--> ABSTRACT: Influence of Dolomite Cement on the Permeability and Capillary Pressure Properties of Quartzose Sandstones, by Alan P. Byrnes, Michael D. Wilson; #91020 (1995).
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Influence of Dolomite Cement on the Permeability and Capillary Pressure Properties of Quartzose Sandstones

Previous HitAlanTop P. Byrnes, Michael D. Wilson

Quartzose sandstones from several formations and basins in the western U.S. were examined for the influence of dolomite cement on petrophysical properties. Samples were selected to range in dolomite cement content from 5-20%, 5-23% porosity, and 0.001-200 md permeability. Matched porosity/permeability plug pairs were obtained from adjacent sites on whole core. Mercury capillary pressure analysis was performed on one sample after porosity and permeability analysis. All dolomite cement was removed from the matching sample by flow-through extraction using 10% HCl. The core was then flushed with fresh water, dried, porosity and permeability reevaluated, and capillary pressure analysis performed. Petrophysical and petrographic characteristics between cores which contained dolo ite and those for which the dolomite had been removed were compared.

Porosity values changed in direct proportion to the dolomite content of each sample (5-20%). Permeability values increased from initial values by a factor of 2 to as much as 50 times. Samples with the highest initial permeability exhibited the least permeability increase while the lowest permeability samples exhibited the greatest increase. Capillary pressure analysis revealed that the principal pore entry throat diameters also increased from 2 to 15 times. Irreducible water saturations for all samples were generally low (7-15%) and decreased by 2-3% after dolomite removal. Pore surface areas were initially low (0.1-.4 m2/g) and decreased by 15-40% with removal of dolomite. These data indicate that some portion of the dolomite cement occurs at pore throats and exerts a sign ficant control on permeability, pore entry throat size, threshold entry pressures and, if early, on subsequent diagenesis, porosity decrease, and oil and water hydrodynamics.

AAPG Search and Discovery Article #91020©1995 AAPG Annual Convention, Houston, Texas, May 5-8, 1995