Daily reservoir-scale subsurface monitoring using ambient seismic noise

Seismic interferometry is applied to continuous seismic recordings spanning 5 days and over 2200 stations at the Valhall Life-of-Field Seismic array in the Norwegian North Sea. We retrieve both fundamental-mode and first-overtone Scholte waves by cross correlation. Ambient seismic noise tomography using the vertical component of this dense array produces group velocity maps of fundamental-mode Scholte waves with high repeatability from only 24 h of recording. This repeatability makes daily reservoir-scale near-surface continuous monitoring of the subsurface feasible. Such monitoring may detect production-related changes over a long time scale (months to years) and may be useful for early detection of short time scale hazards (days to weeks) such as migrating gases and fluids. We validate our velocity maps by comparing them with maps obtained independently from controlled-source data.