American attention has lately been focused on China’s emergence as a competitor for dwindling oil supplies — witness the uproar over CNOOC Ltd.’s failed bid for California’s Unocal Corp. But a different, yet equally intense, energy rivalry sure to have a dramatic effect on geopolitics has been playing out on the far side of the globe. Asia’s other emerging powerhouse, India, is just as hungry for supplies as China. The two are battling each other in oil patches from Sudan to Siberia as they try to secure the resources to fuel their growing economies. So far, the Chinese have the upper hand in the competition.