Unlocking Permanent Subsea Monitoring

Summary Innovative distributed acoustic sensing (DAS) technologies ease permanent subsea monitoring, by facilitating optical interrogation of a maximum of downhole and seabed fibers. This solution enables well monitoring and seismic imaging for reservoir monitoring at production fields and carbon storage sites with reduced hardware cost. Indeed, frequency swept interrogation unlock DAS recordings for long distances, up to 150 km, and in subsea wells. Wavelength multiplexing allows for DAS recordings with fibers originally allocated for other purposes, like fibers carrying communication traffic, or fiber installed as part of a permanent reservoir monitoring (PRM) system, and the fibers of lead-in cables connecting to the downhole fibers. Multiple fibers can be interrogated simultaneously in real-time with only one DAS interrogator to maximize DAS coverage. Finally, the development of the submarine repeatered DAS technique unlocks new frontiers by the interrogation of several thousands of kilometers. Its application will be particularly interesting for permanent DAS monitoring of carbon storage sites far from shore, as well as for pipeline and power cable monitoring.