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Until now there are not many examples of depth imaging based 4D projects in the industry. This study gives us an unique opportunity to compare what effects different time and depth migration methods have on the 4D difference and what significance the migration velocity accuracy has for time-lapse data and its impact on the production management for the Brage field. Different migration trials were performed and arranged according to their increasing ability to handle complex wave-fields resulting from velocity profiles with significant contrasts. The depth migration results were scaled back to time to allow direct comparisons with the PSTM trials before careful post-stack conditioning lead to the 4D differences. Comparison of the OWC attribute maps from the 4D results showed differences in amplitude and positioning where the PSDM methods came out more favourably than the PSTM methods. The 4D differences from the PSDM trials tend to have slightly better consistency and coherency than the PSTM 4D differences and are easier to analyse. PSDM methods appear to give additional confidence in the 4D results on the Brage field and can be favourable for 4D studies even where complexity of the reservoir and the overburden are not too large

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