Ryan, M. CathrynLagasca, Patrick Arceo2022-02-042022-02-042022-01-20Lagasca, P. A. (2022). Delineating the Shallow Free-phase Gas Distribution at an Abandoned Exploration Well, Crystal Geyser (Master's thesis, University of Calgary, Calgary, Canada). Retrieved from https://prism.ucalgary.ca.http://hdl.handle.net/1880/114398Crystal Geyser is an abandoned exploration well and active cold-water geyser driven by the expulsion of CO2 gas. It is a case study of an unsealed well transporting stray CO2 gas to the surface. Previous studies in the Crystal Geyser area inferred the existence of free-phase gas (FPG) accumulations trapped beneath low permeability layers near the geyser, but did not specify their exact locations or depths. In our primary study, we used electrical resistivity tomography to image a siltstone-capped FPG plume within the sandstone aquifer beneath Crystal Geyser. The plume was identified from an anomalously high resistivity zone that was not caused by lithofacies changes or fault displacement, representing a portion of the aquifer with elevated FPG content in the pore space. FPG is transported via Crystal Geyser’s conduit and the nearby Little Grand Wash Fault into a plunging anticline trap. The poor well casing integrity allows FPG to migrate from the conduit into the surrounding aquifer and gas trap. The subsurface FPG plume delineation was compared to the “equivalent CO2 bubbling depth” – the shallowest depth at which the total CO2 mass (free-phase and dissolved-phase CO2) expelled from the geyser would occur in the dissolved phase. The bubbling depth was extrapolated from mass balance calculations based on field estimates of Crystal Geyser’s CO2 and water emissions. The estimated bubbling depth was much shallower than the imaged FPG plume. This underestimation can be caused by the leakage of ascending FPG into the surrounding subsurface, allowed by the poor casing integrity of the well.engUniversity of Calgary graduate students retain copyright ownership and moral rights for their thesis. You may use this material in any way that is permitted by the Copyright Act or through licensing that has been assigned to the document. For uses that are not allowable under copyright legislation or licensing, you are required to seek permission.HydrogeologyElectrical Resistivity TomographyStray gas releaseFree-phase gas plumeGeologyGeophysicsHydrologymaster thesis10.11575/PRISM/39599