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It’S a Small World after All - the Pore Throat Size Spectrum

Nelson, Philip H.1
1 U.S. Geological Survey, Denver, CO.

As extraction of oil and gas from poor-quality reservoir rocks becomes more prevalent in the United States, knowledge of the size and character of pore throats and pore space in these reservoirs with respect to their potential for producing hydrocarbons becomes even more important than in the past. This small “world”, which ranges from angstroms to nearly a millimeter, is viewed through such tools as the optical microscope, scanning electron microscope, mercury injection, and computational chemistry. Permeability provides a length scale that is strongly, but not uniquely, related to pore-throat size. Nor can pore-throat size be determined unambiguously with other techniques. Each method of investigation, whether microimaging, mercury injection, or gas-flow experiments, requires a physical model of pore-throat geometry in order to convert the measurements to a microscopic size. The choice of a flow model influences the choice of a statistic (mean, median, or single value) to represent pore-throat size in a given sample. Experimental results drawn from past studies are combined into a spatial spectrum to help envision the relations among pore-throat sizes in sandstones, tight sandstones, and shales.


AAPG Search and Discovery Article #90090©2009 AAPG Annual Convention and Exhibition, Denver, Colorado, June 7-10, 2009