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Research Interests Experimental studies in subsurface hydrology and reservoir processes, including multiphase flow, phase change, thermal processes, thermal-chemical processes, gas hydrates, coal bed methane, and carbon dioxide sequestration. Other interests include imaging as a tool to investigate flow processes. Production of Gas Hydrates
We tracked the dissociation front in a synthetic methane hydrate/sand sample produced by Laura Stern of the USGS. The first figure is an x-ray CT image of the hydrate/sand sample. The attenuation is higher in the top half where the fraction of sand is higher. In the sequence of images, each image is made by subtracting a reference scan so that changes are identified. We can then clearly follow where the hydrate is dissociating to gas and ice. Water Flow around Unsaturated Cavities – The Drift Shadow The drift shadow is a region below a cavity in an unsaturated environment that is sheltered from downward-percolating water, and is caused by capillary forces being too weak to immediately draw percolating water into this region. The drift shadow has been predicted using numerical and analytical models, but has not been identified in field sites. We are performing a field investigation to find the drift shadow. (Natural Analogue Studies of the Drift Shadow Effect- Powerpoint file)
Geologic Sequestration of Carbon Dioxide
In
this figure, flow paths through a coal sample are identified
by the darker colors. This image sequence contains x-ray CT
slices of a 1.5 inch diameter coal core. Each image is the
difference between two x-ray CT images. In one, liquid CO2
was present in the larger pores, and in the other, a strongly
x-ray attenuating potassium iodide brine was present in the
connected porespace. When the two images are subtracted, the
difference shows where the flow is occurring. Thermal hydrology Associated with Yucca Mountain High-Level Waste Repository
The
ridges identified in these photos are amorphous silica deposited
in a fracture that was heated at the bottom. Water containing dissolved
silica flowed from the top. The implication is that only a small
band of deposited mineral is required to disrupt flow. Scale bars
are 0.5 mm long.
Selected Publications Ghezzehei, T.A., T.J. Kneafsey, and G.W. Su, “Correspondence of the Gardner and van Genuchten relative permeability function parameters," submitted to Water Resources Research, 2006 Kneafsey, T.J., Y. Seol, G.J. Moridis, L. Tomutsa, B.M. Freifeld, “Laboratory measurements on core-scale sediment/hydrate samples to predict reservoir behavior”, Submitted to AAPG Bulletin, November, 2005, LBNL-59085 Kneafsey, T.J., L. Tomutsa, G.J. Moridis, Y. Seol, B.M. Freifeld, C.E. Taylor, and A. Gupta, “Methane Hydrate Formation and Dissociation in a Core-Scale Partially Saturated Sand Sample”, accepted by Journal of Petroleum Science and Engineering, December, 2005. LBNL-59087 Gupta, A., T.J. Kneafsey, G.J. Moridis, Y. Seol, M.B. Kowalsky, E.D. Sloan Jr., “Methane hydrate thermal conductivity in a large heterogeneous porous sample”, J. Phys. Chem. B, 110(33), 16384-16392, 2006. DOI: 10.1021/jp0619639. LBNL-59088 Freifeld, B.M.; Kneafsey, T.J., and Rack, F. “On-Site Geologic Core Analysis Using a Portable X-ray Computed Tomographic System,” From: Rothwell, R.G. 2006. New Techniques in Sediment Core Analysis. Geological Society, London, Special Publications, 267, 165–178. 0305-8719/06/, The Geological Society of London, 2006. LBNL-55698 Kneafsey, T.J., Moridis, G., Freifeld, B., Tomutsa, L., Seol, Y. and Taylor, C.E., 2005. Understanding Methane Hydrate Behavior Using X-ray Computed Tomography, Fire in the Ice, The National Energy Technology Laboratory Methane Hydrate Newsletter, pp. 1-4 LBNL/PUB-926 Salve, R. and T.J. Kneafsey, “Vapor-phase transport in the near-drift environment at Yucca Mountain,” Water Resources Research, Vol. 41, W01012, doi:10.1029/2004WR003373, January 2005, LBNL-55212 Seol, Y., T.J. Kneafsey, and K. Ito, An Evaluation of the Active Fracture Concept with Modeling Unsaturated Flow and Transport in a Fractured Meter-Sized Block of Rock, Vadose Zone Journal, 5(1), 1-13. December 2005, doi:10.2136/vzj2004.0175, LBNL-52818 Freifeld, B.M. and T.J. Kneafsey. "Investigating methane hydrate in sediments using X-ray computed tomography". In Advances in the Study of Gas Hydrates. Kluwer Academic/Plenum Press, 2004. LBNL-55030 Kneafsey, T.J., and Hunt, J.R. “Non-aqueous phase liquid spreading during soil vapor extraction,” Journal of Contaminant Hydrology, 68(3-4), pp. 143-164, 2004. LBNL-46519 Hu,
Q., T.J. Kneafsey, J.J. Roberts, L. Tomutsa, and J.S.Y. Wang¸” Characterizing
Unsaturated Diffusion in Porous Tuff Gravel, Vadose Zone Journal
3, 1425–1438,
2004. LBNL-51504 Dobson, P.F., T.J. Kneafsey, E.L. Sonnenthal, N. Spycher, and J.A. Apps, “Experimental and numerical simulation of dissolution and precipitation: Implications for fracture sealing at Yucca Mountain, Nevada, Journal of Contaminant Hydrology, v 62-63, 459-476, 2003. LBNL-48872 Kneafsey, T.J. and K. Pruess “Laboratory Experiments on Heat-Driven Two-Phase Flows in Natural and Artificial Rock Fractures,” Water Resources Research, Vol. 34, No. 12, p. 3349, December, 1998 . |
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