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The Mississippian Kirkwood reservoir is a 30-ft thick alluvial or deltaic crossbedded sandstone, overlain and underlain by shale. Measurements of grain diameter and sorting, clay content, porosity, permeability, and capillary pressures were made on cores from 5 wells in the reservoir.
The lower part of the reservoir is coarser grained and more permeable than the upper part. Also, feldspar grains in it have been partially altered to kaolin. The upper part is finer grained and less permeable. In contrast to the lower part, it contains illite and minor amounts of kaolinite and generally exhibits calcite cementation and quartz overgrowths.
Measurements of absolute pore size and average pore entry radius disclose larger values of these parameters in the lower part of the sandstone than in the upper. However, surface area and irreducible water saturation have smaller values in the lower part of the sandstone than in the upper. Pore entry size distribution data are in qualitative agreement with Kozeny's analysis and show that pore tortuosity is apparently reflected in the shape of the pore entry distribution curve. Those rocks which have platykurtic pore entry distributions have a more tortuous pore network than those with skewed distributions. A theoretical 2-dimensional model of the pore network involving cubic packing of spherical grains closely describes rock/fluid behavior.
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