CO 2 leakage due to elevated likelihood of poorcement, advanced corrosion, or ineffective plugging (Ide et al. 2006). Groundwater can also beaffected by CO 2 leaking from its storage site into shallower aquifers without any surfaceBasic Research Needs for Geosciences: Facilitating 21 st Century Energy Systems Appendix 1 • 19