Spudded on Saturday, the ST991-1 well is expected to take six weeks to reach an intermediary depth of 10,500 feet.

If the well fails to encounter commercial hydrocarbons to this depth, operatorship will swap to Golden Gate, which will then deepen ST991-1 to the primary objective depth of 15,500 feet. This operation is expected to take a further 45 days.

However, if it is found to be commercial, the well will be completed in the shallow zones for an extended production test.

Golden Gate said the Manzano deep structure was a "world-class" exploration prospect, with an upside P10 potential of 816 billion cubic feet.

In August, Golden Gate accused BNP of breaching a drilling agreement at the Manzano prospect, having failed "for a variety of reasons" to drill an exploration well before releasing the drilling rig.

But last month, the two parties resolved the dispute by reaching an agreement that paved the way for this large prospect to be drilled in the most cost effective manner, which was "substantially" below the original budget estimate.