(Sharecast News) - Development and production company Petrotal said on Tuesday that drilling at Well 20H on the Bretaña field has commenced, allowing for the evaluation and testing of the upper Vivian formation sand, which for the first time will be jointly completed with the main Vivian 2 sand.

So far, Petrotal has only produced from the VS2 sand, where permeability was "an order of magnitude greater "than the VS1 sand.

Petrotal said the 20H well design included a short test of the VS1, to acquire crude samples and test production deliverability, and during a brief production test, the VS1 flowed at an equivalent rate of approximately 320 barrels of oil per day of 18.6 API oil, which was of similar gravity to the VS2 oil.

"PetroTal has decided to complete the 20H well in both sands. Once sufficient production data has been collected, the Company will evaluate the possibility of amending its field development plan to include the VS1, with a view to potentially including the unit in Bretaña's future 2P oil reserves certification. If expectations of low production of formation water volumes from the VS1 are confirmed, oil produced from the VS1 conceptually should not require additional water treatment facilities to be constructed," said Petrotal.

The AIM-listed group added that the well was now drilling ahead in the main VS2 target and was expected to be completed by the end of September.

As of 1005 BST, Petrotal shares were up 1.28% at 39.50p.

Reporting by Iain Gilbert at Sharecast.com