Measuring bedrock fracture hydraulics and geomechanics using low frequency fiber optic distributed acoustic sensing

Remediation of fractured bedrock is typically limited by a poor understanding of the flow system with respect to the contaminated source zone. Flow in fractures occurs in sometimes complicated fracture networks which may result in a bypassing of contamination during active remediation. If monitored natural attenuation (MNA) is the chosen remediation method, demonstrating that monitoring wells are effectively downgradient of the source zone can be a particular challenge. There is a need for technology that can demonstrate hydraulic connection between remediation wells, source zones, and the hydraulically connected fracture network. This must be done without inducing cross-contamination.We describe here a monitoring system that uses a relatively new but commercially available technology known as fiber optic (FO) distributed acoustic sensing (DAS). DAS has recently been used to measure downhole acoustic and seismic signals (Daley et al., 2015). We measured fracture hydraulics by sensing fracture strain in response to fluid stress (Becker et al., in press). (author)