The Oil and Natural Gas Corporation is planning to invest about Rs 12,000 crore (Rs 120 billion) in the coming years to upgrade and redevelop 15 oil and gas fields in the country, which had now become "old", a top executive said on Tuesday.

"These 15 fields out of over 100 were now yielding 80 per cent of the total production. These fields had to be upgraded so that more and more oil and gas could be tapped," A Kaviraj, executive director of ONGC, told a press meet in Chennai, while announcing the Government of India's offer for sale of equity shares of ONGC.

Giving a detailed presentation on the activities of ONGC, Kaviraj said ONGC Videsh Limited, a subsidiary of ONGC, has participation in gas and oil projects in Vietnam, Sudan, Russia, Iran, Iraq, Myanmar, Libya and Syria.

In Russia, the project was in advanced stages and was expected to commence oil production in last fiscal quarter of 2005. In Libya, Iran, Iraq and Syria, the exploration activities were in various stages of completion.

Kaviraj said ONGC produced 206.8 million barrels of oil and 26 billion cubic meters of natural gas for the period ended March 2003.