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

PANEL REPORT: MULTIPHASE FLUID TRANSPORT IN GEOLOGIC MEDIAproduces about 5 million metric tons, or megatons (Mt), of CO 2 per year, which means hundredsto several thousand zero-emission power plants must be brought on line over the next decades.Currently the U.S. has 1,552 coal-fueled power plants (336,000 MW) and 5,467 natural gas-firedpower plants (437,000 MW) (Energy Information Administration 2006)Carbon dioxide, perhaps with other combustion products like oxides of sulfur and nitrogen (SO xand NO x ), persists as a separate fluid phase when injected into deep subsurface formations,thereby leading to a multiphase flow problem. However, this problem is now driven by fluidbeing injected, rather than extracted as it is for oil production. While CO 2 has been injected intodepleted oil reservoirs for about 30 years, and a relatively mature infrastructure exists in placeslike West Texas, the amount injected to run all of the enhanced oil recovery operations in thisregion is about 20 Mt/yr of CO 2 , which corresponds to emissions from about three large powerplants. Direct experience with megaton-scale CO 2 storage, not involving enhanced oil recovery,is limited to two commercial-scale projects, one in the North Sea and one in Algeria (see sidebaron Current CO 2 storage projects: The Sleipner and In Salah projects). Solution of the carbonproblem will require a much larger effort.BASIC SCIENCE CHALLENGES, OPPORTUNITIES AND RESEARCH NEEDSWhile scientists have studied subsurface multiphase fluid systems for many decades, andimportant scientific challenges remain, the carbon problem introduces fundamentally newscientific challenges that must be addressed to provide the proper foundation for meeting criticaltechnical needs. The enormous scale of the carbon problem, the fact that a variety of geologicmedia will need to be used, and the fact that the flow system will fundamentally be driven byoverpressurization (injection) rather than underpressurization (extraction), all lead to challengesthat require fundamental scientific inquiry. The importance of the carbon problem and its newchallenges leads to a new set of basic science questions, and to associated research opportunities.We highlight five important research areas.Emergent behavior in multiphase systems due to physical and chemicalheterogeneity from the pore scale to basin scaleModeling subsurface systems is a formidable task because of the wide disparity in length scalesranging from pore to basin. Furthermore, many of the fluid phases are composed of multiplecomponents; for example, crude oil has hundreds of different components. Research approachesto analyze this highly complex problem require new conceptual and theoretical models ofmultiscale, multiphase, and multicomponent processes, with their numerical implementationultimately involving high-performance computing and model validation with corroboratinglaboratory and field experiments. Theoretical models range from pore-scale models that can beapproached by existing descriptions, e.g., Navier-Stokes equations and their solution throughtechniques like lattice Boltzmann methods, pore-scale network models, Darcy-scale continuummodels, and larger-scale continuum models based in part on stochastic theories (for example,Reeves and Celia 1996; Oren et al. 1998; Prodanovic and Bryant 2006). Development of theoriesto bridge this wide range of scales is still in its infancy. The enormity of the CO 2 problem and itsimpacts up to the basin scale make the issue of proper mathematical representation of processesand phenomena across disparate scales an important grand challenge. Four outstandingchallenges are identified as follows.10 Basic Research Needs for Geosciences: Facilitating 21 st Century Energy Systems