Fitting top seal topography and CO2 layer thickness to time-lapse seismic amplitude maps at Sleipner

Abstract

Injected [Formula: see text] at the Sleipner storage site is migrating into several thin layers. Using a tuning relationship, two different layer thicknesses can give the same reflection amplitude, and it is then not possible to go from amplitudes to [Formula: see text] layer thicknesses without further constraints. Exploiting spatial and time-lapse dependencies in the reflection amplitude maps makes it possible to resolve this ambiguity and create layer thickness maps when the [Formula: see text] flow is gravity dominated. The topography of the sealing cap rock was used as an optimization parameter. Tests were done on synthetic data and real data from the Sleipner [Formula: see text] injection. The resulting topography map for the Sleipner case deviated by 5.3 m on average from simple time-depth mapping, which is within the mapping uncertainty. Although the predictive power is limited, outputs of the method can be used to check if the flow matches a gravity-dominated model or if other flow mechanisms are needed to explain the observations.