Abu Dhabi has extended Japanese energy group Inpex’s concession on its offshore Upper Zakum oil field by 15 years, according to an announcement by the company.

The concession has now been extended to 31 December 2041, with the fiscal terms and conditions revised from the existing agreement.

The Upper Zakum field was initially developed by a joint venture of state-owned Abu Dhabi National Oil Company (Adnoc) and Inpex subsidiary Japan Oil Development Company (Jodco).

In 2006, the US-based ExxonMobil entered the partnership to form Zakum Development Company (Zadco), with the US firm taking a 28 per cent stake, Jodco 12 per cent and Adnoc holding the majority 60 per cent share.

The extension brings Inpex’s contract in line with ExxonMobil’s agreement so that both groups’ deals on the Upper Zakum field expire in 2041.

Zadco is carrying out a major expansion of the field to increase its capacity from 550,000 barrels a day (b/d) to 750,000 b/d, and is studying the possibility of a further increase to 1 million b/d.

The Upper Zakum field, which Zadco believes is the world’s fourth-largest, is located 84 kilometres off the coast of Abu Dhabi. Zadco also operates the smaller Umm al-Dalkh and Satah fields.

The emirate’s largest oil concession, Abu Dhabi Company for Onshore Oil Operations (Adco), expired earlier this month, with Abu Dhabi’s leadership currently assessing bids for a new onshore concession.