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

PANEL REPORT: MULTIPHASE FLUID TRANSPORT IN GEOLOGIC MEDIApoints or flaws in these seals are poor to nonexistent. Especially challenging is the need to assesssmall features (fractures, sand-on-sand contacts) at the millimeter to the few-meter scale, whenthe total area of interest covers hundreds of square kilometers. Regions of heterogeneouspermeability need to be identified. Even regions of slow leakage will need to be monitored overtime.Dynamic imaging for complex multiphase systemsThe resolution of subsurface imaging methods must improve dramatically before we can trackmultiphase fluid movement and behavior in situ. Quantitative imaging of four-dimensional (threespace dimensions plus time) variations in quantities like phase saturations and pressures requiresa more fundamental understanding of how seismic and electromagnetic waves, and other remotesensing methods, depend on the spatial distribution, pressure, and interfacial properties ofmultiple fluid phases in porous and fractured media. Improved theoretical, mathematical andcomputational models for wave propagation in porous media must be developed, with explicitcoupling to models of multiphase flow. Together, the coupled models form the basis for inversemodeling and imaging of relevant flow parameters.Critical paths forward will:(a) Determine remotely imaged features and properties sensitive to multiphase properties ofinterest(b) Develop a theoretical basis for the constitutive relationships between material properties andhow fields and waves interact with them(c) Calibrate these relationships with quantitative laboratory data(d) Demonstrate whether or not models accurately predict experimental behaviors at the fieldscaleFor example, we know that the sensitivity of seismic velocity to increasing saturation depends onthe distribution of the fluids in the pore space. In homogeneously saturated materials, P-wavesensitivity decreases appreciably with increasing gas saturation. However, we know very littleabout the sensitivity of seismic attenuation to saturation, and we cannot distinguish a residualphase saturation (trapped by capillary forces) from a mobile phase occupying the same volumefraction. Additionally, simulations in three spatial dimensions, for example seismic imaging, relyon complex numerical methods implemented on high-performance computers. Inclusion ofmultiscale heterogeneity, time-dependent properties, and the expanded list of parametersrequired for coupled models for wave propagation and flow in porous media, results in hugecomputational domains—perhaps hundreds of billions of nodes and petaflops of computingpower with the accompanying complexities of adaptive and variable meshes, parallel algorithms,and challenges of quantifying uncertainties. Together these form an enormous scientificchallenge.Success in achieving a revolutionary breakthrough in imaging capabilities is expected to havesubstantial technological benefits, including improved oil and gas recovery, improved success inoil and gas exploration, and safer and more secure geological storage of CO 2 . For example, theability to detect and interpret the presence of vertically oriented gas distributions will improveleak detection from geological CO 2 storage reservoirs, as well as help to locate gas chimneys,which are signs of past hydrocarbon migration. Improved quantification of the fraction of pore20 Basic Research Needs for Geosciences: Facilitating 21 st Century Energy Systems