Dual-Well 3D VSP in Deepwater Made Possible by DAS
In late 2012, we acquired a 3D Distributed Acoustic Sensing (DAS) VSP simultaneously in two injector wells in a deepwater field. We utilized seismic shots from a concurrent OBN campaign and pre-existing fiber optic cables (installed on tubing for unrelated purposes). One of the wells was mildly deviated, while the other had a complicated deviated trajectory. We obtained DAS VSP data with clear signals. The raw gathers show not only down-going P, but also PP and PS reflections, and down-going PS conversions. We also observed a surprising azimuthal phase variation in the deviated well, and some noises that underscore the importance of proper fiber connections. We conclude that 3D DAS VSP can be acquired safely and successfully in multiple deepwater wells where fiber optic cable has been installed, including wells inaccessible to geophones.
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