Tapping China’s vast shale-gas reserves has proved more difficult than government planners in Beijing once hoped. In 2012, China’s National Energy Administration projected that, by 2020, from 60 billion to 80 billion cubic meters (bcm) of domestic shale gas would be pumped annually. Earlier this week the country’s energy chief, Wu Xinxiong, slashed the goal in half, to 30 billion bcm by 2020.

According to the U.S. Energy Information Administration, China’s holds theworld’s largest reserves of theoretically recoverable shale gas. But much of it is locked in mountainous regions in western China.

While China’s leaders—concerned about steeply rising energy demand accompanying rapid urbanization—dearly want to emulate the U.S.’s shale-gas boom, it turns out Americans have several practical advantages. For starters, the U.S. shale-gas revolution kicked off in fairly accessible regions: the flatlands of Texas, North Dakota, and Pennsylvania.

So far, explorations in China have identified only one clearly promising shale play:Fuling shale gas field, near the western megalopolis of Chongqing. Sinopec, which controls the Fuling field, projects that its annual shale gas production will reach 5 bcm by 2015 and 10 bcm by 2017. (China trivia fact: Fuling was also the site ofRiver Town, well-known journalist Peter Hessler’s first book chronicling his years as a Peace Corps volunteer in the then-small city on the Yangtze.)

With no other comparable sites yet identified, it’s not clear where the other 20 bcm may come from. While Sinopec is currently at the forefront of China’s shale-gas development, two foreign companies, Royal Dutch Shell (RDSA:LN) and Hess(HES), have secured production-sharing contracts for other potential sites.