Influence of gauge length on DAS VSP data at the Houston Research Center test well

A series of tests have been conducted at the Aramco Houston Research Center (HRC) fiber-optic test facility, assessing the influence of DAS gauge length (GL) on VSP data. This study demonstrates this influence in a shallow (1500 ft) test well equipped with geophones and fiber-optic cables cemented behind the casing. GLs of 2, 4.5, 9, and 12 m are investigated in comparison to vertical geophone data with approximately 11 m receiver spacing. The results show that the optimal GL was 4.5 m, which corresponded to about one-quarter of the dominant seismic wavelength. The optimal GL was obtained by investigating the signal-to-noise ratio of the field shot-records with respect to the various processing products, as well as, the cross-correlation of the DAS corridor-stacks with the geophone corridor-stack. Additionally, we show that the velocity profiles obtained using various GLs were comparable with minimal variation of ±20 m/s. In conclusion, we recommend selecting the GL based on the expected average formation velocity and maximum seismic frequency in order to record optimal DAS VSP data. Presentation Date: Wednesday, October 14, 2020 Session Start Time: 1:50 PM Presentation Time: 4:45 PM Location: 361F Presentation Type: Oral