Sub Salt Imaging Strategy in the Ultra Deep Water Offshore Angola

Adriano P. Sebastiao¹ and Dominic Lawrance^2
1DEX/DGEF, Sonangol, Luanda, Angola
²Angola BU Exploration, bp, Sunbury, United Kingdom

Angolan concessions in the ultra deep water are 5000 Km² block size in average, for a relatively short exploration phase. Here intensive front-end loading of high-end technology and strategy is a crucial necessity to be able to deliver the PSA requirements and evaluate the Block potential.

The initial seismic surveys in the ultra deep water Angola were designed based on the knowledge and success of the deepwater block 14, 15 and 17 dominated by chasing complex channel systems. Thereby the initial dataset were not designed for sub salt provinces.

The Angola ultra deep water is an area with significant amount of near surface salt and having the majority of its potential beneath the very complex salt domes. In order to delivery exploration results a seismic imaging strategy were made in place starting from the non sub salt survey to the news long offsets surveys.

The present paper intends to review the general operator's strategies in the area, most of them “imported” from US Gulf of Mexico, the way that imaging projects were carried out and put together different migrations techniques and results.

A greater confidence on the salt models was built based in the strategy to undertake series of wave migrations simultaneously with Kirchhoff and Beam Steer migrations. A big range of new migration algorithms like Beam Steer, Reverse Time Migration, were tested and proved that the new long offset data and new algorithms provided additional information resulting in 5 (five) sub salt discoveries in Angola and more than 10 (ten) prospects matured.

AAPG International Conference and Exhibition, Cape Town, South Africa 2008 © AAPG Search and Discovery