Fiber Optic Distributed Acoustic Sensing for Stress Measurement and Mitigation of High Stress Hazards at Depth

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The stress conditions present in the ground at depth are one of the most important inputs in rock engineering design. It dictates many important decisions such as the optimal orientation of horizontal wells for geothermal and unconventional gas development, as well as the orientation, dimensioning and support of underground excavations for mining, hydroelectric dams and nuclear waste repositories to ensure safety. Yet despite its importance, it is also the most difficult parameter in rock engineering design to reliably measure. This has led to numerous stress measurement techniques being developed, each with significant limitations and reliability issues. The emergence of fiber optic sensing capabilities offers several advantages that have the potential to overcome these challenges and add important improvements. For this, a Distributed Acoustic Sensing (DAS) fiber optic testing system is being requested to allow lab-scale experiments required to advance innovation to develop a new fiber optic stress measurement technique. The addition of this equipment will allow for stand-alone benchtop testing as well its integration with an existing state-of-the-art rock testing system capable of reproducing the stress, temperature and fluid pressure conditions encountered on deep mining and energy development projects. This will allow us to support our other research programs and student training focussed on improving safety and mitigating hazards related to these activities. The importance of this research is of direct relevance to Canada's economy, as well as the training of the next generation of engineers and geoscientists for our mining and energy sectors. For example, several Canadian mines are approaching depths of 3000 m exposing them to high stress hazards in the form of rockbursting. This has significant safety implications that could impact the economic viability of these mines, especially without improvements in the reliability of stress measurements at these depths. Canada's nuclear waste management program is now searching for a site for a deep repository with the geological conditions necessary to satisfy safety requirements. Assessing the stresses present and potential for rock failure is essential to ensure that the host rock serves its intended purpose of acting as a low permeability barrier to prevent the ingress of water and escape of waste. Hydraulic fracturing operations to enable production from Canada's unconventional gas reservoirs have been subject to public and regulator concerns regarding induced seismicity. These are heightened by knowledge gaps in our understanding of fault slip mechanisms and the factors controlling the likelihood and magnitude of induced seismicity. The experimental equipment being requested in this proposal will help us to accelerate our research programs addressing these challenges by allowing us to image the stress and strain patterns associated with brittle rock deformation and failure.