Three-Component Distributed Acoustic/Seismic Sensing

Fiber-optic distributed acoustic sensing (DAS) has become a revolutionary technology in the field of acoustic/seismic wave detection as it has disruptive advantages over point acoustic/seismic sensors. Especially, DAS has found vital applications in oil/gas exploration and development. However, three-component DAS (3C-DAS) remains an unsolved bottleneck problem as the present DAS is only sensitive to the axial strain, limiting the application range of DAS greatly. Here, we proposed and verified the 3C-DAS concept based on the theory proposed. We processed signals from three independent optical fibers within a specially designed dual-sine-structured sensing cable to realize 3C-DAS. Field trials of the 3C-DAS units were completed outdoor and in the real oilfield, respectively, by using an ultra-sensitive DAS instrument developed. Furthermore, a 100 m-long 3C-DAS cable was designed, fabricated, and tested. The experimental results indicate that 3C-DAS has the statistically comparable signal-to-noise ratio and better imaging resolution due to higher spatial density when compared to electronic 3C geophones. This work pioneers the study of 3C-DAS and paves a way to develop a new generation of vector DAS systems, including 3C-DAS-based geophones, hydrophones, and sonars for imaging geophysical structures with higher fineness, detecting undersea targets with better resolution, and positioning aerial vehicles with higher accuracy.