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The Dalia OBN Project
- Publisher: European Association of Geoscientists & Engineers
- Source: Conference Proceedings, 72nd EAGE Conference and Exhibition incorporating SPE EUROPEC 2010, Jun 2010, cp-161-00408
- ISBN: 978-90-73781-86-3
Abstract
2009, the first “industrial scale” Ocean Bottom Nodes (OBN) project over a fully operational production environment was completed by Total on the Dalia oilfield, Block 17, deep offshore Angola. A repeatability test was also performed as part of the operations. Block 17 geophysical response is characterised by weak absorption effects: frequencies up to 120Hz are often used for reservoir characterisation and monitoring. OBN are passive recording systems and source-to-receiver travel times must be reconciled after acquisition is completed. For these reasons, during all operations, great efforts were addressed to any possible cause of time misalignments, since the smallest errors could actually reflect in degradation of thin sedimentary features. When compared to streamer results, OBN processed data exhibit some minor loss in high frequency content but a clear gain towards the lower end of the spectrum. We demonstrate that OBN and streamer data can successfully be merged and that qualitative and quantitative 4D interpretations are possible, in good agreement with the petrophysical knowledge of the Dalia complex. Finally, the repeatability test validates the business model by which selected targets of a deep offshore field can effectively be monitored by fairly limited patches of retrievable OBN stations.