Helium and methane anomalies in domestic well waters in southwestern Saskatchewan, Canada, and their relationship to other dissolved constituents, oil and gas fields, and tectonic patterns

During the summer of 1976 a regional groundwater survey was undertaken in an area of 18,000 km 2 in southwestern Saskatchewan. Approximately 940 domestic wells and springs were sampled at a density of 1 per 13 km 2 , where possible. The samples were analyzed for up to 30 variables, including He, CH 4 , and many trace and minor elements. The results of the survey are related to regional topographic, geological, and hydrological features. Of particular interest are CH 4 and He anomalies associated with known gas and oil reservoirs in the region. Several anomalies of similar magnitude occur away from known reservoirs and hence may point to new ones. The close association of CH 4 with He, sample depth and deeper “softer” waters, as indicated by the positive correlations of CH 4 with He, Na, CO 2− 3 , HCO − 3 and sample depth is postulated to be a good criterion for distinguishing between reservoir CH 4 and marsh gas. The coincidence of CH 4 and He anomalies with known tectonic features also indicates fracture leakage from depth and the possible existence of oil and gas fields. Regional surveys of domestic well waters can be of use in delineating areas with proven and potential oil and gas reservoirs at depth.