Investigating the Changes in Periodicity of the CO2‐Driven Cold‐Water Geyser Eruptions Through Field Observation at Tenmile Geyser, Utah

CO2‐driven cold‐water geysers periodically ejecting cold water are rare. Although coalescence and expansion of ascending CO2 bubbles can explain the eruption process, the triggering conditions and eruption cycle remain unclear. To clarify the triggering conditions, hydrostatic pressure in the well was decreased by pumping to induce eruptions. All four pumping tests successfully induced eruptions by decreasing the pressure of ∼104 Pa. In the absence of artificial perturbations, similar reductions in pressure were observed during the intervals between two consecutive eruptions (IBEs). During IBE, the atmospheric pressure (Pair) and temperature (Tair) controlled the generation of the CO2 bubbles which directly induced the pressure reduction in the well. Especially under the persistent low Pair and high Tair, the length of IBE showed a minimum value of 3.90 hr during field observations. We suggest that the atmospheric perturbations are the causes of the changes in geyser periodicity, given consistent geological and hydraulic conditions. Plain Language Summary CO2‐driven cold‐water geysers are formed by ascent of CO2 bubbles through vertical migration paths such as man‐made wells drilled into natural CO2 reservoirs. As one possible CO2 leakage pattern from geologic carbon sequestration, CO2‐driven cold‐water geysers have drawn attention in recent years. This study characterized the process based on in situ measurements of the Tenmile well located in the southern Green River area, Utah. To clarify the eruption process, multiple consecutive geyser eruptions were artificially induced to define the triggering conditions. This study concluded that a slight decrease in pressure triggers geyser eruption and atmospheric perturbations cause slight pressure changes during intervals between eruptions within the natural conditions. The eruption periodicity is controlled by the atmospheric conditions over the short term, given consistent geological and hydraulic conditions. Key Points We found the triggering pressures for vigorous geyser eruptions by pumping tests (artificial pressure reductions) in the field The decreases in pressure until the triggering pressure were similar to those caused by changes in atmospheric conditions Geyser eruption periodicity is affected by atmospheric perturbations, given consistent geological and hydraulic conditions