High-resolution discrete fracture network characterization using inclined coreholes in a Silurian dolostone aquifer in Guelph, Ontario
The transport and fate of contaminants in fractured sedimentary rock aquifers depends strongly on the nature and distribution of the fracture network. The current standard practice of using only vertical coreholes to characterize bedrock aquifers can result in significantly biased data that is insufficient for fracture orientation analysis. This study involves the addition of two inclined coreholes to supplement existing data from eleven vertical coreholes at a contaminated site in Guelph, Ontario to reduce the effects of this bias. A suite of high-resolution, depth discrete data collection methods including core logging, borehole geophysics, and hydraulic testing were conducted to determine fracture orientation and spacing as well as hydraulic aperture distributions. The results of the orientation analysis demonstrate that the inclined coreholes were more effective at sampling high-angled fractures than the vertical coreholes and were necessary to identify all three of the dominant fracture sets on the site. The fracture network properties from this study can be used as input parameters for static and dynamic discrete fracture network models to assess current and future risks to municipal supply wells.