Design and deployment of a prototype multicomponent DAS sensor
Kristopher A. H. Innanen, Donald C. Lawton, Kevin W. Hall, Kevin L. Bertram, Malcolm B. Bertram, Henry C. Bland
In 2016-2017 CREWES published a range of analyses and applications of a geometrical model of fibre-optic (DAS) data for arbitrary fibre shapes. Amongst those applications was a multicomponent estimation scheme based on a careful accounting, and combined useage, of the varying fibre directions associated with a shaped cable layout. In 2018 a prototype shaped DAS fibre array was buried to put some of these ideas and their feasibility to the test. In October 2018, “the pretzel” was illuminated from several directions, and shot records were analyzed to assess whether commonly available directional sensitivity is sufficient to permit multiple components of strain to be estimated simultaneously. By picking a P-wave arrival and comparing it to an analytic model, we conclude with a cautious yes. Other important directionality conclusions are also derivable from this experimental setup; for instance, a polarity ambiguity involving the DAS directionality modelling through ac-counting of local fibre tangents is clearly rendered when model and data are compared.