Nexus, which expects to make a FID at the end of the first quarter, said the “firm” financial estimate was based on figures from the final tenders.

Having now completed all front-end engineering and design (FEED) work, Nexus says it has submitted a preliminary field development plan to the relevant authority, which calls for three wells to be tied back to the Santos-operated Patricia/Baleen offshore gathering system and onshore gas plant.

In addition, the company has called tenders for all equipment and services required for the development, while negotiations tenders have been finalised and letters of intent issued.

Nexus has also arranged for the gas pipelines to be laid around this time next year, in time for first output due in the third quarter of 2008.

Based on the proposed development plan, Gaffney, Cline and Associates has confirmed a best contingent resource estimate of 435 petajoules of gas and 5.2 million barrels of condensate for the Longtom field. Its low estimate was 173PJ and 2MMbbl of condensate.

Nexus said it planned to book 350PJ of P50 reserves at Longtom, equivalent to the contracted volume of sales gas at the point of FID.

“This is below the field best estimate and the high estimate indicates scope for additional contracts if production performance and further drilling confirms the field’s upside potential,” it said.