Abstract

Farnham Dome in east-central Utah may be an elongated surface anticline associated with ramp-style thrusting of a Sevier-age decollment in the Jurassic Carmel Formation. Farnham Dome field includes a much broader Laramide-age anticline along the northern plunge of the San Rafael uplift. Pennsylvanian-age reverse faulting associated with the Uncompahgre uplift resulted in local thickening of the Pennsylvanian section, creating potential stratigraphic traps.

Drilling along the crest of Farnham Dome in the 1920s and 1930s resulted in the discovery of a significant deposit of carbon dioxide (CO₂) in the Jurassic Navajo Sandstone and smaller accumulations of CO₂ in Triassic, Permian, and Pennsylvanian reservoirs. Additional drilling and seismic data revealed the surface anticline was a shallow feature on the west flank of the broader anticline that forms the trap for the CO₂. Nearly 5 billion cubic feet (BCF) (0.14 × 10⁹ m³) of CO₂ of an estimated 430 BCF (12.2 × 10⁹ m³) was produced before field abandonment in 1979 for lack of a market. Most of the CO₂ may have migrated into the trap between 10 and 50 Ma. The gas accumulation is hydrologically displaced to the northwest with a lower gas/water contact on the northwest side of the structure.

The Utah Geological Survey (UGS) studied Farnham Dome field as an analogue for sequestration of CO₂ in Rocky Mountain reservoirs such as abandoned oil and gas fields or saline aquifers. A soil-gas survey was conducted over the crest of the dome, many of the faults, and the flanks of the structure. No surface leakage was detected despite proven CO₂ at 2800 feet (850 m). Farnham Dome field is a good example of the potential for long-term sequestration of CO₂ in Rocky Mountain reservoirs. Currently, a newly drilled well is shut in with plans to construct a plant to process the gas to food-grade liquid CO₂.