Application of DAS to reservoir microseismic monitoring: A case study of Xinfengjiang Reservoir in Guangdong, China

The stratigraphic activities of the reservoir pose a serious threat to the safety of life and property of the people around the dam. The Xinfengjiang Reservoir in China is one of the four reservoirs in the world that induce above M6.0 earthquakes, which has an important impact on drinking water and safety in the Greater Bay Area. For earthquakes in reservoirs, terrestrial seismometers are far away from the seismic center, while submarine seismometers (OBS) are difficult to be deployed with data transmission off-real time. Distributed optical fiber Acoustic Sensing (DAS) enables real-time detection of formation activity and is suitable for a variety of extreme environments on land and underwater. With wide spectrum and high stratigraphic resolution, DAS has potential broad application prospects in reservoirs .    In this study, we will show our first (July 2022) and second (May 2023) experiments in Xinfengjiang Reservoir for microseismic monitoring and ambient noise imaging results. Different optical cables (security cables, ordinary submarine cables and high-sensitivity submarine cables) and external environment (land and underwater) are adopted to analyze the seismic signals and noise in Xinfengjiang reservoir. Through the monitoring of seismic events and ambient noise, we will conduct the following studies: (1) the similarities and differences of monitoring signals of different optical cables in DAS equipment; (2) DAS monitoring of seismic and other stratigraphic activities; (3) DAS ambient noise imaging. Through comparative analysis, we will quantitatively analyze the advantages and disadvantages of DAS monitoring reservoir formation activities. Besides, some suggestions are given for the safety of Xinfengjiang reservoir.