As part of the FRS baseline assessment, several Vertical Seismic Profiles were acquired with the intention of testing emerging monitoring techniques such as Distributed Acoustic Sensing (DAS). In this report, we describe the processing flow and discuss the results obtained for a walkaway VSP oriented North-South and centred in the observation well 2. This survey was acquired in July 2017 using two recording systems: fibre optic cables (straight and helical wound fibre) for DAS and a 3C 24-level geophone array. Each section of the report displays a comparison between the straight and helical fibre optic cables and the geophone array. After processing the different datasets, we compared the results of the stacked VSP-CDP transforms with an inline section from a 3D seismic survey crossing through the well. Overall, there is a good correlation between the events in the surface seismic and the VSP-CDP. The CO 2 injection target located at approximately 250 ms is noticeable in each dataset. Nevertheless, there is an apparent discontinuity of the event of interest across the mapped result, particularly for the helical fibre. This assessment shows how DAS measurements seem to be a promising approach for subsurface imaging and continuous monitoring. However, further analysis of DAS is essential to obtain better imaging results, especially for the helical wound fibre optic cable dataset.
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