Reliance has received about 20 to 25 pitches from investment bankers for shale assets, Reliance Chief Financial Officer Alok Agarwal said recently.
Bankers say potential targets include Fort Worth, Texas-headquartered Quicksilver Resources Inc , Denver, Colorado-based Enduring Resources and companies with assets in the Horn River shale formation in Canada.
Another firm on Reliance's radar may be Houston, Texas-based EOG Resources, which said in early August it plans to sell about 180,000 acres in U.S. shale plays -- underground rock formations that hold reserves of oil and natural gas.
Shale gas accounts for between 15 percent and 20 percent of U.S. gas production, but is expected to quadruple in coming years, touching off a scramble among producers large and small for access to resources.
Ambani, the world's fourth richest man according to Forbes magazine, has made no secret of Reliance's overseas ambitions, and is looking to invest in new areas such as shale gas to expand the firm's businesses beyond petrochemicals, refining, oil and natural gas exploration, and retail.
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He could face competition from other firms, including Royal Dutch Shell, Total and Mitsui, which have done shale gas deals previously, and those that have not bought a shale asset yet such as Chevron and Encana.
Reliance is expected to generate free cash flow of $18 billion between this year and the fiscal year that ends in March 2014, giving it plenty of firepower for investment.
The company has raised a war chest of $2 billion by selling stock over the past year, and a top credit rating means financing will be easily available if needed, bankers say.
Last month, the company said it would acquire a 60 percent stake in a joint venture with Carrizo Oil & Gas at the booming Marcellus Shale region in the United States, following similar deals with U.S. firms Atlas Energy and Pioneer Natural Resources earlier in the year.
Joint ventures give independent oil companies, who own much of the acreage in these areas, access to capital and allow foreign oil firms to pick up expertise in new drilling techniques developed for the shales.
"They would love to do a large deal, a $3 to $5 billion type deal somewhere," said one U.S. investment banker familiar with the company's thinking.
"They've only really had to put a few hundred million dollars to work right now. They've got tons of cash on the balance sheet," the banker said.
The bankers mentioned in the story did not want to be identified as they were not authorised to speak with the media.
A U.S. brokerage firm said last week that Reliance is a likely partner for Chesapeake Energy's Eagle Ford shale acreage.
Closely held Chief Oil & Gas, Talon Oil & Gas and Anschutz Exploration Corp -- each of which owns shale assets -- have put themselves up for sale in recent months and could fetch around $5 billion combined, media reports have said.
With three deals in rapid succession, Reliance is shedding the image it once held of being a reluctant bidder, especially since the company has paid rich prices for some shale assets.
Reliance paid $14,000 an acre for the Atlas assets and $11,000 an acre for the Pioneer assets, which analysts say is expensive. Not all shale areas are the same and the value of an asset depends on the quality of the acreage.
While the shale formations have proven to be lucrative, they are also very expensive to develop and environmentally sensitive.
"They've been very aggressive, they are seriously intent in building up a gas business here," said the U.S. investment banker, referring to Reliance's recent deals.
Another banking source said even though other energy firms, such as those from China, may also look at shale gas acreage, a slew of options would prevent a bidding war for any one asset.
Reliance is looking to become one of the key players in the shale business in the United States, the world's biggest energy market, bankers and analysts say.
The joint venture deals allow Reliance to understand and learn the shale gas business, work with good operators, and then enable the company to take a go at it alone, Reliance's Agarwal said in late July.
"If they're really serious about (the shale), they've got to think about building an operating organization and the best way to do it is to buy one," a banker said.