QUANTIFYING VUGGY POROSITY AND ITS ASSOCIATED PERMEABILITY IN A SILURIAN DOLOSTONE AQUIFER USING ACOUSTIC TELEVIEWER IMAGE PROCESSING AND DEPTH DISCRETE HYDRAULIC TESTING

In bedrock aquifers with low matrix permeability, secondary porosity features such as fractures and vugs can make up the primary flow pathways for groundwater. While fractures can be identified and quantified as discrete features using rock core and borehole imaging tools, the quantification of vuggy porosity can be difficult as it is often comprised of small vugs that are irregular in shape and distribution. As the distribution of these secondary porosity features varies throughout the bedrock sequence, open borehole, or bulk hydraulic tests are not sufficient for determining the hydraulic influences of these features. Therefore, numerous complementary, depth discrete datasets are required to develop a thorough understanding of how secondary porosity contributes towards the transmissivity of the aquifer.

This study presents the preliminary results of a technique to quantify the distributions and nature of secondary porosity using acoustic televiewer (ATV) image processing coupled with depth discrete hydraulic testing. The datasets were collected from coreholes in a Silurian dolostone aquifer sequence in Guelph, Ontario, Canada. ATV image processing techniques using the signal amplitude and travel-time data are used to extract and quantify the extent of vuggy porosity, and fracture location and orientations are identified using the image log and continuous rock core data. Transmissivity of the features is determined using, high resolution, depth discrete hydraulic tests such as straddle packer testing and flexible liner transmissivity profiling. Preliminary results show good correlation between the identified secondary porosity and transmissivity data suggesting that these features may play an important role in groundwater flow and contaminant transport in dolostone aquifers.