Summary

Sandstone petrographic and diagenetic analysis within a sequence stratigraphic framework provides a better understanding of the reservoir characteristics in the Eocene Tyee basin, southern Oregon Coast Range. Much primary porosity has been filled with zeolite (heulandite and laumontite), clay (smectite and corrensite), and quartz cement and pseudomatrix, thus diminishing the permeability of potential reservoir rocks. Reservoir-quality porosities and permeabilities, however, are present locally in some highstand delta front sandstone facies in the southern part of the basin as well as secondary dissolution porosity in lowstand turbidite sandstones in the deeper part of the basin to the north. This complex burial diagenesis is due to variations in pore fluid composition in time and space, which is attributed to variations in original detrital mineralogy and regional geothermal gradient in the basin.

AAPG Search and Discovery Article #90937©1998 AAPG Annual Convention and Exhibition, Salt Lake City, Utah