INPEX entered into a production sharing contract (PSC) with the Indonesian Government in October 1966, at that time acquiring a 100% participating interest in the Offshore Mahakam Block. The Attaka Unit was established in April 1970 through the unitization of part of the adjacent blocks owned by INPEX and Unocal (now Chevron), with each company taking a 50% interest. Production of crude oil and natural gas began in 1972. INPEX farmed out a 50% participating interest in the Offshore Mahakam Block to CFP (now TOTAL) in July 1970. This venture subsequently made a series of discoveries in the Bekapai (oil), Handil (oil), Tambora (oil and gas), Tunu (gas), Peciko (gas), Sisi and Nubi (gas) fields, each of which has continued to produce crude oil and natural gas. The crude oil and condensate produced from these fields are shipped mainly to oil refineries and power companies in Japan by tanker from the Santan and Senipah terminals. Most of the natural gas is supplied to the Bontang LNG Plant, then shipped as LNG to Japan and elsewhere.

The Offshore Mahakam Block will continue to be a key profit center for INPEX. In addition, together with TOTAL (the operator), we have been engaged in negotiations with the Indonesian authorities to secure a contract extension beyond 2018 with respect to the Offshore Mahakam Block.

In July 1977, INPEX acquired a 17.5% participating interest in the South Natuna Sea Block B. Later, in January 1994, INPEX increased its total participating interest in the block to 35% with the purchase of an additional 17.5% interest. Crude oil production began in 1979, and supplies of natural gas to Singapore via Indonesia's first international pipeline commenced in 2001. Additional deliveries of natural gas from this pipeline to Malaysia started in 2002. These supply milestones contributed to the extension of the PSC covering the block until 2028.

Production operations in the Belanak oil and gas field, which is part of South Natuna, utilize a world-class floating production, storage and offloading (FPSO) system. Production of crude oil and condensate began in December 2004, with LPG production commencing in April 2007. The Hiu and Kerisi fields came onstream in 2006 and 2007, respectively. Gas production commenced at the North Belut Field in November 2009 and at the Bawal Gas Field in July 2012.

INPEX acquired a 100% participating interest in the Masela Block in November 1998 through an open bid conducted by the Indonesian Government. INPEX proceeded with exploratory activity as the operator, and an exploratory well drilled in 2000 discovered the Abadi Gas Field. Subsequently, six appraisal wells were drilled (two in 2002 and four in 2007–2008), all of which confirmed the presence of gas and condensate column. The Indonesian Government granted its approval to the plan of development for Stage-I (POD-1) for a "floating LNG" with a capacity of 2.5 million tons per year of LNG in December 2010. INPEX is currently conducting preparations for FEED with a view to starting it in the latter half of 2012. We are studying the possibilities for further development exploiting its reserves and plan to begin drilling two or three appraisal wells and one exploration well in the second quarter of 2013.

MI Berau B.V., a joint venture established by INPEX (44%) and Mitsubishi Corporation (56%), acquired in October 2001 an interest of around 22.9% in the Berau Block. MI Berau owns a 16.3% participating interest (including an interest held by INPEX of about 7.17%) in the Tangguh LNG Project, which has been set among the parties of the Berau Block and the adjoining Wiriagar and Muturi blocks. MI Berau Japan Ltd., a joint venture between INPEX (44%) and Mitsubishi Corporation (56%), also acquired approximately 16.5% of the issued and outstanding shares of KG Berau Petroleum Ltd. in October 2007, bringing INPEX's total interest in the project up to approximately 7.79%.

In March 2005, the Indonesian Government approved a development plan for the Tangguh LNG Project and an extension of the PSC until 2035. Development was then conducted, leading to shipments of LNG in July 2009.