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

PRIORITY RESEARCH DIRECTION: TRANSPORT PROPERTIES AND IN SITU CHARACTERIZATIONOF FLUID TRAPPING, ISOLATION, AND IMMOBILIZATIONPrediction of the distribution and efficiency of in situ trapping processesCurrent geophysical techniques are moderately successful at detecting the presence of fluidswithin a reservoir, but are less capable of reliably determining the volume fraction of gas andliquid. The ability to remotely detect the changes that occur in rocks as mineralization occurswould add substantially to our understanding of many natural processes that occur within theEarth. Experiments are needed to understand the chemistry of CO 2 phases and mineralization,the geophysical signatures, and the possible impacts of biological processes that may be used toobserve the progress of mineralization. High-confidence detection of relevant trappingmechanisms within a given storage site, and the spatial and temporal variations of thesemechanisms, will allow for better management of the repository and for confirmation that thefluid has been successfully sequestered. Such detection must be done without physicalpenetration of the repository so that no new potential leak paths are created. This means thatsome geophysical (e.g., remote sensing) approach must be employed. To achieve the requiredlevel of detailed information will require major advances in our ability to both characterize theearth’s subsurface in addition to our ability to interpret spatial-temporal changes detected fromremote sensing.RESEARCH APPROACHESSedimentological process models can be a powerful tool in predicting the continuity of sealingstrata and efficiently developing an approach that verifies this assessment. Seal thickness may bea poor proxy for estimating the quality of a seal. Linking of depositional characteristics—such asbedding thickness with diagenetic effects, compaction or cementation, tectonic and burialhistories with information on stress states—will provide better information on the effectivenessof the seal as a barrier to the migration of injected fluids.Laboratory measurements and simulations are needed that provide new concepts and methodsthat link large-scale multiphase flow and reactive transport behavior to interfacial properties ofmulticomponent fluid-solid systems. Studies of the impacts of dissolution-precipitation reactionsand possible microbial communities on interfacial properties are critically needed. Impacts ofmolecular-scale interfacial mass transport processes, such as removal of interlayer water inswelling clays into supercritical CO 2 , are needed to better predict the impacts of clay desiccationon the capillary properties of originally impermeable intervals.Laboratory experiments can be carried out using physical models that investigate trapping andisolation mechanisms simultaneously with use of characterization methods, so that relevantgeophysical signatures of trapping can be investigated. Such experiments may include thesimultaneous use of neutron scattering and acoustic measurements of rocks undergoingmineralization to investigate the relation between mineralization/cementing within pores andobservable geophysical parameters. Other spectroscopic approaches for detailed characterizationof changes induced within rocks may provide valuable information to help understand trappingmechanisms and their remote detection with geophysical techniques.Fundamental research is needed on propagation, scattering, nonlinear effects, and attenuation ofcontinuous and pulsed waveforms in geological media over a wide range of electromagnetic andacoustic frequencies and amplitudes. The objective is to be able to locate and resolve fault andBasic Research Needs for Geosciences: Facilitating 21 st Century Energy Systems 135