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Design considerations for using Distributed Acoustic Sensing for cross‐well seismics: A case study for CO 2 storage
Author(s) -
Wuestefeld Andreas,
Weinzierl Wolfgang
Publication year - 2020
Publication title -
geophysical prospecting
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.735
H-Index - 79
eISSN - 1365-2478
pISSN - 0016-8025
DOI - 10.1111/1365-2478.12965
Subject(s) - wireline , distributed acoustic sensing , regional geology , engineering geology , economic geology , geology , toolbox , environmental geology , seismology , fiber optic sensor , optical fiber , computer science , engineering , mechanical engineering , volcanism , telecommunications , wireless , tectonics
Downhole monitoring with fibre‐optic Distributed Acoustic Sensing (DAS) systems offers unprecedented spatial resolution. At the same time, costs are reduced since repeated wireline surveys can be replaced by the permanent installation of comparatively cheap fibre cables. However, the single component nature of fibre data requires novel approaches when designing a monitoring project such as cross‐well seismics. At the example of the shallow CO 2 injection test site in Svelvik, Norway, we model the evolution of velocity changes during CO 2 injection based on rock physics theory. Different cross‐well seismic design scenarios are then considered to evaluate the best design and the limits of this method to detect containment breach. We present a series of evaluation tools to compare the effect of different well spacings for cross‐well seismic tomography. In addition to travel‐times, we also consider characteristic amplitude changes along the fibre unique to DAS strain measurements, which might add a constraint to the inversion. We also compare the effect of using helical fibres instead of classical straight fibres. We thus present a toolbox to evaluate and compare different monitoring design options for fibre optic downhole installations for cross‐well monitoring.