Enhancing Ground Imaging Capabilities with New Seismic Sources and Fiber-Optic Cables

What is it about?

This research shows how combining advanced tools can improve the way we 'see' underground. Scientists often use a method called cross-well surveys to map what's below the surface, which is important for understanding the possibility to use a site for applications such as storing carbon dioxide (to fight climate change) or harnessing geothermal energy. Two key technologies can improve this process: active seismic sources and Distributed Acoustic Sensing (DAS) using fiber-optic cables. Active seismic sources send controlled sound waves into the ground that are powerful and consistent. These waves travel through the underground strata and DAS picks up the vibrations using fiber optic cables. It is possible to use ordinary communication cables, as used for internet data transfer, for DAS data collection, this can make the technology cheap compared to expensive specialized sensors. The combination of the two technologies works well because the active sources produce strong signals that DAS can clearly detect, even in noisy environments. This helps scientists get more accurate and reliable images of underground structures to understand how suitable site is for geothermal energy or carbon dioxide storage use. The research also tested two designs of fiber: linear (straight) and helical (spiral) fibers within a cable. Each has strengths and by using both types together, the system a more detailed picture of the underground. Together, these technologies provide a powerful, cost-effective way to get clear, detailed images of the subsurface for efficient management of natural resources.

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Photo by Compare Fibre on Unsplash

Photo by Compare Fibre on Unsplash

Why is it important?

This research highlights the critical advances in subsurface imaging that are essential for environmental sustainability, energy efficiency and natural resource management. Traditional seismic imaging tools, such as hydrophones and geophones, are costly and surveys are time-consuming. Distributed Acoustic Sensing (DAS), a technology that uses fiber-optic cables to detect subsurface vibrations, offers a more efficient and accessible alternative with repeatable surveys. The integration of DAS with various active seismic sources further improves the reliability and resolution of imaging. Active sources provide consistent, high-energy signals that DAS can detect in different environments, increasing signal-to-noise ratio and enabling the identification of subtle subsurface changes. This combination is particularly effective for time-lapse monitoring in carbon capture and storage (CCS) and geothermal projects. By testing two fiber designs - linear and helical - the study demonstrates how each excels in different conditions and shows that combining them improves image quality. This dual approach overcomes challenges such as signal-to-noise (S/N) limitations and ensures more comprehensive data collection, which is critical for energy applications such as CCS, geothermal systems and hydrocarbon extraction. These capabilities are essential for mitigating climate change, transitioning to sustainable energy practices and improving the efficiency of resource extraction. The combined use of linear and helical fibers in DAS cables expands the versatility of seismic imaging by overcoming the limitations of each design. Together they reduce data gaps and ambiguities, enabling higher resolution imaging in complex geological environments. By advancing DAS technology and its applications, this research paves the way for scalable, cost-effective and sustainable solutions to subsurface monitoring challenges.

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