Oil giant BP is to pay Indian energy firm Reliance Industries $7.2bn (£4.42bn) after its acquisition of a 30% interest in several Indian production blocks was completed on Tuesday.The FTSE 100 company will have an interest in 21 oil and gas production sharing contracts that Reliance operates in India, including the KG D6 block that currently produces about 1.6bn cubic feet of gas per day - 40% of the country's total gas production."This significant step will commence the planned alliance which will operate across the gas value chain in India, from exploration and production to distribution and marketing. The completion of the deal delivers one of the largest ever foreign direct investments into India," the statement said.A further $1.8bn will be paid subject to certain exploration successes."This is the beginning of what we expect to be a long and successful working partnership with Reliance, building on the strengths of each company," said BP's chief executive Bob Dudley. "This major investment is directly aligned with our strategy of creating long-term value by forming alliances with strong national partners, gaining material positions in significant hydrocarbon basins and increasing our exposure to growing energy markets."By 14:41, BP's shares were trading 2.43% higher at 395.7p.BC