HR: 0800h
AN: H31D-0448    [Abstracts]
TI: Estimating the Permeability of Carbonate Rocks using Image Analysis and Effective Medium Theory
AU: Jurgawczynski, M
EM: mathieu.jurgawczynski@imperial.ac.uk
AF: Dept. of Earth Science and Engineering, Imperial College, London, Sw7 2AZ United Kingdom
AU: Jing, X
EM: x.jing@imperial.ac.uk
AF: Dept. of Earth Science and Engineering, Imperial College, London, Sw7 2AZ United Kingdom
AU: * Zimmerman, R W
EM: r.w.zimmerman@imperial.ac.uk
AF: Dept. of Earth Science and Engineering, Imperial College, London, Sw7 2AZ United Kingdom
AB: A methodology was recently developed to estimate the permeability of sedimentary rocks from two-dimensional pore images [Lock et al., J. Appl. Phys., 2002]. The only data required from the images are the areas and perimeters of the individual pores. The hydraulic conductivities of the individual pores are estimated from their areas and perimeters using the hydraulic radius approximation. Stereological correction factors are applied to determine the true cross-sectional shapes from the images, and to determine the true number density of pores per unit area. A constriction factor accounts for the variation of the cross-sectional area along the tube length. The pores are assumed to be arranged in a cubic lattice, after which the effective-medium equation of Kirkpatrick is used to estimate the effective conductance of the pores. Finally, the permeability is estimated from the effective pore conductance and the number density of pores. When applied to several data sets of sandstones, having permeabilities in the range of 20-1400 mD, the permeability estimates were always within roughly a factor of two of the values measured in the laboratory. This methodology is now being applied to a set carbonate rocks, having permeabilities in the range of 0.5 to 25 mD. Carbonates generally have more complex and heterogeneous pore structures than do sandstones. Nevertheless, our preliminary results how that, for rocks that do not contain appreciable amounts of vugs that are unconnected to the main conducting pore space, the method again yields permeabilities within a factor of two of the measured values. However, when applied to vuggy carbonates, the predictions may be too high by several orders of magnitude. The error in these cases arises from including isolated vugs in our calculation of the effective pore conductance. These vugs are easily identified by eye. However, as our aim has been to develop a rapid, objective permeability estimation method that requires little if any subjective intervention by the user, we are currently trying to develop automated ways of identifying the unconnected vugs, so as to remove them from the calculations.
DE: 5114 Permeability and porosity
DE: 5139 Transport properties
DE: 1829 Groundwater hydrology
SC: Hydrology [H]
MN: 2004 AGU Fall Meeting