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AAPG Rocky Mountain Section Meeting

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Helium Potential in the Holbrook Basin, Arizona

Abstract

The Holbrook Basin is located on the Colorado Plateau, it is deeply eroded and the remaining sedimentary rocks are mostly Paleozoic and lower Triassic in age. Structures are compressional, low-relief monoclines. The Permian Coconino aeolian sandstone is the primary reservoir for Helium. It has produced 9 bcfg (gross) mostly from 1961 to 1977, but some more recently. The percentage of Helium is high at 8 to 9% (90% Nitrogen). The Coconino is at shallow depths in the basin. It is an active regional aquifer that results in tilted gas/water contacts and the risk of water flushing in closures with small vertical relief. In many areas it is too shallow for an effective vertical seal. New regional maps show where the Coconino is deep enough and the major structures in the basin. Secondary reservoirs both above and below the Coconino are the main objectives for recent drilling. They were deposited in less continuous depositional environments. The Supai formation below the Coconino has sands and carbonates in cycles of evaporite deposition; good seals, less continuity avoids water flushing. Supai helium shows are widespread in the basin and have been posted on the regional maps, up to a few percent Helium with Nitrogen. In the southeastern part of the basin, CO2 substitutes for Nitrogen. One field was delineated in anticipation of a CO2 pipeline, Helium is less than 1% but that is still economically significant.