Rangely field is in Rio Blanco County, Colorado, on a doubly plunging anticline of Laramide age. The Rangely structure is asymmetrical with the steepest flank to the southwest. The Permo-Pennsylvanian Weber Sandstone is the primary producing formation with cumulative production exceeding 670 million bbl of oil. The Weber is a subarkosic arenite deposited in an eolian regime. It interfingers with the alluvial Maroon Formation in the southern and southeastern portions of Rangely field. Isopach maps of the Pennsylvanian formations suggest a paleotectonic platform in the Rangely area and a Permo-Pennsylvanian north-south-trending arch west of the Laramide-age Douglas Creek arch. Hydrocarbons migrated into the Rangely area prior to the Laramide orogeny and were stratigraphical y trapped at the Weber-Maroon transition zone. Subsequent Laramide structure localized and hydrocarbon accumulation.

Diagenetic history of the Weber Sandstone differs between the Uinta and Piceance basins. Weber diagenesis in the Uinta basin is dominated by silica precipitation and porosity appears to be residual primary. Weber diagenesis in the Piceance basin includes dissolution of detrital material and precipitation of a complex sequence of carbonate cements. Weber porosity in the Piceance basin appears to be both residual primary and secondary. The boundary between these two diagenetic regimes appears to coincide with the Pennsylvanian paleoarch.

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