Oil and Natural Gas Corporation (ONGC) made a net profit of Rs 12,500 crore in the last financial year and Rs 30,000 crore in the last three years, CMD Subir Raha said."Our growth in the hydro-carbon sector and as an oil and gas exploration company during the period was satisfactory", Raha said.Raha said ONGC was now working on an ambitious joint venture project for setting up a 750 MW, gas-based thermal unit at Palatana in South Tripura to be completed in 30 months.In the project - ONGC Tripura Power Project (CGCTTP) - the Tripura government will have 24%, ONGC and the rest will be collected by selling equity share in the market, he said.