A baseline determination of CO₂ and CH₄ fluxes and soil-gas concentrations of CO₂ and CH₄ was made over the Teapot Dome oil field in the Naval Petroleum Reserve 3 in Natrona County, Wyoming, United States. This was done in anticipation of the experimentation with CO₂ sequestration in the Pennsylvanian Tensleep Sandstone underlying the field at a depth of 5500 ft (1680 m). The measurements were made in January 2004 to capture the system with minimum biological activity in the soils, resulting in a minimum CO₂ flux and a maximum CH₄ flux. The CO₂ fluxes were measured in the field with an infrared spectroscopic method. The CH₄ fluxes were determined from gas-chromatographic measurements on discrete samples from under the flux chambers. The CO₂ and CH₄ were determined at 30-, 60-, and 100-cm (11-, 23-, and 39-in.) depths in soil gas by gas chromatography. A total of 40 locations had triplicate flux measurements using 1.00-m² (10.763-ft²) chambers, and soil gas was sampled at single points at each of the 40 locations.

Carbon dioxide fluxes averaged 227.1 mg CO₂ m² day¹, a standard deviation of 186.9 mg m² day¹, and a range of 281.7 to 732.9 mg m² day¹, not including one location with subsurface infrastructure contamination. Methane fluxes averaged 0.137 mg CH₄ m² day¹, standard deviation of 0.326 mg m² day¹, and a range of 0.481 to 1.14 mg m² day¹, not including the same contaminated location.

Soil-gas CO₂ concentrations increased with depth, averaging 618, 645, and 1010 ppmv at 30, 60, and 100 cm (11, 23, and 39 in.), respectively. Soil-gas CH₄ concentrations averaged 0.128, 0.114, and 0.093 ppmv at 30, 60, and 100 cm (11, 23, and 39 in.), respectively. The decrease in CH₄ with depth reflects a slow rate of methanotrophic oxidation, even during winter conditions. The ¹³C of the soil gas CO₂ was also determined in the soil-gas samples and in the atmosphere. These data demonstrated that the increased CO₂ with depth was derived from the biological oxidation of soil organic matter.