Presalt seismic surveys planned off Gabon

CGGVeritas will shoot 2D seismic surveys in deep water off north and south Gabon in advance of the June-December 2010 licensing round, the country's first since 1999.

By OGJ editors
HOUSTON, Mar. 5 -- CGGVeritas will shoot 2D seismic surveys in deep water off north and south Gabon in advance of the June-December 2010 licensing round, the country's first since 1999.

The round will focus on the deepwater presalt region analogous to large deepwater discoveries off Brazil.

The northern survey involves a 2,200-km grid specifically designed to highlight Tertiary and Cretaceous plays.

In the south, a 7,400-km very long offset survey will provide the best possible imaging to help identify traps below Aptian salt. The Zone Sud survey is part of a three-phase program designed to provide a full understanding of the region in a timely and cost-effective way.

The first step is basinwide depth modeling using existing data and a CGGVeritas test line. Next, a comprehensive gravity gradiometry survey will provide detail on the salt architecture, and the information will be used to constrain prestack depth migration models. The third phase is the acquisition of a targeted 2D grid.

The potential for further acquisition, including 3D, will be assessed after the three-phase program is complete.

Steven Toothill, chief geologist of the contractor's East Africa-Middle East region, said, "The complexity of the salt bodies in the South Gabon basin would warrant 3D seismic coverage. However, to shoot a 3D survey over the whole area of more than 50,000 sq km would take too long and be prohibitively expensive.

"A well planned 2D survey, specifically designed to target below the salt, will be sufficient to delineate structures. This will allow oil companies to evaluate the area, make their bids and then follow up with high-specification 3D surveys, such as wide-azimuth, to provide better illumination below the salt."

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