oa Improving Signal-to-Noise Ratios of DAS Data Using Beamforming and Coherent Stacking

Distributed Acoustic Sensing (DAS) holds promise as a valuable tool for monitoring seismic activities in downhole environments. DAS arrays with 1-meter channel spacing offer advantages over traditional geophone arrays. Nevertheless, DAS measurements often suffer from limited signal-to-noise ratios (SNR). In an effort to mitigate this challenge, we implement the beamforming and coherent-stacking (BCS) method to enhance SNR in DAS data collected during a 2019 fracture stimulation project at the Utah Frontier Observatory for Research in Geothermal Energy (FORGE) site. Simultaneously, a 12-level 3C geophone array was deployed in the same observation well to monitor induced microearthquakes. The DAS system, featuring 1-meter fiber channel spacing and a 10-meter gauge length, was compared to the 3C geophone array with a 30-meter depth interval. Both systems shared a time domain sampling rate of 0.5 milliseconds. By employing BCS techniques, we significantly improved SNR in DAS data, aligning it with the vertical-component waveform from a 3C geophone at the same depth. This enhancement, which closely resembled 3C geophone recordings, has promising implications for improving first-arrival time measurements and subsurface imaging. Future work aims to automate BCS processing and first arrival time picking using AI algorithms, further advancing the utility of DAS technology in seismic monitoring.