India’s biggest oil and gas producer will pay as much as $1.2 billion to buy a majority stake in a gas field off the country’s east coast, aiming to boost production as the country seeks to cut energy imports. State-owned Oil and Natural Gas Corp. Ltd.’s board approved the purchase of an 80 percent stake in Gujarat State Petroleum Corp.’s deepwater block in the Krishna Godavari basin, it said in a statement on Friday.