CHENGDU, China -- A convoy of white vans barreled down a dusty road three hours south of this provincial capital in late September. Lush valleys were drying out after another long and turbulent rainy season. U.S. and Chinese government officials and brass from the nations' biggest oil and gas companies tailed their police escort deeper into Sichuan province. Truck traffic clogged the road, bisecting vegetable patches and rice paddies that seemed to disappear into the fog that morning. Around a final bend, the sunburst insignia on PetroChina's flag soared above the first horizontal natural gas well drilled in a Chinese shale basin.