Indian energy giant Reliance Industries will pay $1.7 billion to form a joint venture in the Marcellus Shale with U.S.-based Atlas Energy, gaining an overseas presence by becoming the latest foreign company to buy into the promising U.S. natural-gas shales. India's biggest company will gain a 40 percent stake in Atlas' operations in the booming Marcellus Shale-a natural-gas project that spans parts of Pennsylvania, West Virginia, and New York, and which according to some geologists could hold enough natural gas to supply the United States for a decade. Reliance has been seeking to expand its presence outside India, enter new markets, and broaden its various businesses, including refining, oil and natural-gas exploration, and petrochemicals. With Friday's move, Reliance joins several international energy companies, including British Petroleum (BP), Total, Statoil, and Mitsui, that have invested in the shale formations that could hold vast amounts of natural gas. While the shale has proven to be lucrative, it is also very expensive to develop. The joint ventures have given independent oil companies who own much of the land above the formations access to capital and should allow foreign energy companies to gain expertise in new drilling techniques developed for the shales.