State-owned Oil and Natural Gas Corp on Friday invited proposals from firms willing to partner with it in raising oil and gas production from its 64 marginal fields. These 64 fields have been clubbed into 17 onshore contract areas that have a cumulative 300 million tonne of oil and oil equivalent natural gas reserves, the company said in a statement here. ONGC wants partners who can raise output beyond a pre-agreed baseline and will share revenues from such incremental production with them.