The usage of Distributed Acoustic Sensing (DAS) in geophysics is attractive due to its dense spatial sampling and low operation cost if the optical fiber is easily accessible. In the borehole environment, optical fibers for DAS are often readily available as a part of other sensing tools, such as for temperature and pressure. Although the DAS system promises unlimited potential for reservoir monitoring and surface seismic acquisition, the single axial strain measurement of DAS along the fiber is inadequate to fully characterize the different wave modes, thus making reservoir characterization di cult. We propose a configuration using five equally spaced helical optical fibers and a straight optical fiber to obtain six different strain projections. This system allows us to reconstruct all components of the 3D strain tensor at any given location along the fiber. Using the condition number of the matrix product of the averaging and projection matrices, we can systematically search for the optimum design parameters for our configuration. Numerical examples demonstrate the effectiveness of our proposed method to successful reconstruction of the six component strain tensor from wavefields of arbitrary complexity.

Presentation Date: Thursday, September 28, 2017

Start Time: 9:45 AM

Location: 362D

Presentation Type: ORAL

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