Paris-based CGG has completed a huge 3D seismic data shoot over four frontier blocks located east of Sao Tome & Principe that are operated by Lisbon-based Galp Energia and US player Kosmos Energy, writes Iain Esau.

Joao Casacao, a petroleum geologist at Galp, said the “last shot” of the 16,000 square kilometre survey took place on 20 August.

CGG’s Oceanic Endeavour vessel began the survey work in February this year.

Speaking at the PESGB/HGS Africa E&P event last week, Casacao said with the new 3D data “we expect we can really assess the full prospectivity” of a play that Galp has named the Sao Tome & Principe basin.

Industry has shown little interest in exploring this area which is sandwiched between Sao Tome & Principe, north Gabon and southern Equatorial Guinea.

This is due to a widespread belief that the Sao Tome & Principe basin sits on top of oceanic crust, has a “cold thermal regime” and therefore has no source rock. Or, if it has source rock, it is not mature.

However, Galp and Kosmos are trying to challenge these suppositions.

Casacao remarked that recent studies indicate the basin is “warmer than expected,” has “thick sediment” and “source rock… should be mature”.

Recent analysis of oil seeps on each of the two islands predicts that Upper Cretaceous marine source rocks should be oil mature and that reservoirs exist of the same age.

Of the four blocks, Galp operates block 6 while Kosmos operates blocks 5, 11 and 12.

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CGG completes frontier 3D seismic shoot off Sao Tome