Sensitivity for Monitoring Array of Distributed Acoustic Sensors (DAS) in a Vertical Borehole

We have developed an open-source comprehensive Python framework, named PyNetDesign (Anikiev, 2025), for testing and designing microseismic monitoring networks, including Distributed Acoustic Sensors (DAS) and studied sensitivity of seismicity for a simple downhole monitoring scenario.The sensitivity is quantified by determining the magnitude of detectable seismic events for a specific microseismic monitoring network, i.e. estimating the minimum moment magnitude detectable using the given network or receivers.We illustrate a straightforward scenario using homogeneous velocity models with various monitoring network geometries and noise levels to evaluate the specific features of monitoring with DAS.Magnitude sensitivity is represented in the form of horizontal or vertical slices through a 3D grid.The core algorithms in PyNetDesign are implemented using NumPy vectorization.In the input/output part PyNetDesign relies on Pandas library.Visualization is based on Matplotlib and Plotly. ObjectivesAssessing the performance of a seismic monitoring network is needed to ensure meeting of regulatory requirements as well as understanding and interpretation of observed seismicity.Traditionally, monitoring networks utilize point seismic receivers, such as geophones or accelerometers.Such networks consist of discrete sensors placed at specific locations to measure ground motion.In contrast, DAS employs fiber-optic cables to detect seismic signals continuously along the optic cable, offering a much denser spatial sampling while being sensitive only to ground motion along the cable.The main difference between the DAS and point sensor networks is in special sampling and sensitivity: geophones provide high sensitivity at discrete points in all 3 spatial components of ground motion, while DAS enables spatially continuous monitoring over extensive areas.Our newly developed software permits the evaluation of performance of the classical point sensors with the novel (DAS) method.In this study we show basic performance of the DAS monitoring from a vertical borehole -the most common deployment.We also simulate the DAS cable monitoring with a single three-component (3C) geophone on surface and to evaluate added value of point sensors.DAS is a technology that uses fiber optic cables to detect and measure acoustic signals over long distances but limited only to the motion along the cable, with the optical fiber itself serving as the sensing element.The gauge length in DAS refers to the segment of the fiber over which strain measurements are averaged, determining the spatial resolution of the sensing system.Shorter gauge lengths yield finer detail but potentially lower signal strength.