Name
Temporary distributed fibre optic deployment for monitoring seismic and aseismic processes during hydraulic fracturing
Description
Distributed acoustic sensing (DAS) has transformed hydraulic fracture (HF) monitoring in recent years. We report two projects, called the Canadian Dip-in DAS (CanDiD) projects, in which a temporary optical fiber was deployed to monitor HF operations. The main goal of these projects was to evaluate the effectiveness of a retrievable optical fiber for HF monitoring, based on the analysis of both microseismic and low-frequency DAS signals. The DAS recordings from zipper-frac completions in horizontal wells exhibit clear signatures of aseismic cross-well strain. These signals enable fracture azimuth to be determined, indicative of the maximum horizontal stress (SHmax) direction. Using a machine-learning-based approach, microseismic events were detected and processed, including innovative methods to determine hypocentres from a single fiber. Numerous coherent noise events, which we interpret as high-frequency waves that propagate along the wireline due to stick-slip on the wireline, initiated in close proximity to the fracture tips. Low-frequency DAS signals from the CanDiD-2 project provide evidence for aseismic processes including fracture initiation, reactivation and termination. The results of these investigations demonstrate the utility of temporary fibre optic deployments to provide insights about fracture geometry, stress orientations, and aseismic deformation processes.