USING DISSOLVED OXYGEN ALTERATION TO IDENTIFY CONNECTING TRANSMISSIVE FRACTURES AND DETERMINE VERTICAL FLOW VELOCITY IN CRYSTALLINE BEDROCK WELLS

Due to the complexity of fracture flow, characterization and remediation becomes difficult and expensive when contamination is introduced to a system. Boreholes provide a path for contaminant spread vertically between fractures. Likewise, fractures provide a path for contaminants to spread between wells. Identification of transmissive fractures and flow direction is crucial for effective remediation- particularly the identification of fractures connecting wells, which may further transmit contaminants. The application of traditional downhole geophysical and tracer methods in fracture flow characterization is not widespread amongst the environmental consulting community, primarily owing to high costs. This can result in prolonged and inefficient remediation efforts.

This study uses dissolved oxygen alteration to successfully identify connecting transmissive fractures between two sets of crystalline bedrock wells and determine vertical flow velocity in a wellbore at the University of Connecticut in Storrs. This is an expansion of the dissolved oxygen method originally developed by Chlebica and Robbins (2013), which entails bubbling air into a well, followed by conducting dissolved oxygen profiles with time. By monitoring the changes in dissolved oxygen concentrations, flow patterns in the well are determined. The dissolved oxygen method provides a cost-effective addition or alternative to traditional characterization.