The Perth-based company said that CGGVeritas would now process the data and deliver it to Otto by September or October for interpretation.

The 145-square-kilometre 3D seismic acquired in Service Contract (SC) 51 formed the last part of the Trinity Survey covering the Argao and Cabilao prospects.

Target zones in the anticlinal Argao structure potentially contained up to 270 million barrels of recoverable oil in conventional sandstone reservoirs.

Otto said the observance of 'direct hydrocarbon indicators'(DHIs) on existing 2D data supported the presence of hydrocarbons.

The 3D seismic would allow more detailed evaluation of the DHIs and determine the best drilling location to target three potential horizon objectives in the Argao structure, Otto added.

Cabilao was an adjacent reef structure also covered by the 3D survey and a potential follow-up exploration well targeting up to 150MMbbl of recoverable oil.

Otto said that because of their close proximity, success in one prospect would mean a great chance of success in the other.

The company said its total acquired seismic was: 116sq.km of 3D data over the Calauit and Calauit South Oil accumulations in SC50; 954km of 2D data in the deepwater permit SC55; and 145sq.km of 3D seismic over the Argao and Cabilao prospects in SC51.

The next step in the exploration program was an extensive environmental survey, due to start in the next few months, in the Cebu-Bohol Straits to prepare for drilling the Argao structure in 2008.

Otto said it had deferred acquisition of the 261km of planned 2D data in SC51 at the request of the Filipino Department of Energy, because a local non-government organisation had challenged the validity of an environmental permit issued by the Department of Environment and Natural Resources allowing Otto to acquire seismic in the Cebu-Bohol Straits.

The company said the 2D data was not critical to the short-term drilling plans for SC51 and could be acquired at a later date.

"CGGVeritas have performed magnificently. Their environmental, health and safety record was first rate and they have saved Otto Energy substantial sums by their efficient operations and ability to finish this phase of our Philippines exploration program ahead of schedule and under budget," said Otto chief executive Alex Parks.

"This extensive program of seismic data, acquired over all three permits, will allow further evaluation of our prospects and detailed planning for drilling in 2008. Importantly, the new data will significantly increase our ability to seek substantial farm-in partners for all our licences in the Philippines," he added.