East Natuna gas field

The East Natuna gas field (former name: Natuna D-Alpha block) is a large natural gas field located in the South China Sea off northern Natuna Island, Indonesia. It is within the disagreed area claimed by China.

History
The field was discovered in 1973 by Agip. In 1980, the Indonesian state-owned oil company Pertamina and Exxon formed a joint venture to develop Natuna D-Alpha. However, due to the high content the partnership was not able to start production. In 1995, the Indonesian government signed a contract with Exxon but in 2007, the contract was terminated. In 2008, the block was awarded to Pertamina.

The new agreement was signed between Pertamina and ExxonMobil in 2010. Correspondingly, the field was renamed East Natuna to be geographically more precise. In 2011, the principal of agreement was signed between Pertamina, ExxonMobil, Total S.A. and Petronas. In 2012, Petronas was replaced by PTT Exploration and Production. As of 2016, negotiations about the new principal of agreement have not finalized and consequently, a production sharing contract is not signed.

Reserves and development
The East Natuna gas field is located in the Greater Sarawak Basin (East Natuna Basin) about 1100 km north of Jakarta and 225 km northeast of the Natuna Islands covering approximately 310 km2. The reservoir is at a water depth of 145 m within the Miocene Terumbu Formation with a crest at 2658 m subsea. A maximum column height is 1638 m. The thickness of the formation varies between 300 and 1525 m.  The estimated resource in place of the East Natuna field is around 222 e12cuft, of which total proven reserves of natural gas are 46 e12cuft, and production is forecast to be around 1.98 e9cuft/d. The content of the resource is about 71%.

The development of East Natuna is expected to cost US$20–40 billion. To save costs, the joint development of East Natuna, Tuna block (Premier Oil 65%, Mitsui Oil Exploration 35%), and South Natuna Sea Block B (ConocoPhillips 40%, Inpex 35%, Chevron Corporation 25%) has been proposed. Production is expected to be viable only if the oil price exceeds $100 per barrel. The production is expected to start not before 2030.