A preliminary natural-gas deal between Russia and China signed over the weekend paves the way for opening up a second major gas supply conduit between the two countries and lowering natural-gas prices in Asia. The deal comes less than six months after the two countries signed a landmark $400 billion gas deal and will intensify competition among billion-dollar natural gas projects aimed at Asian markets. Alexei Miller , chief executive of Russia’s gas monopoly Gazprom OAO , and Zhou Jiping , chairman of China National Petroleum Corp., signed a “framework agreement” in Beijing on Sunday for supplying natural gas through pipelines into western China, Gazprom said in a statement.