Reverse time migration approaches for DAS VSP

Jorge E. Monsegny, Donald C. Lawton, Daniel O. Trad

Distributed acoustic sensing is a promising technology for seismic monitoring that uses optical fibre as a sensing element instead of geophones. In contrast to geophones, it produces a signal proportional to the strain, or strain rate depending on the vendor, instead of particle velocity. To apply processing techniques, like migration, this strain is usually transformed to particle velocity. We perform the migration directly in the strain domain and an associated pressure domain by modifying the wave equation. We compare their results on the reflectivity by using a synthetic model and compare the migration results with data from the Containment and Monitoring Institute Field Research Station. In the synthetic example we obtained a good match between the migrated amplitudes at the reflector depth and the theoretical reflection coefficients. The real data migrations showed a quality similar to the usual path of transforming to vertical particle velocity before migration.