Marine seismic exploration has long relied on complex and costly towed streamers to investigate the geological structure of sea shelves and identify mineral deposits. However, a recent study published in Engineering introduces a novel fiber-optic marine towed streamer seismic acquisition system based on distributed acoustic sensing (DAS) technology, which simplifies the design and manufacturing process while maintaining effectiveness.

Traditional marine towed streamers typically use piezoelectric hydrophones or fiber-optic interferometric hydrophones, which are not only complex and costly but also challenging to manufacture. The new system, developed by researchers from Peking University, the National Engineering Research Center for Gas Hydrate Exploration and Development, and other institutions, features a unique design that removes the need for optical components within the streamer, thereby streamlining the system architecture and manufacturing process.

The study validated the system’s effectiveness through a sea trial conducted in the slope zone of a basin in the South China Sea, with water depths ranging from 500 to 2000 m. This trial marked the first successful application of distributed fiber-optic towed streamers for marine seismic exploration, enabling the effective detection of complex sedimentary structures in the surveyed area.

The core of the new system is the heterodyne demodulation distributed acoustic sensing (HD-DAS) system, which uses a pair of pulses with a fixed frequency difference to function as a moving interferometer along the sensing fiber. This design achieves an extremely low noise floor and a high signal-to-noise ratio. The gauge length of the DAS system was determined to be 5 m, and the spatial sampling interval was 1 m. The sampling rate for each trace was 4 kHz, with data down-sampled to 1 kHz after applying a low-pass filter to prevent aliasing.

Two types of distributed fiber-optic towed streamer cables were developed: the helically wound fiber distributed sensing towed streamer cable (HW-TSC) and the discrete-sensor towed streamer cable (DS-TSC). The HW-TSC features a single-mode optical fiber helically wound around a polyethylene mandrel, while the DS-TSC incorporates optical fibers wound on multiple hydrophone skeletons, eliminating the need for optical components and simplifying the system.

During the sea trial, the towed streamer system effectively captured reflection and structural information of formation interfaces, providing valuable insights into the complex sedimentary processes occurring in the slope zone of the basin. The results showed that the distributed fiber-optic towed streamers have significant potential for future geological surveying applications.

The study also investigated the impact of vessel speed on flow noise, finding that a speed of 4 kn (1 kn = 0.514444 m·s⁻¹) resulted in the lowest flow noise for all streamer cables tested. The oil-filled DS-TSC exhibited the lowest flow noise and the highest signal-to-noise ratio, while the HW-TSC showed the highest flow noise but demonstrated effective imaging of the shallow seabed due to its small channel spacing and large number of sensing channels.

The research concludes that the marine towed streamer seismic acquisition system using DAS technology has significant potential for fine marine seismic exploration, such as the exploration of natural gas hydrate reservoirs. Future improvements, such as adding an oil-filled layer to the HW-TSC to reduce flow noise and controlling the cable’s posture in seawater, could further enhance the system’s performance.

The paper “Marine Seismic Exploration with Distributed Acoustic Sensing,” is authored by Xiangge He, Pengfei Wen, Qingqing Su, Hui Yang, Lijuan Gu, Min Zhang, Hailong Lu. Full text of the open access paper: https://doi.org/10.1016/j.eng.2025.04.007. For more information about Engineering, visit the website at https://www.sciencedirect.com/journal/engineering.