During the summer of 1976 a regional groundwater survey was undertaken in an area of 18,000 km2 in southwestern Saskatchewan. Approximately 940 domestic wells and springs were sampled at a density of 1 per 13 km2, where possible. The samples were anlayzed for up to 30 variables, including He, CH4, and many trace and minor elements. The results of the survey are related to regional topographic, geological, and hydrological features. Of particular interest are CH4 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 CH4 with He, sample depth and deeper ''softer'' waters, as indicated by the positive correlations of CH4 with He, Na, CO2-3, HCO-3 and sample depth is postulated to be a good criterion for distinguishing between reservoir CH4 and marsh gas. The coincidence of CH4 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.